This is grx249um.inf, produced by makeinfo version 4.13 from grx2.tex.

INFO-DIR-SECTION Libraries
START-INFO-DIR-ENTRY
* GRX: (grx).                   The GRX Graphics Library.
END-INFO-DIR-ENTRY


File: grx249um.inf,  Node: Top,  Next: A User Manual For GRX2

            GRX 2.4.9 User's Manual
***********************

A 2D graphics library for DOS, Linux, X11 and Win32
***************************************************
 Based on the original doc written by: Csaba Biegl on August 10, 1992
       Updated by: Mariano Alvarez Fernandez on August 17, 2000
                      Last update: July 10, 2012

Abstract
********

*GRX* is a 2D graphics library originaly written by Csaba Biegl for DJ
Delorie's DOS port of the GCC compiler. Now it support a big range of
platforms, the main four are: DOS (DJGPPv2), Linux console, X11 and
Win32 (Mingw). On DOS it supports VGA, EGA and VESA compliant cards.
On Linux console it uses svgalib or the framebuffer. On X11 it must
work on any X11R5 (or later). From the 2.4 version, GRX comes with a
Win32 driver.  The framebuffer Linux console driver was new in 2.4.2.
From 2.4.7 there is a support for x86_64 bits Linux machines and a
support for an SDL driver on MingW and X11. On MingW and X11 it runs on
a window with the original driver, and either full screen or on a
window with the SDL driver.

* Menu:

* A User Manual For GRX2::


File: grx249um.inf,  Node: A User Manual For GRX2,  Next: Hello world,  Prev: Top,  Up: Top

GRX2 User's Manual
******************

* Menu:

* Top::
* Hello world::
* Data types and function declarations::
* Setting the graphics driver::
* Setting video modes::
* Graphics contexts::
* Context use::
* Color management::
* Portable use of a few colors::
* Graphics primitives::
* Non-clipping graphics primitives::
* Customized line drawing::
* Pattern filled graphics primitives::
* Patterned line drawing::
* Image manipulation::
* Text drawing::
* Drawing in user coordinates::
* Graphics cursors::
* Keyboard input::
* Mouse event handling::
* Writing/reading PNM graphics files::
* Writing/reading PNG graphics files::
* Writing/reading JPEG graphics files::
* Miscellaneous functions::
* BGI interface::
* Pascal interface::
* References::


File: grx249um.inf,  Node: Hello world,  Next: Data types and function declarations,  Prev: A User Manual For GRX2,  Up: A User Manual For GRX2

Hello world
===========

The next program draws a double frame around the screen and writes
"Hello, GRX world" centered. Then it waits after a key is pressed.

     #include <string.h>
     #include <grx20.h>
     #include <grxkeys.h>

     int main()
     {
       char *message = "Hello, GRX world";
       int x, y;
       GrTextOption grt;

       GrSetMode( GR_default_graphics );

       grt.txo_font = &GrDefaultFont;
       grt.txo_fgcolor.v = GrWhite();
       grt.txo_bgcolor.v = GrBlack();
       grt.txo_direct = GR_TEXT_RIGHT;
       grt.txo_xalign = GR_ALIGN_CENTER;
       grt.txo_yalign = GR_ALIGN_CENTER;
       grt.txo_chrtype = GR_BYTE_TEXT;

       GrBox( 0,0,GrMaxX(),GrMaxY(),GrWhite() );
       GrBox( 4,4,GrMaxX()-4,GrMaxY()-4,GrWhite() );

       x = GrMaxX()/2;
       y = GrMaxY()/2;
       GrDrawString( message,strlen( message ),x,y,&grt );

       GrKeyRead();

       return 0;
     }
How to compile the hello world (assuming the GRX library was previously
installed)
       DJGPP: gcc -o hellogrx.exe hellogrx.c -lgrx20
       Mingw: gcc -o hellogrx.exe hellogrx.c -lgrx20 -mwindows
       X11  : gcc -o hellogrx hellogrx.c -D__XWIN__ -I/usr/X11R6/include
              -lgrx20X -L/usr/X11R6/lib -lX11
       Linux: gcc -o hellogrx hellogrx.c -lgrx20 -lvga

       For the SDL driver:
       Mingw: gcc -o hellogrx.exe hellogrx.c -lgrx20S -lSDL
       X11  : gcc -o hellogrx hellogrx.c -D__XWIN__ -I/usr/X11R6/include
              -lgrx20S -lSDL -lpthread -L/usr/X11R6/lib -lX11

       For x86_64 systems add -m32 or -m64 for 32/64 bits executables
       and replace /lib by /lib64 or /lib32 as needed


File: grx249um.inf,  Node: Data types and function declarations,  Next: Setting the graphics driver,  Prev: Hello world,  Up: A User Manual For GRX2

Data types and function declarations
====================================

All public data structures and graphics primitives meant for usage by
the application program are declared/prototyped in the header files (in
the 'include' sub-directory):

        * grdriver.h   graphics driver format specifications
        * grfontdv.h   format of a font when loaded into memory
        * grx20.h      drawing-related structures and functions
        * grxkeys.h    platform independent key definitions

     User programs normally only include *include/grx20.h* and *include/grxkeys.h*


File: grx249um.inf,  Node: Setting the graphics driver,  Next: Setting video modes,  Prev: Data types and function declarations,  Up: A User Manual For GRX2

Setting the graphics driver
===========================

The graphics driver is normally set by the final user by the environment
variable GRX20DRV, but a program can set it using:

     int GrSetDriver(char *drvspec);

The drvspec string has the same format as the environment variable:

     <driver> gw <width> gh <height> nc <colors>

Available drivers are for:

     * DOS => herc, stdvga, stdega, et4000, cl5426, mach64, ati28800, s3, VESA, memory
     * Linux => svgalib, linuxfb, memory
     * X11 => xwin, memory
     * Win32 => win32, memory
     * SDL (Win32 and X11) => sdl::fs, sdl::ww, memory

The xwin and win32 drivers are windowed.  The SDL driver on the same
systems can be either fullscreen (::fs) or windowed (::ww).

The optionals gw, gh and nc parameters set the desired default graphics
mode.  Normal values for 'nc' are 2, 16, 256, 64K and 16M. The current
driver name can be obtained from:

     GrCurrentVideoDriver()->name


File: grx249um.inf,  Node: Setting video modes,  Next: Graphics contexts,  Prev: Setting the graphics driver,  Up: A User Manual For GRX2

Setting video modes
===================

Before a program can do any graphics drawing it has to configure the
graphics driver for the desired graphics mode. It is done with the
GrSetMode function as follows:

     int GrSetMode(int which,...);

On succes it returns non-zero (TRUE). The which parameter can be one of
the following constants, declared in grx20.h:

     typedef enum _GR_graphicsModes {
       GR_80_25_text,
       GR_default_text,
       GR_width_height_text,
       GR_biggest_text,
       GR_320_200_graphics,
       GR_default_graphics,
       GR_width_height_graphics,
       GR_biggest_noninterlaced_graphics,
       GR_biggest_graphics,
       GR_width_height_color_graphics,
       GR_width_height_color_text,
       GR_custom_graphics,
       GR_width_height_bpp_graphics,
       GR_width_height_bpp_text,
       GR_custom_bpp_graphics,
       GR_NC_80_25_text,
       GR_NC_default_text,
       GR_NC_width_height_text,
       GR_NC_biggest_text,
       GR_NC_320_200_graphics,
       GR_NC_default_graphics,
       GR_NC_width_height_graphics,
       GR_NC_biggest_noninterlaced_graphics,
       GR_NC_biggest_graphics,
       GR_NC_width_height_color_graphics,
       GR_NC_width_height_color_text,
       GR_NC_custom_graphics,
       GR_NC_width_height_bpp_graphics,
       GR_NC_width_height_bpp_text,
       GR_NC_custom_bpp_graphics,
     } GrGraphicsMode;

The GR_width_height_text and GR_width_height_graphics modes require the
two size arguments: int width and int height.

The GR_width_height_color_graphics and GR_width_height_color_text modes
require three arguments: int width, int height and GrColor colors.

The GR_width_height_bpp_graphics and GR_width_height_bpp_text modes
require three arguments: int width, int height and int bpp (bits per
plane instead number of colors).

The GR_custom_graphics and GR_custom_bpp_graphics modes require five
arguments: int width, int height, GrColor colors or int bpp, int vx and
int vy.  Using this modes you can set a virtual screen of vx by vy size.

A call with any other mode does not require any arguments.

The GR_NC_... modes are equivalent to the GR_.. ones, but they don't
clear the video memory.

Graphics drivers can provide info of the supported graphics modes, use
the next code skeleton to colect the data:

     {
       GrFrameMode fm;
       const GrVideoMode *mp;
       for(fm =GR_firstGraphicsFrameMode; fm <= GR_lastGraphicsFrameMode; fm++) {
         mp = GrFirstVideoMode(fm);
         while( mp != NULL ) {
           ..
           .. use the mp info
           ..
           mp = GrNextVideoMode(mp))
         }
       }
     }

Don't worry if you don't understand it, normal user programs don't need
to know about FrameModes. The GrVideoMode structure has the following
fields:

     typedef struct _GR_videoMode GrVideoMode;

     struct _GR_videoMode {
       char    present;                    /* is it really available? */
       char    bpp;                        /* log2 of # of colors */
       short   width,height;               /* video mode geometry */
       short   mode;                       /* BIOS mode number (if any) */
       int     lineoffset;                 /* scan line length */
       int     privdata;                   /* driver can use it for anything */
       struct _GR_videoModeExt *extinfo;   /* extra info (maybe shared) */
     };

The width, height and bpp members are the useful information if you are
interested in set modes other than the GR_default_graphics.

A user-defined function can be invoked every time the video mode is
changed (i.e. GrSetMode is called). This function should not take any
parameters and don't return any value. It can be installed (for all
subsequent GrSetMode calls) with the:

     void GrSetModeHook(void (*hookfunc)(void));

function. The current graphics mode (one of the valid mode argument
values for GrSetMode) can be obtained with the:

     GrGraphicsMode GrCurrentMode(void);

function, while the type of the installed graphics adapter can be
determined with the:

     GrVideoAdapter GrAdapterType(void);

function. GrAdapterType returns the type of the adapter as one of the
following symbolic constants (defined in grx20.h):

     typedef enum _GR_videoAdapters {
       GR_UNKNOWN = (-1),     /* not known (before driver set) */
       GR_VGA,                /* VGA adapter */
       GR_EGA,                /* EGA adapter */
       GR_HERC,               /* Hercules mono adapter */
       GR_8514A,              /* 8514A or compatible */
       GR_S3,                 /* S3 graphics accelerator */
       GR_XWIN,               /* X11 driver */
       GR_WIN32,              /* WIN32 driver */
       GR_LNXFB,              /* Linux framebuffer */
       GR_SDL,                /* SDL driver */
       GR_MEM                 /* memory only driver */
     } GrVideoAdapter;

Note that the VESA driver return GR_VGA here.


