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Improve implementation of GetClosestSupportedFormat (#15577)

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* Indexed textures are now used for <8bpp surfaces and for indexed surfaces with transparency.
* If the software renderer is using RGB565 or BGR565, it now successfully detects a suitable 32-bit alpha format for converting the colour key.
* Matching pixel layouts are prioritized rather than just the number of bytes per pixel.
This commit is contained in:
Cameron Cawley
2026-09-01 23:14:44 +01:00
committed by GitHub
parent 46a942a3e3
commit 79a4ea1c54
1 changed files with 48 additions and 54 deletions
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102
src/render/SDL_render.c
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@@ -1427,7 +1427,7 @@ static bool IsSupportedFormat(SDL_Renderer *renderer, SDL_PixelFormat format)
return false;
}
static SDL_PixelFormat GetClosestSupportedFormat(SDL_Renderer *renderer, SDL_PixelFormat format)
static SDL_PixelFormat GetClosestSupportedFormat(SDL_Renderer *renderer, SDL_PixelFormat format, bool hasAlpha)
{
int i;
@@ -1463,17 +1463,34 @@ static SDL_PixelFormat GetClosestSupportedFormat(SDL_Renderer *renderer, SDL_Pix
return renderer->texture_formats[i];
}
}
} else if (SDL_ISPIXELFORMAT_INDEXED(format)) {
for (i = 0; i < renderer->num_texture_formats; ++i) {
// Converting between <8bpp formats is not supported yet
if (renderer->texture_formats[i] == SDL_PIXELFORMAT_INDEX8) {
return renderer->texture_formats[i];
}
}
} else {
bool hasAlpha = SDL_ISPIXELFORMAT_ALPHA(format);
bool isIndexed = SDL_ISPIXELFORMAT_INDEXED(format);
int size = SDL_BYTESPERPIXEL(format);
int type = SDL_PIXELTYPE(format);
int layout = SDL_PIXELLAYOUT(format);
hasAlpha = hasAlpha || SDL_ISPIXELFORMAT_ALPHA(format);
// We just want to match the first format that has the same channels
for (i = 0; i < renderer->num_texture_formats; ++i) {
if (!SDL_ISPIXELFORMAT_FOURCC(renderer->texture_formats[i]) &&
SDL_BYTESPERPIXEL(renderer->texture_formats[i]) == size &&
SDL_ISPIXELFORMAT_ALPHA(renderer->texture_formats[i]) == hasAlpha &&
SDL_ISPIXELFORMAT_INDEXED(renderer->texture_formats[i]) == isIndexed) {
SDL_PIXELTYPE(renderer->texture_formats[i]) == type &&
SDL_PIXELLAYOUT(renderer->texture_formats[i]) == layout &&
SDL_ISPIXELFORMAT_ALPHA(renderer->texture_formats[i]) == hasAlpha) {
return renderer->texture_formats[i];
}
}
}
if (hasAlpha) {
// The default format may still lack an alpha channel
for (i = 0; i < renderer->num_texture_formats; ++i) {
if (!SDL_ISPIXELFORMAT_FOURCC(renderer->texture_formats[i]) &&
SDL_ISPIXELFORMAT_ALPHA(renderer->texture_formats[i])) {
return renderer->texture_formats[i];
}
}
@@ -1571,7 +1588,7 @@ SDL_Texture *SDL_CreateTextureWithProperties(SDL_Renderer *renderer, SDL_Propert
SDL_PropertiesID native_props = SDL_CreateProperties();
if (!texture_is_fourcc_and_target) {
closest_format = GetClosestSupportedFormat(renderer, format);
closest_format = GetClosestSupportedFormat(renderer, format, false);
} else {
closest_format = renderer->texture_formats[0];
}
@@ -1687,7 +1704,10 @@ static bool SDL_UpdateTextureFromSurface(SDL_Texture *texture, SDL_Rect *rect, S
if (surface->format == texture->format &&
SDL_GetSurfaceColorspace(surface) == texture->colorspace) {
if (SDL_ISPIXELFORMAT_ALPHA(surface->format) && SDL_SurfaceHasColorKey(surface)) {
if (SDL_ISPIXELFORMAT_INDEXED(surface->format)) {
// Update Texture directly - the color key is handled later
direct_update = true;
} else if (SDL_ISPIXELFORMAT_ALPHA(surface->format) && SDL_SurfaceHasColorKey(surface)) {
/* Surface and Renderer formats are identical.
