Cocoa: impl. performance boost for dnd

It turns out that registering drag types for each NSView that can
receive drop events is _really_ slow. And many widget in Qt
subscribe for DnD (QTextEdit, QScrollArea, etc), so the result is
an application that will spend startup time preparing for DnD. For
some edge cases, we're talking several seconds!
This patch removes this overhead by moving drag type registering
out of NSView, and into NSWindow (that is, QCocoaWindow and
QCocoaPanel).

Task-number: QT-1586
Reviewed-by: Prasanth

7 files changed, 151 insertions, 65 deletions

diff --git a/src/gui/kernel/qcocoapanel_mac_p.h b/src/gui/kernel/qcocoapanel_mac_p.h
index 69dca1efc6..f35d9fb63d 100644
--- a/src/gui/kernel/qcocoapanel_mac_p.h
+++ b/src/gui/kernel/qcocoapanel_mac_p.h
@@ -54,10 +54,16 @@
 #ifdef QT_MAC_USE_COCOA
 #import <Cocoa/Cocoa.h>
 
+QT_FORWARD_DECLARE_CLASS(QStringList);
+
 @interface QT_MANGLE_NAMESPACE(QCocoaPanel) : NSPanel {
     bool leftButtonIsRightButton;
+    QStringList *currentCustomDragTypes;
 }
 
 + (Class)frameViewClassForStyleMask:(NSUInteger)styleMask;
+- (void)registerDragTypes;
+
 @end
 #endif
+
diff --git a/src/gui/kernel/qcocoasharedwindowmethods_mac_p.h b/src/gui/kernel/qcocoasharedwindowmethods_mac_p.h
index f3472400ac..8dd03aaad5 100644
--- a/src/gui/kernel/qcocoasharedwindowmethods_mac_p.h
+++ b/src/gui/kernel/qcocoasharedwindowmethods_mac_p.h
@@ -54,8 +54,31 @@
 QT_BEGIN_NAMESPACE
 extern Qt::MouseButton cocoaButton2QtButton(NSInteger buttonNum); // qcocoaview.mm
 extern QPointer<QWidget> qt_button_down; //qapplication_mac.cpp
+extern const QStringList& qEnabledDraggedTypes(); // qmime_mac.cpp
+
+Q_GLOBAL_STATIC(QPointer<QWidget>, currentDragTarget);
+
 QT_END_NAMESPACE
 
+- (id)initWithContentRect:(NSRect)contentRect
+    styleMask:(NSUInteger)windowStyle
+    backing:(NSBackingStoreType)bufferingType
+    defer:(BOOL)deferCreation
+{
+    self = [super initWithContentRect:contentRect styleMask:windowStyle
+        backing:bufferingType defer:deferCreation];
+    if (self) {
+        currentCustomDragTypes = 0;
+    }
+    return self;
+}
+
+- (void)dealloc
+{
+    delete currentCustomDragTypes;
+    [super dealloc];
+}
+
 - (BOOL)canBecomeKeyWindow
 {
     QWidget *widget = [self QT_MANGLE_NAMESPACE(qt_qwidget)];
@@ -185,3 +208,106 @@ QT_END_NAMESPACE
     return [super frameViewClassForStyleMask:styleMask];
 }
 
