WinComm/forms

Remote Forms System

A remote GUI system for Windows 3.1. Forms are designed visually in Delphi 1.0's IDE, converted to a text protocol by a Linux tool, and served to a Delphi 1.0 client over serial. The client creates native Windows 3.1 controls and sends user events back to the server.

Architecture

  Linux                            Serial              Windows 3.1
 +-----------------+         +----------------+     +------------------+
 | Delphi IDE      |         |                |     |                  |
 | design → .DFM   |         |   Transport    |     |  TFormClient     |
 |        |        |         |  (newline-     |     |  creates native  |
 |    dfm2form     |         |  delimited)    |     |  controls from   |
 |        |        |         |                |     |  commands, sends |
 |    .form file   |         |  Server -----> |---->|  events back     |
 |        |        |         |  commands      |     |                  |
 |  FormServerT    |         |                |     |                  |
 |  loads .form,   |         |  <----- Client |<----|                  |
 |  sends commands |         |  events        |     |                  |
 +-----------------+         +----------------+     +------------------+

Components

File	Language	Platform	Purpose
dfm2form.c	C	Linux	Converts binary DFM to .form text
formsrv.h	C	Linux	Server library header
formsrv.c	C	Linux	Server library implementation
formcli.pas	Pascal	Win 3.1	Client form engine (Delphi 1.0)
protocol.md	—	—	Protocol specification

Building

make              # builds dfm2form and formsrv.o
make clean        # removes build artifacts

Requires GCC on Linux. The Delphi unit (formcli.pas) is compiled as part of a Delphi 1.0 project on Windows.

DFM Converter

dfm2form reads Delphi 1.0 binary DFM files (TPF0 format) and outputs .form files containing protocol commands. The form ID in the output is a placeholder (0); the server assigns a dynamic ID when it streams the file to the client.

dfm2form <input.dfm> [output.form]

Examples:

dfm2form login.dfm                    # output to stdout
dfm2form login.dfm login.form         # output to file

Output is a sequence of protocol commands:

FORM.CREATE 0 400 300 "Login"
CTRL.CREATE 0 1 Label 20 20 100 17 Caption="Username:"
CTRL.CREATE 0 2 Edit 120 18 200 21 Text="" MaxLength=32 TabOrder=0
CTRL.CREATE 0 3 Label 20 52 100 17 Caption="Password:"
CTRL.CREATE 0 4 Edit 120 50 200 21 Text="" MaxLength=32 TabOrder=1
CTRL.CREATE 0 5 Button 245 90 75 25 Caption="OK" TabOrder=2
CTRL.CREATE 0 6 Button 160 90 75 25 Caption="Cancel" TabOrder=3
EVENT.BIND 0 5 Enter
FORM.SHOW 0

The placeholder 0 IDs are replaced at runtime by formServerSendForm.

The converter maps Delphi class names to protocol control types, extracts geometry and properties, and emits EVENT.BIND for any event handler assignments in the DFM that are not auto-wired (see Events below). Unknown control classes are skipped with a warning.

Server Library (C)

The server streams .form files from disk to a remote client through a pluggable transport interface, assigning dynamic form IDs. It also receives events from the client and dispatches them to a callback.

Transport Interface

Implement FormTransportT to connect the server to your communication channel:

typedef struct {
    int  (*readMessage)(char *buf, int32_t maxLen, void *ctx);
    void (*writeMessage)(const char *buf, void *ctx);
    void *ctx;
} FormTransportT;

• readMessage — Read one complete message into buf. Return the number of bytes read, or 0 if no message is available. Must not block.
• writeMessage — Send a null-terminated message string. The transport adds framing (e.g., CR+LF for serial).
• ctx — Opaque pointer passed through to both callbacks.

