[PATCH v2 1/2] ui/cocoa: capture all keys and combos when mouse is grabbed

[Akihiko Odaki]

From: Gustavo Noronha Silva <gustavo@noronha.dev.br>

Applications such as Gnome may use Alt-Tab and Super-Tab for different
purposes, some use Ctrl-arrows so we want to allow qemu to handle
everything when it captures the mouse/keyboard.

However, Mac OS handles some combos like Command-Tab and Ctrl-arrows
at an earlier part of the event handling chain, not letting qemu see it.

We add a global Event Tap that allows qemu to see all events when the
mouse is grabbed. Note that this requires additional permissions.

See:

https://developer.apple.com/documentation/coregraphics/1454426-cgeventtapcreate?language=objc#discussion
https://support.apple.com/en-in/guide/mac-help/mh32356/mac

Acked-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Gustavo Noronha Silva <gustavo@noronha.dev.br>
Message-Id: <20210713213200.2547-2-gustavo@noronha.dev.br>
Signed-off-by: Akihiko Odaki <akihiko.odaki@gmail.com>
---
 qapi/ui.json    | 16 ++++++++++++
 qemu-options.hx |  3 +++
 ui/cocoa.m      | 65 ++++++++++++++++++++++++++++++++++++++++++++++++-
 3 files changed, 83 insertions(+), 1 deletion(-)

diff --git a/qapi/ui.json b/qapi/ui.json
index 4a13f883a30..ff0a04da792 100644
--- a/qapi/ui.json
+++ b/qapi/ui.json
@@ -1260,6 +1260,21 @@
 { 'struct'  : 'DisplayCurses',
   'data'    : { '*charset'       : 'str' } }
 
+##
+# @DisplayCocoa:
+#
+# Cocoa display options.
+#
+# @full-grab: Capture all key presses, including system combos. This
+#             requires accessibility permissions, since it performs
+#             a global grab on key events. (default: off)
+#             See https://support.apple.com/en-in/guide/mac-help/mh32356/mac
+#
+# Since: 7.0
+##
+{ 'struct'  : 'DisplayCocoa',
+  'data'    : { '*full-grab'     : 'bool' } }
+
 ##
 # @DisplayType:
 #
@@ -1338,6 +1353,7 @@
   'discriminator' : 'type',
   'data'    : {
       'gtk': { 'type': 'DisplayGTK', 'if': 'CONFIG_GTK' },
+      'cocoa': { 'type': 'DisplayCocoa', 'if': 'CONFIG_COCOA' },
       'curses': { 'type': 'DisplayCurses', 'if': 'CONFIG_CURSES' },
       'egl-headless': { 'type': 'DisplayEGLHeadless',
                         'if': { 'all': ['CONFIG_OPENGL', 'CONFIG_GBM'] } },
diff --git a/qemu-options.hx b/qemu-options.hx
index 094a6c1d7c2..4df9ccc3446 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -1916,6 +1916,9 @@ DEF("display", HAS_ARG, QEMU_OPTION_display,
 #if defined(CONFIG_CURSES)
     "-display curses[,charset=<encoding>]\n"
 #endif
+#if defined(CONFIG_COCOA)
+    "-display cocoa[,full_grab=on|off]\n"
+#endif
 #if defined(CONFIG_OPENGL)
     "-display egl-headless[,rendernode=<file>]\n"
 #endif
diff --git a/ui/cocoa.m b/ui/cocoa.m
index 8ab9ab5e84d..bfd602a96b9 100644
--- a/ui/cocoa.m
+++ b/ui/cocoa.m
@@ -308,11 +308,13 @@ @interface QemuCocoaView : NSView
     BOOL isMouseGrabbed;
     BOOL isFullscreen;
     BOOL isAbsoluteEnabled;
+    CFMachPortRef eventsTap;
 }
 - (void) switchSurface:(pixman_image_t *)image;
 - (void) grabMouse;
 - (void) ungrabMouse;
 - (void) toggleFullScreen:(id)sender;
+- (void) setFullGrab:(id)sender;
 - (void) handleMonitorInput:(NSEvent *)event;
 - (bool) handleEvent:(NSEvent *)event;
 - (bool) handleEventLocked:(NSEvent *)event;
@@ -335,6 +337,19 @@ - (void) raiseAllKeys;
 
 QemuCocoaView *cocoaView;
 
