examples: Added input/02-joystick-events

examples/CMakeLists.txt

@@ -141,6 +141,7 @@ add_sdl_example_executable(audio-simple-playback-callback SOURCES audio/02-simpl
 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(input-joystick-events SOURCES input/02-joystick-events/joystick-events.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/02-joystick-events/README.txt

@@ -0,0 +1,2 @@
+This example code looks for joystick input in the event handler, and
+reports any changes as a flood of info.

examples/input/02-joystick-events/joystick-events.c

@@ -0,0 +1,232 @@
+/*
+ * This example code looks for joystick input in the event handler, and
+ * reports any changes as a flood of info.
+ *
+ * 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. */
+
+#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_Color colors[64];
+
+#define MOTION_EVENT_COOLDOWN 40
+
+typedef struct EventMessage
+{
+    char *str;
+    SDL_Color color;
+    Uint64 start_ticks;
+    struct EventMessage *next;
+} EventMessage;
+
+static EventMessage messages;
+static EventMessage *messages_tail = &messages;
+
+static const char *hat_state_string(Uint8 state)
+{
+    switch (state) {
+        case SDL_HAT_CENTERED: return "CENTERED";
+        case SDL_HAT_UP: return "UP";
+        case SDL_HAT_RIGHT: return "RIGHT";
+        case SDL_HAT_DOWN: return "DOWN";
+        case SDL_HAT_LEFT: return "LEFT";
+        case SDL_HAT_RIGHTUP: return "RIGHT+UP";
+        case SDL_HAT_RIGHTDOWN: return "RIGHT+DOWN";
+        case SDL_HAT_LEFTUP: return "LEFT+UP";
+        case SDL_HAT_LEFTDOWN: return "LEFT+DOWN";
+        default: break;
+    }
+    return "UNKNOWN";
+}
+
+static const char *battery_state_string(SDL_PowerState state)
+{
+    switch (state) {
+        case SDL_POWERSTATE_ERROR: return "ERROR";
+        case SDL_POWERSTATE_UNKNOWN: return "UNKNOWN";
+        case SDL_POWERSTATE_ON_BATTERY: return "ON BATTERY";
+        case SDL_POWERSTATE_NO_BATTERY: return "NO BATTERY";
+        case SDL_POWERSTATE_CHARGING: return "CHARGING";
+        case SDL_POWERSTATE_CHARGED: return "CHARGED";
+        default: break;
+    }
+    return "UNKNOWN";
+}
+
+static void add_message(SDL_JoystickID jid, const char *fmt, ...)
+{
+    const SDL_Color *color = &colors[((size_t) jid) % SDL_arraysize(colors)];
+    EventMessage *msg = NULL;
+    char *str = NULL;
+    va_list ap;
+
+    msg = (EventMessage *) SDL_calloc(1, sizeof (*msg));
+    if (!msg) {
+        return;  // oh well.
+    }
+
+    va_start(ap, fmt);
+    SDL_vasprintf(&str, fmt, ap);
+    va_end(ap);
+    if (!str) {
+        SDL_free(msg);
+        return;  // oh well.
+    }
+
+    msg->str = str;
+    SDL_copyp(&msg->color, color);
+    msg->start_ticks = SDL_GetTicks();
+    msg->next = NULL;
+
+    messages_tail->next = msg;
+    messages_tail = msg;
+}
+
+
+/* This function runs once at startup. */
+SDL_AppResult SDL_AppInit(void **appstate, int argc, char *argv[])
+{
+    int i;
+
+    SDL_SetAppMetadata("Example Input Joystick Events", "1.0", "com.example.input-joystick-events");
+
+    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-events", 640, 480, 0, &window, &renderer)) {
+        SDL_Log("Couldn't create window/renderer: %s", SDL_GetError());
+        return SDL_APP_FAILURE;
+    }
+
+    colors[0].r = colors[0].g = colors[0].b = colors[0].a = 255;
+    for (i = 1; 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;
+    }
+
+    add_message(0, "Please plug in a joystick.");
+
+    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(). */
+        const SDL_JoystickID which = event->jdevice.which;
+        SDL_Joystick *joystick = SDL_OpenJoystick(which);
+        if (!joystick) {
+            add_message(which, "Joystick #%u add, but not opened: %s", (unsigned int) which, SDL_GetError());
+        } else {
+            add_message(which, "Joystick #%u ('%s') added", (unsigned int) which, SDL_GetJoystickName(joystick));
+        }