File: grx249um.inf,  Node: Graphics contexts,  Next: Context use,  Prev: Setting video modes,  Up: A User Manual For GRX2

Graphics contexts
=================

The library supports a set of drawing regions called contexts (the
GrContext structure). These can be in video memory or in system memory.
Contexts in system memory always have the same memory organization as
the video memory. When GrSetMode is called, a default context is
created which maps to the whole graphics screen. Contexts are described
by the GrContext data structure:

     typedef struct _GR_context GrContext;

     struct _GR_context {
       struct _GR_frame    gc_frame;       /* frame buffer info */
       struct _GR_context *gc_root;        /* context which owns frame */
       int    gc_xmax;                     /* max X coord (width  - 1) */
       int    gc_ymax;                     /* max Y coord (height - 1) */
       int    gc_xoffset;                  /* X offset from root's base */
       int    gc_yoffset;                  /* Y offset from root's base */
       int    gc_xcliplo;                  /* low X clipping limit */
       int    gc_ycliplo;                  /* low Y clipping limit */
       int    gc_xcliphi;                  /* high X clipping limit */
       int    gc_ycliphi;                  /* high Y clipping limit */
       int    gc_usrxbase;                 /* user window min X coordinate */
       int    gc_usrybase;                 /* user window min Y coordinate */
       int    gc_usrwidth;                 /* user window width  */
       int    gc_usrheight;                /* user window height */
     # define gc_baseaddr                  gc_frame.gf_baseaddr
     # define gc_selector                  gc_frame.gf_selector
     # define gc_onscreen                  gc_frame.gf_onscreen
     # define gc_memflags                  gc_frame.gf_memflags
     # define gc_lineoffset                gc_frame.gf_lineoffset
     # define gc_driver                    gc_frame.gf_driver
     };

The following four functions return information about the layout of and
memory occupied by a graphics context of size width by height in the
current graphics mode (as set up by GrSetMode):

     int GrLineOffset(int width);
     int GrNumPlanes(void);
     long GrPlaneSize(int w,int h);
     long GrContextSize(int w,int h);

GrLineOffset always returns the offset between successive pixel rows of
the context in bytes. GrNumPlanes returns the number of bitmap planes
in the current graphics mode. GrContextSize calculates the total amount
of memory needed by a context, while GrPlaneSize calculates the size of
a bitplane in the context. The function:

     GrContext *GrCreateContext(int w,int h,char far *memory[4],GrContext *where);

can be used to create a new context in system memory. The NULL pointer
is also accepted as the value of the memory and where arguments, in
this case the library allocates the necessary amount of memory
internally. It is a general convention in the library that functions
returning pointers to any GRX specific data structure have a last
argument (most of the time named where in the prototypes) which can be
used to pass the address of the data structure which should be filled
with the result. If this where pointer has the value of NULL, then the
library allocates space for the data structure internally.

The memory argument is really a 4 pointer array, each pointer must
point to space to handle GrPlaneSize(w,h) bytes, really only
GrNumPlanes() pointers must be malloced, the rest can be NULL.
Nevertheless the normal use (see below) is

     gc = GrCreateContext(w,h,NULL,NULL);

so yo don't need to care about.

The function:

     GrContext *GrCreateSubContext(int x1,int y1,int x2,int y2,
                                   const GrContext *parent,GrContext *where);

creates a new sub-context which maps to a part of an existing context.
The coordinate arguments (x1 through y2) are interpreted relative to
the parent context's limits. Pixel addressing is zero-based even in
sub-contexts, i.e. the address of the top left pixel is (0,0) even in a
sub-context which has been mapped onto the interior of its parent
context.

Sub-contexts can be resized, but not their parents (i.e. anything
returned by GrCreateContext or set up by GrSetMode cannot be resized -
because this could lead to irrecoverable "loss" of drawing memory. The
following function can be used for this purpose:

     void GrResizeSubContext(GrContext *context,int x1,int y1,int x2,int y2);

The current context structure is stored in a static location in the
library.  (For efficiency reasons - it is used quite frequently, and
this way no pointer dereferencing is necessary.) The context stores all
relevant information about the video organization, coordinate limits,
etc... The current context can be set with the:

     void GrSetContext(const GrContext *context);

function. This function will reset the current context to the full
graphics screen if it is passed the NULL pointer as argument. The value
of the current context can be saved into a GrContext structure pointed
to by where using:

     GrContext *GrSaveContext(GrContext *where);

(Again, if where is NULL, the library allocates the space.) The next two
functions:

     const GrContext *GrCurrentContext(void);
     const GrContext *GrScreenContext(void);

return the current context and the screen context respectively.
Contexts can be destroyed with:

     void GrDestroyContext(GrContext *context);

This function will free the memory occupied by the context only if it
was allocated originally by the library. The next three functions set
up and query the clipping limits associated with the current context:

     void GrSetClipBox(int x1,int y1,int x2,int y2);
     void GrGetClipBox(int *x1p,int *y1p,int *x2p,int *y2p);
     void GrResetClipBox(void);

GrResetClipBox sets the clipping limits to the limits of context. These
are the limits set up initially when a context is created. There are
three similar functions to sets/gets the clipping limits of any context:

     void  GrSetClipBoxC(GrContext *c,int x1,int y1,int x2,int y2);
     void  GrGetClipBoxC(const GrContext *c,int *x1p,int *y1p,int *x2p,int *y2p);
     void  GrResetClipBoxC(GrContext *c);

The limits of the current context can be obtained using the following
functions:

     int GrMaxX(void);
     int GrMaxY(void);
     int GrSizeX(void);
     int GrSizeY(void);

The Max functions return the biggest valid coordinate, while the Size
functions return a value one higher. The limits of the graphics screen
(regardless of the current context) can be obtained with:

     int GrScreenX(void);
     int GrScreenY(void);

If you had set a virtual screen (using a custom graphics mode), the
limits of the virtual screen can be fetched with:

     int GrVirtualX(void);
     int GrVirtualY(void);

The routine:

     int GrScreenIsVirtual(void);

returns non zero if a virtual screen is set. The rectangle showed in
the real screen can be set with:

     int GrSetViewport(int xpos,int ypos);

and the current viewport position can be obtained by:

     int GrViewportX(void);
     int GrViewportY(void);


File: grx249um.inf,  Node: Context use,  Next: Color management,  Prev: Graphics contexts,  Up: A User Manual For GRX2

Context use
===========

Here is a example of normal context use:

     GrContext *grc;

     if( (grc = GrCreateContext( w,h,NULL,NULL )) == NULL ){
       ...process the error
       }
     else {
       GrSetContext( grc );
       ...do some drawing
       ...and probably bitblt to the screen context
       GrSetContext( NULL ); /* the screen context! */
       GrDestroyContext( grc );
       }

But if you have a GrContext variable (not a pointer) you want to use
(probably because is static to some routines) you can do:

     static GrContext grc; /* not a pointer!! */

     if( GrCreateContext( w,h,NULL,&grc )) == NULL ) {
       ...process the error
      }
     else {
       GrSetContext( &grc );
       ...do some drawing
       ...and probably bitblt to the screen context
       GrSetContext( NULL ); /* the screen context! */
       GrDestroyContext( &grc );
       }

Note that GrDestoryContext knows if grc was automatically malloced or
not!!

Only if you don't want GrCreateContext use malloc at all, you must
allocate the memory buffers and pass it to GrCreateContext.

Using GrCreateSubContext is the same, except it doesn't need the buffer,
because it uses the parent buffer.

See the *test/winclip.c* and *test/wintest.c* examples.


File: grx249um.inf,  Node: Color management,  Next: Portable use of a few colors,  Prev: Context use,  Up: A User Manual For GRX2

Color management
================

GRX defines the type GrColor for color variables. GrColor it's a 32 bits
integer. The 8 left bits are reserved for the write mode (see below).
The 24 bits right are the color value.

The library supports two models for color management. In the 'indirect'
(or color table) model, color values are indices to a color table. The
color table slots will be allocated with the highest resolution
supported by the hardware (EGA: 2 bits, VGA: 6 bits) with respect to
the component color intensities. In the 'direct' (or RGB) model, color
values map directly into component color intensities with
non-overlapping bitfields of the color index representing the component
colors.

Color table model is supported until 256 color modes. The RGB model is
supported in 256 color and up color modes.

In RGB model the color index map to component color intensities depend
on the video mode set, so it can't be assumed the component color
bitfields (but if you are curious check the GrColorInfo global
structure in grx20.h).

After the first GrSetMode call two colors are always defined: black and
white.  The color values of these two colors are returned by the
functions:

     GrColor GrBlack(void);
     GrColor GrWhite(void);

GrBlack() is guaranteed to be 0.

The library supports five write modes (a write mode descibes the
operation between the actual bit color and the one to be set): write,
XOR, logical OR, logical AND and IMAGE. These can be selected with
OR-ing the color value with one of the following constants declared in
grx20.h :

     #define GrWRITE       0UL            /* write color */
     #define GrXOR         0x01000000UL   /* to "XOR" any color to the screen */
     #define GrOR          0x02000000UL   /* to "OR" to the screen */
     #define GrAND         0x03000000UL   /* to "AND" to the screen */
     #define GrIMAGE       0x04000000UL   /* blit: write, except given color */

The GrIMAGE write mode only works with the bitblt function.  By
convention, the no-op color is obtained by combining color value 0
(black) with the XOR operation. This no-op color has been defined in
grx20.h as:

     #define GrNOCOLOR     (GrXOR | 0)    /* GrNOCOLOR is used for "no" color */

The write mode part and the color value part of a GrColor variable can
be obtained OR-ing it with one of the following constants declared in
grx20.h:

     #define GrCVALUEMASK  0x00ffffffUL   /* color value mask */
     #define GrCMODEMASK   0xff000000UL   /* color operation mask */

The number of colors in the current graphics mode is returned by the:

     GrColor GrNumColors(void);

function, while the number of unused, available color can be obtained by
calling:

     GrColor GrNumFreeColors(void);

Colors can be allocated with the:

     GrColor GrAllocColor(int r,int g,int b);
     GrColor GrAllocColor2(long hcolor);

functions (component intensities can range from 0 to 255, hcolor must
be in 0xRRGGBB format), or with the:

     GrColor GrAllocCell(void);

function. In the second case the component intensities of the returned
color can be set with:

     void GrSetColor(GrColor color,int r,int g,int b);

In the color table model both Alloc functions return GrNOCOLOR if there
are no more free colors available. In the RGB model GrNumFreeColors
returns 0 and GrAllocCell always returns GrNOCOLOR, as colors returned
by GrAllocCell are meant to be changed - what is not supposed to be
done in RGB mode. Also note that GrAllocColor operates much more
efficiently in RGB mode, and that it never returns GrNOCOLOR in this
case.

Color table entries can be freed (when not in RGB mode) by calling:

     void GrFreeColor(GrColor color);

The component intensities of any color can be queried using one of this
function:

     void GrQueryColor(GrColor c,int *r,int *g,int *b);
     void GrQueryColor2(GrColor c,long *hcolor);

Initially the color system is in color table (indirect) model if there
are 256 or less colors. 256 color modes can be put into the RGB model
by calling:

     void GrSetRGBcolorMode(void);

The color system can be reset (i.e. put back into color table model if
possible, all colors freed except for black and white) by calling:

     void GrResetColors(void);

The function:

     void GrRefreshColors(void);

reloads the currently allocated color values into the video hardware.
This function is not needed in typical applications, unless the display
adapter is programmed directly by the application.

This functions:

     GrColor GrAllocColorID(int r,int g,int b);
     GrColor GrAllocColor2ID(long hcolor);
     void GrQueryColorID(GrColor c,int *r,int *g,int *b);
     void GrQueryColor2ID(GrColor c,long *hcolor);

are inlined versions (except if you compile GRX with GRX_SKIP_INLINES
defined) to be used in the RGB model (in the color table model they
call the normal routines).

See the *test/rgbtest.c* and *test/colorops.c* examples.


