[PATCH 1/2] ui/cocoa.m: Add full keyboard grab support

[John Arbuckle <programmingkidx@gmail.com>]

There are keyboard shortcuts that are vital for use in a guest that runs Mac OS.
These shortcuts are reserved for Mac OS use only which makes having the guest
see them impossible on a Mac OS host - until now. This patch will enable the
user to decide if the guest should see all keyboard shortcuts using a menu item.
This patch adds a new menu called Options and a new menu item called
"Full Keyboard Grab". Simply selecting this menu item will turn the feature on
or off at any time. Mac OS requires the user to enable access to assistive
devices to use this feature. How to do this varies with each Mac OS version.
Based on patch by Gustavo Noronha Silva <gustavo@noronha.dev.br>. 

Signed-off-by: John Arbuckle <programmingkidx@gmail.com>
---
 ui/cocoa.m | 112 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 112 insertions(+)

diff --git a/ui/cocoa.m b/ui/cocoa.m
index 9f72844b07..fdef9e9901 100644
--- a/ui/cocoa.m
+++ b/ui/cocoa.m
@@ -114,6 +114,9 @@ static void cocoa_switch(DisplayChangeListener *dcl,
 typedef void (^CodeBlock)(void);
 typedef bool (^BoolCodeBlock)(void);
 
+static CFMachPortRef eventsTap = NULL;
+static CFRunLoopSourceRef eventsTapSource = NULL;
+
 static void with_iothread_lock(CodeBlock block)
 {
     bool locked = qemu_mutex_iothread_locked();
@@ -332,10 +335,27 @@ - (float) cdx;
 - (float) cdy;
 - (QEMUScreen) gscreen;
 - (void) raiseAllKeys;
+- (void) setFullGrab;
 @end
 
 QemuCocoaView *cocoaView;
 
+// Part of the full keyboard grab system
+static CGEventRef handleTapEvent(CGEventTapProxy proxy, CGEventType type,
+CGEventRef cgEvent, void *userInfo)
+{
+    QemuCocoaView *cocoaView = (QemuCocoaView*) 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
 {
@@ -361,6 +381,12 @@ - (void) dealloc
     }
 
     qkbd_state_free(kbd);
+    if (eventsTap) {
+        CFRelease(eventsTap);
+    }
+    if (eventsTapSource) {
+        CFRelease(eventsTapSource);
+    }
     [super dealloc];
 }
 
@@ -1086,6 +1112,50 @@ - (void) raiseAllKeys
         qkbd_state_lift_all_keys(kbd);
     });
 }
+
+// Inserts the event tap.
+// This enables us to receive keyboard events that Mac OS would
+// otherwise not let us see - like Command-Option-Esc.
+- (void) setFullGrab
+{
+    COCOA_DEBUG("QemuCocoaView: setFullGrab\n");
+    NSString *advice = @"Try enabling access to assistive devices";
+    CGEventMask mask = CGEventMaskBit(kCGEventKeyDown) |
+    CGEventMaskBit(kCGEventKeyUp) | CGEventMaskBit(kCGEventFlagsChanged);
+    eventsTap = CGEventTapCreate(kCGHIDEventTap, kCGHeadInsertEventTap,
+                                 kCGEventTapOptionDefault, mask, handleTapEvent,
+                                 self);
+    if (!eventsTap) {
+        @throw [NSException
+                 exceptionWithName:@"Tap failure"
+                reason:[NSString stringWithFormat:@"%@\n%@", @"Could not "
+                        "create event tap.", advice]
+                userInfo:nil];
+    } else {
+        COCOA_DEBUG("Global events tap created! Will capture system key"
+                    " combos.\n");
+    }
+
+    eventsTapSource =
+    CFMachPortCreateRunLoopSource(kCFAllocatorDefault, eventsTap, 0);
+    if (!eventsTapSource ) {
+        @throw [NSException
+                 exceptionWithName:@"Tap failure"
+                 reason:@"Could not obtain current CFRunLoop source."
+                userInfo:nil];
+    }
+    CFRunLoopRef runLoop = CFRunLoopGetCurrent();
+    if (!runLoop) {
+           @throw [NSException
+                 exceptionWithName:@"Tap failure"
+                 reason:@"Could not obtain current CFRunLoop."
+                userInfo:nil];
+    }
+
+    CFRunLoopAddSource(runLoop, eventsTapSource, kCFRunLoopDefaultMode);
+    CFRelease(eventsTapSource);
+}
+
 @end
 
 
@@ -1117,6 +1187,7 @@ - (void)openDocumentation:(NSString *)filename;
 - (IBAction) do_about_menu_item: (id) sender;
 - (void)make_about_window;
 - (void)adjustSpeed:(id)sender;
+- (IBAction)doFullGrab:(id)sender;
 @end
 
 @implementation QemuCocoaAppController
@@ -1569,6 +1640,35 @@ - (void)adjustSpeed:(id)sender
     COCOA_DEBUG("cpu throttling at %d%c\n", cpu_throttle_get_percentage(), '%');
 }
 
+// The action method to the 'Options->Full Keyboard Grab' menu item
+- (IBAction)doFullGrab:(id) sender
+{
+    @try
+    {
+        // Set the state of the menu item
+        // if already checked
+        if ([sender state] == NSControlStateValueOn) {
+            // remove runloop source
+            CFRunLoopSourceInvalidate(eventsTapSource);
+            if (!eventsTap) {
+                CFRelease(eventsTap);
+            }
+            [sender setState: NSControlStateValueOff];
+        }
+
+        // if not already checked
+        else {
+            [cocoaView setFullGrab];
+            [sender setState: NSControlStateValueOn];
+        }
+    }
+    @catch(NSException *e) {
+        NSBeep();
+        NSLog(@"Exception in doFullGrab: %@", [e reason]);
+        QEMU_Alert([e reason]);
+    }
+}
+
 @end
 
 @interface QemuApplication : NSApplication
@@ -1655,6 +1755,18 @@ static void create_initial_menus(void)
     [menuItem setSubmenu:menu];
     [[NSApp mainMenu] addItem:menuItem];
 
+    // Options menu
+    menu = [[NSMenu alloc] initWithTitle:@"Options"];
+
+    [menu addItem: [[[NSMenuItem alloc] initWithTitle:
+                         @"Full Keyboard Grab" action:@selector(doFullGrab:)
+                                        keyEquivalent:@""] autorelease]];
+
+    menuItem = [[[NSMenuItem alloc] initWithTitle:@"Options" action:nil
+                                    keyEquivalent:@""] autorelease];
+    [menuItem setSubmenu:menu];
+    [[NSApp mainMenu] addItem:menuItem];
+
     // Window menu
     menu = [[NSMenu alloc] initWithTitle:@"Window"];
     [menu addItem: [[[NSMenuItem alloc] initWithTitle:@"Minimize" action:@selector(performMiniaturize:) keyEquivalent:@"m"] autorelease]]; // Miniaturize
-- 
2.24.3 (Apple Git-128)