Handle SDL gamepad events

Introduce a gamepad processor trait, similar to the keyboard processor
and mouse processor traits.

Handle gamepad events received from SDL, convert them to scrcpy-specific
gamepad events, and forward them to the gamepad processor.

Further commits will provide AOA and UHID implementations of the gamepad
processor trait.

PR #5270 <https://github.com/Genymobile/scrcpy/pull/5270>

Co-authored-by: Luiz Henrique Laurini <luizhenriquelaurini@gmail.com>

app/src/input_events.h

@@ -323,6 +323,38 @@ enum sc_mouse_button {
     SC_MOUSE_BUTTON_X2 = SDL_BUTTON(SDL_BUTTON_X2),
 };
 
+// Use the naming from SDL3 for gamepad axis and buttons:
+// <https://wiki.libsdl.org/SDL3/README/migration>
+
+enum sc_gamepad_axis {
+    SC_GAMEPAD_AXIS_UNKNOWN = -1,
+    SC_GAMEPAD_AXIS_LEFTX = SDL_CONTROLLER_AXIS_LEFTX,
+    SC_GAMEPAD_AXIS_LEFTY = SDL_CONTROLLER_AXIS_LEFTY,
+    SC_GAMEPAD_AXIS_RIGHTX = SDL_CONTROLLER_AXIS_RIGHTX,
+    SC_GAMEPAD_AXIS_RIGHTY = SDL_CONTROLLER_AXIS_RIGHTY,
+    SC_GAMEPAD_AXIS_LEFT_TRIGGER = SDL_CONTROLLER_AXIS_TRIGGERLEFT,
+    SC_GAMEPAD_AXIS_RIGHT_TRIGGER = SDL_CONTROLLER_AXIS_TRIGGERRIGHT,
+};
+
+enum sc_gamepad_button {
+    SC_GAMEPAD_BUTTON_UNKNOWN = -1,
+    SC_GAMEPAD_BUTTON_SOUTH = SDL_CONTROLLER_BUTTON_A,
+    SC_GAMEPAD_BUTTON_EAST = SDL_CONTROLLER_BUTTON_B,
+    SC_GAMEPAD_BUTTON_WEST = SDL_CONTROLLER_BUTTON_X,
+    SC_GAMEPAD_BUTTON_NORTH = SDL_CONTROLLER_BUTTON_Y,
+    SC_GAMEPAD_BUTTON_BACK = SDL_CONTROLLER_BUTTON_BACK,
+    SC_GAMEPAD_BUTTON_GUIDE = SDL_CONTROLLER_BUTTON_GUIDE,
+    SC_GAMEPAD_BUTTON_START = SDL_CONTROLLER_BUTTON_START,
+    SC_GAMEPAD_BUTTON_LEFT_STICK = SDL_CONTROLLER_BUTTON_LEFTSTICK,
+    SC_GAMEPAD_BUTTON_RIGHT_STICK = SDL_CONTROLLER_BUTTON_RIGHTSTICK,
+    SC_GAMEPAD_BUTTON_LEFT_SHOULDER = SDL_CONTROLLER_BUTTON_LEFTSHOULDER,
+    SC_GAMEPAD_BUTTON_RIGHT_SHOULDER = SDL_CONTROLLER_BUTTON_RIGHTSHOULDER,
+    SC_GAMEPAD_BUTTON_DPAD_UP = SDL_CONTROLLER_BUTTON_DPAD_UP,
+    SC_GAMEPAD_BUTTON_DPAD_DOWN = SDL_CONTROLLER_BUTTON_DPAD_DOWN,
+    SC_GAMEPAD_BUTTON_DPAD_LEFT = SDL_CONTROLLER_BUTTON_DPAD_LEFT,
+    SC_GAMEPAD_BUTTON_DPAD_RIGHT = SDL_CONTROLLER_BUTTON_DPAD_RIGHT,
+};
+
 static_assert(sizeof(enum sc_mod) >= sizeof(SDL_Keymod),
               "SDL_Keymod must be convertible to sc_mod");
 