File: grx249um.inf,  Node: Portable use of a few colors,  Next: Graphics primitives,  Prev: Color management,  Up: A User Manual For GRX2

Portable use of a few colors
============================

People that only want to use a few colors find the GRX color handling a
bit confusing, but it gives the power to manage a lot of color deeps
and two color models. Here are some guidelines to easily use the famous
16 ega colors in GRX programs. We need this GRX function:

     GrColor *GrAllocEgaColors(void);

it returns a 16 GrColor array with the 16 ega colors alloced (really
it's a trivial function, read the source src/setup/colorega.c). We can
use a construction like that:

First, in your C code make a global pointer, and init it after set the
graphics mode:

     GrColor *egacolors;
     ....
     int your_setup_function( ... )
     {
       ...
       GrSetMode( ... )
       ...
       egacolors = GrAllocEgaColors();
       ...
     }

Next, add this to your main include file:

     extern GrColor *egacolors;
     #define BLACK        egacolors[0]
     #define BLUE         egacolors[1]
     #define GREEN        egacolors[2]
     #define CYAN         egacolors[3]
     #define RED          egacolors[4]
     #define MAGENTA      egacolors[5]
     #define BROWN        egacolors[6]
     #define LIGHTGRAY    egacolors[7]
     #define DARKGRAY     egacolors[8]
     #define LIGHTBLUE    egacolors[9]
     #define LIGHTGREEN   egacolors[10]
     #define LIGHTCYAN    egacolors[11]
     #define LIGHTRED     egacolors[12]
     #define LIGHTMAGENTA egacolors[13]
     #define YELLOW       egacolors[14]
     #define WHITE        egacolors[15]

Now you can use the defined colors in your code. Note that if you are
in color table model in a 16 color mode, you have exhausted the color
table. Note too that this don't work to initialize static variables
with a color, because egacolors is not initialized.


File: grx249um.inf,  Node: Graphics primitives,  Next: Non-clipping graphics primitives,  Prev: Portable use of a few colors,  Up: A User Manual For GRX2

Graphics primitives
===================

The screen, the current context or the current clip box can be cleared
(i.e.  set to a desired background color) by using one of the following
three functions:

     void GrClearScreen(GrColor bg);
     void GrClearContext(GrColor bg);
     void GrClearClipBox(GrColor bg);

Any context can be cleared using this function:
     void GrClearContextC(GrContext *ctx, GrColor bg);

Thanks to the special GrColor definition, you can do more than simple
clear with this functions, by example with:

     GrClearScreen( GrWhite()|GrXOR );

the graphics screen is negativized, do it again and the screen is
restored.

The following line drawing graphics primitives are supported by the
library:

     void GrPlot(int x,int y,GrColor c);
     void GrLine(int x1,int y1,int x2,int y2,GrColor c);
     void GrHLine(int x1,int x2,int y,GrColor c);
     void GrVLine(int x,int y1,int y2,GrColor c);
     void GrBox(int x1,int y1,int x2,int y2,GrColor c);
     void GrCircle(int xc,int yc,int r,GrColor c);
     void GrEllipse(int xc,int yc,int xa,int ya,GrColor c);
     void GrCircleArc(int xc,int yc,int r,int start,int end,int style,GrColor c);
     void GrEllipseArc(int xc,int yc,int xa,int ya,
                       int start,int end,int style,GrColor c);
     void GrPolyLine(int numpts,int points[][2],GrColor c);
     void GrPolygon(int numpts,int points[][2],GrColor c);

All primitives operate on the current graphics context. The last
argument of these functions is always the color to use for the drawing.
The HLine and VLine primitives are for drawing horizontal and vertical
lines. They have been included in the library because they are more
efficient than the general line drawing provided by GrLine. The ellipse
primitives can only draw ellipses with their major axis parallel with
either the X or Y coordinate axis. They take the half X and Y axis
length in the xa and ya arguments. The arc (circle and ellipse) drawing
functions take the start and end angles in tenths of degrees (i.e.
meaningful range: 0 ... 3600). The angles are interpreted
counter-clockwise starting from the positive X axis. The style argument
can be one of this defines from grx20.h:

     #define GR_ARC_STYLE_OPEN       0
     #define GR_ARC_STYLE_CLOSE1     1
     #define GR_ARC_STYLE_CLOSE2     2

GR_ARC_STYLE_OPEN draws only the arc, GR_ARC_STYLE_CLOSE1 closes the
arc with a line between his start and end point, GR_ARC_STYLE_CLOSE1
draws the typical cake slice. This routine:

     void GrLastArcCoords(int *xs,int *ys,int *xe,int *ye,int *xc,int *yc);

can be used to retrieve the start, end, and center points used by the
last arc drawing functions.

See the *test/circtest.c* and *test/arctest.c* examples.

The polyline and polygon primitives take the address of an n by 2
coordinate array. The X values should be stored in the elements with 0
second index, and the Y values in the elements with a second index
value of 1. Coordinate arrays passed to the polygon primitive can
either contain or omit the closing edge of the polygon - the primitive
will append it to the list if it is missing.

See the *test/polytest.c* example.

Because calculating the arc points it's a very time consuming
operation, there are two functions to pre-calculate the points, that
can be used next with polyline and polygon primitives:

     int  GrGenerateEllipse(int xc,int yc,int xa,int ya,
                            int points[GR_MAX_ELLIPSE_POINTS][2]);
     int  GrGenerateEllipseArc(int xc,int yc,int xa,int ya,int start,int end,
                               int points[GR_MAX_ELLIPSE_POINTS][2]);

The following filled primitives are available:

     void GrFilledBox(int x1,int y1,int x2,int y2,GrColor c);
     void GrFramedBox(int x1,int y1,int x2,int y2,int wdt,const GrFBoxColors *c);
     void GrFilledCircle(int xc,int yc,int r,GrColor c);
     void GrFilledEllipse(int xc,int yc,int xa,int ya,GrColor c);
     void GrFilledCircleArc(int xc,int yc,int r,
                            int start,int end,int style,GrColor c);
     void GrFilledEllipseArc(int xc,int yc,int xa,int ya,
                             int start,int end,int style,GrColor c);
     void GrFilledPolygon(int numpts,int points[][2],GrColor c);
     void GrFilledConvexPolygon(int numpts,int points[][2],GrColor c);

Similarly to the line drawing, all of the above primitives operate on
the current graphics context. The GrFramedBox primitive can be used to
draw motif-like shaded boxes and "ordinary" framed boxes as well. The
x1 through y2 coordinates specify the interior of the box, the border
is outside this area, wdt pixels wide. The primitive uses five
different colors for the interior and four borders of the box which are
specified in the GrFBoxColors structure:

     typedef struct {
       GrColor fbx_intcolor;
       GrColor fbx_topcolor;
       GrColor fbx_rightcolor;
       GrColor fbx_bottomcolor;
       GrColor fbx_leftcolor;
     } GrFBoxColors;

The GrFilledConvexPolygon primitive can be used to fill convex
polygons. It can also be used to fill some concave polygons whose
boundaries do not intersect any horizontal scan line more than twice.
All other concave polygons have to be filled with the (somewhat less
efficient) GrFilledPolygon primitive. This primitive can also be used
to fill several disjoint non­overlapping polygons in a single operation.

The function:

     void GrFloodFill(int x, int y, GrColor border, GrColor c);

flood-fills the area bounded by the color border using x, y like the
starting point.

Floodspill is a color replacer, replacing color A with color B.  This
is quite useful for highlighting a selected item in a list,  or changing
a selected color(s) in a multi colored area.

     void GrFloodSpill(int x1, int y1, int x2, int y2,
                      GrColor old_c, GrColor new_c)

replaces old color with new color in the rectangle bounded by x1, y1,
x2, y2.

     void GrFloodSpillC(GrContext *ctx, int x1, int y1, int x2, int y2,
                       GrColor old_c, GrColor new_c)

as above but in the specified context.

     void GrFloodSpill2(int x1, int y1, int x2, int y2,
                       GrColor old_c1, GrColor new_c1,
                       GrColor old_c2, GrColor new_c2)

replaces 2 colors, a one stop shop for highlighting a selection in a
list.

     void GrFloodSpillC2(GrContext *ctx, int x1, int y1, int x2, int y2,
                       GrColor old_c1, GrColor new_c1,
                       GrColor old_c2, GrColor new_c2)

as above but in the specified context.

The current color value of any pixel in the current context can be
obtained with:

     GrColor GrPixel(int x,int y);

and:

     GrColor GrPixelC(GrContext *c,int x,int y);

do the same for any context.

Rectangular areas can be transferred within a context or between
contexts by calling:

     void GrBitBlt(GrContext *dest,int x,int y,GrContext *source,
                   int x1,int y1,int x2,int y2,GrColor op);

x, y is the position in the destination context, and x1, y1, x2, y2 the
area from the source context to be transfered. The op argument should
be one of supported color write modes (GrWRITE, GrXOR, GrOR, GrAND,
GrIMAGE), it will control how the pixels from the source context are
combined with the pixels in the destination context (the GrIMAGE op
must be ored with the color value to be handled as transparent). If
either the source or the destination context argument is the NULL
pointer then the current context is used for that argument.

See the *test/blittest.c* example.

A efficient form to get/put pixels from/to a context can be achieved
using the next functions:

     const GrColor *GrGetScanline(int x1,int x2,int yy);
     const GrColor *GrGetScanlineC(GrContext *ctx,int x1,int x2,int yy);
     void GrPutScanline(int x1,int x2,int yy,const GrColor *c, GrColor op);

The Get functions return a pointer to a static GrColor pixel array (or
NULL if they fail) with the color values of a row (yy) segment (x1 to
x2). GrGetScanline uses the current context. GrGestScanlineC uses the
context ctx (that can be NULL to refer to the current context). Note
that the output is only valid until the next GRX call.

GrPutScanline puts the GrColor pixel array c on the yy row segmet
defined by x1 to x2 in the current context using the op operation. op
can be any of GrWRITE, GrXOR, GrOR, GrAND or GrIMAGE. Data in c must
fit GrCVALUEMASK otherwise the results are implementation dependend. So
you can't supply operation code with the pixel data!.


File: grx249um.inf,  Node: Non-clipping graphics primitives,  Next: Customized line drawing,  Prev: Graphics primitives,  Up: A User Manual For GRX2

Non-clipping graphics primitives
================================

There is a non-clipping version of some of the elementary primitives.
These are somewhat more efficient than the regular versions. These are
to be used only in situations when it is absolutely certain that no
drawing will be performed beyond the boundaries of the current context.
Otherwise the program will almost certainly crash! The reason for
including these functions is that they are somewhat more efficient than
the regular, clipping versions. ALSO NOTE: These function do not check
for conflicts with the mouse cursor. (See the explanation about the
mouse cursor handling later in this document.) The list of the
supported non-clipping primitives:

     void GrPlotNC(int x,int y,GrColor c);
     void GrLineNC(int x1,int y1,int x2,int y2,GrColor c);
     void GrHLineNC(int x1,int x2,int y,GrColor c);
     void GrVLineNC(int x,int y1,int y2,GrColor c);
     void GrBoxNC(int x1,int y1,int x2,int y2,GrColor c);
     void GrFilledBoxNC(int x1,int y1,int x2,int y2,GrColor c);
     void GrFramedBoxNC(int x1,int y1,int x2,int y2,int wdt,const GrFBoxColors *c);
     void grbitbltNC(GrContext *dst,int x,int y,GrContext *src,
                     int x1,int y1,int x2,int y2,GrColor op);
     GrColor GrPixelNC(int x,int y);
     GrColor GrPixelCNC(GrContext *c,int x,int y);


File: grx249um.inf,  Node: Customized line drawing,  Next: Pattern filled graphics primitives,  Prev: Non-clipping graphics primitives,  Up: A User Manual For GRX2

Customized line drawing
=======================

The basic line drawing graphics primitives described previously always
draw continuous lines which are one pixel wide. There is another group
of line drawing functions which can be used to draw wide and/or
patterned lines. These functions have similar parameter passing
conventions as the basic ones with one difference: instead of the color
value a pointer to a structure of type GrLineOption has to be passed to
them. The definition of the GrLineOption structure:

     typedef struct {
       GrColor lno_color;             /* color used to draw line */
       int     lno_width;             /* width of the line */
       int     lno_pattlen;           /* length of the dash pattern */
       unsigned char *lno_dashpat;    /* draw/nodraw pattern */
     } GrLineOption;

The lno_pattlen structure element should be equal to the number of
alternating draw - no draw section length values in the array pointed
to by the lno_dashpat element. The dash pattern array is assumed to
begin with a drawn section. If the pattern length is equal to zero a
continuous line is drawn.