+static CGEventRef handleTapEvent(CGEventTapProxy proxy, CGEventType type, 
CGEventRef cgEvent, void *userInfo)
+{
+    QemuCocoaView *cocoaView = userInfo;
+    NSEvent* event = [NSEvent eventWithCGEvent:cgEvent];
+    if ([cocoaView isMouseGrabbed] && [cocoaView handleEvent:event]) {
+        COCOA_DEBUG("Global events tap: qemu handled the event, capturing!\n");
+        return NULL;
+    }
+    COCOA_DEBUG("Global events tap: qemu did not handle the event, letting it 
through...\n");
+
+    return cgEvent;
+}
+
 @implementation QemuCocoaView
 - (id)initWithFrame:(NSRect)frameRect
 {
@@ -360,6 +375,11 @@ - (void) dealloc
     }
 
     qkbd_state_free(kbd);
+
+    if (eventsTap) {
+        CFRelease(eventsTap);
+    }
+
     [super dealloc];
 }
 
@@ -654,6 +674,36 @@ - (void) toggleFullScreen:(id)sender
     }
 }
 
+- (void) setFullGrab:(id)sender
+{
+    COCOA_DEBUG("QemuCocoaView: setFullGrab\n");
+
+    CGEventMask mask = CGEventMaskBit(kCGEventKeyDown) | 
CGEventMaskBit(kCGEventKeyUp) | CGEventMaskBit(kCGEventFlagsChanged);
+    eventsTap = CGEventTapCreate(kCGHIDEventTap, kCGHeadInsertEventTap, 
kCGEventTapOptionDefault,
+                                 mask, handleTapEvent, self);
+    if (!eventsTap) {
+        warn_report("Could not create event tap, system key combos will not be 
captured.\n");
+        return;
+    } else {
+        COCOA_DEBUG("Global events tap created! Will capture system key 
combos.\n");
+    }
+
+    CFRunLoopRef runLoop = CFRunLoopGetCurrent();
+    if (!runLoop) {
+        warn_report("Could not obtain current CF RunLoop, system key combos 
will not be captured.\n");
+        return;
+    }
+
+    CFRunLoopSourceRef tapEventsSrc = 
CFMachPortCreateRunLoopSource(kCFAllocatorDefault, eventsTap, 0);
+    if (!tapEventsSrc ) {
+        warn_report("Could not obtain current CF RunLoop, system key combos 
will not be captured.\n");
+        return;
+    }
+
+    CFRunLoopAddSource(runLoop, tapEventsSrc, kCFRunLoopDefaultMode);
+    CFRelease(tapEventsSrc);
+}
+
 - (void) toggleKey: (int)keycode {
     qkbd_state_key_event(kbd, keycode, !qkbd_state_key_get(kbd, keycode));
 }
@@ -1281,6 +1331,13 @@ - (void)toggleFullScreen:(id)sender
     [cocoaView toggleFullScreen:sender];
 }
 
+- (void) setFullGrab:(id)sender
+{
+    COCOA_DEBUG("QemuCocoaAppController: setFullGrab\n");
+
+    [cocoaView setFullGrab:sender];
+}
+
 /* Tries to find then open the specified filename */
 - (void) openDocumentation: (NSString *) filename
 {
@@ -2057,11 +2114,17 @@ static void cocoa_display_init(DisplayState *ds, 
DisplayOptions *opts)
     qemu_sem_wait(&app_started_sem);
     COCOA_DEBUG("cocoa_display_init: app start completed\n");
 
+    QemuCocoaAppController* controller = 
(QemuCocoaAppController*)[[NSApplication sharedApplication] delegate];
     /* if fullscreen mode is to be used */
     if (opts->has_full_screen && opts->full_screen) {
         dispatch_async(dispatch_get_main_queue(), ^{
             [NSApp activateIgnoringOtherApps: YES];
-            [(QemuCocoaAppController *)[[NSApplication sharedApplication] 
delegate] toggleFullScreen: nil];
+            [controller toggleFullScreen: nil];
+        });
+    }
+    if (opts->u.cocoa.has_full_grab && opts->u.cocoa.full_grab) {
+        dispatch_async(dispatch_get_main_queue(), ^{
+            [controller setFullGrab: nil];
         });
     }
     if (opts->has_show_cursor && opts->show_cursor) {
-- 
2.32.0 (Apple Git-132)