From 95134f6d58da5c7ad2cfc796861720dc6eb0b28c Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Tue, 24 Sep 2024 13:54:35 -0400
Subject: [PATCH] examples: Added renderer/15-cliprect
---
examples/CMakeLists.txt | 1 +
examples/renderer/15-cliprect/README.txt | 5 +
examples/renderer/15-cliprect/cliprect.c | 135 +++++++++++++++++++++++
3 files changed, 141 insertions(+)
create mode 100644 examples/renderer/15-cliprect/README.txt
create mode 100644 examples/renderer/15-cliprect/cliprect.c
diff --git a/examples/CMakeLists.txt b/examples/CMakeLists.txt
index 3ee5c00a1a81c..5de17c5737315 100644
--- a/examples/CMakeLists.txt
+++ b/examples/CMakeLists.txt
@@ -132,6 +132,7 @@ add_sdl_example_executable(renderer-scaling-textures SOURCES renderer/09-scaling
add_sdl_example_executable(renderer-geometry SOURCES renderer/10-geometry/geometry.c DATAFILES ${CMAKE_CURRENT_SOURCE_DIR}/../test/sample.bmp)
add_sdl_example_executable(renderer-color-mods SOURCES renderer/11-color-mods/color-mods.c DATAFILES ${CMAKE_CURRENT_SOURCE_DIR}/../test/sample.bmp)
add_sdl_example_executable(renderer-viewport SOURCES renderer/14-viewport/viewport.c DATAFILES ${CMAKE_CURRENT_SOURCE_DIR}/../test/sample.bmp)
+add_sdl_example_executable(renderer-cliprect SOURCES renderer/15-cliprect/cliprect.c DATAFILES ${CMAKE_CURRENT_SOURCE_DIR}/../test/sample.bmp)
add_sdl_example_executable(audio-simple-playback SOURCES audio/01-simple-playback/simple-playback.c)
add_sdl_example_executable(audio-simple-playback-callback SOURCES audio/02-simple-playback-callback/simple-playback-callback.c)
add_sdl_example_executable(audio-load-wav SOURCES audio/03-load-wav/load-wav.c DATAFILES ${CMAKE_CURRENT_SOURCE_DIR}/../test/sample.wav)
diff --git a/examples/renderer/15-cliprect/README.txt b/examples/renderer/15-cliprect/README.txt
new file mode 100644
index 0000000000000..48c9f1fed37ee
--- /dev/null
+++ b/examples/renderer/15-cliprect/README.txt
@@ -0,0 +1,5 @@
+This example creates an SDL window and renderer, loads a texture
+from a .bmp file, and stretches it across the window. Each frame, we move
+the clipping rectangle around, so only a small square of the texture is
+actually drawn.
+
diff --git a/examples/renderer/15-cliprect/cliprect.c b/examples/renderer/15-cliprect/cliprect.c
new file mode 100644
index 0000000000000..5e17b3ab7251f
--- /dev/null
+++ b/examples/renderer/15-cliprect/cliprect.c
@@ -0,0 +1,135 @@
+/*
+ * This example creates an SDL window and renderer, and then draws a scene
+ * to it every frame, while sliding around a clipping rectangle.
+ *
+ * This code is public domain. Feel free to use it for any purpose!
+ */
+
+#define SDL_MAIN_USE_CALLBACKS 1 /* use the callbacks instead of main() */
+#include <SDL3/SDL.h>
+#include <SDL3/SDL_main.h>
+
+#define WINDOW_WIDTH 640
+#define WINDOW_HEIGHT 480
+#define CLIPRECT_SIZE 250
+#define CLIPRECT_SPEED 200 /* pixels per second */
+
+/* We will use this renderer to draw into this window every frame. */
+static SDL_Window *window = NULL;
+static SDL_Renderer *renderer = NULL;
+static SDL_Texture *texture = NULL;
+static SDL_FPoint cliprect_position;
+static SDL_FPoint cliprect_direction;
+static Uint64 last_time = 0;
+
+/* A lot of this program is examples/renderer/02-primitives, so we have a good
+ visual that we can slide a clip rect around. The actual new magic in here
+ is the SDL_SetRenderClipRect() function. */
+
+/* This function runs once at startup. */
+SDL_AppResult SDL_AppInit(void **appstate, int argc, char *argv[])
+{
+ SDL_Surface *surface = NULL;
+ char *bmp_path = NULL;
+
+ if (!SDL_Init(SDL_INIT_VIDEO)) {
+ SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR, "Couldn't initialize SDL!", SDL_GetError(), NULL);
+ return SDL_APP_FAILURE;
+ }
+
+ if (!SDL_CreateWindowAndRenderer("examples/renderer/primitives", WINDOW_WIDTH, WINDOW_HEIGHT, 0, &window, &renderer)) {
+ SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR, "Couldn't create window/renderer!", SDL_GetError(), NULL);
+ return SDL_APP_FAILURE;
+ }
+
+ cliprect_direction.x = cliprect_direction.y = 1.0f;
+
+ last_time = SDL_GetTicks();
+
+ /* Textures are pixel data that we upload to the video hardware for fast drawing. Lots of 2D
+ engines refer to these as "sprites." We'll do a static texture (upload once, draw many
+ times) with data from a bitmap file. */
+
+ /* SDL_Surface is pixel data the CPU can access. SDL_Texture is pixel data the GPU can access.