Example, a white line 3 bits wide (thick) and pattern 6 bits draw, 4
bits nodraw:

     GrLineOption mylineop;
     ...
     mylineop.lno_color = GrWhite();
     mylineop.lno_width = 3;
     mylineop.lno_pattlen = 2;
     mylineop.lno_dashpat = "\x06\x04";

The available custom line drawing primitives:

     void GrCustomLine(int x1,int y1,int x2,int y2,const GrLineOption *o);
     void GrCustomBox(int x1,int y1,int x2,int y2,const GrLineOption *o);
     void GrCustomCircle(int xc,int yc,int r,const GrLineOption *o);
     void GrCustomEllipse(int xc,int yc,int xa,int ya,const GrLineOption *o);
     void GrCustomCircleArc(int xc,int yc,int r,
                            int start,int end,int style,const GrLineOption *o);
     void GrCustomEllipseArc(int xc,int yc,int xa,int ya,
                             int start,int end,int style,const GrLineOption *o);
     void GrCustomPolyLine(int numpts,int points[][2],const GrLineOption *o);
     void GrCustomPolygon(int numpts,int points[][2],const GrLineOption *o);

See the *test/linetest.c* example.


File: grx249um.inf,  Node: Pattern filled graphics primitives,  Next: Patterned line drawing,  Prev: Customized line drawing,  Up: A User Manual For GRX2

Pattern filled graphics primitives
==================================

The library also supports a pattern filled version of the basic filled
primitives described above. These functions have similar parameter
passing conventions as the basic ones with one difference: instead of
the color value a pointer to an union of type 'GrPattern' has to be
passed to them. The GrPattern union can contain either a bitmap or a
pixmap fill pattern. The first integer slot in the union determines
which type it is. Bitmap fill patterns are rectangular arrays of bits,
each set bit representing the foreground color of the fill operation,
and each zero bit representing the background. Both the foreground and
background colors can be combined with any of the supported logical
operations. Bitmap fill patterns have one restriction: their width must
be eight pixels. Pixmap fill patterns are very similar to contexts. The
relevant structure declarations (from grx20.h):

     /*
      * BITMAP: a mode independent way to specify a fill pattern of two
      *   colors. It is always 8 pixels wide (1 byte per scan line), its
      *   height is user-defined. SET THE TYPE FLAG TO ZERO!!!
      */
     typedef struct _GR_bitmap {
       int     bmp_ispixmap;          /* type flag for pattern union */
       int     bmp_height;            /* bitmap height */
       char   *bmp_data;              /* pointer to the bit pattern */
       GrColor bmp_fgcolor;           /* foreground color for fill */
       GrColor bmp_bgcolor;           /* background color for fill */
       int     bmp_memflags;          /* set if dynamically allocated */
     } GrBitmap;

     /*
      * PIXMAP: a fill pattern stored in a layout identical to the video RAM
      *   for filling using 'bitblt'-s. It is mode dependent, typically one
      *   of the library functions is used to build it. KEEP THE TYPE FLAG
      *   NONZERO!!!
      */
     typedef struct _GR_pixmap {
       int     pxp_ispixmap;          /* type flag for pattern union */
       int     pxp_width;             /* pixmap width (in pixels)  */
       int     pxp_height;            /* pixmap height (in pixels) */
       GrColor pxp_oper;              /* bitblt mode (SET, OR, XOR, AND, IMAGE) */
       struct _GR_frame pxp_source;   /* source context for fill */
     } GrPixmap;

     /*
      * Fill pattern union -- can either be a bitmap or a pixmap
      */
     typedef union _GR_pattern {
       int      gp_ispixmap;          /* nonzero for pixmaps */
       GrBitmap gp_bitmap;            /* fill bitmap */
       GrPixmap gp_pixmap;            /* fill pixmap */
     } GrPattern;

This define group (from grx20.h) help to acces the GrPattern menbers:

     #define gp_bmp_data                     gp_bitmap.bmp_data
     #define gp_bmp_height                   gp_bitmap.bmp_height
     #define gp_bmp_fgcolor                  gp_bitmap.bmp_fgcolor
     #define gp_bmp_bgcolor                  gp_bitmap.bmp_bgcolor

     #define gp_pxp_width                    gp_pixmap.pxp_width
     #define gp_pxp_height                   gp_pixmap.pxp_height
     #define gp_pxp_oper                     gp_pixmap.pxp_oper
     #define gp_pxp_source                   gp_pixmap.pxp_source

Bitmap patterns can be easily built from initialized character arrays
and static structures by the C compiler, thus no special support is
included in the library for creating them. The only action required
from the application program might be changing the foreground and
background colors as needed. Pixmap patterns are more difficult to
build as they replicate the layout of the video memory which changes
for different video modes. For this reason the library provides three
functions to create pixmap patterns in a mode-independent way:

     GrPattern *GrBuildPixmap(const char *pixels,int w,int h,const GrColorTableP colors);
     GrPattern *GrBuildPixmapFromBits(const char *bits,int w,int h,
                                      GrColor fgc,GrColor bgc);
     GrPattern *GrConvertToPixmap(GrContext *src);

GrBuildPixmap build a pixmap from a two dimensional (w by h) array of
characters. The elements in this array are used as indices into the
color table specified with the argument colors. (This means that
pixmaps created this way can use at most 256 colors.) The color table
pointer:

     typedef GrColor *GrColorTableP;

should point to an array of integers with the first element being the
number of colors in the table and the color values themselves starting
with the second element. NOTE: any color modifiers (GrXOR, GrOR, GrAND)
OR-ed to the elements of the color table are ignored.

The GrBuildPixmapFromBits function builds a pixmap fill pattern from
bitmap data. It is useful if the width of the bitmap pattern is not
eight as such bitmap patterns can not be used to build a GrBitmap
structure.

The GrConvertToPixmap function converts a graphics context to a pixmap
fill pattern. It is useful when the pattern can be created with
graphics drawing operations. NOTE: the pixmap pattern and the original
context share the drawing RAM, thus if the context is redrawn the fill
pattern changes as well. Fill patterns which were built by library
routines can be destroyed when no longer needed (i.e. the space
occupied by them can be freed) by calling:

     void GrDestroyPattern(GrPattern *p);

NOTE: when pixmap fill patterns converted from contexts are destroyed,
the drawing RAM is not freed. It is freed when the original context is
destroyed.  Fill patterns built by the application have to be destroyed
by the application as well (if this is needed).

The list of supported pattern filled graphics primitives is shown
below. These functions are very similar to their solid filled
counterparts, only their last argument is different:

     void GrPatternFilledPlot(int x,int y,GrPattern *p);
     void GrPatternFilledLine(int x1,int y1,int x2,int y2,GrPattern *p);
     void GrPatternFilledBox(int x1,int y1,int x2,int y2,GrPattern *p);
     void GrPatternFilledCircle(int xc,int yc,int r,GrPattern *p);
     void GrPatternFilledEllipse(int xc,int yc,int xa,int ya,GrPattern *p);
     void GrPatternFilledCircleArc(int xc,int yc,int r,int start,int end,
                                   int style,GrPattern *p);
     void GrPatternFilledEllipseArc(int xc,int yc,int xa,int ya,int start,int end,
                                    int style,GrPattern *p);
     void GrPatternFilledConvexPolygon(int numpts,int points[][2],GrPattern *p);
     void GrPatternFilledPolygon(int numpts,int points[][2],GrPattern *p);
     void GrPatternFloodFill(int x, int y, GrColor border, GrPattern *p);

Strictly speaking the plot and line functions in the above group are not
filled, but they have been included here for convenience.


File: grx249um.inf,  Node: Patterned line drawing,  Next: Image manipulation,  Prev: Pattern filled graphics primitives,  Up: A User Manual For GRX2

Patterned line drawing
======================

The custom line drawing functions introduced above also have a version
when the drawn sections can be filled with a (pixmap or bitmap) fill
pattern. To achieve this these functions must be passed both a custom
line drawing option (GrLineOption structure) and a fill pattern
(GrPattern union). These two have been combined into the GrLinePattern
structure:

     typedef struct {
       GrPattern     *lnp_pattern;    /* fill pattern */
       GrLineOption  *lnp_option;     /* width + dash pattern */
     } GrLinePattern;

All patterned line drawing functions take a pointer to this structure
as their last argument. The list of available functions:

     void GrPatternedLine(int x1,int y1,int x2,int y2,GrLinePattern *lp);
     void GrPatternedBox(int x1,int y1,int x2,int y2,GrLinePattern *lp);
     void GrPatternedCircle(int xc,int yc,int r,GrLinePattern *lp);
     void GrPatternedEllipse(int xc,int yc,int xa,int ya,GrLinePattern *lp);
     void GrPatternedCircleArc(int xc,int yc,int r,int start,int end,
                               int style,GrLinePattern *lp);
     void GrPatternedEllipseArc(int xc,int yc,int xa,int ya,int start,int end,
                                int style,GrLinePattern *lp);
     void GrPatternedPolyLine(int numpts,int points[][2],GrLinePattern *lp);
     void GrPatternedPolygon(int numpts,int points[][2],GrLinePattern *lp);


File: grx249um.inf,  Node: Image manipulation,  Next: Text drawing,  Prev: Patterned line drawing,  Up: A User Manual For GRX2

Image manipulation
==================

GRX defines the GrImage type like a GrPixmap synonym:

     #define GrImage GrPixmap

nevertheless the GrImage type enforces the image character of this
object, so for compatibility with future GRX versions use the next
functions if you need to convert between GrImage and GrPixmap objects:

     GrImage *GrImageFromPattern(GrPattern *p);
     GrPattern *GrPatternFromImage(GrImage *p);

the GrImageFromPattern function returns NULL if the GrPattern given is
not a GrPixmap.

Like pixmaps patterns images are dependent of the actual video mode
set. So the library provides functions to create images in a
mode-independent way:

     GrImage *GrImageBuild(const char *pixels,int w,int h,const GrColorTableP colors);
     GrImage *GrImageFromContext(GrContext *c);

these functions work like the GrBuildPixmap and GrConvertToPixmap ones.
Remember: the image and the original context share the drawing RAM.

There are a number of functions to display all or part of an image in
the current context:

     void GrImageDisplay(int x,int y, GrImage *i);
     void GrImageDisplayExt(int x1,int y1,int x2,int y2, GrImage *i);
     void GrImageFilledBoxAlign(int xo,int yo,int x1,int y1,int x2,int y2,
                                GrImage *p);
     void GrImageHLineAlign(int xo,int yo,int x,int y,int width,GrImage *p);
     void GrImagePlotAlign(int xo,int yo,int x,int y,GrImage *p);

GrImageDisplay display the whole image using x, y like the upper left
corner in the current context. GrImageDisplayExt display as much as it
can (repiting the image if necesary) in the rectangle defined by x1, y1
and x2, y2.

GrImageFilledBoxAlign is a most general funtion (really the later two
call it) display as much as it can in the defined rectangle using xo,
yo like the align point, it is the virtual point in the destination
context (it doesn't need to be into the rectangle) with that the upper
left image corner is aligned.

GrImageHLineAlign and GrImagePlotAlign display a row segment or a point
of the image at x y position using the xo, yo allign point.

The most usefull image funtions are these:

     GrImage *GrImageInverse(GrImage *p,int flag);
     GrImage *GrImageStretch(GrImage *p,int nwidth,int nheight);

GrImageInverse creates a new image object, flipping p left-right or
top-down as indicated by flag that can be:

     #define GR_IMAGE_INVERSE_LR  0x01  /* inverse left right */
     #define GR_IMAGE_INVERSE_TD  0x02  /* inverse top down */

GrImageStretch creates a new image stretching p to nwidth by nheight.

