ui/cocoa: add option to swap Option and Command

On Mac OS X the Option key maps to Alt and Command to Super/Meta. This change
swaps them around so that Alt is the key closer to the space bar and Meta/Super
is between Control and Alt, like on non-Mac keyboards.

It is a cocoa display option, disabled by default.

Acked-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Akihiko Odaki <akihiko.odaki@gmail.com>
Signed-off-by: Gustavo Noronha Silva <gustavo@noronha.dev.br>
Message-Id: <20210713213200.2547-3-gustavo@noronha.dev.br>

qapi/ui.json

@@ -1102,10 +1102,16 @@
 #             a global grab on key events. (default: off)
 #             See https://support.apple.com/en-in/guide/mac-help/mh32356/mac
 #
+# @swap-option-command: Swap the Option and Command keys so that their key
+#                       codes match their position on non-Mac keyboards and
+#                       you can use Meta/Super and Alt where you expect them.
+#                       (default: off)
+#
 # Since: 6.1
 ##
 { 'struct'  : 'DisplayCocoa',
-  'data'    : { '*full-grab'     : 'bool' } }
+  'data'    : { '*full-grab'           : 'bool',
+                '*swap-option-command' : 'bool' } }
 
 ##
 # @DisplayType:

qemu-options.hx

@@ -1797,7 +1797,8 @@ DEF("display", HAS_ARG, QEMU_OPTION_display,
     "-display curses[,charset=<encoding>]\n"
 #endif
 #if defined(CONFIG_COCOA)
-    "-display cocoa[,full_grab=on|off]\n"
+    "-display cocoa[,full-grab=on|off]\n"
+    "              [,swap-option-command=on|off]\n"
 #endif
 #if defined(CONFIG_OPENGL)
     "-display egl-headless[,rendernode=<file>]\n"

ui/cocoa.m

@@ -73,6 +73,7 @@
 typedef struct {
     int width;
     int height;
+    bool swap_option_command;
 } QEMUScreen;
 
 static void cocoa_update(DisplayChangeListener *dcl,
@@ -330,6 +331,7 @@ - (void) setAbsoluteEnabled:(BOOL)tIsAbsoluteEnabled;
  */
 - (BOOL) isMouseGrabbed;
 - (BOOL) isAbsoluteEnabled;
+- (BOOL) isSwapOptionCommandEnabled;
 - (float) cdx;
 - (float) cdy;
 - (QEMUScreen) gscreen;
@@ -685,6 +687,13 @@ - (void) setFullGrab:(id)sender
     CFRelease(tapEventsSrc);
 }
 
+- (void) setSwapOptionCommand:(id)sender
+{
+    COCOA_DEBUG("QemuCocoaView: setSwapOptionCommand\n");
+
+    screen.swap_option_command = true;
+}
+
 - (void) toggleKey: (int)keycode {
     qkbd_state_key_event(kbd, keycode, !qkbd_state_key_get(kbd, keycode));
 }
@@ -834,12 +843,22 @@ - (bool) handleEventLocked:(NSEvent *)event
         qkbd_state_key_event(kbd, Q_KEY_CODE_CTRL_R, false);
     }
     if (!(modifiers & NSEventModifierFlagOption)) {
-        qkbd_state_key_event(kbd, Q_KEY_CODE_ALT, false);
-        qkbd_state_key_event(kbd, Q_KEY_CODE_ALT_R, false);
+        if ([self isSwapOptionCommandEnabled]) {
+            qkbd_state_key_event(kbd, Q_KEY_CODE_META_L, false);
+            qkbd_state_key_event(kbd, Q_KEY_CODE_META_R, false);
+        } else {
+            qkbd_state_key_event(kbd, Q_KEY_CODE_ALT, false);
+            qkbd_state_key_event(kbd, Q_KEY_CODE_ALT_R, false);
+        }
     }
     if (!(modifiers & NSEventModifierFlagCommand)) {
-        qkbd_state_key_event(kbd, Q_KEY_CODE_META_L, false);
-        qkbd_state_key_event(kbd, Q_KEY_CODE_META_R, false);
+        if ([self isSwapOptionCommandEnabled]) {
+            qkbd_state_key_event(kbd, Q_KEY_CODE_ALT, false);
+            qkbd_state_key_event(kbd, Q_KEY_CODE_ALT_R, false);
+        } else {
+            qkbd_state_key_event(kbd, Q_KEY_CODE_META_L, false);
+            qkbd_state_key_event(kbd, Q_KEY_CODE_META_R, false);
+        }
     }
 
