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Changed transparent window test

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This adds more alpha colours to hopefully diagnose problems with software transparency a bit better.

Theoretically, the squares should be less visible the less alpha down, but with SDL_BLENDMODE_NONE, this is not the case, we need to use SDL_BLENDMODE_BLEND instead.
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Project_HSI 2026-02-03 07:42:06 +10:00 • committed by GitHub
parent eb181c8d1a
commit 8c8f2bc86e
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1 changed files with 6 additions and 3 deletions
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9
test/testsoftwaretransparent.c
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@ -27,19 +27,21 @@ static void draw(SDL_Renderer *renderer)
SDL_RenderClear(renderer);
if (w >= 3 * SQUARE_SIZE && h >= 3 * SQUARE_SIZE) {
SDL_SetRenderDrawColor(renderer, 255, 0, 0, 255);
rect.x = 0.0f;
rect.y = 0.0f;
SDL_SetRenderDrawColor(renderer, 255, 0, 0, 255);
SDL_RenderFillRect(renderer, &rect);
rect.y = h - SQUARE_SIZE;
SDL_SetRenderDrawColor(renderer, 255, 0, 0, 170);
SDL_RenderFillRect(renderer, &rect);
rect.x = w - SQUARE_SIZE;
SDL_SetRenderDrawColor(renderer, 255, 0, 0, 85);
SDL_RenderFillRect(renderer, &rect);
rect.y = 0.0f;
SDL_SetRenderDrawColor(renderer, 255, 0, 0, 0);
SDL_RenderFillRect(renderer, &rect);
}
@ -82,7 +84,8 @@ int main(int argc, char *argv[])
}
/* Make sure we're setting the alpha channel while drawing */
SDL_SetRenderDrawBlendMode(renderer, SDL_BLENDMODE_NONE);
/* But also make sure we're setting it to premultiplied alpha and not straight alpha. */
SDL_SetRenderDrawBlendMode(renderer, SDL_BLENDMODE_BLEND);
/* We're ready to go! */
while (!done) {