+-(void)registerDragTypes
+{
+    // Calling registerForDraggedTypes below is slow, so only do
+    // it once for each window, or when the custom types change.
+    QMacCocoaAutoReleasePool pool;
+    const QStringList& customTypes = qEnabledDraggedTypes();
+    if (currentCustomDragTypes == 0 || *currentCustomDragTypes != customTypes) {
+        if (currentCustomDragTypes == 0)
+            currentCustomDragTypes = new QStringList();
+        *currentCustomDragTypes = customTypes;
+        const NSString* mimeTypeGeneric = @"com.trolltech.qt.MimeTypeName";
+        NSMutableArray *supportedTypes = [NSMutableArray arrayWithObjects:NSColorPboardType,
+                       NSFilenamesPboardType, NSStringPboardType,
+                       NSFilenamesPboardType, NSPostScriptPboardType, NSTIFFPboardType,
+                       NSRTFPboardType, NSTabularTextPboardType, NSFontPboardType,
+                       NSRulerPboardType, NSFileContentsPboardType, NSColorPboardType,
+                       NSRTFDPboardType, NSHTMLPboardType, NSPICTPboardType,
+                       NSURLPboardType, NSPDFPboardType, NSVCardPboardType,
+                       NSFilesPromisePboardType, NSInkTextPboardType,
+                       NSMultipleTextSelectionPboardType, mimeTypeGeneric, nil];
+        // Add custom types supported by the application.
+        for (int i = 0; i < customTypes.size(); i++) {
+           [supportedTypes addObject:reinterpret_cast<const NSString *>(QCFString::toCFStringRef(customTypes[i]))];
+        }
+        [self registerForDraggedTypes:supportedTypes];
+    }
+}
+
+- (QWidget *)dragTargetHitTest:(id <NSDraggingInfo>)sender
+{
+    // Do a hittest to find the NSView under the
+    // mouse, and return the corresponding QWidget:
+    NSPoint windowPoint = [sender draggingLocation];
+    NSView *candidateView = [[self contentView] hitTest:windowPoint];
+    if (![candidateView isKindOfClass:[QT_MANGLE_NAMESPACE(QCocoaView) class]])
+        return 0;
+    return [static_cast<QT_MANGLE_NAMESPACE(QCocoaView) *>(candidateView) qt_qwidget];
+}
+
+- (NSDragOperation)draggingEntered:(id <NSDraggingInfo>)sender
+{
+    // The user dragged something into the window. Send a draggingEntered message
+    // to the QWidget under the mouse. As the drag moves over the window, and over
+    // different widgets, we will handle enter and leave events from within 
+    // draggingUpdated below. The reason why we handle this ourselves rather than
+    // subscribing for drag events directly in QCocoaView is that calling 
+    // registerForDraggedTypes on the views will severly degrade initialization time
+    // for an application that uses a lot of drag subscribing widgets.
+
+    QWidget *target = [self dragTargetHitTest:sender];
+    if (!target)
+        return [super draggingEntered:sender];
+    if (target->testAttribute(Qt::WA_DropSiteRegistered) == false)
+        return NSDragOperationNone;
+
+    *currentDragTarget() = target;
+    return [reinterpret_cast<NSView *>((*currentDragTarget())->winId()) draggingEntered:sender];
+ }
+
+- (NSDragOperation)draggingUpdated:(id < NSDraggingInfo >)sender
+{
+    QWidget *target = [self dragTargetHitTest:sender];
+    if (!target)
+        return [super draggingUpdated:sender];
+
+    if (target == *currentDragTarget()) {
+        // The drag continues to move over the widget that we have sendt
+        // a draggingEntered message to. So just update the view:
+        return [reinterpret_cast<NSView *>((*currentDragTarget())->winId()) draggingUpdated:sender];
+    } else {
+        // The widget under the mouse has changed.
+        // So we need to fake enter/leave events:
+        if (*currentDragTarget())
+            [reinterpret_cast<NSView *>((*currentDragTarget())->winId()) draggingExited:sender];
+        if (target->testAttribute(Qt::WA_DropSiteRegistered) == false) {
+            *currentDragTarget() = 0;
+            return NSDragOperationNone;
+        }
+        *currentDragTarget() = target;
+        return [reinterpret_cast<NSView *>((*currentDragTarget())->winId()) draggingEntered:sender];
+    }
+}
+
+- (void)draggingExited:(id < NSDraggingInfo >)sender
+{
+    if (*currentDragTarget())
+        [reinterpret_cast<NSView *>((*currentDragTarget())->winId()) draggingExited:sender];
+    else
+        [super draggingExited:sender];
+    *currentDragTarget() = 0;
+}
+
+- (BOOL)performDragOperation:(id < NSDraggingInfo >)sender
+{
+    BOOL dropAccepted = NO;
+    if (*currentDragTarget())
+        dropAccepted = [reinterpret_cast<NSView *>((*currentDragTarget())->winId()) performDragOperation:sender];
+    else
+        return [super performDragOperation:sender];
+    *currentDragTarget() = 0;
+    return dropAccepted;
+}
+
diff --git a/src/gui/kernel/qcocoaview_mac.mm b/src/gui/kernel/qcocoaview_mac.mm
index ddd8ca611c..212684bff6 100644
--- a/src/gui/kernel/qcocoaview_mac.mm
+++ b/src/gui/kernel/qcocoaview_mac.mm
@@ -81,7 +81,6 @@ Q_GLOBAL_STATIC(DnDParams, qMacDnDParams);
 extern void qt_mac_update_cursor_at_global_pos(const QPoint &globalPos); // qcursor_mac.mm
 extern bool qt_sendSpontaneousEvent(QObject *, QEvent *); // qapplication.cpp
 extern OSViewRef qt_mac_nativeview_for(const QWidget *w); // qwidget_mac.mm
-extern const QStringList& qEnabledDraggedTypes(); // qmime_mac.cpp
 extern QPointer<QWidget> qt_mouseover; //qapplication_mac.mm
 extern QPointer<QWidget> qt_button_down; //qapplication_mac.cpp
 
@@ -212,7 +211,6 @@ extern "C" {
     composingText = new QString();
     composing = false;
     sendKeyEvents = true;
-    currentCustomTypes = 0;
     [self setHidden:YES];
     return self;
 }
@@ -227,34 +225,6 @@ extern "C" {
                                                object:self];
 }
 