To destroy a image objet when you don't need it any more use:

     void GrImageDestroy(GrImage *i);

See the *test/imgtest.c* example.


File: grx249um.inf,  Node: Text drawing,  Next: Drawing in user coordinates,  Prev: Image manipulation,  Up: A User Manual For GRX2

Text drawing
============

The library supports loadable fonts. When in memory they are bit-mapped
(i.e.  not scalable!) fonts. A driver design allow GRX to load
different font formats, the last GRX release come with drivers to load
the GRX own font format and the BGI Borland format for all platforms
supported, the X11 version can load X11 fonts too.

The GRX distribution come with a font collection in the GRX own format.
Some of these fonts were converted from VGA fonts. These fonts have all
256 characters from the PC-437 codepage. Some additional fonts were
converted from fonts in the MIT X11 distribution. Most of these are
ISO-8859-1 coded. Fonts also have family names. The following font
families are included:

     Font file name       Family  Description
     pc<W>x<H>[t].fnt     pc      VGA font, fixed
     xm<W>x<H>[b][i].fnt  X_misc  X11, fixed, miscellaneous group
     char<H>[b][i].fnt    char    X11, proportional, charter family
     cour<H>[b][i].fnt    cour    X11, fixed, courier
     helve<H>[b][i].fnt   helve   X11, proportional, helvetica
     lucb<H>[b][i].fnt    lucb    X11, proportional, lucida bright
     lucs<H>[b][i].fnt    lucs    X11, proportional, lucida sans serif
     luct<H>[b][i].fnt    luct    X11, fixed, lucida typewriter
     ncen<H>[b][i].fnt    ncen    X11, proportional, new century schoolbook
     symb<H>.fnt          symbol  X11, proportional, greek letters, symbols
     tms<H>[b][i].fnt     times   X11, proportional, times

In the font names <W> means the font width, <H> the font height. Many
font families have bold and/or italic variants. The files containing
these fonts contain a 'b' and/or 'i' character in their name just
before the extension.  Additionally, the strings "_bold" and/or "_ital"
are appended to the font family names. Some of the pc VGA fonts come in
thin formats also, these are denoted by a 't' in their file names and
the string "_thin" in their family names.

The GrFont structure hold a font in memory. A number of 'pc' fonts are
built-in to the library and don't need to be loaded:

     extern  GrFont          GrFont_PC6x8;
     extern  GrFont          GrFont_PC8x8;
     extern  GrFont          GrFont_PC8x14;
     extern  GrFont          GrFont_PC8x16;

Other fonts must be loaded with the GrLoadFont function. If the font
file name starts with any path separator character or character
sequence (':', '/' or '\') then it is loaded from the specified
directory, otherwise the library try load the font first from the
current directory and next from the default font path.  The font path
can be set up with the GrSetFontPath function. If the font path is not
set then the value of the 'GRXFONT' environment variable is used as the
font path. If GrLoadFont is called again with the name of an already
loaded font then it will return a pointer to the result of the first
loading. Font loading routines return NULL if the font was not found.
When not needed any more, fonts can be unloaded (i.e. the storage
occupied by them freed) by calling GrUnloadFont.

The prototype declarations for these functions:

     GrFont *GrLoadFont(char *name);
     void GrUnloadFont(GrFont *font);
     void GrSetFontPath(char *path_list);

Using these functions:

     GrFont *GrLoadConvertedFont(char *name,int cvt,int w,int h,
                                 int minch,int maxch);
     GrFont *GrBuildConvertedFont(const GrFont *from,int cvt,int w,int h,
                                  int minch,int maxch);

a new font can be generated from a file font or a font in memory, the
'cvt' argument direct the conversion or-ing the desired operations from
these defines:

     /*
      * Font conversion flags for 'GrLoadConvertedFont'. OR them as desired.
      */
     #define GR_FONTCVT_NONE         0     /* no conversion */
     #define GR_FONTCVT_SKIPCHARS    1     /* load only selected characters */
     #define GR_FONTCVT_RESIZE       2     /* resize the font */
     #define GR_FONTCVT_ITALICIZE    4     /* tilt font for "italic" look */
     #define GR_FONTCVT_BOLDIFY      8     /* make a "bold"(er) font  */
     #define GR_FONTCVT_FIXIFY       16    /* convert prop. font to fixed wdt */
     #define GR_FONTCVT_PROPORTION   32    /* convert fixed font to prop. wdt */

GR_FONTCVT_SKIPCHARS needs 'minch' and 'maxch' arguments.

GR_FONTCVT_RESIZE needs 'w' and 'h' arguments.

The function:

     void GrDumpFnaFont(const GrFont *f, char *fileName);

writes a font to an ascii font file, so it can be quickly edited with a
text editor. For a description of the ascii font format, see the
fna.txt file.

The function:

     void GrDumpFont(const GrFont *f,char *CsymbolName,char *fileName);

writes a font to a C source code file, so it can be compiled and linked
with a user program. GrDumpFont would not normally be used in a release
program because its purpose is to produce source code. When the source
code is compiled and linked into a program distributing the font file
with the program in not necessary, avoiding the possibility of the font
file being deleted or corrupted.

You can use the premade fnt2c.c program (see the source, it's so
simple) to dump a selected font to source code, by example:

     fnt2c helv15 myhelv15 myhelv15.c

Next, if this line is included in your main include file:

     extern GrFont myhelv15

and "myhelv15.c" compiled and linked with your project, you can use
'myhelv15' in every place a GrFont is required.

This simple function:

     void GrTextXY(int x,int y,char *text,GrColor fg,GrColor bg);

draw text in the current context in the standard direction, using the
GrDefaultFont (mapped in the grx20.h file to the GrFont_PC8x14 font)
with x, y like the upper left corner and the foreground and background
colors given (note that bg equal to GrNOCOLOR make the background
transparent).

For other functions the GrTextOption structure specifies how to draw a
character string:

     typedef struct _GR_textOption {      /* text drawing option structure */
       struct _GR_font     *txo_font;      /* font to be used */
       union  _GR_textColor txo_fgcolor;   /* foreground color */
       union  _GR_textColor txo_bgcolor;   /* background color */
       char    txo_chrtype;                /* character type (see above) */
       char    txo_direct;                 /* direction (see above) */
       char    txo_xalign;                 /* X alignment (see above) */
       char    txo_yalign;                 /* Y alignment (see above) */
     } GrTextOption;

     typedef union _GR_textColor {        /* text color union */
       GrColor       v;                    /* color value for "direct" text */
       GrColorTableP p;                    /* color table for attribute text */
     } GrTextColor;

The text can be rotated in increments of 90 degrees (txo_direct),
alignments can be set in both directions (txo_xalign and txo_yalign),
and separate fore and background colors can be specified. The accepted
text direction values:

     #define GR_TEXT_RIGHT           0       /* normal */
     #define GR_TEXT_DOWN            1       /* downward */
     #define GR_TEXT_LEFT            2       /* upside down, right to left */
     #define GR_TEXT_UP              3       /* upward */
     #define GR_TEXT_DEFAULT         GR_TEXT_RIGHT

The accepted horizontal and vertical alignment option values:

     #define GR_ALIGN_LEFT           0       /* X only */
     #define GR_ALIGN_TOP            0       /* Y only */
     #define GR_ALIGN_CENTER         1       /* X, Y   */
     #define GR_ALIGN_RIGHT          2       /* X only */
     #define GR_ALIGN_BOTTOM         2       /* Y only */
     #define GR_ALIGN_BASELINE       3       /* Y only */
     #define GR_ALIGN_DEFAULT        GR_ALIGN_LEFT

Text strings can be of three different types: one character per byte
(i.e. the usual C character string, this is the default), one character
per 16-bit word (suitable for fonts with a large number of characters),
and a PC-style character-attribute pair. In the last case the
GrTextOption structure must contain a pointer to a color table of size
16 (fg color bits in attrib) or 8 (bg color bits). (The color table
format is explained in more detail in the previous section explaining
the methods to build fill patterns.) The supported text types:

     #define GR_BYTE_TEXT            0       /* one byte per character */
     #define GR_WORD_TEXT            1       /* two bytes per character */
     #define GR_ATTR_TEXT            2       /* chr w/ PC style attribute byte */

The PC-style attribute text uses the same layout (first byte: character,
second: attributes) and bitfields as the text mode screen on the PC.
The only difference is that the 'blink' bit is not supported (it would
be very time consuming - the PC text mode does it with hardware
support). This bit is used instead to control the underlined display of
characters. For convenience the following attribute manipulation macros
have been declared in grx20.h:

     #define GR_BUILD_ATTR(fg,bg,ul) \
             (((fg) & 15) | (((bg) & 7) << 4) | ((ul) ? 128 : 0))
     #define GR_ATTR_FGCOLOR(attr)   (((attr)     ) &  15)
     #define GR_ATTR_BGCOLOR(attr)   (((attr) >> 4) &   7)
     #define GR_ATTR_UNDERLINE(attr) (((attr)     ) & 128)

Text strings of the types GR_BYTE_TEXT and GR_WORD_TEXT can also be
drawn underlined. This is controlled by OR-ing the constant
GR_UNDERLINE_TEXT to the foreground color value:

     #define GR_UNDERLINE_TEXT       (GrXOR << 4)

After the application initializes a text option structure with the
desired values it can call one of the following two text drawing
functions:

     void GrDrawChar(int chr,int x,int y,const GrTextOption *opt);
     void GrDrawString(void *text,int length,int x,int y,const GrTextOption *opt);

NOTE: text drawing is fastest when it is drawn in the 'normal'
direction, and the character does not have to be clipped. It this case
the library can use the appropriate low-level video RAM access routine,
while in any other case the text is drawn pixel-by-pixel by the
higher-level code.

There are pattern filed versions too:

     void GrPatternDrawChar(int chr,int x,int y,const GrTextOption *opt,GrPattern *p);
     void GrPatternDrawString(void *text,int length,int x,int y,const GrTextOption *opt,
                              GrPattern *p);
     void GrPatternDrawStringExt(void *text,int length,int x,int y,
                                 const GrTextOption *opt,GrPattern *p);

The size of a font, a character or a text string can be obtained by
calling one of the following functions. These functions also take into
consideration the text direction specified in the text option structure
passed to them.

     int  GrFontCharPresent(const GrFont *font,int chr);
     int  GrFontCharWidth(const GrFont *font,int chr);
     int  GrFontCharHeight(const GrFont *font,int chr);
     int  GrFontCharBmpRowSize(const GrFont *font,int chr);
     int  GrFontCharBitmapSize(const GrFont *font,int chr);
     int  GrFontStringWidth(const GrFont *font,void *text,int len,int type);
     int  GrFontStringHeight(const GrFont *font,void *text,int len,int type);
     int  GrProportionalTextWidth(const GrFont *font,void *text,int len,int type);
     int  GrCharWidth(int chr,const GrTextOption *opt);
     int  GrCharHeight(int chr,const GrTextOption *opt);
     void GrCharSize(int chr,const GrTextOption *opt,int *w,int *h);
     int  GrStringWidth(void *text,int length,const GrTextOption *opt);
     int  GrStringHeight(void *text,int length,const GrTextOption *opt);
     void GrStringSize(void *text,int length,const GrTextOption *opt,int *w,int *h);

The GrTextRegion structure and its associated functions can be used to
implement a fast (as much as possible in graphics modes) rectangular
text window using a fixed font. Clipping for such windows is done in
character size increments instead of pixels (i.e. no partial characters
are drawn). Only fixed fonts can be used in their natural size.
GrDumpText will cache the code of the drawn characters in the buffer
pointed to by the 'backup' slot (if it is non-NULL) and will draw a
character only if the previously drawn character in that grid element
is different.