API

// Create/destroy
FormServerT *formServerCreate(FormTransportT *transport);
void         formServerDestroy(FormServerT *server);

// Stream a .form file to the client, assigning a dynamic form ID.
// Returns the assigned form ID, or -1 on error.
int32_t      formServerSendForm(FormServerT *server, const char *path);

// Form visibility
void         formServerShowForm(FormServerT *server, int32_t formId);
void         formServerHideForm(FormServerT *server, int32_t formId);

// Destroy a form on the client.
void         formServerDestroyForm(FormServerT *server, int32_t formId);

// Update a control property
void         formServerSetProp(FormServerT *server, int32_t formId,
                               int32_t ctrlId, const char *prop,
                               const char *value);

// Bind/unbind opt-in events
void         formServerBindEvent(FormServerT *server, int32_t formId,
                                 int32_t ctrlId, const char *eventName);
void         formServerUnbindEvent(FormServerT *server, int32_t formId,
                                   int32_t ctrlId, const char *eventName);

// Set event callback
void         formServerSetEventCallback(FormServerT *server,
                                        EventCallbackT cb, void *userData);

// Poll for one incoming event.  Returns true if an event was processed.
bool         formServerPollEvent(FormServerT *server);

Event Callback

typedef void (*EventCallbackT)(int32_t formId, int32_t ctrlId,
                               const char *eventName, const char *data,
                               void *userData);

• formId / ctrlId — Identify which control fired the event.
• eventName — "Click", "Change", "Select", etc.
• data — Event-specific data (may be empty). See the Events section below for formats.

Server Example

#include "formsrv.h"

void onEvent(int32_t formId, int32_t ctrlId, const char *eventName, const char *data, void *userData) {
    printf("Event: form=%d ctrl=%d event=%s data=%s\n",
           formId, ctrlId, eventName, data);

    FormServerT *server = (FormServerT *)userData;

    // React to a button click by updating a label
    if (ctrlId == 5 && strcmp(eventName, "Click") == 0) {
        formServerSetProp(server, formId, 1, "Caption", "\"Clicked!\"");
    }
}

int main(void) {
    FormTransportT transport = { myReadFn, myWriteFn, myCtx };
    FormServerT *server = formServerCreate(&transport);

    formServerSetEventCallback(server, onEvent, server);

    int32_t formId = formServerSendForm(server, "login.form");

    // Main loop
    while (running) {
        formServerPollEvent(server);
    }

    formServerDestroy(server);
    return 0;
}

Client Engine (Delphi 1.0)

The client receives protocol commands, creates native Windows 3.1 controls, and sends user events back through the transport.

Transport Interface

Subclass TFormTransport to provide your communication channel:

TFormTransport = class(TObject)
public
  function ReadMessage(Buf: PChar; BufSize: Integer): Integer; virtual; abstract;
  procedure WriteMessage(Buf: PChar; Len: Integer); virtual; abstract;
end;

• ReadMessage — Read one complete message into Buf. Return the number of bytes read, or 0 if no message is available.
• WriteMessage — Send Len bytes from Buf as a complete message.

PChar-based (not short strings) to handle messages up to 4096 bytes.

Serial Transport Example

TSerialTransport = class(TFormTransport)
private
  FComm:    TKPComm;
  FRecvBuf: array[0..4095] of Char;
  FRecvLen: Integer;
public
  function ReadMessage(Buf: PChar; BufSize: Integer): Integer; override;
  procedure WriteMessage(Buf: PChar; Len: Integer); override;
end;

function TSerialTransport.ReadMessage(Buf: PChar; BufSize: Integer): Integer;
var
  S:   string;
  I:   Integer;
  Len: Integer;
begin
  Result := 0;
  { Accumulate serial data }
  S := FComm.Input;
  if Length(S) > 0 then
  begin
    Move(S[1], FRecvBuf[FRecvLen], Length(S));
    Inc(FRecvLen, Length(S));
  end;
  { Scan for newline }
  for I := 0 to FRecvLen - 1 do
  begin
    if FRecvBuf[I] = #10 then
    begin
      Len := I;
      if (Len > 0) and (FRecvBuf[Len - 1] = #13) then
        Dec(Len);
      if Len > BufSize - 1 then
        Len := BufSize - 1;
      Move(FRecvBuf, Buf^, Len);
      Buf[Len] := #0;
      { Shift remainder }
      Move(FRecvBuf[I + 1], FRecvBuf, FRecvLen - I - 1);
      Dec(FRecvLen, I + 1);
      Result := Len;
      Exit;
    end;
  end;
end;