     switch ([event type]) {
@@ -871,28 +890,44 @@ - (bool) handleEventLocked:(NSEvent *)event
 
                 case kVK_Option:
                     if (!!(modifiers & NSEventModifierFlagOption)) {
-                        [self toggleKey:Q_KEY_CODE_ALT];
+                        if ([self isSwapOptionCommandEnabled]) {
+                            [self toggleKey:Q_KEY_CODE_META_L];
+                        } else {
+                            [self toggleKey:Q_KEY_CODE_ALT];
+                        }
                     }
                     break;
 
                 case kVK_RightOption:
                     if (!!(modifiers & NSEventModifierFlagOption)) {
-                        [self toggleKey:Q_KEY_CODE_ALT_R];
+                        if ([self isSwapOptionCommandEnabled]) {
+                            [self toggleKey:Q_KEY_CODE_META_R];
+                        } else {
+                            [self toggleKey:Q_KEY_CODE_ALT_R];
+                        }
                     }
                     break;
 
                 /* Don't pass command key changes to guest unless mouse is grabbed */
                 case kVK_Command:
                     if (isMouseGrabbed &&
                         !!(modifiers & NSEventModifierFlagCommand)) {
-                        [self toggleKey:Q_KEY_CODE_META_L];
+                        if ([self isSwapOptionCommandEnabled]) {
+                            [self toggleKey:Q_KEY_CODE_ALT];
+                        } else {
+                            [self toggleKey:Q_KEY_CODE_META_L];
+                        }
                     }
                     break;
 
                 case kVK_RightCommand:
                     if (isMouseGrabbed &&
                         !!(modifiers & NSEventModifierFlagCommand)) {
-                        [self toggleKey:Q_KEY_CODE_META_R];
+                        if ([self isSwapOptionCommandEnabled]) {
+                            [self toggleKey:Q_KEY_CODE_ALT_R];
+                        } else {
+                            [self toggleKey:Q_KEY_CODE_META_R];
+                        }
                     }
                     break;
             }
@@ -1121,6 +1156,7 @@ - (void) setAbsoluteEnabled:(BOOL)tIsAbsoluteEnabled {
 }
 - (BOOL) isMouseGrabbed {return isMouseGrabbed;}
 - (BOOL) isAbsoluteEnabled {return isAbsoluteEnabled;}
+- (BOOL) isSwapOptionCommandEnabled {return screen.swap_option_command;}
 - (float) cdx {return cdx;}
 - (float) cdy {return cdy;}
 - (QEMUScreen) gscreen {return screen;}
@@ -1317,6 +1353,13 @@ - (void) setFullGrab:(id)sender
     [cocoaView setFullGrab:sender];
 }
 
+- (void) setSwapOptionCommand:(id)sender
+{
+    COCOA_DEBUG("QemuCocoaAppController: setSwapOptionCommand\n");
+
+    [cocoaView setSwapOptionCommand:sender];
+}
+
 /* Tries to find then open the specified filename */
 - (void) openDocumentation: (NSString *) filename
 {
@@ -2101,6 +2144,11 @@ static void cocoa_display_init(DisplayState *ds, DisplayOptions *opts)
             [controller setFullGrab: nil];
         });
     }
+    if (opts->u.cocoa.has_swap_option_command && opts->u.cocoa.swap_option_command) {
+        dispatch_async(dispatch_get_main_queue(), ^{
+            [controller setSwapOptionCommand: nil];
+        });
+    }
     if (opts->has_show_cursor && opts->show_cursor) {
         cursor_hide = 0;
     }