+ Load a .bmp into a surface, move it to a texture from there. */
+ SDL_asprintf(&bmp_path, "%ssample.bmp", SDL_GetBasePath()); /* allocate a string of the full file path */
+ surface = SDL_LoadBMP(bmp_path);
+ if (!surface) {
+ SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR, "Couldn't load bitmap!", SDL_GetError(), NULL);
+ return SDL_APP_FAILURE;
+ }
+
+ SDL_free(bmp_path); /* done with this, the file is loaded. */
+
+ texture = SDL_CreateTextureFromSurface(renderer, surface);
+ if (!texture) {
+ SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR, "Couldn't create static texture!", SDL_GetError(), NULL);
+ return SDL_APP_FAILURE;
+ }
+
+ SDL_DestroySurface(surface); /* done with this, the texture has a copy of the pixels now. */
+
+ return SDL_APP_CONTINUE; /* carry on with the program! */
+}
+
+/* This function runs when a new event (mouse input, keypresses, etc) occurs. */
+SDL_AppResult SDL_AppEvent(void *appstate, SDL_Event *event)
+{
+ if (event->type == SDL_EVENT_QUIT) {
+ return SDL_APP_SUCCESS; /* end the program, reporting success to the OS. */
+ }
+ return SDL_APP_CONTINUE; /* carry on with the program! */
+}
+
+/* This function runs once per frame, and is the heart of the program. */
+SDL_AppResult SDL_AppIterate(void *appstate)
+{
+ const SDL_Rect cliprect = { (int) SDL_roundf(cliprect_position.x), (int) SDL_roundf(cliprect_position.y), CLIPRECT_SIZE, CLIPRECT_SIZE };
+ const Uint64 now = SDL_GetTicks();
+ const float elapsed = ((float) (now - last_time)) / 1000.0f; /* seconds since last iteration */
+ const float distance = elapsed * CLIPRECT_SPEED;
+
+ /* Set a new clipping rectangle position */
+ cliprect_position.x += distance * cliprect_direction.x;
+ if (cliprect_position.x < 0.0f) {
+ cliprect_position.x = 0.0f;
+ cliprect_direction.x = 1.0f;
+ } else if (cliprect_position.x >= (WINDOW_WIDTH - CLIPRECT_SIZE)) {
+ cliprect_position.x = (WINDOW_WIDTH - CLIPRECT_SIZE) - 1;
+ cliprect_direction.x = -1.0f;
+ }
+
+ cliprect_position.y += distance * cliprect_direction.y;
+ if (cliprect_position.y < 0.0f) {
+ cliprect_position.y = 0.0f;
+ cliprect_direction.y = 1.0f;
+ } else if (cliprect_position.y >= (WINDOW_HEIGHT - CLIPRECT_SIZE)) {
+ cliprect_position.y = (WINDOW_HEIGHT - CLIPRECT_SIZE) - 1;
+ cliprect_direction.y = -1.0f;
+ }
+ SDL_SetRenderClipRect(renderer, &cliprect);
+
+ last_time = now;
+
+ /* okay, now draw! */
+
+ /* Note that SDL_RenderClear is _not_ affected by the clipping rectangle! */
+ SDL_SetRenderDrawColor(renderer, 33, 33, 33, 255); /* grey, full alpha */
+ SDL_RenderClear(renderer); /* start with a blank canvas. */
+
+ /* stretch the texture across the entire window. Only the piece in the
+ clipping rectangle will actually render, though! */
+ SDL_RenderTexture(renderer, texture, NULL, NULL);
+
+ SDL_RenderPresent(renderer); /* put it all on the screen! */
+
+ return SDL_APP_CONTINUE; /* carry on with the program! */
+}
+
+/* This function runs once at shutdown. */
+void SDL_AppQuit(void *appstate)
+{
+ SDL_DestroyTexture(texture);
+ /* SDL will clean up the window/renderer for us. */
+}
+