+    } else if (event->type == SDL_EVENT_JOYSTICK_REMOVED) {
+        const SDL_JoystickID which = event->jdevice.which;
+        SDL_Joystick *joystick = SDL_GetJoystickFromID(which);
+        if (joystick) {
+            SDL_CloseJoystick(joystick);  /* the joystick was unplugged. */
+        }
+        add_message(which, "Joystick #%u removed", (unsigned int) which);
+    } else if (event->type == SDL_EVENT_JOYSTICK_AXIS_MOTION) {
+        static Uint64 axis_motion_cooldown_time = 0;  /* these are spammy, only show every X milliseconds. */
+        const Uint64 now = SDL_GetTicks();
+        if (now >= axis_motion_cooldown_time) {
+            const SDL_JoystickID which = event->jaxis.which;
+            axis_motion_cooldown_time = now + MOTION_EVENT_COOLDOWN;
+            add_message(which, "Joystick #%u axis %d -> %d", (unsigned int) which, (int) event->jaxis.axis, (int) event->jaxis.value);
+        }
+    } else if (event->type == SDL_EVENT_JOYSTICK_BALL_MOTION) {
+        static Uint64 ball_motion_cooldown_time = 0;  /* these are spammy, only show every X milliseconds. */
+        const Uint64 now = SDL_GetTicks();
+        if (now >= ball_motion_cooldown_time) {
+            const SDL_JoystickID which = event->jball.which;
+            ball_motion_cooldown_time = now + MOTION_EVENT_COOLDOWN;
+            add_message(which, "Joystick #%u ball %d -> %d, %d", (unsigned int) which, (int) event->jball.ball, (int) event->jball.xrel, (int) event->jball.yrel);
+        }
+    } else if (event->type == SDL_EVENT_JOYSTICK_HAT_MOTION) {
+        const SDL_JoystickID which = event->jhat.which;
+        add_message(which, "Joystick #%u hat %d -> %s", (unsigned int) which, (int) event->jhat.hat, hat_state_string(event->jhat.value));
+    } else if ((event->type == SDL_EVENT_JOYSTICK_BUTTON_UP) || (event->type == SDL_EVENT_JOYSTICK_BUTTON_DOWN)) {
+        const SDL_JoystickID which = event->jbutton.which;
+        add_message(which, "Joystick #%u button %d -> %s", (unsigned int) which, (int) event->jbutton.button, event->jbutton.down ? "PRESSED" : "RELEASED");
+    } else if (event->type == SDL_EVENT_JOYSTICK_BATTERY_UPDATED) {
+        const SDL_JoystickID which = event->jbattery.which;
+        add_message(which, "Joystick #%u battery -> %s - %d%%", (unsigned int) which, battery_state_string(event->jbattery.state), event->jbattery.percent);
+    }
+
+    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 msg_lifetime = 3500.0f;  /* milliseconds a message lives for. */
+    EventMessage *msg = messages.next;
+    float prev_y = 0.0f;
+    int winw = 640, winh = 480;
+
+    SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
+    SDL_RenderClear(renderer);
+    SDL_GetWindowSize(window, &winw, &winh);
+
+    while (msg) {
+        float x, y;
+        const float life_percent = ((float) (now - msg->start_ticks)) / msg_lifetime;
+        if (life_percent >= 1.0f) {  /* msg is done. */
+            messages.next = msg->next;
+            if (messages_tail == msg) {
+                messages_tail = &messages;
+            }
+            SDL_free(msg->str);
+            SDL_free(msg);
+            msg = messages.next;
+            continue;
+        }
+        x = (((float) winw) - (SDL_strlen(msg->str) * SDL_DEBUG_TEXT_FONT_CHARACTER_SIZE)) / 2.0f;
+        y = ((float) winh) * life_percent;
+        if ((prev_y != 0.0f) && ((prev_y - y) < ((float) SDL_DEBUG_TEXT_FONT_CHARACTER_SIZE))) {
+            msg->start_ticks = now;
+            break;  // wait for the previous message to tick up a little.
+        }
+
+        SDL_SetRenderDrawColor(renderer, msg->color.r, msg->color.g, msg->color.b, (Uint8) (((float) msg->color.a) * (1.0f - life_percent)));
+        SDL_RenderDebugText(renderer, x, y, msg->str);
+
+        prev_y = y;
+        msg = msg->next;
+    }
+
+    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)
+{
+    /* SDL will clean up the window/renderer for us. We let the joysticks leak. */
+}