This can speed up text scrolling significantly in graphics modes. The
supported text types are the same as above.

     typedef struct {                     /* fixed font text window desc. */
       struct _GR_font     *txr_font;      /* font to be used */
       union  _GR_textColor txr_fgcolor;   /* foreground color */
       union  _GR_textColor txr_bgcolor;   /* background color */
       void   *txr_buffer;                 /* pointer to text buffer */
       void   *txr_backup;                 /* optional backup buffer */
       int     txr_width;                  /* width of area in chars */
       int     txr_height;                 /* height of area in chars */
       int     txr_lineoffset;             /* offset in buffer(s) between rows */
       int     txr_xpos;                   /* upper left corner X coordinate */
       int     txr_ypos;                   /* upper left corner Y coordinate */
       char    txr_chrtype;                /* character type (see above) */
     } GrTextRegion;

     void GrDumpChar(int chr,int col,int row,const GrTextRegion *r);
     void GrDumpText(int col,int row,int wdt,int hgt,const GrTextRegion *r);
     void GrDumpTextRegion(const GrTextRegion *r);

The GrDumpTextRegion function outputs the whole text region, while
GrDumpText draws only a user-specified part of it. GrDumpChar updates
the character in the buffer at the specified location with the new
character passed to it as argument and then draws the new character on
the screen as well. With these functions you can simulate a text mode
window, write chars directly to the txr_buffer and call
GrDumpTextRegion when you want to update the window (or GrDumpText if
you know the area to update is small).

See the *test/fonttest.c* example.


File: grx249um.inf,  Node: Drawing in user coordinates,  Next: Graphics cursors,  Prev: Text drawing,  Up: A User Manual For GRX2

Drawing in user coordinates
===========================

There is a second set of the graphics primitives which operates in user
coordinates. Every context has a user to screen coordinate mapping
associated with it. An application specifies the user window by calling
the GrSetUserWindow function.

     void GrSetUserWindow(int x1,int y1,int x2,int y2);

A call to this function it in fact specifies the virtual coordinate
limits which will be mapped onto the current context regardless of the
size of the context. For example, the call:

     GrSetUserWindow(0,0,11999,8999);

tells the library that the program will perform its drawing operations
in a coordinate system X:0...11999 (width = 12000) and Y:0...8999
(height = 9000).  This coordinate range will be mapped onto the total
area of the current context.  The virtual coordinate system can also be
shifted. For example:

     GrSetUserWindow(5000,2000,16999,10999);

The user coordinates can even be used to turn the usual left-handed
coordinate system (0:0 corresponds to the upper left corner) to a right
handed one (0:0 corresponds to the bottom left corner) by calling:

     GrSetUserWindow(0,8999,11999,0);

The library also provides three utility functions for the query of the
current user coordinate limits and for converting user coordinates to
screen coordinates and vice versa.

     void GrGetUserWindow(int *x1,int *y1,int *x2,int *y2);
     void GrGetScreenCoord(int *x,int *y);
     void GrGetUserCoord(int *x,int *y);

If an application wants to take advantage of the user to screen
coordinate mapping it has to use the user coordinate version of the
graphics primitives.  These have exactly the same parameter passing
conventions as their screen coordinate counterparts. NOTE: the user
coordinate system is not initialized by the library! The application
has to set up its coordinate mapping before calling any of the use
coordinate drawing functions - otherwise the program will almost
certainly exit (in a quite ungraceful fashion) with a 'division by
zero' error.  The list of supported user coordinate drawing functions:

     void GrUsrPlot(int x,int y,GrColor c);
     void GrUsrLine(int x1,int y1,int x2,int y2,GrColor c);
     void GrUsrHLine(int x1,int x2,int y,GrColor c);
     void GrUsrVLine(int x,int y1,int y2,GrColor c);
     void GrUsrBox(int x1,int y1,int x2,int y2,GrColor c);
     void GrUsrFilledBox(int x1,int y1,int x2,int y2,GrColor c);
     void GrUsrFramedBox(int x1,int y1,int x2,int y2,int wdt,GrFBoxColors *c);
     void GrUsrCircle(int xc,int yc,int r,GrColor c);
     void GrUsrEllipse(int xc,int yc,int xa,int ya,GrColor c);
     void GrUsrCircleArc(int xc,int yc,int r,int start,int end,
                         int style,GrColor c);
     void GrUsrEllipseArc(int xc,int yc,int xa,int ya,int start,int end,
                          int style,GrColor c);
     void GrUsrFilledCircle(int xc,int yc,int r,GrColor c);
     void GrUsrFilledEllipse(int xc,int yc,int xa,int ya,GrColor c);
     void GrUsrFilledCircleArc(int xc,int yc,int r,int start,int end,
                               int style,GrColor c);
     void GrUsrFilledEllipseArc(int xc,int yc,int xa,int ya,int start,int end,
                                int style,GrColor c);
     void GrUsrPolyLine(int numpts,int points[][2],GrColor c);
     void GrUsrPolygon(int numpts,int points[][2],GrColor c);
     void GrUsrFilledConvexPolygon(int numpts,int points[][2],GrColor c);
     void GrUsrFilledPolygon(int numpts,int points[][2],GrColor c);
     void GrUsrFloodFill(int x, int y, GrColor border, GrColor c);
     GrColor GrUsrPixel(int x,int y);
     GrColor GrUsrPixelC(GrContext *c,int x,int y);
     void GrUsrCustomLine(int x1,int y1,int x2,int y2,const GrLineOption *o);
     void GrUsrCustomBox(int x1,int y1,int x2,int y2,const GrLineOption *o);
     void GrUsrCustomCircle(int xc,int yc,int r,const GrLineOption *o);
     void GrUsrCustomEllipse(int xc,int yc,int xa,int ya,const GrLineOption *o);
     void GrUsrCustomCircleArc(int xc,int yc,int r,int start,int end,
                               int style,const GrLineOption *o);
     void GrUsrCustomEllipseArc(int xc,int yc,int xa,int ya,int start,int end,
                                int style,const GrLineOption *o);
     void GrUsrCustomPolyLine(int numpts,int points[][2],const GrLineOption *o);
     void GrUsrCustomPolygon(int numpts,int points[][2],const GrLineOption *o);
     void GrUsrPatternedLine(int x1,int y1,int x2,int y2,GrLinePattern *lp);
     void GrUsrPatternedBox(int x1,int y1,int x2,int y2,GrLinePattern *lp);
     void GrUsrPatternedCircle(int xc,int yc,int r,GrLinePattern *lp);
     void GrUsrPatternedEllipse(int xc,int yc,int xa,int ya,GrLinePattern *lp);
     void GrUsrPatternedCircleArc(int xc,int yc,int r,int start,int end,
                                  int style,GrLinePattern *lp);
     void GrUsrPatternedEllipseArc(int xc,int yc,int xa,int ya,int start,int end,
                                   int style,GrLinePattern *lp);
     void GrUsrPatternedPolyLine(int numpts,int points[][2],GrLinePattern *lp);
     void GrUsrPatternedPolygon(int numpts,int points[][2],GrLinePattern *lp);
     void GrUsrPatternFilledPlot(int x,int y,GrPattern *p);
     void GrUsrPatternFilledLine(int x1,int y1,int x2,int y2,GrPattern *p);
     void GrUsrPatternFilledBox(int x1,int y1,int x2,int y2,GrPattern *p);
     void GrUsrPatternFilledCircle(int xc,int yc,int r,GrPattern *p);
     void GrUsrPatternFilledEllipse(int xc,int yc,int xa,int ya,GrPattern *p);
     void GrUsrPatternFilledCircleArc(int xc,int yc,int r,int start,int end,int style,GrPattern *p);
     void GrUsrPatternFilledEllipseArc(int xc,int yc,int xa,int ya,int start,int end,int style,GrPattern *p);
     void GrUsrPatternFilledConvexPolygon(int numpts,int points[][2],GrPattern *p);
     void GrUsrPatternFilledPolygon(int numpts,int points[][2],GrPattern *p);
     void GrUsrPatternFloodFill(int x, int y, GrColor border, GrPattern *p);
     void GrUsrDrawChar(int chr,int x,int y,const GrTextOption *opt);
     void GrUsrDrawString(char *text,int length,int x,int y,const GrTextOption *opt);
     void GrUsrTextXY(int x,int y,char *text,GrColor fg,GrColor bg);


File: grx249um.inf,  Node: Graphics cursors,  Next: Keyboard input,  Prev: Drawing in user coordinates,  Up: A User Manual For GRX2

Graphics cursors
================

The library provides support for the creation and usage of an unlimited
number of graphics cursors. An application can use these cursors for
any purpose.  Cursors always save the area they occupy before they are
drawn. When moved or erased they restore this area. As a general rule
of thumb, an application should erase a cursor before making changes to
an area it occupies and redraw the cursor after finishing the drawing.
Cursors are created with the GrBuildCursor function:

     GrCursor *GrBuildCursor(char far *pixels,int pitch,int w,int h,
                             int xo,int yo,const GrColorTableP c);

The pixels, w (=width), h (=height) and c (= color table) arguments are
similar to the arguments of the pixmap building library function
GrBuildPixmap (see that paragraph for a more detailed explanation.),
but with two differences.  First, is not assumed that the pixels data
is w x h sized, the pitch argument set the offset between rows. Second,
the pixmap data is interpreted slightly differently, any pixel with
value zero is taken as a "transparent" pixel, i.e.  the background will
show through the cursor pattern at that pixel. A pixmap data byte with
value = 1 will refer to the first color in the table, and so on.

The xo (= X offset) and yo (= Y offset) arguments specify the position
(from the top left corner of the cursor pattern) of the cursor's "hot
point".

The GrCursor data structure:

     typedef struct _GR_cursor {
       struct _GR_context work;            /* work areas (4) */
       int     xcord,ycord;                /* cursor position on screen */
       int     xsize,ysize;                /* cursor size */
       int     xoffs,yoffs;                /* LU corner to hot point offset */
       int     xwork,ywork;                /* save/work area sizes */
       int     xwpos,ywpos;                /* save/work area position on screen */
       int     displayed;                  /* set if displayed */
     } GrCursor;

is typically not used (i.e. read or changed) by the application
program, it should just pass pointers to these structures to the
appropriate library functions. Other cursor manipulation functions:

     void GrDisplayCursor(GrCursor *cursor);
     void GrEraseCursor(GrCursor *cursor);
     void GrMoveCursor(GrCursor *cursor,int x,int y);
     void GrDestroyCursor(GrCursor *cursor);

See the *test/curstest.c* example.


File: grx249um.inf,  Node: Keyboard input,  Next: Mouse event handling,  Prev: Graphics cursors,  Up: A User Manual For GRX2

Keyboard input
==============

GRX can handle platform independant key input. The file grxkeys.h
defines the keys to be used in the user's program. This is an extract:

     #define GrKey_Control_A            0x0001
     #define GrKey_Control_B            0x0002
     #define GrKey_Control_C            0x0003
     ...
     #define GrKey_A                    0x0041
     #define GrKey_B                    0x0042
     #define GrKey_C                    0x0043
     ...
     #define GrKey_F1                   0x013b
     #define GrKey_F2                   0x013c
     #define GrKey_F3                   0x013d
     ...
     #define GrKey_Alt_F1               0x0168
     #define GrKey_Alt_F2               0x0169
     #define GrKey_Alt_F3               0x016a

But you can be confident that the standard ASCII is right maped.  The
GrKeyType type is defined to store keycodes:

     typedef unsigned short GrKeyType;

This function:

     int GrKeyPressed(void);

returns non zero if there are any keycode waiting, that can be read
with:

     GrKeyType GrKeyRead(void);

The function:

     int GrKeyStat(void);

returns a keyboard status word, or-ing it with the next defines it can
be known the status of some special keys:

     #define GR_KB_RIGHTSHIFT    0x01      /* right shift key depressed */
     #define GR_KB_LEFTSHIFT     0x02      /* left shift key depressed */
     #define GR_KB_CTRL          0x04      /* CTRL depressed */
     #define GR_KB_ALT           0x08      /* ALT depressed */
     #define GR_KB_SCROLLOCK     0x10      /* SCROLL LOCK active */
     #define GR_KB_NUMLOCK       0x20      /* NUM LOCK active */
     #define GR_KB_CAPSLOCK      0x40      /* CAPS LOCK active */
     #define GR_KB_INSERT        0x80      /* INSERT state active */
     #define GR_KB_SHIFT         (GR_KB_LEFTSHIFT | GR_KB_RIGHTSHIFT)

See the *test/keys.c* example.