procedure TSerialTransport.WriteMessage(Buf: PChar; Len: Integer);
var
  Msg: string;
begin
  Msg := StrPas(Buf) + #13#10;
  FComm.Output := Msg;
end;

Using TFormClient

var
  Transport: TSerialTransport;
  Client:    TFormClient;

{ Setup }
Transport := TSerialTransport.Create;
Transport.FComm := KPComm1;   { your TKPComm instance }
Client := TFormClient.Create(Transport);

{ Main loop (PeekMessage style) }
while not Terminated do
begin
  while PeekMessage(Msg, 0, 0, 0, PM_REMOVE) do
  begin
    TranslateMessage(Msg);
    DispatchMessage(Msg);
  end;
  Client.ProcessMessages;   { pumps incoming commands }
  Yield;
end;

{ Cleanup }
Client.Free;
Transport.Free;

ProcessMessages calls ReadMessage in a loop until no more messages are available, dispatching each command as it arrives.

Supported Controls

Type	Delphi Class	Description
Label	TLabel	Static text label
Edit	TEdit	Single-line text input
Button	TButton	Push button
CheckBox	TCheckBox	Check box with label
ListBox	TListBox	Scrollable list of items
ComboBox	TComboBox	Drop-down list with text input
Memo	TMemo	Multi-line text input
Image	TImage	Bitmap image display (BMP only)
GroupBox	TGroupBox	Cosmetic grouping frame
RadioButton	TRadioButton	Radio button (one group/form)
Panel	TPanel	Cosmetic container panel
ScrollBar	TScrollBar	Horizontal or vertical scrollbar
MediaPlayer	TMediaPlayer	MCI media player control
MainMenu	TMainMenu	Form main menu bar
PopupMenu	TPopupMenu	Context (right-click) menu
MenuItem	TMenuItem	Menu item (child of menu)
RadioGroup	TRadioGroup	Grouped radio buttons
BitBtn	TBitBtn	Button with bitmap glyph
SpeedButton	TSpeedButton	Flat toolbar-style button
TabSet	TTabSet	Tab strip (no pages)
Notebook	TNotebook	Multi-page container
TabbedNotebook	TTabbedNotebook	Tabbed multi-page container
MaskEdit	TMaskEdit	Masked text input
Outline	TOutline	Hierarchical tree list
Bevel	TBevel	Cosmetic beveled line/box
Header	THeader	Column header bar
ScrollBox	TScrollBox	Scrollable container
StringGrid	TStringGrid	Editable string grid

Creating Controls

Controls are created with CTRL.CREATE, specifying position, size, and optional inline properties:

CTRL.CREATE <formId> <ctrlId> <type> <left> <top> <width> <height> [Key="val" ...]

Example:

CTRL.CREATE 1 3 Edit 120 50 200 21 Text="hello" MaxLength=32 TabOrder=1

Control IDs are positive integers assigned by the server. They must be unique within a form.

Updating Controls

Properties can be changed at any time after creation with CTRL.SET:

CTRL.SET <formId> <ctrlId> Key="val" [Key="val" ...]

Example:

CTRL.SET 1 3 Text="world" Enabled=0

Properties

Caption

• Applies to: Label, Button, CheckBox, GroupBox, RadioButton, Panel, MenuItem, RadioGroup, BitBtn, SpeedButton
• Format: Quoted string
• Example: Caption="Submit"

The display text for labels, buttons, check boxes, group boxes, radio buttons, panels, menu items, radio groups, and bitmap/speed buttons.

Text

• Applies to: Edit, ComboBox, Memo, MaskEdit
• Format: Quoted string
• Example: Text="Hello world"

The editable text content. For Memo controls, use \n for line breaks within the quoted string:

CTRL.SET 1 5 Text="Line one\nLine two\nLine three"

Items

• Applies to: ListBox, ComboBox, RadioGroup, TabSet, Notebook, TabbedNotebook, Outline, Header
• Format: Quoted string, items separated by \n
• Example: Items="Red\nGreen\nBlue"

Replaces the entire item list. The control is cleared before the new items are added.

Checked

• Applies to: CheckBox, RadioButton, MenuItem
• Format: 0 (unchecked) or 1 (checked)
• Example: Checked=1

Enabled

• Applies to: All control types
• Format: 0 (disabled) or 1 (enabled)
• Example: Enabled=0

Visible

• Applies to: All control types
• Format: 0 (hidden) or 1 (visible)
• Example: Visible=0

MaxLength

• Applies to: Edit, MaskEdit
• Format: Integer (0 = no limit)
• Example: MaxLength=50

Maximum number of characters the user can type.

ReadOnly

• Applies to: Edit, Memo
• Format: 0 (editable) or 1 (read-only)
• Example: ReadOnly=1

ScrollBars

• Applies to: Memo
• Format: Integer 0-3
• Values:
  • 0 — ssNone (no scroll bars)
  • 1 — ssHorizontal
  • 2 — ssVertical
  • 3 — ssBoth
• Example: ScrollBars=2

ItemIndex

• Applies to: ListBox, ComboBox, RadioGroup, TabSet, Notebook, TabbedNotebook
• Format: Integer (-1 = no selection)
• Example: ItemIndex=2

TabOrder

• Applies to: All windowed controls (all types except Label and Image)
• Format: Integer
• Example: TabOrder=3

Controls the keyboard tab navigation order within the form.

Stretch

• Applies to: Image
• Format: 0 (off) or 1 (on)
• Example: Stretch=1

When enabled, the image is stretched to fill the control bounds.

Center

• Applies to: Image
• Format: 0 (off) or 1 (on)
• Example: Center=1

When enabled, the image is centered within the control bounds.

Transparent

• Applies to: Image
• Format: 0 (off) or 1 (on)
• Example: Transparent=1

When enabled, the image background is transparent.

Picture

• Applies to: Image
• Format: Quoted string (filename)
• Example: Picture="images\logo.bmp"

BMP file to display. The path is resolved relative to the client's BasePath setting. Subdirectories are allowed.

Note: dfm2form does not emit Picture from DFM files because image data is stored as a binary blob in the DFM. Set Picture at runtime via CTRL.SET or by manually editing the .form file.

BevelOuter

• Applies to: Panel
• Format: Integer 0-2
• Values:
  • 0 — bvNone
  • 1 — bvLowered
  • 2 — bvRaised
• Example: BevelOuter=2

BevelInner

• Applies to: Panel
• Format: Integer 0-2
• Values:
  • 0 — bvNone
  • 1 — bvLowered
  • 2 — bvRaised
• Example: BevelInner=1

BorderStyle (Panel)

• Applies to: Panel
• Format: 0 (bsNone) or 1 (bsSingle)
• Example: BorderStyle=1

Kind

• Applies to: ScrollBar, BitBtn
• Format: Integer
• Values (ScrollBar): 0 (sbHorizontal), 1 (sbVertical)
• Values (BitBtn): 0 (bkCustom), 1 (bkOK), 2 (bkCancel), 3 (bkHelp), 4 (bkYes), 5 (bkNo), 6 (bkClose), 7 (bkAbort), 8 (bkRetry), 9 (bkIgnore), 10 (bkAll)
• Example: Kind=1

Min

• Applies to: ScrollBar
• Format: Integer
• Example: Min=0

Max

• Applies to: ScrollBar
• Format: Integer
• Example: Max=100

Position

• Applies to: ScrollBar
• Format: Integer
• Example: Position=50

LargeChange

• Applies to: ScrollBar
• Format: Integer
• Example: LargeChange=10

The amount the position changes when the user clicks the scroll bar track.

SmallChange

• Applies to: ScrollBar
• Format: Integer
• Example: SmallChange=1

The amount the position changes when the user clicks an arrow button.

FileName

• Applies to: MediaPlayer
• Format: Quoted string (file path)
• Example: FileName="sounds\intro.wav"

Media file to open. The path is resolved relative to the client's BasePath setting.

DeviceType

• Applies to: MediaPlayer
• Format: Quoted string
• Example: DeviceType="dtWaveAudio"

MCI device type. Valid values: dtAutoSelect, dtAVIVideo, dtCDAudio, dtDAT, dtDigitalVideo, dtMMMovie, dtOther, dtOverlay, dtScanner, dtSequencer, dtVCR, dtVideodisc, dtWaveAudio.

AutoOpen

• Applies to: MediaPlayer
• Format: 0 (off) or 1 (on)
• Example: AutoOpen=1

When enabled, the media file is opened automatically when FileName is set.

Command

• Applies to: MediaPlayer
• Format: Quoted string
• Example: Command="Play"

Pseudo-property that triggers a method call instead of setting a value. Valid commands: Open, Play, Stop, Close, Pause, Resume, Rewind, Next, Previous.

Parent

• Applies to: MenuItem
• Format: Integer (ctrlId of parent menu or menu item)
• Example: Parent=1

Specifies the parent for a menu item. The parent can be a MainMenu, PopupMenu, or another MenuItem (for submenus).

Columns

• Applies to: RadioGroup
• Format: Integer
• Example: Columns=2

Number of columns for the radio button layout.

ShortCut

• Applies to: MenuItem
• Format: Integer (Delphi ShortCut value)
• Example: ShortCut=16467

Keyboard accelerator for the menu item. Uses Delphi's ShortCut encoding (virtual key + modifier flags).

PopupMenu

• Applies to: Any visual control
• Format: Integer (ctrlId of a PopupMenu)
• Example: PopupMenu=2

Associates a PopupMenu with a control. When the user right-clicks the control, the popup menu is displayed.

Layout

• Applies to: BitBtn, SpeedButton
• Format: Integer 0-3
• Values:
  • 0 — blGlyphLeft
  • 1 — blGlyphRight
  • 2 — blGlyphTop
  • 3 — blGlyphBottom
• Example: Layout=2

Position of the glyph relative to the caption text.

NumGlyphs

• Applies to: BitBtn, SpeedButton
• Format: Integer (1-4)
• Example: NumGlyphs=2

Number of glyph images in the bitmap (up, disabled, clicked, down).

GroupIndex

• Applies to: SpeedButton
• Format: Integer (0 = no group)
• Example: GroupIndex=1

Speed buttons with the same non-zero GroupIndex act as a radio group.

Down

• Applies to: SpeedButton
• Format: 0 (up) or 1 (down)
• Example: Down=1

Whether the speed button is pressed. Only meaningful when GroupIndex is non-zero.

AllowAllUp

• Applies to: SpeedButton
• Format: 0 (off) or 1 (on)
• Example: AllowAllUp=1

When enabled, all speed buttons in a group can be unpressed.

EditMask

• Applies to: MaskEdit
• Format: Quoted string
• Example: EditMask="(999) 000-0000;1;_"

Input mask string (mask;save literals;blank char).