--(void)registerDragTypes
-{
-    QMacCocoaAutoReleasePool pool;
-    // Calling registerForDraggedTypes is slow, so only do it once for each widget
-    // or when the custom types change.
-    const QStringList& customTypes = qEnabledDraggedTypes();
-    if (currentCustomTypes == 0 || *currentCustomTypes != customTypes) {
-        if (currentCustomTypes == 0)
-            currentCustomTypes = new QStringList();
-        *currentCustomTypes = customTypes;
-        const NSString* mimeTypeGeneric = @"com.trolltech.qt.MimeTypeName";
-	NSMutableArray *supportedTypes = [NSMutableArray arrayWithObjects:NSColorPboardType,
-                                   NSFilenamesPboardType, NSStringPboardType,
-                                   NSFilenamesPboardType, NSPostScriptPboardType, NSTIFFPboardType,
-                                   NSRTFPboardType, NSTabularTextPboardType, NSFontPboardType,
-                                   NSRulerPboardType, NSFileContentsPboardType, NSColorPboardType,
-                                   NSRTFDPboardType, NSHTMLPboardType, NSPICTPboardType,
-                                   NSURLPboardType, NSPDFPboardType, NSVCardPboardType,
-                                   NSFilesPromisePboardType, NSInkTextPboardType,
-                                   NSMultipleTextSelectionPboardType, mimeTypeGeneric, nil];
-        // Add custom types supported by the application.
-        for (int i = 0; i < customTypes.size(); i++) {
-           [supportedTypes addObject:reinterpret_cast<const NSString *>(QCFString::toCFStringRef(customTypes[i]))];
-        }
-        [self registerForDraggedTypes:supportedTypes];
-    }
-}
-
 - (void)resetCursorRects
 {
     QWidget *cursorWidget = qwidget;
@@ -300,15 +270,9 @@ extern "C" {
 
 - (NSDragOperation)draggingEntered:(id <NSDraggingInfo>)sender
 {
-    if (qwidget->testAttribute(Qt::WA_DropSiteRegistered) == false)
-        return NSDragOperationNone;
+    // NB: This function is called from QCoocaWindow/QCocoaPanel rather than directly
+    // from Cocoa. They modify the drag target, and might fake enter/leave events.
     NSPoint windowPoint = [sender draggingLocation];
-    if (qwidget->testAttribute(Qt::WA_TransparentForMouseEvents)) {
-        // pass the drag enter event to the view underneath.
-        NSView *candidateView = [[[self window] contentView] hitTest:windowPoint];
-        if (candidateView && candidateView != self)
-            return [candidateView draggingEntered:sender];
-    }
     dragEnterSequence = [sender draggingSequenceNumber];
     [self addDropData:sender];
     QMimeData *mimeData = dropData;
@@ -360,13 +324,9 @@ extern "C" {
 
 - (NSDragOperation)draggingUpdated:(id < NSDraggingInfo >)sender
 {
+    // NB: This function is called from QCoocaWindow/QCocoaPanel rather than directly
+    // from Cocoa. They modify the drag target, and might fake enter/leave events.
     NSPoint windowPoint = [sender draggingLocation];
-    if (qwidget->testAttribute(Qt::WA_TransparentForMouseEvents)) {
-        // pass the drag move event to the view underneath.
-        NSView *candidateView = [[[self window] contentView] hitTest:windowPoint];
-        if (candidateView && candidateView != self)
-            return [candidateView draggingUpdated:sender];
-    }
     // in cases like QFocusFrame, the view under the mouse might
     // not have received the drag enter. Generate a synthetic
     // drag enter event for that view.
@@ -414,14 +374,10 @@ extern "C" {
 
 - (void)draggingExited:(id < NSDraggingInfo >)sender
 {
+    // NB: This function is called from QCoocaWindow/QCocoaPanel rather than directly
+    // from Cocoa. They modify the drag target, and might fake enter/leave events.
+    Q_UNUSED(sender);
     dragEnterSequence = -1;
-    if (qwidget->testAttribute(Qt::WA_TransparentForMouseEvents)) {
-        // try sending the leave event to the last view which accepted drag enter.
-        DnDParams *dndParams = [QT_MANGLE_NAMESPACE(QCocoaView) currentMouseEvent];
-        NSView *candidateView = [[[self window] contentView] hitTest:dndParams->activeDragEnterPos];
-        if (candidateView && candidateView != self)
-            return [candidateView draggingExited:sender];
-    }
     // drag enter event was rejected, so ignore the move event.
     if (dropData) {
         QDragLeaveEvent de;
@@ -432,14 +388,10 @@ extern "C" {
 
