Debian Patches

Status for gearhead/1.310+git20240929-1

Patch Description Author Forwarded Bugs Origin Last update
terminal-drawing-order Copied from https://github.com/jwvhewitt/gearhead-1/pull/86
===================================================================		 no
unixpaths no
dejavu-core no
fix-sdl3-compat-rendering Fix sprite rendering broken by SDL3-compat stack (Patch by claude.ai)
.
On a default modern Debian/Ubuntu system the runtime SDL 1.2 library is the
sdl12-compat shim, which now further sits on top of sdl2-compat, which sits
on top of SDL3. The user's strace confirms this: libSDL-1.2.so.0,
libSDL2-2.0.so.0 and libSDL3.so.0 are all loaded. SDL 1.2 idioms that worked
on real SDL 1.2 (and on sdl12-compat directly against SDL2) fall over when
the chain bottoms out at SDL3, because SDL3 changed surface semantics and
the two-layer shim doesn't reliably re-implement every legacy detail.
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Three concrete bugs caused by this:
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1. Mecha sprites disappear. The pilot-color recoloring routine
(MakeSwapBitmap in sdlgfx.pp) used to create an 8-bit indexed surface
with a curated palette, blit the 24-bit RGB mecha sprite into it
(relying on SDL to color-quantize), and then redefine palette entries to
substitute pilot colors. SDL3 dropped automatic RGB->indexed
quantization in blits and sdl2-compat doesn't reimplement it: the blit
silently writes no pixels, the destination's pre-filled colorkey blue
stays, and the resulting "sprite" is fully transparent. Mecha vanish;
their shadows (Items_Sprite, loaded with empty Color and bypassing
MakeSwapBitmap) still render. Title-screen "shadows but no mecha".
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2. Translucent surfaces render solid. Water tiles, the infobox backdrop,
and the mini-map sprite all relied on SDL_SetAlpha (per-surface alpha
modulation, SDL_SRCALPHA) combined with the surface's colorkey for
transparency. The screen format the AddSprite path converts to has no
alpha mask (Amask=0), so the per-surface alpha modifier has nothing to
multiply into and is silently dropped. The surface blits opaque, so
water tiles are solid bright blue over the grass and the infobox is
fully opaque.
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3. RGBA-source sprites render with the colorkey-blue background opaque.
Wall sprites, mecha portrait sprites, and other RGBA-source PNGs load
as SDL surfaces with a per-pixel alpha channel. On real SDL 1.2,
SDL_SetColorKey followed by SDL_ConvertSurface(..., SDL_SRCCOLORKEY)
converts the colorkey blue into transparent pixels in the destination.
Under the shim chain this doesn't reliably happen for RGBA sources, so
the converted surface still has the blue background as opaque pixels.
DrawAlphaSprite (used for "fade nearby walls so you can see the
player") makes the bug worse because SDL_SetAlpha on a colorkeyed
surface drops the colorkey through the compat layer. In-game effect:
every building wall renders as a solid blue block.
.
The unifying fix is to stop depending on SDL's flag-and-modifier
transparency semantics and instead store per-pixel alpha in the surface,
which every SDL stack handles identically.
.
- Rewrite MakeSwapBitmap to do the color swap directly in 24-bit RGB,
inspecting each pixel's (r,g,b) to classify it as transparent / grey /
red ramp / yellow ramp / green ramp, and writing the swap color scaled
by the source intensity. No indexed intermediate.
- Add BakeAlphaIntoSprite, which replaces a sprite's surface with an
RGBA8888 copy: alpha=0 for colorkey-blue pixels, alpha=N elsewhere.
- Call BakeAlphaIntoSprite(it, 255) at the end of AddSprite so every
loaded sprite is normalized to per-pixel-alpha transparency. This is
the fix for the wall-blue-block bug; it also makes every downstream
alpha operation work on every stack.
- Replace the static per-surface SDL_SetAlpha calls (water_sprite1,
water_sprite2, infobox_backdrop, mini_map_sprite) with
BakeAlphaIntoSprite(..., N). Idempotent over the AddSprite bake.
- Rewrite DrawAlphaSprite to do the alpha blend manually pixel-by-pixel,
skipping colorkey-blue pixels and blending the rest with
Alpha_Level/255 over the destination. SDL_SetAlpha-via-shim drops the
colorkey; manual blend respects it. Runs only for sprites within ~one
tile of the camera center, so the per-frame cost is negligible.
.
Verified by building gearhead-sdl against the user's source plus these
changes and running under both (a) system sdl12-compat 1.2.68 with no
sdl2-compat in the chain and (b) sdl12-compat 1.2.76 + sdl2-compat + SDL3
all built from upstream, which reproduces the user's reported breakage.
Before the patch (a) renders correctly while (b) shows mecha vanish, water
solid, and walls as blue blocks. After the patch both stacks render
correctly across multiple random map seeds (mecha visible on shadows,
water properly translucent, wall sprites show their actual texture).		 Kari Pahula <kaol@debian.org> invalid 2026-05-16

All known versions for source package 'gearhead'

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