@@ -380,6 +412,33 @@ struct sc_touch_event {
     float pressure;
 };
 
+enum sc_gamepad_device_event_type {
+    SC_GAMEPAD_DEVICE_ADDED,
+    SC_GAMEPAD_DEVICE_REMOVED,
+};
+
+// As documented in <https://wiki.libsdl.org/SDL2/SDL_JoystickID>:
+// The ID value starts at 0 and increments from there. The value -1 is an
+// invalid ID.
+#define SC_GAMEPAD_ID_INVALID UINT32_C(-1)
+
+struct sc_gamepad_device_event {
+    enum sc_gamepad_device_event_type type;
+    uint32_t gamepad_id;
+};
+
+struct sc_gamepad_button_event {
+    uint32_t gamepad_id;
+    enum sc_action action;
+    enum sc_gamepad_button button;
+};
+
+struct sc_gamepad_axis_event {
+    uint32_t gamepad_id;
+    enum sc_gamepad_axis axis;
+    int16_t value;
+};
+
 static inline uint16_t
 sc_mods_state_from_sdl(uint16_t mods_state) {
     return mods_state;
@@ -444,4 +503,43 @@ sc_mouse_buttons_state_from_sdl(uint32_t buttons_state) {
     return buttons_state;
 }
 
+static inline enum sc_gamepad_device_event_type
+sc_gamepad_device_event_type_from_sdl_type(uint32_t type) {
+    assert(type == SDL_CONTROLLERDEVICEADDED
+        || type == SDL_CONTROLLERDEVICEREMOVED);
+    if (type == SDL_CONTROLLERDEVICEADDED) {
+        return SC_GAMEPAD_DEVICE_ADDED;
+    }
+    return SC_GAMEPAD_DEVICE_REMOVED;
+}
+
+static inline enum sc_gamepad_axis
+sc_gamepad_axis_from_sdl(uint8_t axis) {
+    if (axis <= SDL_CONTROLLER_AXIS_TRIGGERRIGHT) {
+        // SC_GAMEPAD_AXIS_* constants are initialized from
+        // SDL_CONTROLLER_AXIS_*
+        return axis;
+    }
+    return SC_GAMEPAD_AXIS_UNKNOWN;
+}
+
+static inline enum sc_gamepad_button
+sc_gamepad_button_from_sdl(uint8_t button) {
+    if (button <= SDL_CONTROLLER_BUTTON_DPAD_RIGHT) {
+        // SC_GAMEPAD_BUTTON_* constants are initialized from
+        // SDL_CONTROLLER_BUTTON_*
+        return button;
+    }
+    return SC_GAMEPAD_BUTTON_UNKNOWN;
+}
+
+static inline enum sc_action
+sc_action_from_sdl_controllerbutton_type(uint32_t type) {
+    assert(type == SDL_CONTROLLERBUTTONDOWN || type == SDL_CONTROLLERBUTTONUP);
+    if (type == SDL_CONTROLLERBUTTONDOWN) {
+        return SC_ACTION_DOWN;
+    }
+    return SC_ACTION_UP;
+}
+
 #endif

app/src/input_manager.c

@@ -56,16 +56,18 @@ void
 sc_input_manager_init(struct sc_input_manager *im,
                       const struct sc_input_manager_params *params) {
     // A key/mouse processor may not be present if there is no controller
-    assert((!params->kp && !params->mp) || params->controller);
+    assert((!params->kp && !params->mp && !params->gp) || params->controller);
     // A processor must have ops initialized
     assert(!params->kp || params->kp->ops);
     assert(!params->mp || params->mp->ops);
+    assert(!params->gp || params->gp->ops);
 
     im->controller = params->controller;
     im->fp = params->fp;
     im->screen = params->screen;
     im->kp = params->kp;
     im->mp = params->mp;
+    im->gp = params->gp;
 
     im->mouse_bindings = params->mouse_bindings;
     im->legacy_paste = params->legacy_paste;
@@ -920,6 +922,78 @@ sc_input_manager_process_mouse_wheel(struct sc_input_manager *im,
     im->mp->ops->process_mouse_scroll(im->mp, &evt);
 }
 
