From c030e6f782d8641e7bd8c1dc2d58788cab4f2e4d Mon Sep 17 00:00:00 2001 From: "Ryan C. Gordon" Date: Sat, 28 Dec 2024 14:58:53 -0500 Subject: [PATCH] examples/pen/01-drawing-lines: Match render target size to renderer output. Otherwise, on HiDPI displays (like a retina iPad), the lines you draw don't match where the pen is touching. --- examples/pen/01-drawing-lines/drawing-lines.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/examples/pen/01-drawing-lines/drawing-lines.c b/examples/pen/01-drawing-lines/drawing-lines.c index 6d2430acd0..a530ab60fd 100644 --- a/examples/pen/01-drawing-lines/drawing-lines.c +++ b/examples/pen/01-drawing-lines/drawing-lines.c @@ -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;