From 3413617cb6487b93d8181772faa80c8743abed46 Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Thu, 19 Sep 2024 15:07:36 -0400
Subject: [PATCH] examples: added renderer/04-points
---
examples/CMakeLists.txt | 1 +
examples/renderer/02-primitives/README.txt | 4 +
examples/renderer/03-lines/renderer-lines.c | 2 +-
examples/renderer/04-points/README.txt | 3 +
examples/renderer/04-points/renderer-points.c | 118 ++++++++++++++++++
5 files changed, 127 insertions(+), 1 deletion(-)
create mode 100644 examples/renderer/04-points/README.txt
create mode 100644 examples/renderer/04-points/renderer-points.c
diff --git a/examples/CMakeLists.txt b/examples/CMakeLists.txt
index 7a3498a1dcf06..fb4db69fa2a3f 100644
--- a/examples/CMakeLists.txt
+++ b/examples/CMakeLists.txt
@@ -123,6 +123,7 @@ endmacro()
add_sdl_example_executable(renderer-clear SOURCES renderer/01-clear/renderer-clear.c)
add_sdl_example_executable(renderer-primitives SOURCES renderer/02-primitives/renderer-primitives.c)
add_sdl_example_executable(renderer-lines SOURCES renderer/03-lines/renderer-lines.c)
+add_sdl_example_executable(renderer-points SOURCES renderer/04-points/renderer-points.c)
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/02-primitives/README.txt b/examples/renderer/02-primitives/README.txt
index 1e2bfce8b794e..82da8e52f5e8c 100644
--- a/examples/renderer/02-primitives/README.txt
+++ b/examples/renderer/02-primitives/README.txt
@@ -1,3 +1,7 @@
This example creates an SDL window and renderer, and then draws some lines,
rectangles and points to it every frame.
+This is just a quick overview of simple drawing primitives; futher examples
+will explore them in more detail.
+
+
diff --git a/examples/renderer/03-lines/renderer-lines.c b/examples/renderer/03-lines/renderer-lines.c
index b2c8cf2cc7826..459af73d1cae6 100644
--- a/examples/renderer/03-lines/renderer-lines.c
+++ b/examples/renderer/03-lines/renderer-lines.c
@@ -56,7 +56,7 @@ SDL_AppResult SDL_AppIterate(void *appstate)
};
/* as you can see from this, rendering draws over whatever was drawn before it. */
- SDL_SetRenderDrawColor(renderer, 100, 100, 100, 255); /* black, full alpha */
+ SDL_SetRenderDrawColor(renderer, 100, 100, 100, 255); /* grey, full alpha */
SDL_RenderClear(renderer); /* start with a blank canvas. */
/* You can draw lines, one at a time, like these brown ones... */
diff --git a/examples/renderer/04-points/README.txt b/examples/renderer/04-points/README.txt
new file mode 100644
index 0000000000000..00e941911f4a8
--- /dev/null
+++ b/examples/renderer/04-points/README.txt
@@ -0,0 +1,3 @@
+This example creates an SDL window and renderer, and then draws a bunch of
+single points, moving across the screen.
+
diff --git a/examples/renderer/04-points/renderer-points.c b/examples/renderer/04-points/renderer-points.c
new file mode 100644
index 0000000000000..468a30abd4a2e
--- /dev/null
+++ b/examples/renderer/04-points/renderer-points.c
@@ -0,0 +1,118 @@
+/*
+ * This example creates an SDL window and renderer, and then draws some points
+ * to it every frame.
+ *
+ * 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 Uint64 last_time = 0;
+
+#define WINDOW_WIDTH 640
+#define WINDOW_HEIGHT 480
+
+#define NUM_POINTS 500
+#define MIN_PIXELS_PER_SECOND 30 /* move at least this many pixels per second. */
+#define MAX_PIXELS_PER_SECOND 60 /* move this many pixels per second at most. */
+
+/* (track everything as parallel arrays instead of a array of structs,
+ so we can pass the coordinates to the renderer in a single function call.) */
+
+/* Points are plotted as a set of X and Y coordinates.
+ (0, 0) is the top left of the window, and larger numbers go down
+ and to the right. This isn't how geometry works, but this is pretty
+ standard in 2D graphics. */
+static SDL_FPoint points[NUM_POINTS];
+static float point_speeds[NUM_POINTS];
+
+/* This function runs once at startup. */
+SDL_AppResult SDL_AppInit(void **appstate, int argc, char *argv[])
+{
+ int i;
+
+ 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/points", WINDOW_WIDTH, WINDOW_HEIGHT, 0, &window, &renderer)) {
+ SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR, "Couldn't create window/renderer!", SDL_GetError(), NULL);
+ return SDL_APP_FAILURE;
+ }
+
+ SDL_srand(0); /* seed the random number generator */
+
+ /* set up the data for a bunch of points. */
+ for (i = 0; i < SDL_arraysize(points); i++) {
+ points[i].x = SDL_randf() * ((float) WINDOW_WIDTH);
+ points[i].y = SDL_randf() * ((float) WINDOW_HEIGHT);
+ point_speeds[i] = MIN_PIXELS_PER_SECOND + (SDL_randf() * (MAX_PIXELS_PER_SECOND - MIN_PIXELS_PER_SECOND));
+ }
+
+ last_time = SDL_GetTicks();
+
+ 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 Uint64 now = SDL_GetTicks();
+ const float elapsed = ((float) (now - last_time)) / 1000.0f; /* seconds since last iteration */
+ int i;
+
+ /* let's move all our points a little for a new frame. */
+ for (i = 0; i < SDL_arraysize(points); i++) {
+ const float distance = elapsed * point_speeds[i];
+ points[i].x += distance;
+ points[i].y += distance;
+ if ((points[i].x >= WINDOW_WIDTH) || (points[i].y >= WINDOW_HEIGHT)) {
+ /* off the screen; restart it elsewhere! */
+ if (SDL_rand(2)) {
+ points[i].x = SDL_randf() * ((float) WINDOW_WIDTH);
+ points[i].y = 0.0f;
+ } else {
+ points[i].x = 0.0f;
+ points[i].y = SDL_randf() * ((float) WINDOW_HEIGHT);
+ }
+ point_speeds[i] = MIN_PIXELS_PER_SECOND + (SDL_randf() * (MAX_PIXELS_PER_SECOND - MIN_PIXELS_PER_SECOND));
+ }
+ }
+
+ last_time = now;
+
+ /* 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. */
+ SDL_SetRenderDrawColor(renderer, 255, 255, 255, 255); /* white, full alpha */
+ SDL_RenderPoints(renderer, points, SDL_arraysize(points)); /* draw all the points! */
+
+ /* You can also draw single points with SDL_RenderPoint(), but it's
+ cheaper (sometimes significantly so) to do them all at once. */
+
+ 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 will clean up the window/renderer for us. */
+}
+