+static void
+sc_input_manager_process_gamepad_device(struct sc_input_manager *im,
+                                       const SDL_ControllerDeviceEvent *event) {
+    SDL_JoystickID id;
+    if (event->type == SDL_CONTROLLERDEVICEADDED) {
+        SDL_GameController *gc = SDL_GameControllerOpen(event->which);
+        if (!gc) {
+            LOGW("Could not open game controller");
+            return;
+        }
+
+        SDL_Joystick *joystick = SDL_GameControllerGetJoystick(gc);
+        if (!joystick) {
+            LOGW("Could not get controller joystick");
+            SDL_GameControllerClose(gc);
+            return;
+        }
+
+        id = SDL_JoystickInstanceID(joystick);
+    } else if (event->type == SDL_CONTROLLERDEVICEREMOVED) {
+        id = event->which;
+
+        SDL_GameController *gc = SDL_GameControllerFromInstanceID(id);
+        if (gc) {
+            SDL_GameControllerClose(gc);
+        } else {
+            LOGW("Unknown gamepad device removed");
+        }
+    } else {
+        // Nothing to do
+        return;
+    }
+
+    struct sc_gamepad_device_event evt = {
+        .type = sc_gamepad_device_event_type_from_sdl_type(event->type),
+        .gamepad_id = id,
+    };
+    im->gp->ops->process_gamepad_device(im->gp, &evt);
+}
+
+static void
+sc_input_manager_process_gamepad_axis(struct sc_input_manager *im,
+                                      const SDL_ControllerAxisEvent *event) {
+    enum sc_gamepad_axis axis = sc_gamepad_axis_from_sdl(event->axis);
+    if (axis == SC_GAMEPAD_AXIS_UNKNOWN) {
+        return;
+    }
+
+    struct sc_gamepad_axis_event evt = {
+        .gamepad_id = event->which,
+        .axis = axis,
+        .value = event->value,
+    };
+    im->gp->ops->process_gamepad_axis(im->gp, &evt);
+}
+
+static void
+sc_input_manager_process_gamepad_button(struct sc_input_manager *im,
+                                       const SDL_ControllerButtonEvent *event) {
+    enum sc_gamepad_button button = sc_gamepad_button_from_sdl(event->button);
+    if (button == SC_GAMEPAD_BUTTON_UNKNOWN) {
+        return;
+    }
+
+    struct sc_gamepad_button_event evt = {
+        .gamepad_id = event->which,
+        .action = sc_action_from_sdl_controllerbutton_type(event->type),
+        .button = button,
+    };
+    im->gp->ops->process_gamepad_button(im->gp, &evt);
+}
+
 static bool
 is_apk(const char *file) {
     const char *ext = strrchr(file, '.');
@@ -992,6 +1066,27 @@ sc_input_manager_handle_event(struct sc_input_manager *im,
             }
             sc_input_manager_process_touch(im, &event->tfinger);
             break;
+        case SDL_CONTROLLERDEVICEADDED:
+        case SDL_CONTROLLERDEVICEREMOVED:
+            // Handle device added or removed even if paused
+            if (!im->gp) {
+                break;
+            }
+            sc_input_manager_process_gamepad_device(im, &event->cdevice);
+            break;
+        case SDL_CONTROLLERAXISMOTION:
+            if (!im->gp || paused) {
+                break;
+            }
+            sc_input_manager_process_gamepad_axis(im, &event->caxis);
+            break;
+        case SDL_CONTROLLERBUTTONDOWN:
+        case SDL_CONTROLLERBUTTONUP:
+            if (!im->gp || paused) {
+                break;
+            }
+            sc_input_manager_process_gamepad_button(im, &event->cbutton);
+            break;
         case SDL_DROPFILE: {
             if (!control) {
                 break;

app/src/input_manager.h

@@ -11,6 +11,7 @@
 #include "file_pusher.h"
 #include "fps_counter.h"
 #include "options.h"
+#include "trait/gamepad_processor.h"
 #include "trait/key_processor.h"
 #include "trait/mouse_processor.h"
 
