examples: added input/01-joystick-polling

examples/CMakeLists.txt

@@ -140,6 +140,7 @@ add_sdl_example_executable(audio-simple-playback SOURCES audio/01-simple-playbac
 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)
 add_sdl_example_executable(audio-multiple-streams SOURCES audio/04-multiple-streams/multiple-streams.c)
+add_sdl_example_executable(input-joystick-polling SOURCES input/01-joystick-polling/joystick-polling.c)
 add_sdl_example_executable(camera-read-and-draw SOURCES camera/01-read-and-draw/read-and-draw.c)
 add_sdl_example_executable(pen-drawing-lines SOURCES pen/01-drawing-lines/drawing-lines.c)
 add_sdl_example_executable(demo-snake SOURCES demo/01-snake/snake.c)

examples/input/01-joystick-polling/README.txt

@@ -0,0 +1,2 @@
+This example code looks for the current joystick state once per frame,
+and draws a visual representation of it.

examples/input/01-joystick-polling/joystick-polling.c

@@ -0,0 +1,193 @@
+/*
+ * This example code looks for the current joystick state once per frame,
+ * and draws a visual representation of it.
+ *
+ * This code is public domain. Feel free to use it for any purpose!
+ */
+
+/* Joysticks are low-level interfaces: there's something with a bunch of
+   buttons, axes and hats, in no understood order or position. This is
+   a flexible interface, but you'll need to build some sort of configuration
+   UI to let people tell you what button, etc, does what. On top of this
+   interface, SDL offers the "gamepad" API, which works with lots of devices,
+   and knows how to map arbitrary buttons and such to look like an
+   Xbox/PlayStation/etc gamepad. This is easier, and better, for many games,
+   but isn't necessarily a good fit for complex apps and hardware. A flight
+   simulator, a realistic racing game, etc, might want this interface instead
+   of gamepads. */
+
+/* SDL can handle multiple joysticks, but for simplicity, this program only
+   deals with the first stick it sees. */
+
+#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_Joystick *joystick = NULL;
+static SDL_Color colors[64];
+
+/* This function runs once at startup. */
+SDL_AppResult SDL_AppInit(void **appstate, int argc, char *argv[])
+{
+    int i;
+
+    SDL_SetAppMetadata("Example Input Joystick Polling", "1.0", "com.example.input-joystick-polling");
+
+    if (!SDL_Init(SDL_INIT_VIDEO | SDL_INIT_JOYSTICK)) {
+        SDL_Log("Couldn't initialize SDL: %s", SDL_GetError());
+        return SDL_APP_FAILURE;
+    }
+
+    if (!SDL_CreateWindowAndRenderer("examples/input/joystick-polling", 640, 480, 0, &window, &renderer)) {
+        SDL_Log("Couldn't create window/renderer: %s", SDL_GetError());
+        return SDL_APP_FAILURE;
+    }
+
+    for (i = 0; i < SDL_arraysize(colors); i++) {
+        colors[i].r = SDL_rand(255);
+        colors[i].g = SDL_rand(255);
+        colors[i].b = SDL_rand(255);
+        colors[i].a = 255;
+    }
+
+    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. */
+    } else if (event->type == SDL_EVENT_JOYSTICK_ADDED) {
+        /* this event is sent for each hotplugged stick, but also each already-connected joystick during SDL_Init(). */
+        if (joystick == NULL) {  /* we don't have a stick yet and one was added, open it! */
+            joystick = SDL_OpenJoystick(event->jdevice.which);
+            if (!joystick) {
+                SDL_Log("Failed to open joystick ID %u: %s", (unsigned int) event->jdevice.which, SDL_GetError());
+            }
+        }
+    } else if (event->type == SDL_EVENT_JOYSTICK_REMOVED) {
+        if (joystick && (SDL_GetJoystickID(joystick) == event->jdevice.which)) {
+            SDL_CloseJoystick(joystick);  /* our joystick was unplugged. */
+            joystick = NULL;
+        }
+    }
+    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)
+{
+    int winw = 640, winh = 480;
+    const char *text = "Plug in a joystick, please.";
+    float x, y;
+    int i;
+
+    if (joystick) {  /* we have a stick opened? */
+        text = SDL_GetJoystickName(joystick);
+    }
+
+    SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
+    SDL_RenderClear(renderer);
+    SDL_GetWindowSize(window, &winw, &winh);
+
+    /* note that you can get input as events, instead of polling, which is
+       better since it won't miss button presses if the system is lagging,
+       but often times checking the current state per-frame is good enough,
+       and maybe better if you'd rather _drop_ inputs due to lag. */
+
+    if (joystick) {  /* we have a stick opened? */
+        const float size = 30.0f;
+        int total;
+
+        /* draw axes as bars going across middle of screen. We don't know if it's an X or Y or whatever axis, so we can't do more than this. */
+        total = SDL_GetNumJoystickAxes(joystick);
+        y = (float) ((winh - (total * size)) / 2);
+        x = ((float) winw) / 2.0f;
+        for (i = 0; i < total; i++) {
+            const SDL_Color *color = &colors[i % SDL_arraysize(colors)];
+            const float val = (((float) SDL_GetJoystickAxis(joystick, i)) / 32767.0f);  /* make it -1.0f to 1.0f */
+            const float dx = x + (val * x);
+            const SDL_FRect dst = { dx, y, x - SDL_fabsf(dx), size };
+            SDL_SetRenderDrawColor(renderer, color->r, color->g, color->b, color->a);
+            SDL_RenderFillRect(renderer, &dst);
+            y += size;
+        }
+
+        /* draw buttons as blocks across top of window. We only know the button numbers, but not where they are on the device. */
+        total = SDL_GetNumJoystickButtons(joystick);
+        x = (float) ((winw - (total * size)) / 2);
+        for (i = 0; i < total; i++) {
+            const SDL_Color *color = &colors[i % SDL_arraysize(colors)];
+            const SDL_FRect dst = { x, 0.0f, size, size };
+            if (SDL_GetJoystickButton(joystick, i)) {
+                SDL_SetRenderDrawColor(renderer, color->r, color->g, color->b, color->a);
+            } else {
+                SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
+            }
+            SDL_RenderFillRect(renderer, &dst);
+            SDL_SetRenderDrawColor(renderer, 255, 255, 255, color->a);
+            SDL_RenderRect(renderer, &dst);  /* outline it */
+            x += size;
+        }
+
+        /* draw hats across the bottom of the screen. */
+        total = SDL_GetNumJoystickHats(joystick);
+        x = ((float) ((winw - (total * (size * 2.0f))) / 2.0f)) + (size / 2.0f);
+        y = ((float) winh) - size;
+        for (i = 0; i < total; i++) {
+            const SDL_Color *color = &colors[i % SDL_arraysize(colors)];
+            const float thirdsize = size / 3.0f;
+            const SDL_FRect cross[] = { { x, y + thirdsize, size, thirdsize }, { x + thirdsize, y, thirdsize, size } };
+            const Uint8 hat = SDL_GetJoystickHat(joystick, i);
+
+            SDL_SetRenderDrawColor(renderer, 90, 90, 90, 255);
+            SDL_RenderFillRects(renderer, cross, SDL_arraysize(cross));
+
+            SDL_SetRenderDrawColor(renderer, color->r, color->g, color->b, color->a);
+
+            if (hat & SDL_HAT_UP) {
+                const SDL_FRect dst = { x + thirdsize, y, thirdsize, thirdsize };
+                SDL_RenderFillRect(renderer, &dst);
+            }
+
+            if (hat & SDL_HAT_RIGHT) {
+                const SDL_FRect dst = { x + (thirdsize * 2), y + thirdsize, thirdsize, thirdsize };
+                SDL_RenderFillRect(renderer, &dst);
+            }
+
+            if (hat & SDL_HAT_DOWN) {
+                const SDL_FRect dst = { x + thirdsize, y + (thirdsize * 2), thirdsize, thirdsize };
+                SDL_RenderFillRect(renderer, &dst);
+            }
+
+            if (hat & SDL_HAT_LEFT) {
+                const SDL_FRect dst = { x, y + thirdsize, thirdsize, thirdsize };
+                SDL_RenderFillRect(renderer, &dst);
+            }
+
+            x += size * 2;
+        }
+    }
+
+    x = (((float) winw) - (SDL_strlen(text) * SDL_DEBUG_TEXT_FONT_CHARACTER_SIZE)) / 2.0f;
+    y = (((float) winh) - SDL_DEBUG_TEXT_FONT_CHARACTER_SIZE) / 2.0f;
+    SDL_SetRenderDrawColor(renderer, 255, 255, 255, 255);
+    SDL_RenderDebugText(renderer, x, y, text);
+    SDL_RenderPresent(renderer);
+
+    return SDL_APP_CONTINUE;  /* carry on with the program! */
+}
+
+/* This function runs once at shutdown. */
+void SDL_AppQuit(void *appstate, SDL_AppResult result)
+{
+    if (joystick) {
+        SDL_CloseJoystick(joystick);
+    }
+
+    /* SDL will clean up the window/renderer for us. */
+}