Scott Duensing
e8a7812233
Load Windows 3.x .FON (NE resource containers) and raw .FNT font files for use with ExtTextOut. Multiple fonts can be active simultaneously. All available .FON files contain v2 fonts but VBESVGA.DRV requires v3 in 386 protected mode, so the loader converts on load. - Add NE resource table structures (NeResourceTypeT, NeResourceEntryT) - Add WdrvFontT opaque type with load/unload API - Implement buildFontFromFnt() v2→v3 converter - Implement wdrvLoadFontFon() NE resource parser - Move font from per-driver to global singleton (wdrvLoadFontBuiltin) - Add WdrvFontT parameter to wdrvExtTextOut (NULL = built-in) - Add Demo 6: Courier, Sans Serif, System fonts side by side - Copy fon/*.FON to bin/ during build Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
133 lines
8 KiB
Markdown
133 lines
8 KiB
Markdown
# Win31drv Project Memory
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## Build Environment
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- DJGPP cross-compiler: `~/djgpp/djgpp/bin/i586-pc-msdosdjgpp-gcc` (GCC 12.2.0)
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- DJGPP binutils need `libfl.so.2`: stored in `tools/lib/` (Makefiles set LD_LIBRARY_PATH)
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- CWSDPMI zip stored in `tools/cwsdpmi.zip` (extracted to bin/ during build)
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- DOSBox-X: `flatpak run com.dosbox_x.DOSBox-X` (installed as user flatpak)
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- CWSDPMI.EXE in `bin/` directory for DPMI support under DOSBox-X
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- Config: `dosbox-x.conf` with S3 Trio64 machine type, 64MB RAM
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## Project Structure
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```
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windriver/
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├── Makefile # Top-level: builds demo, calls win31drv/Makefile
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├── demo.c # Demo program
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├── dosbox-x.conf # DOSBox-X config (S3 SVGA)
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├── obj/ # Demo object files
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├── bin/ # Executables + CWSDPMI.EXE
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└── win31drv/ # Library
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├── Makefile # Builds libwindrv.a
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├── obj/ # Library objects
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├── neload.c/h # NE format loader
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├── neformat.h # NE structures
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├── thunk.c/h # 32→16 bit thunking
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├── windrv.c/h # Main API
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├── winstub.c/h # Windows API stubs
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├── winddi.h # DDI structures
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└── wintypes.h # Win16 types
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```
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## DJGPP Portability Notes
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- `uint32_t` is `unsigned long` (not `unsigned int`) in DJGPP — use `PRIu32`/`PRIX32` from `<inttypes.h>`
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- Always include `<stdarg.h>` explicitly for `va_list`/`va_start`/`va_end`
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- Headers must be self-contained (include their own dependencies)
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## Thunking Architecture Notes
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- **SS == DS == DGROUP**: Win3.x drivers assume SS == DS == DGROUP. VBESVGA's BBLT.ASM does
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`PrestoChangeoSelector(SS, WorkSelector)` to create a code alias for compiled blit code.
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thunkCall16 uses dgroupSel as SS (SP=0xFFF0) when available. Without this, the code alias
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has the wrong base and the CPU executes garbage.
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- **Register corruption with -O2 inlining**: When demo.c's demoDrawing is inlined into main,
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DJGPP GCC 12.2.0 mishandles callee-saved registers across thunk calls in long functions.
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Fix: `__attribute__((noinline))` on demoDrawing. Symptom: handle pointer corrupted to
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a ColorInfo return value (e.g. 0xFF0001F6) between Demo 2 and Demo 3.
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## DOSBox-X Driver Notes
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- `waitForEngine()`: GP_STAT port 0x9AE8 bit 9 polling — S3 only (gIsS3 guard)
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- **S3 detection**: Probe CR30 chip ID register. S3 chips: 0x81-0xE1. ET4000: 0x00.
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Only apply S3-specific setup (cursor disable, dispYOffset, setDisplayStart) when isS3=true
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AND driver is not VGA-class (1bpp/4planes).
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- **Pattern scratch artifact**: S3 driver writes 8x8 dithered brush pattern to VRAM at fixed
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position (~(144,1)-(151,8)) during accelerated pattern fills. Fixed by shifting CRTC display
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start down 10 scanlines (`dispYOffset`) so the scratch area is off-screen.
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- **`-fno-gcse` required for windrv.c**: With -O2 GCSE, stack layout causes issues during
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16-bit driver calls. Only windrv.c needs this. See `WINDRV_CFLAGS` in win31drv/Makefile.
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- Output DDI (polylines/rectangles) requires a **physical pen** from RealizeObject, not a
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raw LogPen16T. The pen must be in DGROUP (same as brush, drawMode, PDEVICE).
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- `wdrvUnloadDriver` does NOT auto-call Disable — caller must handle text mode restore
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- `sleep()` hangs under DOSBox-X because BIOS timer ticks don't advance without I/O
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- Debug output: `-d` flag enables verbose logging in neload, winstub, thunk, and windrv
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- Known issue: mode mismatch HW=800x600 vs GDIINFO=640x480
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## DGROUP Stack Management
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- VGA.DRV ships with DGROUP[0x0A]=0xFFFF (stack bottom = top of segment → no stack).
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Its BitBlt prolog calls a stack check function at 0x18CA that compares available stack
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against [SS:0x0A]. With 0xFFFF, ALL functions fail immediately (return 0).
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- Fix: patch [0x0A] to objBase after extending DGROUP. Only done when original = 0xFFFF.