OutlineStyle

• Applies to: Outline
• Format: Integer 0-6
• Values:
  • 0 — osText
  • 1 — osPlusMinusText
  • 2 — osPlusMinus
  • 3 — osPictureText
  • 4 — osPicturePlusMinusText
  • 5 — osTreeText
  • 6 — osTreePictureText
• Example: OutlineStyle=5

Shape

• Applies to: Bevel
• Format: Integer 0-5
• Values:
  • 0 — bsBox
  • 1 — bsFrame
  • 2 — bsTopLine
  • 3 — bsBottomLine
  • 4 — bsLeftLine
  • 5 — bsRightLine
• Example: Shape=2

Style (Bevel)

• Applies to: Bevel
• Format: 0 (bsLowered) or 1 (bsRaised)
• Example: Style=1

ColCount

• Applies to: StringGrid
• Format: Integer (default 5)
• Example: ColCount=10

Number of columns in the grid.

RowCount

• Applies to: StringGrid
• Format: Integer (default 5)
• Example: RowCount=20

Number of rows in the grid.

FixedCols

• Applies to: StringGrid
• Format: Integer (default 1)
• Example: FixedCols=1

Number of non-scrollable columns on the left.

FixedRows

• Applies to: StringGrid
• Format: Integer (default 1)
• Example: FixedRows=1

Number of non-scrollable rows at the top.

DefaultColWidth

• Applies to: StringGrid
• Format: Integer (pixels)
• Example: DefaultColWidth=80

DefaultRowHeight

• Applies to: StringGrid
• Format: Integer (pixels)
• Example: DefaultRowHeight=20

Options (StringGrid)

• Applies to: StringGrid
• Format: Integer (bitmask)
• Example: Options=1549

Bitmask of TGridOption values:

Bit	Value	Option	Description
0	0x0001	goFixedVertLine	Vertical lines on fixed
1	0x0002	goFixedHorzLine	Horizontal lines on fixed
2	0x0004	goVertLine	Vertical lines on cells
3	0x0008	goHorzLine	Horizontal lines on cells
4	0x0010	goRangeSelect	Allow range selection
5	0x0020	goDrawFocusSelected	Draw focused cell selected
6	0x0040	goRowSizing	Allow row resizing
7	0x0080	goColSizing	Allow column resizing
8	0x0100	goRowMoving	Allow row moving
9	0x0200	goColMoving	Allow column moving
10	0x0400	goEditing	Allow in-place editing
11	0x0800	goTabs	Tab between cells
12	0x1000	goThumbTracking	Track scrollbar thumb

Cells

• Applies to: StringGrid
• Format: Quoted string (tab-delimited columns, \n-delimited rows)
• Example: Cells="Name\tAge\nAlice\t30\nBob\t25"

Bulk-loads all cell data. Columns are separated by tab characters, rows by newlines. Row 0 is the first row (typically fixed header).

Cell

• Applies to: StringGrid
• Format: Quoted string (col,row,value)
• Example: Cell="1,2,Hello"

Sets a single cell value. Column and row are zero-based indices.

BasePath

BasePath is a property on TFormClient (not a protocol property). Set it before loading forms to specify where file-based properties (Picture, FileName) resolve relative paths. Example:

Client.BasePath := 'C:\MYAPP';

A Picture value of "images\logo.bmp" then resolves to C:\MYAPP\images\logo.bmp.

Events

Auto-wired Events

These events are automatically connected when a control is created. No EVENT.BIND command is needed.

Control Type	Event	Data Sent
Button	Click	(none)
CheckBox	Click	(none)
RadioButton	Click	(none)
Edit	Change	"new text"
Memo	Change	"new text"
ScrollBar	Change	<position>
ListBox	Select	<index> "selected text"
ComboBox	Select	<index> "selected text"
ComboBox	Change	"new text"
MenuItem	Click	(none)
RadioGroup	Click	<itemIndex>
BitBtn	Click	(none)
SpeedButton	Click	(none)
TabSet	Change	<tabIndex>
TabbedNotebook	Change	<pageIndex>
MaskEdit	Change	"new text"
StringGrid	SelectCell	<col> <row>

Opt-in Events

These events require an explicit EVENT.BIND command before the client will send them. Use EVENT.UNBIND to disconnect.

