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

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(-)

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) {
>