File: grx249um.inf,  Node: Mouse event handling,  Next: Writing/reading PNM graphics files,  Prev: Keyboard input,  Up: A User Manual For GRX2

Mouse event handling
====================

All mouse services need the presence of a mouse. An application can test
whether a mouse is available by calling the function:

     int  GrMouseDetect(void);

which will return zero if no mouse (or mouse driver) is present,
non-zero otherwise. The mouse must be initialized by calling one (and
only one) of these functions:

     void GrMouseInit(void);
     void GrMouseInitN(int queue_size);

GrMouseInit sets a event queue (see below) size to GR_M_QUEU_SIZE
(128). A user supply event queue size can be set calling GrMouseInitN
instead.

It is a good practice to call GrMouseUnInit before exiting the program.
This will restore any interrupt vectors hooked by the program to their
original values.

     void GrMouseUnInit(void);

The mouse can be controlled with the following functions:

     void GrMouseSetSpeed(int spmult,int spdiv);
     void GrMouseSetAccel(int thresh,int accel);
     void GrMouseSetLimits(int x1,int y1,int x2,int y2);
     void GrMouseGetLimits(int *x1,int *y1,int *x2,int *y2);
     void GrMouseWarp(int x,int y);

The library calculates the mouse position only from the mouse mickey
counters.  (To avoid the limit and 'rounding to the next multiple of
eight' problem with some mouse driver when it finds itself in a
graphics mode unknown to it.) The parameters to the GrMouseSetSpeed
function specify how coordinate changes are obtained from mickey
counter changes, multipling by spmult and dividing by spdiv. In high
resolution graphics modes the value of one just works fine, in low
resolution modes (320x200 or similar) it is best set the spdiv to two or
three. (Of course, it also depends on the sensitivity the mouse.) The
GrMouseSetAccel function is used to control the ballistic effect: if a
mouse coordinate changes between two samplings by more than the thresh
parameter, the change is multiplied by the accel parameter. NOTE: some
mouse drivers perform similar calculations before reporting the
coordinates in mickeys. In this case the acceleration done by the
library will be additional to the one already performed by the mouse
driver. The limits of the mouse movement can be set (passed limits will
be clipped to the screen) with GrMouseSetLimits (default is the whole
screen) and the current limits can be obtained with GrMouseGetLimits.
GrMouseWarp sets the mouse cursor to the specified position.

As typical mouse drivers do not know how to draw mouse cursors in high
resolution graphics modes, the mouse cursor is drawn by the library.
The mouse cursor can be set with:

     void GrMouseSetCursor(GrCursor *cursor);
     void GrMouseSetColors(GrColor fg,GrColor bg);

GrMouseSetColors uses an internal arrow pattern, the color fg will be
used as the interior of it and bg will be the border. The current mouse
cursor can be obtained with:

     GrCursor *GrMouseGetCursor(void);

The mouse cursor can be displayed/erased with:

     void GrMouseDisplayCursor(void);
     void GrMouseEraseCursor(void);

The mouse cursor can be left permanently displayed. All graphics
primitives except for the few non-clipping functions check for
conflicts with the mouse cursor and erase it before the drawing if
necessary. Of course, it may be more efficient to erase the cursor
manually before a long drawing sequence and redraw it after completion.
The library provides an alternative pair of calls for this purpose
which will erase the cursor only if it interferes with the drawing:

     int  GrMouseBlock(GrContext *c,int x1,int y1,int x2,int y2);
     void GrMouseUnBlock(int return_value_from_GrMouseBlock);

GrMouseBlock should be passed the context in which the drawing will
take place (the usual convention of NULL meaning the current context is
supported) and the limits of the affected area. It will erase the
cursor only if it interferes with the drawing. When the drawing is
finished GrMouseUnBlock must be called with the argument returned by
GrMouseBlock.

The status of the mouse cursor can be obtained with calling
GrMouseCursorIsDisplayed. This function will return non-zero if the
cursor is displayed, zero if it is erased.

     int  GrMouseCursorIsDisplayed(void);

The library supports (beside the simple cursor drawing) three types of
"rubberband" attached to the mouse cursor. The GrMouseSetCursorMode
function is used to select the cursor drawing mode.

     void GrMouseSetCursorMode(int mode,...);

The parameter mode can have the following values:

     #define GR_M_CUR_NORMAL   0    /* MOUSE CURSOR modes: just the cursor */
     #define GR_M_CUR_RUBBER   1    /* rect. rubber band (XOR-d to the screen) */
     #define GR_M_CUR_LINE     2    /* line attached to the cursor */
     #define GR_M_CUR_BOX      3    /* rectangular box dragged by the cursor */

GrMouseSetCursorMode takes different parameters depending on the cursor
drawing mode selected. The accepted call formats are:

     GrMouseSetCursorMode(M_CUR_NORMAL);
     GrMouseSetCursorMode(M_CUR_RUBBER,xanchor,yanchor,GrColor);
     GrMouseSetCursorMode(M_CUR_LINE,xanchor,yanchor,GrColor);
     GrMouseSetCursorMode(M_CUR_BOX,dx1,dy1,dx2,dy2,GrColor);

The anchor parameters for the rubberband and rubberline modes specify a
fixed screen location to which the other corner of the primitive is
bound. The dx1 through dy2 parameters define the offsets of the corners
of the dragged box from the hotpoint of the mouse cursor. The color
value passed is always XOR-ed to the screen, i.e. if an application
wants the rubberband to appear in a given color on a given background
then it has to pass the XOR of these two colors to GrMouseSetCursorMode.

The GrMouseGetEvent function is used to obtain the next mouse or
keyboard event. It takes a flag with various bits encoding the type of
event needed. It returns the event in a GrMouseEvent structure. The
relevant declarations from grx20.h:

     void GrMouseGetEvent(int flags,GrMouseEvent *event);

     typedef struct _GR_mouseEvent {    /* mouse event buffer structure */
       int  flags;                       /* event type flags (see above) */
       int  x,y;                         /* mouse coordinates */
       int  buttons;                     /* mouse button state */
       int  key;                         /* key code from keyboard */
       int  kbstat;                      /* keybd status (ALT, CTRL, etc..) */
       long dtime;                       /* time since last event (msec) */
     } GrMouseEvent;

The event structure has been extended with a keyboard status word (thus
a program can check for combinations like ALT-<left mousebutton press>)
and a time stamp which can be used to check for double clicks, etc...
The following macros have been defined in grx20.h to help in creating
the control flag for GrMouseGetEvent and decoding the various bits in
the event structure:

     #define GR_M_MOTION         0x001       /* mouse event flag bits */
     #define GR_M_LEFT_DOWN      0x002
     #define GR_M_LEFT_UP        0x004
     #define GR_M_RIGHT_DOWN     0x008
     #define GR_M_RIGHT_UP       0x010
     #define GR_M_MIDDLE_DOWN    0x020
     #define GR_M_MIDDLE_UP      0x040
     #define GR_M_BUTTON_DOWN    (GR_M_LEFT_DOWN  | GR_M_MIDDLE_DOWN | \
                                  GR_M_RIGHT_DOWN | GR_M_P4_DOWN | GR_M_P5_DOWN)
     #define GR_M_BUTTON_UP      (GR_M_LEFT_UP    | GR_M_MIDDLE_UP   | \
                                  GR_M_RIGHT_UP   | GR_M_P4_UP  | GR_M_P5_UP)
     #define GR_M_BUTTON_CHANGE  (GR_M_BUTTON_UP  | GR_M_BUTTON_DOWN )

     #define GR_M_LEFT           0x01        /* mouse button index bits */
     #define GR_M_RIGHT          0x02
     #define GR_M_MIDDLE         0x04
     #define GR_M_P4             0x08        /* wheel rolls up */
     #define GR_M_P5             0x10        /* wheel rolls down */

     #define GR_M_KEYPRESS       0x080        /* other event flag bits */
     #define GR_M_POLL           0x100
     #define GR_M_NOPAINT        0x200
     #define GR_COMMAND          0x1000
     #define GR_M_EVENT          (GR_M_MOTION | GR_M_KEYPRESS | \
                                  GR_M_BUTTON_CHANGE | GR_COMMAND)

GrMouseGetEvent will display the mouse cursor if it was previously
erased and the GR_M_NOPAINT bit is not set in the flag passed to it. In
this case it will also erase the cursor after an event has been
obtained.

GrMouseGetEvent block until a event is produced, except if the
GR_M_POLL bit is set in the flag passed to it.

Another version of GetEvent:

     void GrMouseGetEventT(int flags,GrMouseEvent *event,long timout_msecs);

can be istructed to wait timout_msec for the presence of an event. Note
that event->dtime is only valid if any event occured (event->flags !=
0) otherwise it's set as -1. Additionally event timing is real world
time even in X11 && Linux.

If there are one or more events waiting the function:

     int  GrMousePendingEvent(void);

returns non-zero value.

The generation of mouse and keyboard events can be individually enabled
or disabled (by passing a non-zero or zero, respectively, value in the
corresponding enable_XX parameter) by calling:

     void GrMouseEventEnable(int enable_kb,int enable_ms);

Note that GrMouseInit set both by default. If you want to use
GrMouseGetEvent and GrKeyRead at the same time, a call to
GrMouseEventEnable( 0,1 ) is needed before input process.

See the *test/mousetst.c* example.


File: grx249um.inf,  Node: Writing/reading PNM graphics files,  Next: Writing/reading PNG graphics files,  Prev: Mouse event handling,  Up: A User Manual For GRX2

Writing/reading PNM graphics files
==================================

GRX includes functions to load/save a context from/to a PNM file.

PNM is a group of simple graphics formats from the NetPbm
(http://netpbm.sourceforge.net) distribution. NetPbm can convert
from/to PNM lots of graphics formats, and apply some transformations to
PNM files.  (Note. You don't need the NetPbm distribution to use this
functions).

There are six PNM formats:

       P1 text PBM (bitmap)
       P2 text PGM (gray scale)
       P3 text PPM (real color)
       P4 binary PBM (bitmap)
       P5 binary PGM (gray scale)
       P6 binary PPM (real color)

GRX can handle the binary formats only (get the NetPbm distribution if
you need convert text to binary formats).

To save a context in a PNM file you have three functions:

     int GrSaveContextToPbm( GrContext *grc, char *pbmfn, char *docn );
     int GrSaveContextToPgm( GrContext *grc, char *pgmfn, char *docn );
     int GrSaveContextToPpm( GrContext *grc, char *ppmfn, char *docn );

they work both in RGB and palette modes, grc must be a pointer to the
context to be saved, if it is NULL the current context is saved; p-mfn
is the file name to be created and docn is an optional text comment to
be written in the file, it can be NULL. Three functions return 0 on
succes and -1 on error.

GrSaveContextToPbm dumps a context in a PBM file (bitmap). If the pixel
color isn't Black it asumes White.

