Replace Ctrl by Meta for volume shortcuts on MacOS

Ctrl+UP and Ctrl+DOWN are already used by the window manager on MacOS.

Use Cmd key instead (like on VLC).

README.md

@@ -134,8 +134,8 @@ scrcpy -f
  | click on `BACK`                        | `Ctrl`+`b` \| _Right-click²_  |
  | click on `APP_SWITCH`                  | `Ctrl`+`s`                    |
  | click on `MENU`                        | `Ctrl`+`m`                    |
- | click on `VOLUME_UP`                   | `Ctrl`+`↑` _(up)_             |
- | click on `VOLUME_DOWN`                 | `Ctrl`+`↓` _(down)_           |
+ | click on `VOLUME_UP`                   | `Ctrl`+`↑` _(up)_   (`Cmd`+`↑` on MacOS) |
+ | click on `VOLUME_DOWN`                 | `Ctrl`+`↓` _(down)_ (`Cmd`+`↓` on MacOS) |
  | click on `POWER`                       | `Ctrl`+`p`                    |
  | turn screen on                         | _Right-click²_                |
  | paste computer clipboard to device     | `Ctrl`+`v`                    |

app/src/input_manager.c

@@ -154,14 +154,14 @@ void input_manager_process_key(struct input_manager *input_manager,
     SDL_bool alt = event->keysym.mod & (KMOD_LALT | KMOD_RALT);
     SDL_bool meta = event->keysym.mod & (KMOD_LGUI | KMOD_RGUI);
 
-    if (alt | meta) {
+    if (alt) {
         // no shortcut involves Alt or Meta, and they should not be forwarded
         // to the device
         return;
     }
 
     // capture all Ctrl events
-    if (ctrl) {
+    if (ctrl | meta) {
         SDL_bool shift = event->keysym.mod & (KMOD_LSHIFT | KMOD_RSHIFT);
         if (shift) {
             // currently, there is no shortcut involving SHIFT
@@ -173,61 +173,73 @@ void input_manager_process_key(struct input_manager *input_manager,
         SDL_bool repeat = event->repeat;
         switch (keycode) {
             case SDLK_h:
-                if (!repeat) {
+                if (ctrl && !meta && !repeat) {
                     action_home(input_manager->controller, action);
                 }
                 return;
             case SDLK_b: // fall-through
             case SDLK_BACKSPACE:
-                if (!repeat) {
+                if (ctrl && !meta && !repeat) {
                     action_back(input_manager->controller, action);
                 }
                 return;
             case SDLK_s:
-                if (!repeat) {
+                if (ctrl && !meta && !repeat) {
                     action_app_switch(input_manager->controller, action);
                 }
                 return;
             case SDLK_m:
-                if (!repeat) {
+                if (ctrl && !meta && !repeat) {
                     action_menu(input_manager->controller, action);
                 }
                 return;
             case SDLK_p:
-                if (!repeat) {
+                if (ctrl && !meta && !repeat) {
                     action_power(input_manager->controller, action);
                 }
                 return;
             case SDLK_DOWN:
-                // forward repeated events
-                action_volume_down(input_manager->controller, action);
+#ifdef __APPLE__
+                if (!ctrl && meta) {
+#else
+                if (ctrl && !meta) {
+#endif
+                    // forward repeated events
+                    action_volume_down(input_manager->controller, action);
+                }
                 return;
             case SDLK_UP:
-                // forward repeated events
-                action_volume_up(input_manager->controller, action);
+#ifdef __APPLE__
+                if (!ctrl && meta) {
+#else
+                if (ctrl && !meta) {
+#endif
+                    // forward repeated events
+                    action_volume_up(input_manager->controller, action);
+                }
                 return;
             case SDLK_v:
-                if (!repeat && event->type == SDL_KEYDOWN) {
+                if (ctrl && !meta && !repeat && event->type == SDL_KEYDOWN) {
                     clipboard_paste(input_manager->controller);
                 }
                 return;
             case SDLK_f:
-                if (!repeat && event->type == SDL_KEYDOWN) {
+                if (ctrl && !meta && !repeat && event->type == SDL_KEYDOWN) {
                     screen_switch_fullscreen(input_manager->screen);
                 }
                 return;
             case SDLK_x:
-                if (!repeat && event->type == SDL_KEYDOWN) {
+                if (ctrl && !meta && !repeat && event->type == SDL_KEYDOWN) {
                     screen_resize_to_fit(input_manager->screen);
                 }
                 return;
             case SDLK_g:
-                if (!repeat && event->type == SDL_KEYDOWN) {
+                if (ctrl && !meta && !repeat && event->type == SDL_KEYDOWN) {
                     screen_resize_to_pixel_perfect(input_manager->screen);
                 }
                 return;
             case SDLK_i:
-                if (!repeat && event->type == SDL_KEYDOWN) {
+                if (ctrl && !meta && !repeat && event->type == SDL_KEYDOWN) {
                     switch_fps_counter_state(input_manager->frames);
                 }
                 return;