@@ -21,6 +22,7 @@ struct sc_input_manager {
 
     struct sc_key_processor *kp;
     struct sc_mouse_processor *mp;
+    struct sc_gamepad_processor *gp;
 
     struct sc_mouse_bindings mouse_bindings;
     bool legacy_paste;
@@ -50,6 +52,7 @@ struct sc_input_manager_params {
     struct sc_screen *screen;
     struct sc_key_processor *kp;
     struct sc_mouse_processor *mp;
+    struct sc_gamepad_processor *gp;
 
     struct sc_mouse_bindings mouse_bindings;
     bool legacy_paste;

app/src/scrcpy.c

@@ -484,6 +484,11 @@ scrcpy(struct scrcpy_options *options) {
         }
     }
 
+    if (SDL_Init(SDL_INIT_GAMECONTROLLER)) {
+        LOGE("Could not initialize SDL gamepad: %s", SDL_GetError());
+        goto end;
+    }
+
     sdl_configure(options->video_playback, options->disable_screensaver);
 
     // Await for server without blocking Ctrl+C handling
@@ -734,6 +739,7 @@ aoa_complete:
             .fp = fp,
             .kp = kp,
             .mp = mp,
+            .gp = NULL,
             .mouse_bindings = options->mouse_bindings,
             .legacy_paste = options->legacy_paste,
             .clipboard_autosync = options->clipboard_autosync,

app/src/screen.c

@@ -477,6 +477,7 @@ sc_screen_init(struct sc_screen *screen,
         .screen = screen,
         .kp = params->kp,
         .mp = params->mp,
+        .gp = params->gp,
         .mouse_bindings = params->mouse_bindings,
         .legacy_paste = params->legacy_paste,
         .clipboard_autosync = params->clipboard_autosync,

app/src/screen.h

@@ -78,6 +78,7 @@ struct sc_screen_params {
     struct sc_file_pusher *fp;
     struct sc_key_processor *kp;
     struct sc_mouse_processor *mp;
+    struct sc_gamepad_processor *gp;
 
     struct sc_mouse_bindings mouse_bindings;
     bool legacy_paste;

app/src/trait/gamepad_processor.h

@@ -0,0 +1,50 @@
+#ifndef SC_GAMEPAD_PROCESSOR_H
+#define SC_GAMEPAD_PROCESSOR_H
+
+#include "common.h"
+
+#include <assert.h>
+#include <stdbool.h>
+
+#include "input_events.h"
+
+/**
+ * Gamepad processor trait.
+ *
+ * Component able to handle gamepads devices and inject buttons and axis events.
+ */
+struct sc_gamepad_processor {
+    const struct sc_gamepad_processor_ops *ops;
+};
+
+struct sc_gamepad_processor_ops {
+
+    /**
+     * Process a gamepad device added or removed
+     *
+     * This function is mandatory.
+     */
+    void
+    (*process_gamepad_device)(struct sc_gamepad_processor *gp,
+                              const struct sc_gamepad_device_event *event);
+
+    /**
+     * Process a gamepad axis event
+     *
+     * This function is mandatory.
+     */
+    void
+    (*process_gamepad_axis)(struct sc_gamepad_processor *gp,
+                            const struct sc_gamepad_axis_event *event);
+
+    /**
+     * Process a gamepad button event
+     *
+     * This function is mandatory.
+     */
+    void
+    (*process_gamepad_button)(struct sc_gamepad_processor *gp,
+                              const struct sc_gamepad_button_event *event);
+};
+
+#endif