GrSaveContextToPgm dumps a context in a PGM file (gray scale). The
colors are quantized to gray scale using .299r + .587g + .114b.

GrSaveContextToPpm dumps a context in a PPM file (real color).  To load
a PNM file in a context you must use:

     int GrLoadContextFromPnm( GrContext *grc, char *pnmfn );

it support reading PBM, PGM and PPM binary files. grc must be a pointer
to the context to be written, if it is NULL the current context is
used; p-mfn is the file name to be read. If context dimensions are
lesser than pnm dimensions, the function loads as much as it can. If
color mode is not in RGB mode, the routine allocates as much colors as
it can. The function returns 0 on succes and -1 on error.

To query the file format, width and height of a PNM file you can use:

     int GrQueryPnm( char *ppmfn, int *width, int *height, int *maxval );

pnmfn is the name of pnm file; width returns the pnm width; height
returns the pnm height; maxval returns the max color component value.
The function returns 1 to 6 on success (the PNM format) or -1 on error.

The two next functions:

     int GrLoadContextFromPnmBuffer( GrContext *grc, const char *pnmbuf );
     int GrQueryPnmBuffer( const char *pnmbuf, int *width, int *height, int *maxval );

work like GrLoadContextFromPnm and GrQueryPnmBuffer, but they get his
input from a buffer instead of a file. This way, pnm files can be
embeded in a program (using the bin2c program by example).


File: grx249um.inf,  Node: Writing/reading PNG graphics files,  Next: Writing/reading JPEG graphics files,  Prev: Writing/reading PNM graphics files,  Up: A User Manual For GRX2

Writing/reading PNG graphics files
==================================

GRX includes functions to load/save a context from/to a png file. But
note, for this purpose it needs the libpng
(http://www.libpng.org/pub/png/libpng.html) library, and to enable the
png support before make the GRX lib.

Use next function to save a context in a PNG file:

     int GrSaveContextToPng( GrContext *grc, char *pngfn );

it works both in RGB and palette modes, grc must be a pointer to the
context to be saved, if it is NULL the current context is saved; pngfn
is the file name to be created.  The function returns 0 on succes and
-1 on error.

To load a PNG file in a context you must use:

     int GrLoadContextFromPng( GrContext *grc, char *pngfn, int use_alpha );

grc must be a pointer to the context to be written, if it is NULL the
current context is used; pngfn is the file name to be read; set
use_alpha to 1 if you want to use the image alpha channel (if
available). If context dimensions are lesser than png dimensions, the
function loads as much as it can. If color mode is not in RGB mode, the
routine allocates as much colors as it can. The function returns 0 on
succes and -1 on error.

To query the width and height of a PNG file you can use:

     int GrQueryPng( char *pngfn, int *width, int *height );

pngfn is the name of png file; width returns the png width; height
returns the png height.  The function returns 0 on success or -1 on
error.

The function:

     int GrPngSupport( void );

returns 1 if there is png support in the library, 0 otherwise. If there
is not support for png, dummy functions are added to the library,
returning error (-1) ever.


File: grx249um.inf,  Node: Writing/reading JPEG graphics files,  Next: Miscellaneous functions,  Prev: Writing/reading PNG graphics files,  Up: A User Manual For GRX2

Writing/reading PNG graphics files
==================================

GRX includes functions to load/save a context from/to a jpeg file. But
note, for this purpose it needs the libjpeg (http://www.ijg.org)
library, and to enable the jpeg support before make the GRX lib.

Use next function to save a context in a JPEG file:

     int GrSaveContextToJpeg( GrContext *grc, char *jpegfn, int quality );

it works both in RGB and palette modes, grc must be a pointer to the
context to be saved, if it is NULL the current context is saved; jpegfn
is the file name to be created; quality is a number between 1 and 100
to drive the compression quality, use higher values for better quality
(and bigger files), you can use 75 as a standard value, normally a
value between 50 and 95 is good.  The function returns 0 on succes and
-1 on error.

This function saves a context in a grayscale JPEG file:

     int GrSaveContextToGrayJpeg( GrContext *grc, char *jpegfn, int quality );

parameters and return codes are like in GrSaveContextToJpeg.  The
colors are quantized to gray scale using .299r + .587g + .114b.

To load a JPEG file in a context you must use:

     int GrLoadContextFromJpeg( GrContext *grc, char *jpegfn, int scale );

grc must be a pointer to the context to be written, if it is NULL the
current context is used; jpegfn is the file name to be read; set scale
to 1, 2, 4 or 8 to reduce the loaded image to 1/1, 1/2, 1/4 or 1/8. If
context dimensions are lesser than jpeg dimensions, the function loads
as much as it can. If color mode is not in RGB mode, the routine
allocates as much colors as it can. The function returns 0 on succes
and -1 on error.

To query the width and height of a JPEG file you can use:

     int GrQueryJpeg( char *jpegfn, int *width, int *height );

jpegfn is the name of jpeg file; width returns the jpeg width; height
returns the jpeg height.  The function returns 0 on success or -1 on
error.

The function:

     int GrJpegSupport( void );

returns 1 if there is jpeg support in the library, 0 otherwise. If
there is not support for jpeg, dummy functions are added to the
library, returning error (-1) ever.


File: grx249um.inf,  Node: Miscellaneous functions,  Next: BGI interface,  Prev: Writing/reading JPEG graphics files,  Up: A User Manual For GRX2

Miscellaneous functions
=======================

Here we will describe some miscellaneous functions.

     unsigned GrGetLibraryVersion(void);

GrGetLibraryVersion returns the GRX version API, like a hexadecimal
coded number. By example 0x0241 means 2.4.1 Because grx20.h defines the
GRX_VERSION_API macro, you can check if both, the library and the
include file, are in the same version using if(GrGetLibraryVersion() ==
GRX_VERSION_API )

     unsigned GrGetLibrarySystem(void);

This functions returns a unsigned integer identifing the system you are
working in. grx20.h defines some macros you can use:

     /* these are the supported configurations: */
     #define GRX_VERSION_TCC_8086_DOS        1   /* also works with BCC */
     #define GRX_VERSION_GCC_386_DJGPP       2   /* DJGPP v2 */
     #define GRX_VERSION_GCC_386_LINUX       3   /* the real stuff */
     #define GRX_VERSION_GENERIC_X11         4   /* generic X11 version */
     #define GRX_VERSION_WATCOM_DOS4GW       5   /* GS - Watcom C++ 11.0 32 Bit
     #define GRX_VERSION_GCC_386_WIN32       7   /* WIN32 using Mingw32 */
     #define GRX_VERSION_MSC_386_WIN32       8   /* WIN32 using MS-VC */
     #define GRX_VERSION_GCC_386_CYG32       9   /* WIN32 using CYGWIN */
     #define GRX_VERSION_GCC_386_X11        10   /* X11 version */
     #define GRX_VERSION_GCC_X86_64_LINUX   11   /* console framebuffer 64 */
     #define GRX_VERSION_GCC_X86_64_X11     12   /* X11 version 64 */

Note. On Linux, GrGetLibrarySystem returns GRX_VERSION_GCC_386_LINUX
even in the X11 version.

     void GrSetWindowTitle(char *title);
GrSetWindowTitle sets the main window title in the X11 an Win32
versions. It doesn't do nothing in the DOS and Linux-SvgaLib versions.

     void GrSleep(int msec);
This function stops the program execution for msec miliseconds.

     long GrMsecTime( void );
This function gives the current time with millisecond resolution

     void GrFlush( void );
This funnction flushes the graphics window. Not dummy because useful
only on X11 when switching between graphics and console windows open
simultaneously.

      GrContext *GrCreateFrameContext(GrFrameMode md,int w,int h,
                 char far *memory[4],GrContext *where);
This function is like GrCreateContext, except that you can specify any
valid memory frame mode, not only the Screen associated frame mode. It
can be used for special purposes (see GrBitBlt1bpp for an example).

      void GrBitBlt1bpp(GrContext *dst,int dx,int dy,GrContext *src,
           int x1,int y1,int x2,int y2,GrColor fg,GrColor bg);
This special function does a bitblt from a 1bpp context (a bitmap
really), using fg and bg like the color+opcode when bit=1 and bit=0
respectively. Here is an example:

        pContext = GrCreateFrameContext(GR_frameRAM1, sizex, sizey, NULL, NULL);
        /* draw something (black and white) into the bitmap */
        GrSetContext(pContext);
        GrClearContext( GrBlack() );
        GrLine(0, 0, sizex-1, sizey-1, GrWhite());
        GrLine(0, sizey-1, sizex-1, 0, GrWhite());

        /* Put the bitmap into the screen */
        GrSetContext(NULL);
        fcolor = GrAllocColor( 255,0,0 );
        bcolor = GrAllocColor( 0,0,255 );
        GrBitBlt1bpp(NULL,x,y,pContext,0,0,sizex-1,sizey-1,fcolor,bcolor);


File: grx249um.inf,  Node: BGI interface,  Next: Pascal interface,  Prev: Miscellaneous functions,  Up: A User Manual For GRX2

BGI interface
=============

From the 2.3.1 version, GRX includes the BCC2GRX library created by
Hartmut Schirmer. The BCC2GRX was created to allow users of GRX to
compile graphics programs written for Borland-C++ and Turbo-C graphics
interface. BCC2GRX is not a convenient platform to develop new BGI
programs. Of course you should use native GRX interface in such cases!

Read the readme.bgi file for more info.


File: grx249um.inf,  Node: Pascal interface,  Next: References,  Prev: BGI interface,  Up: A User Manual For GRX2

Pascal interface
================

The Pascal (gpc) support is produced by two unit files *pascal/grx.pas*
and *pascal/bgi/graph.pas* which are the Pascal translations of the C
header files *include/grx20.h + include/grxkeys.h* and
*include/libbcc.h*.

Compilation of the examples and installation of the header files is
allowed by setting INCLUDE_GPC_SUPPORT=y in makedef.grx.

The unit files contain at the  beginning instructions to load the
required libraries (libgrx20..., depending on the system) and addon
libraries (e.g. libpng).  You can uncomment manually the addons you
want.  You can also use the configure script which does that
automatically, together with editing the makedefs.grx file.

By default they are installed in a *units* directory below the
INSTALLDIR directory. But you can put them where you like.


File: grx249um.inf,  Node: References,  Prev: Pascal interface,  Up: A User Manual For GRX2

References
==========

Official GRX site              `http://grx.gnu.de'
GRX mailing list archive       `http://grx.gnu.de/archive/grx/en/'
MGRX site (fork from GRX)      `http://mgrx.fgrim.com'
NetPbm distribution            `http://netpbm.sourceforge.net'
PNG library                    `http://www.libpng.org/pub/png/libpng.html'
JPEG library                   `http://www.ijg.org'
TIFF library                   `http://www.remotesensing.org/libtiff/'



Tag Table:
Node: Top198
Node: A User Manual For GRX21387
Node: Hello world2236
Node: Data types and function declarations4021
Node: Setting the graphics driver4755
Node: Setting video modes5866
Node: Graphics contexts10923
Node: Context use18111
Node: Color management19492
Node: Portable use of a few colors24538
Node: Graphics primitives26456
Node: Non-clipping graphics primitives35143
Node: Customized line drawing36646
Node: Pattern filled graphics primitives39000
Node: Patterned line drawing45938
Node: Image manipulation47507
Node: Text drawing50338
Node: Drawing in user coordinates64451
Node: Graphics cursors70791
Node: Keyboard input73353
Node: Mouse event handling75355
Node: Writing/reading PNM graphics files84879
Node: Writing/reading PNG graphics files87934
Node: Writing/reading JPEG graphics files89779
Node: Miscellaneous functions92098
Node: BGI interface95535
Node: Pascal interface96080
Node: References97023

End Tag Table
