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examples/pen/01-drawing-lines: Match render target size to renderer output.

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Otherwise, on HiDPI displays (like a retina iPad), the lines you draw don't
match where the pen is touching.
This commit is contained in:
Ryan C. Gordon
2024-12-28 14:58:53 -05:00
parent 0ad3a18937
commit c030e6f782
1 changed files with 6 additions and 1 deletions
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7
examples/pen/01-drawing-lines/drawing-lines.c
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@@ -23,6 +23,8 @@ static float previous_touch_y = -1.0f;
/* This function runs once at startup. */
SDL_AppResult SDL_AppInit(void **appstate, int argc, char *argv[])
{
int w, h;
SDL_SetAppMetadata("Example Pen Drawing Lines", "1.0", "com.example.pen-drawing-lines");
if (!SDL_Init(SDL_INIT_VIDEO)) {
@@ -37,7 +39,10 @@ SDL_AppResult SDL_AppInit(void **appstate, int argc, char *argv[])
/* we make a render target so we can draw lines to it and not have to record and redraw every pen stroke each frame.
Instead rendering a frame for us is a single texture draw. */
render_target = SDL_CreateTexture(renderer, SDL_PIXELFORMAT_RGBA8888, SDL_TEXTUREACCESS_TARGET, 640, 480);
/* make sure the render target matches output size (for hidpi displays, etc) so drawing matches the pen's position on a tablet display. */
SDL_GetRenderOutputSize(renderer, &w, &h);
render_target = SDL_CreateTexture(renderer, SDL_PIXELFORMAT_RGBA8888, SDL_TEXTUREACCESS_TARGET, w, h);
if (!render_target) {
SDL_Log("Couldn't create render target: %s", SDL_GetError());
return SDL_APP_FAILURE;