[QT] fix OSX dock icon window reopening

fixes #5878

src/qt/macdockiconhandler.mm

@@ -11,52 +11,46 @@
 
 #undef slots
 #include <Cocoa/Cocoa.h>
+#include <objc/objc.h>
+#include <objc/message.h>
 
 #if QT_VERSION < 0x050000
 extern void qt_mac_set_dock_menu(QMenu *);
 #endif
 
-@interface DockIconClickEventHandler : NSObject
-{
-    MacDockIconHandler* dockIconHandler;
-}
+static MacDockIconHandler *s_instance = NULL;
 
-@end
+bool dockClickHandler(id self,SEL _cmd,...) {
+    Q_UNUSED(self)
+    Q_UNUSED(_cmd)
     
-@implementation DockIconClickEventHandler
+    s_instance->handleDockIconClickEvent();
     
-- (id)initWithDockIconHandler:(MacDockIconHandler *)aDockIconHandler
-{
-    self = [super init];
-    if (self) {
-        dockIconHandler = aDockIconHandler;
-
-        [[NSAppleEventManager sharedAppleEventManager]
-            setEventHandler:self
-                andSelector:@selector(handleDockClickEvent:withReplyEvent:)
-              forEventClass:kCoreEventClass
-                 andEventID:kAEReopenApplication];
-    }
-    return self;
+    // Return NO (false) to suppress the default OS X actions
+    return false;
 }
 
-- (void)handleDockClickEvent:(NSAppleEventDescriptor*)event withReplyEvent:(NSAppleEventDescriptor*)replyEvent
-{
-    Q_UNUSED(event)
-    Q_UNUSED(replyEvent)
-
-    if (dockIconHandler) {
-        dockIconHandler->handleDockIconClickEvent();
+void setupDockClickHandler() {
+    Class cls = objc_getClass("NSApplication");
+    id appInst = objc_msgSend((id)cls, sel_registerName("sharedApplication"));
+    
+    if (appInst != NULL) {
+        id delegate = objc_msgSend(appInst, sel_registerName("delegate"));
+        Class delClass = (Class)objc_msgSend(delegate,  sel_registerName("class"));
+        SEL shouldHandle = sel_registerName("applicationShouldHandleReopen:hasVisibleWindows:");
+        if (class_getInstanceMethod(delClass, shouldHandle))
+            class_replaceMethod(delClass, shouldHandle, (IMP)dockClickHandler, "B@:");
+        else
+            class_addMethod(delClass, shouldHandle, (IMP)dockClickHandler,"B@:");
     }
 }
 
-@end
 
 MacDockIconHandler::MacDockIconHandler() : QObject()
 {
     NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
 
-    this->m_dockIconClickEventHandler = [[DockIconClickEventHandler alloc] initWithDockIconHandler:this];
+    setupDockClickHandler();
     this->m_dummyWidget = new QWidget();
     this->m_dockMenu = new QMenu(this->m_dummyWidget);
     this->setMainWindow(NULL);
@@ -119,7 +113,6 @@ void MacDockIconHandler::setIcon(const QIcon &icon)
 
 MacDockIconHandler *MacDockIconHandler::instance()
 {
-    static MacDockIconHandler *s_instance = NULL;
     if (!s_instance)
         s_instance = new MacDockIconHandler();
     return s_instance;