* Intermediate conversion is needed to convert color key to alpha (SDL_ConvertColorkeyToAlpha()). */
direct_update = false;
@@ -1720,7 +1740,7 @@ static bool SDL_UpdateTextureFromSurface(SDL_Texture *texture, SDL_Rect *rect, S
}
}
if (texture->format == surface->format && surface->palette) {
if (SDL_ISPIXELFORMAT_INDEXED(texture->format) && surface->palette) {
// Copy the palette to the new texture
SDL_Palette *existing = surface->palette;
SDL_Palette *palette = SDL_CreatePalette(existing->ncolors);
@@ -1735,6 +1755,21 @@ static bool SDL_UpdateTextureFromSurface(SDL_Texture *texture, SDL_Rect *rect, S
}
}
if (SDL_ISPIXELFORMAT_INDEXED(texture->format) && SDL_SurfaceHasColorKey(surface)) {
Uint32 key;
SDL_Color col;
SDL_Palette *palette;
palette = SDL_GetTexturePalette(texture);
if (!palette || !SDL_GetSurfaceColorKey(surface, &key) || key >= (Uint32)palette->ncolors) {
return false;
}
col = palette->colors[key];
col.a = SDL_ALPHA_TRANSPARENT;
SDL_SetPaletteColors(palette, &col, key, 1);
}
{
Uint8 r, g, b, a;
SDL_BlendMode blendMode;
@@ -1808,38 +1843,9 @@ SDL_Texture *SDL_CreateTextureFromSurface(SDL_Renderer *renderer, SDL_Surface *s
}
}
// Look for 10-bit pixel formats if needed
if (format == SDL_PIXELFORMAT_UNKNOWN && SDL_ISPIXELFORMAT_10BIT(surface->format)) {
for (i = 0; i < renderer->num_texture_formats; ++i) {
if (SDL_ISPIXELFORMAT_10BIT(renderer->texture_formats[i])) {
format = renderer->texture_formats[i];
break;
}
}
}
// Look for floating point pixel formats if needed
if (format == SDL_PIXELFORMAT_UNKNOWN &&
(SDL_ISPIXELFORMAT_10BIT(surface->format) || SDL_ISPIXELFORMAT_FLOAT(surface->format))) {
for (i = 0; i < renderer->num_texture_formats; ++i) {
if (SDL_ISPIXELFORMAT_FLOAT(renderer->texture_formats[i])) {
format = renderer->texture_formats[i];
break;
}
}
}
// Fallback, choose a valid pixel format
if (format == SDL_PIXELFORMAT_UNKNOWN) {
format = renderer->texture_formats[0];
// See what the best texture format is
bool needAlpha;
if (SDL_ISPIXELFORMAT_ALPHA(surface->format) || SDL_SurfaceHasColorKey(surface)) {
needAlpha = true;
} else {
needAlpha = false;
}
bool needAlpha = SDL_SurfaceHasColorKey(surface);
// If palette contains alpha values, promotes to alpha format
if (surface->palette) {
@@ -1850,19 +1856,7 @@ SDL_Texture *SDL_CreateTextureFromSurface(SDL_Renderer *renderer, SDL_Surface *s
}
}
// Indexed formats don't support the transparency needed for color-keyed surfaces
bool preferIndexed = SDL_ISPIXELFORMAT_INDEXED(surface->format) && !needAlpha;
int size = SDL_BYTESPERPIXEL(format);
for (i = 0; i < renderer->num_texture_formats; ++i) {
if (!SDL_ISPIXELFORMAT_FOURCC(renderer->texture_formats[i]) &&
SDL_BYTESPERPIXEL(renderer->texture_formats[i]) == size &&
SDL_ISPIXELFORMAT_ALPHA(renderer->texture_formats[i]) == needAlpha &&
SDL_ISPIXELFORMAT_INDEXED(renderer->texture_formats[i]) == preferIndexed) {
format = renderer->texture_formats[i];
break;
}
}
format = GetClosestSupportedFormat(renderer, surface->format, needAlpha);
}
surface_colorspace = SDL_GetSurfaceColorspace(surface);
@@ -1892,7 +1886,7 @@ SDL_Texture *SDL_CreateTextureFromSurface(SDL_Renderer *renderer, SDL_Surface *s
SDL_SetNumberProperty(props, SDL_PROP_TEXTURE_CREATE_WIDTH_NUMBER, surface->w);
SDL_SetNumberProperty(props, SDL_PROP_TEXTURE_CREATE_HEIGHT_NUMBER, surface->h);
texture = SDL_CreateTextureWithProperties(renderer, props);
texture = SDL_CreateTextureWithProperties(renderer, props);
SDL_DestroyProperties(props);
if (!texture) {
return NULL;