Gamepad code in SDL3 C code

examples/sdl-gamepad-example.c

@@ -0,0 +1,103 @@
+#define SDL_MAIN_USE_CALLBACKS
+
+#include <SDL3/SDL.h>
+#include <SDL3/SDL_main.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+
+static const int WIDTH = 800;
+static const int HEIGHT = 600;
+
+typedef struct {
+    SDL_Window* window;
+    SDL_Renderer* renderer;
+
+    SDL_Gamepad* gamepad;
+} AppState;
+
+SDL_AppResult SDL_AppInit(void ** appstate, int argc, char** argv) {
+    AppState* app_state = malloc(sizeof(AppState));
+    *app_state = (AppState){};
+    *appstate = app_state;
+
+    if (!SDL_Init(SDL_INIT_VIDEO | SDL_INIT_CAMERA | SDL_INIT_GAMEPAD)) {
+        SDL_Log("couldn't initialize properly: %s", SDL_GetError());
+        return SDL_APP_FAILURE;
+    }
+
+    if (!SDL_CreateWindowAndRenderer("SDL3 Gamepad Demo", WIDTH, HEIGHT, 0, &(app_state->window), &(app_state->renderer))) {
+        SDL_Log("couldn't initialize window/renderer properly: %s", SDL_GetError());
+        return SDL_APP_FAILURE;
+
+    }
+
+    return SDL_APP_CONTINUE;
+}
+
+SDL_AppResult SDL_AppIterate(void* appstate) {
+
+    AppState* app_state = appstate;
+
+    SDL_Gamepad* gamepad = app_state->gamepad;
+    if (gamepad) {  /* we have a stick opened? */
+
+        Sint16 leftx = SDL_GetGamepadAxis(gamepad, SDL_GAMEPAD_AXIS_LEFTX);
+        Sint16 lefty = SDL_GetGamepadAxis(gamepad, SDL_GAMEPAD_AXIS_LEFTY);
+
+        Sint16 rightx = SDL_GetGamepadAxis(gamepad, SDL_GAMEPAD_AXIS_RIGHTX);
+        Sint16 righty = SDL_GetGamepadAxis(gamepad, SDL_GAMEPAD_AXIS_RIGHTY);
+
+        Sint16 left_trigger = SDL_GetGamepadAxis(gamepad, SDL_GAMEPAD_AXIS_LEFT_TRIGGER);
+        Sint16 right_trigger = SDL_GetGamepadAxis(gamepad, SDL_GAMEPAD_AXIS_RIGHT_TRIGGER);
+
+        SDL_Log("left_x: %d, left_y: %d", leftx, lefty);
+        SDL_Log("right_x: %d, right_y: %d", rightx, righty);
+        SDL_Log("left_trigger: %d, right_trigger: %d", left_trigger, right_trigger);
+    }
+
+    SDL_Renderer* renderer = app_state->renderer;
+
+    const double now = ((double)SDL_GetTicks()) / 1000.0;  /* convert from milliseconds to seconds. */
+    const float red = (float) (0.5 + 0.5 * SDL_sin(now));
+    const float green = (float) (0.5 + 0.5 * SDL_sin(now + SDL_PI_D * 2 / 3));
+    const float blue = (float) (0.5 + 0.5 * SDL_sin(now + SDL_PI_D * 4 / 3));
+
+    SDL_SetRenderDrawColorFloat(renderer, red, green, blue, SDL_ALPHA_OPAQUE_FLOAT);  /* new color, full alpha. */
+    /* clear the window to the draw color. */
+    SDL_RenderClear(renderer);
+
+    /* put the newly-cleared rendering on the screen. */
+    SDL_RenderPresent(renderer);
+
+    return SDL_APP_CONTINUE;
+}
+
+SDL_AppResult SDL_AppEvent(void* appstate, SDL_Event *event) {
+    AppState* app_state = (AppState*) appstate;
+
+    if (event->type == SDL_EVENT_QUIT) {
+        return SDL_APP_SUCCESS;
+    } else if (event->type == SDL_EVENT_GAMEPAD_ADDED) {
+        if (app_state->gamepad == NULL) {
+            SDL_Gamepad* pad = SDL_OpenGamepad(event->gdevice.which);
+            if (!pad) {
+                SDL_Log("Failed to open gamepad ID %u: %s", (unsigned int) event->gdevice.which, SDL_GetError());
+            } else {
+                const char* gamepad_name = SDL_GetGamepadName(pad);
+                SDL_Log("Opening gamepad ID: %u", event->gdevice.which);
+                SDL_Log("Gamepad name: %s", gamepad_name);
+                app_state->gamepad = pad;
+            }
+        }
+    } else if (event->type == SDL_EVENT_GAMEPAD_REMOVED) {
+        SDL_Log("Removing gamepad ID: %u", event->gdevice.which);
+        if (app_state->gamepad && (SDL_GetGamepadID(app_state->gamepad) == event->gdevice.which)) {
+            SDL_CloseGamepad(app_state->gamepad);  /* our controller was unplugged. */
+            app_state->gamepad = NULL;
+        }
+    }
+    return SDL_APP_CONTINUE;
+}
+
+void SDL_AppQuit(void* appstate, SDL_AppResult result) {}

justfile

@@ -38,6 +38,10 @@ _perform_nix_patch binary-name:
 build-c-webcam-demo:
     @just _build-c-example examples/sdl-webcam-example.c c-webcam-example
 
+[group: "C_build"]
+build-c-gamepad-example:
+    @just _build-c-example examples/sdl-gamepad-example.c c-gamepad-example
+
 # Build one of the C SDL3 examples
 [group: "C_build"]
 _build-c-example c-sourcefile binary-name: