From 1ed3dac02143321af05a8713b35b617a4349d411 Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Mon, 23 Sep 2024 14:13:53 -0400
Subject: [PATCH] examples: Added renderer/14-viewport
(This intentionally skips a few example numbers, as I intend to fill in some
other topics before this, later.)
---
examples/CMakeLists.txt | 1 +
examples/renderer/14-viewport/README.txt | 4 +
examples/renderer/14-viewport/viewport.c | 134 +++++++++++++++++++++++
3 files changed, 139 insertions(+)
create mode 100644 examples/renderer/14-viewport/README.txt
create mode 100644 examples/renderer/14-viewport/viewport.c
diff --git a/examples/CMakeLists.txt b/examples/CMakeLists.txt
index 92b02afb192da..3ee5c00a1a81c 100644
--- a/examples/CMakeLists.txt
+++ b/examples/CMakeLists.txt
@@ -131,6 +131,7 @@ add_sdl_example_executable(renderer-rotating-textures SOURCES renderer/08-rotati
add_sdl_example_executable(renderer-scaling-textures SOURCES renderer/09-scaling-textures/scaling-textures.c DATAFILES ${CMAKE_CURRENT_SOURCE_DIR}/../test/sample.bmp)
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(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/14-viewport/README.txt b/examples/renderer/14-viewport/README.txt
new file mode 100644
index 0000000000000..9da7c7ab15d27
--- /dev/null
+++ b/examples/renderer/14-viewport/README.txt
@@ -0,0 +1,4 @@
+This example creates an SDL window and renderer, loads a texture
+from a .bmp file, and then draws it a few times each frame, adjusting
+the viewport before each draw.
+
diff --git a/examples/renderer/14-viewport/viewport.c b/examples/renderer/14-viewport/viewport.c
new file mode 100644
index 0000000000000..3001a61dc63e2
--- /dev/null
+++ b/examples/renderer/14-viewport/viewport.c
@@ -0,0 +1,134 @@
+/*
+ * This example creates an SDL window and renderer, and then draws some
+ * textures to it every frame, adjusting the viewport.
+ *
+ * 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>
+
+/* 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 int texture_width = 0;
+static int texture_height = 0;
+
+#define WINDOW_WIDTH 640
+#define WINDOW_HEIGHT 480
+
+/* 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/viewport", WINDOW_WIDTH, WINDOW_HEIGHT, 0, &window, &renderer)) {
+ SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR, "Couldn't create window/renderer!", SDL_GetError(), NULL);
+ return SDL_APP_FAILURE;
+ }
+
+ /* 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_width = surface->w;
+ texture_height = surface->h;
+
+ 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)
+{
+ SDL_FRect dst_rect = { 0, 0, (float) texture_width, (float) texture_height };
+ SDL_Rect viewport;
+
+ /* Setting a viewport has the effect of limiting the area that rendering
+ can happen, and making coordinate (0, 0) live somewhere else in the
+ window. It does _not_ scale rendering to fit the viewport. */
+
+ /* 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_RenderClear(renderer); /* start with a blank canvas. */
+
+ /* Draw once with the whole window as the viewport. */
+ viewport.x = 0;
+ viewport.y = 0;
+ viewport.w = WINDOW_WIDTH / 2;
+ viewport.h = WINDOW_HEIGHT / 2;
+ SDL_SetRenderViewport(renderer, NULL); /* NULL means "use the whole window" */
+ SDL_RenderTexture(renderer, texture, NULL, &dst_rect);
+
+ /* top right quarter of the window. */
+ viewport.x = WINDOW_WIDTH / 2;
+ viewport.y = WINDOW_HEIGHT / 2;
+ viewport.w = WINDOW_WIDTH / 2;
+ viewport.h = WINDOW_HEIGHT / 2;
+ SDL_SetRenderViewport(renderer, &viewport);
+ SDL_RenderTexture(renderer, texture, NULL, &dst_rect);
+
+ /* bottom 20% of the window. Note it clips the width! */
+ viewport.x = 0;
+ viewport.y = WINDOW_HEIGHT - (WINDOW_HEIGHT / 5);
+ viewport.w = WINDOW_WIDTH / 5;
+ viewport.h = WINDOW_HEIGHT / 5;
+ SDL_SetRenderViewport(renderer, &viewport);
+ SDL_RenderTexture(renderer, texture, NULL, &dst_rect);
+
+ /* what happens if you try to draw above the viewport? It should clip! */
+ viewport.x = 100;
+ viewport.y = 200;
+ viewport.w = WINDOW_WIDTH;
+ viewport.h = WINDOW_HEIGHT;
+ SDL_SetRenderViewport(renderer, &viewport);
+ dst_rect.y = -50;
+ SDL_RenderTexture(renderer, texture, NULL, &dst_rect);
+
+ 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. */
+}
+