Event	Data Sent	Notes
Click	(none)	Image, GroupBox, Panel only
DblClick	(none)	Double-click on any control
Notify	(none)	MediaPlayer playback notification
KeyDown	<vkCode>	Windows virtual key code
KeyUp	<vkCode>	Windows virtual key code
Enter	(none)	Control received focus
Exit	(none)	Control lost focus
MouseDown	<x> <y> <button>	0=left, 1=right, 2=middle
MouseUp	<x> <y> <button>	0=left, 1=right, 2=middle
MouseMove	<x> <y> 0	Coordinates relative to control
SetEditText	<col> <row> "text"	StringGrid in-place edit

Form Close Event

When the user clicks the form's close button, the client sends:

EVENT <formId> 0 Close

The form is not automatically destroyed. The server must send FORM.DESTROY to close it, or FORM.HIDE to hide it, or ignore the event to keep it open.

Event Message Format

All events from client to server follow this format:

EVENT <formId> <ctrlId> <eventName> [<data>]

Binding Example

EVENT.BIND 1 3 KeyDown        (server sends)
EVENT 1 3 KeyDown 13           (client sends back when Enter pressed)
EVENT.UNBIND 1 3 KeyDown      (server disconnects)

Menu Hierarchy Example

Menus are built using flat CTRL.CREATE commands with Parent properties to establish the hierarchy:

CTRL.CREATE 1 1 MainMenu 0 0 0 0
CTRL.CREATE 1 2 MenuItem 0 0 0 0 Caption="&File" Parent=1
CTRL.CREATE 1 3 MenuItem 0 0 0 0 Caption="&Open" Parent=2 ShortCut=16463
CTRL.CREATE 1 4 MenuItem 0 0 0 0 Caption="&Save" Parent=2 ShortCut=16467
CTRL.CREATE 1 5 MenuItem 0 0 0 0 Caption="E&xit" Parent=2
CTRL.CREATE 1 6 MenuItem 0 0 0 0 Caption="&Help" Parent=1
CTRL.CREATE 1 7 MenuItem 0 0 0 0 Caption="&About" Parent=6

This creates a menu bar with File (Open, Save, Exit) and Help (About). MenuItem ctrl 2 is a child of MainMenu ctrl 1; ctrl 3-5 are children of the File item (ctrl 2); ctrl 7 is a child of the Help item (ctrl 6).

String Encoding

All strings in the protocol are double-quoted. The following escape sequences are recognized:

Escape	Character
\"	Literal "
\\	Literal \
\n	Newline (LF)
\r	Carriage return
\t	Tab

Transport Layer

The protocol is transport-agnostic. Both the C server and Delphi client communicate through abstract interfaces that deliver whole messages. The current implementation uses newline-delimited serial (CR+LF framing), but the transport can be replaced without changing any protocol or application code.

Requirements

• ReadMessage must be non-blocking (return 0 if no data).
• WriteMessage sends one complete message per call.
• Transport handles framing — the protocol layer never sees delimiters.

Limitations

• RadioButton grouping: All RadioButtons on a form belong to one group. Use RadioGroup for multiple independent radio groups per form.
• Image format: Only BMP files are supported for the Picture property.
• dfm2form and Picture: The converter cannot extract image filenames from DFM files (image data is stored as a binary blob). Set Picture at runtime via CTRL.SET or by manually editing the .form file.
• GroupBox and Panel: These are cosmetic-only containers. The protocol has no child containment — all controls are direct children of the form.

Limits

Limit	Value
Max message length	4096 bytes
Max controls per form	256
Form ID range	1-65535 (stored in high word of Tag)
Control ID range	1-65535 (stored in low word of Tag)