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render: Remove the logical presentation render target.

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Now we render directly to the window, scaling as appropriate. This fixes some
concerns the render target introduced, like the quality of the final scaled
output, how to step outside of the logical size temporarily to draw some
things sharply at the native resolution, and loss of sub-pixel precision.

Fixes #8736.
This commit is contained in:
Ryan C. Gordon
2024-09-16 13:33:16 -04:00
parent bf7a48cdcc
commit 54459def69
16 changed files with 293 additions and 387 deletions
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2
examples/renderer/02-primitives/primitives.c
View File

@@ -55,7 +55,7 @@ SDL_AppResult SDL_AppIterate(void *appstate)
SDL_FRect rect;
/* as you can see from this, rendering draws over whatever was drawn before it. */
SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255); /* black, full alpha */
SDL_SetRenderDrawColor(renderer, 33, 33, 33, 255); /* dark gray, full alpha */
SDL_RenderClear(renderer); /* start with a blank canvas. */
/* draw a filled rectangle in the middle of the canvas. */

38
examples/renderer/17-read-pixels/read-pixels.c
View File

@@ -19,9 +19,11 @@
static SDL_Window *window = NULL;
static SDL_Renderer *renderer = NULL;
static SDL_Texture *texture = NULL;
static SDL_Texture *converted_texture = NULL;
static int texture_width = 0;
static int texture_height = 0;
static SDL_Texture *converted_texture = NULL;
static int converted_texture_width = 0;
static int converted_texture_height = 0;
#define WINDOW_WIDTH 640
#define WINDOW_HEIGHT 480
@@ -68,12 +70,6 @@ SDL_AppResult SDL_AppInit(void **appstate, int argc, char *argv[])
SDL_DestroySurface(surface); /* done with this, the texture has a copy of the pixels now. */
converted_texture = SDL_CreateTexture(renderer, SDL_PIXELFORMAT_RGBA8888, SDL_TEXTUREACCESS_STREAMING, WINDOW_WIDTH, WINDOW_HEIGHT);
if (!texture) {
SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR, "Couldn't create conversion texture!", SDL_GetError(), NULL);
return SDL_APP_FAILURE;
}
return SDL_APP_CONTINUE; /* carry on with the program! */
}
@@ -111,8 +107,13 @@ SDL_AppResult SDL_AppIterate(void *appstate)
center.y = texture_height / 2.0f;
SDL_RenderTextureRotated(renderer, texture, NULL, &dst_rect, rotation, &center, SDL_FLIP_NONE);
/* this whole thing is _super_ expensive. Seriously, don't do this in real life. */
/* this next whole thing is _super_ expensive. Seriously, don't do this in real life. */
/* Download the pixels of what has just been rendered. This has to wait for the GPU to finish rendering it and everything before it,
and then make an expensive copy from the GPU to system RAM! */
surface = SDL_RenderReadPixels(renderer, NULL);
/* This is also expensive, but easier: convert the pixels to a format we want. */
if (surface && (surface->format != SDL_PIXELFORMAT_RGBA8888) && (surface->format != SDL_PIXELFORMAT_BGRA8888)) {
SDL_Surface *converted = SDL_ConvertSurface(surface, SDL_PIXELFORMAT_RGBA8888);
SDL_DestroySurface(surface);
@@ -120,6 +121,18 @@ SDL_AppResult SDL_AppIterate(void *appstate)
}
if (surface) {
/* Rebuild converted_texture if the dimensions have changed (window resized, etc). */
if ((surface->w != converted_texture_width) || (surface->h != converted_texture_height)) {
SDL_DestroyTexture(converted_texture);
converted_texture = SDL_CreateTexture(renderer, SDL_PIXELFORMAT_RGBA8888, SDL_TEXTUREACCESS_STREAMING, surface->w, surface->h);
if (!converted_texture) {
SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR, "Couldn't (re)create conversion texture!", SDL_GetError(), NULL);
return SDL_APP_FAILURE;
}
converted_texture_width = surface->w;
converted_texture_height = surface->h;
}
/* Turn each pixel into either black or white. This is a lousy technique but it works here.
In real life, something like Floyd-Steinberg dithering might work
better: https://en.wikipedia.org/wiki/Floyd%E2%80%93Steinberg_dithering*/
@@ -130,9 +143,10 @@ SDL_AppResult SDL_AppIterate(void *appstate)
Uint8 *p = (Uint8 *) (&pixels[x]);
const Uint32 average = (((Uint32) p[1]) + ((Uint32) p[2]) + ((Uint32) p[3])) / 3;
if (average == 0) {
p[0] = 0; // turn off alpha for pure black pixels.
p[0] = p[3] = 0xFF; p[1] = p[2] = 0; /* make pure black pixels red. */
} else {
p[1] = p[2] = p[3] = (average > 50) ? 0xFF : 0x00; /* make everything else either black or white. */
}
p[1] = p[2] = p[3] = (average > 50) ? 0xFF : 0x00;
}
}
@@ -142,8 +156,8 @@ SDL_AppResult SDL_AppIterate(void *appstate)
/* draw the texture to the top-left of the screen. */
dst_rect.x = dst_rect.y = 0.0f;
dst_rect.w = ((float) WINDOW_WIDTH) / 2.0f;
dst_rect.h = ((float) WINDOW_WIDTH) / 2.0f;
dst_rect.w = ((float) WINDOW_WIDTH) / 4.0f;
dst_rect.h = ((float) WINDOW_HEIGHT) / 4.0f;
SDL_RenderTexture(renderer, converted_texture, NULL, &dst_rect);
}