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


From: BALATON Zoltan
Subject: Re: [PATCH 1/2] ui/cocoa: capture all keys and combos when mouse is grabbed
Date: Sun, 6 Mar 2022 12:28:44 +0100 (CET)

On Sun, 6 Mar 2022, Akihiko Odaki wrote:
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..1e9893419fe 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: 6.1
+##
+{ '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..c41bc615d33 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 = (QemuCocoaView*) userInfo;

Extra space between cast and userinfo? Do you need explicit cast at all? In C at least void * does not need explicit cast, not sure about Objective-C but if it's not needed you could just remove the cast.

Regards,
BALATON Zoltan

+    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) {




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