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- S3TRIO.DRV and VBESVGA.DRV have [0x0A]=0x0000 — no patching needed.
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- **Do NOT unconditionally overwrite DGROUP offsets 0x00-0x0F** — VBESVGA.DRV stores
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driver-specific data there (0x030A at offset 0, 0x01 at offset 4).
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## BitBlt Source Device Rules
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- For pattern-only ROPs (PATCOPY=0xF0, BLACKNESS=0x00, WHITENESS=0xFF, etc.),
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lpSrcDev must be NULL (0:0) per DDI spec. VGA.DRV rejects non-NULL source for
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pattern-only ROPs. S3TRIO.DRV tolerates it but correct behavior is NULL.
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- Source dependency check: `ropNeedsSrc = (((rop8 >> 2) ^ rop8) & 0x33) != 0`
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## ExtTextOut DDI Notes
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- **Font format**: VBESVGA.DRV requires .FNT v3 (fsVersion=0x0300) when BigFontFlags is set
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(386 protected mode with WF_PMODE + WF_CPU386). v2 (0x0200) is rejected at runtime.
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- **v3 char table**: at file offset 0x94 (fs30CharOffset), 6-byte entries {WORD width, DWORD offset}.
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The DWORD offset is absolute from the font segment base. Use FntCharEntry30T.
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- **Bitmap layout**: per-character contiguous (16 bytes per char for 8x16 font, stride=1 between rows).
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VGA BIOS 8x16 font (INT 10h AH=11h AL=30h BH=06) is already in this format — no transpose needed.
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- **lpClipRect must NOT be NULL**: VBESVGA's get_clip unconditionally dereferences lpClipRect
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(STRBLT.ASM:1008 "We assume that we will never get passed a null rectangle"). Pass a RECT
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covering the full screen (0, 0, 0x7FFF, 0x7FFF).
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- **lpTextXForm**: declared but never read by VBESVGA — pass NULL.
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- **lp_font offset**: passed as fontSel:0x42 (points to fsType within the .FNT block).
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- **Return value**: DX bit 15 = error. AX=0 is NOT necessarily failure.
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## INT 10h ES Translation
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- Different INT 10h function families use different ES:offset registers:
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VBE 4Fxx → ES:DI, AH=10h (palette) → ES:DX, AH=11h (fonts) → ES:BP, AH=1Bh → ES:DI
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- Only specific AL subfunctions use ES as a buffer pointer; most don't
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- Copy sizes must be exact (17 bytes for palette, CX*3 for DAC blocks, etc.)
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- Copy direction matters: "Set" = copy-in only, "Read/Get" = copy-out only
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## WINFLAGS Handling
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- **WF_80x87 NOT used**: We don't save/restore FPU state across thunk boundaries
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- **VGA-class drivers need WF_STANDARD**: VGA.DRV's physical_enable hangs in Enhanced
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mode (polls VDD that doesn't exist). Auto-detected after Enable(style=1) returns
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1bpp/4planes GDIINFO → repatch __WINFLAGS in all segments (0x0025→0x0015).
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- SVGA drivers (S3TRIO, VBESVGA) use WF_ENHANCED normally
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## ET4000 Driver Notes
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- ET4000.DRV from Win 3.x distribution is SZDD-compressed; decompress with `msexpand`
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(rename to .DR_ first, output is .DR without the V — rename to .DRV)
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- DOSBox-X machine type: `svga_et4000` for ET4000 hardware emulation
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- ET4000 is 640x480 8bpp, software-rendered (no accelerator engine in DOSBox-X)
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- CR30=0x00 on ET4000 → isS3=false → no S3 engine wait, no display start shift
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## Font Loading Notes
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- .FON files are NE containers with RT_FONT (type 8) resources; each resource is raw .FNT data
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- All Win 3.x .FON files contain v2 fonts (0x0200); VBESVGA.DRV requires v3 (0x0300)
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- v2→v3 conversion: insert 30-byte extension at 0x76, expand 4-byte char table to 6-byte entries
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- **v2 char table offsets are absolute from segment base**, not relative to fsBitsOffset.
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Correct v3 offset = v2offset + shift (where shift = newBitmapOff - origBitsOff)
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- `wdrvLoadFontFon(path, index)` loads from .FON; `wdrvLoadFontFnt(path)` loads raw .FNT
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- `wdrvLoadFontBuiltin()` returns the VGA ROM 8x16 singleton; must NOT be passed to wdrvUnloadFont
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- `wdrvExtTextOut` takes a `WdrvFontT font` parameter (NULL = built-in)
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- Available test fonts in `fon/`: COURE.FON (8x13, 9x16, 12x20), SSERIFE.FON, SERIFE.FON, VGASYS.FON, etc.
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## Current Demo Status
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- S3TRIO.DRV, VBESVGA.DRV, VGA.DRV, ET4000.DRV all work: Load → Enable → Draw → Disable → Unload
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- Demo 1: Fill rectangles (BitBlt) — works
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- Demo 2: Pixel patterns (Pixel) — works
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- Demo 3: Lines/starburst (Output/Polyline) — works
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- Demo 4: Screen-to-screen blit (BitBlt SRCCOPY) — works
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- Demo 5: ExtTextOut text rendering — works (VBESVGA.DRV)
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- VGA.DRV: 640x480 4-plane 16-color mode; limited color palette but functional
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- ET4000.DRV: 640x480 8bpp on svga_et4000; software-only, no hw acceleration
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- Drivers stored in `drivers/` directory, copied to `bin/` during build
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