When the mouse is grabbed it's constrained to the client area, not the window frame.
diff --git a/src/video/cocoa/SDL_cocoamousetap.m b/src/video/cocoa/SDL_cocoamousetap.m
index fd79296..8f95ac3 100644
--- a/src/video/cocoa/SDL_cocoamousetap.m
+++ b/src/video/cocoa/SDL_cocoamousetap.m
@@ -63,6 +63,7 @@ Cocoa_MouseTapCallback(CGEventTapProxy proxy, CGEventType type, CGEventRef event
SDL_MouseEventTapData *tapdata = (SDL_MouseEventTapData*)refcon;
SDL_Mouse *mouse = SDL_GetMouse();
SDL_Window *window = SDL_GetKeyboardFocus();
+ NSWindow *nswindow = ((SDL_WindowData *) window->driverdata)->nswindow;
NSRect windowRect;
CGPoint eventLocation;
@@ -93,7 +94,7 @@ Cocoa_MouseTapCallback(CGEventTapProxy proxy, CGEventType type, CGEventRef event
/* This is the same coordinate system as Cocoa uses. */
eventLocation = CGEventGetUnflippedLocation(event);
- windowRect = [((SDL_WindowData *) window->driverdata)->nswindow frame];
+ windowRect = [nswindow contentRectForFrameRect:[nswindow frame]];
if (!NSPointInRect(NSPointFromCGPoint(eventLocation), windowRect)) {