 - (BOOL)performDragOperation:(id <NSDraggingInfo>)sender
 {
+    // NB: This function is called from QCoocaWindow/QCocoaPanel rather than directly
+    // from Cocoa. They modify the drag target, and might fake enter/leave events.
     NSPoint windowPoint = [sender draggingLocation];
     dragEnterSequence = -1;
-    if (qwidget->testAttribute(Qt::WA_TransparentForMouseEvents)) {
-        // pass the drop event to the view underneath.
-        NSView *candidateView = [[[self window] contentView] hitTest:windowPoint];
-        if (candidateView && candidateView != self)
-            return [candidateView performDragOperation:sender];
-    }
     [self addDropData:sender];
 
     NSPoint globalPoint = [[sender draggingDestinationWindow] convertBaseToScreen:windowPoint];
@@ -469,8 +421,6 @@ extern "C" {
 {
     delete composingText;
     [[NSNotificationCenter defaultCenter] removeObserver:self];
-    delete currentCustomTypes;
-    [self unregisterDraggedTypes];
     [super dealloc];
 }
 
diff --git a/src/gui/kernel/qcocoaview_mac_p.h b/src/gui/kernel/qcocoaview_mac_p.h
index d549177b12..e6ff4234a2 100644
--- a/src/gui/kernel/qcocoaview_mac_p.h
+++ b/src/gui/kernel/qcocoaview_mac_p.h
@@ -87,7 +87,6 @@ Q_GUI_EXPORT
     int composingLength;
     bool sendKeyEvents;
     QString *composingText;
-    QStringList *currentCustomTypes;
     NSInteger dragEnterSequence;
 }
 - (id)initWithQWidget:(QWidget *)widget widgetPrivate:(QWidgetPrivate *)widgetprivate;
@@ -97,7 +96,6 @@ Q_GUI_EXPORT
 - (NSDragOperation)draggingUpdated:(id < NSDraggingInfo >)sender;
 - (void)draggingExited:(id < NSDraggingInfo >)sender;
 - (BOOL)performDragOperation:(id <NSDraggingInfo>)sender;
-- (void)registerDragTypes;
 - (void)removeDropData;
 - (void)addDropData:(id <NSDraggingInfo>)sender;
 - (void)setSupportedActions:(NSDragOperation)actions;
diff --git a/src/gui/kernel/qcocoawindow_mac_p.h b/src/gui/kernel/qcocoawindow_mac_p.h
index 91c5d4ee01..ea3461c8cc 100644
--- a/src/gui/kernel/qcocoawindow_mac_p.h
+++ b/src/gui/kernel/qcocoawindow_mac_p.h
@@ -70,9 +70,12 @@ QT_FORWARD_DECLARE_CLASS(QStringList);
 
 @interface QT_MANGLE_NAMESPACE(QCocoaWindow) : NSWindow {
     bool leftButtonIsRightButton;
+    QStringList *currentCustomDragTypes;
 }
 
 + (Class)frameViewClassForStyleMask:(NSUInteger)styleMask;
+- (void)registerDragTypes;
+
 @end
 #endif
 
diff --git a/src/gui/kernel/qnsthemeframe_mac_p.h b/src/gui/kernel/qnsthemeframe_mac_p.h
index af1406b86b..c8c7f4ac98 100644
--- a/src/gui/kernel/qnsthemeframe_mac_p.h
+++ b/src/gui/kernel/qnsthemeframe_mac_p.h
@@ -157,7 +157,7 @@
 - (void)resetCursorRects;
 - (char)shouldBeTreatedAsInkEvent:fp8;
 - (char)_shouldBeTreatedAsInkEventInInactiveWindow:fp8;
-- hitTest:(struct _NSPoint)fp8;
+//- hitTest:(struct _NSPoint)fp8; // collides with hittest in qcocoasharedwindowmethods_mac_p.h
 - (NSRect)_leftGroupRect;
 - (NSRect)_rightGroupRect;
 - (void)_updateWidgets;
diff --git a/src/gui/kernel/qwidget_mac.mm b/src/gui/kernel/qwidget_mac.mm
index 1907ccaa5c..c75358d5a5 100644
--- a/src/gui/kernel/qwidget_mac.mm
+++ b/src/gui/kernel/qwidget_mac.mm
@@ -4554,9 +4554,12 @@ void QWidgetPrivate::registerDropSite(bool on)
 #ifndef QT_MAC_USE_COCOA
     SetControlDragTrackingEnabled(qt_mac_nativeview_for(q), on);
 #else
-    NSView *view = qt_mac_nativeview_for(q);
-    if (on && [view isKindOfClass:[QT_MANGLE_NAMESPACE(QCocoaView) class]]) {
-        [static_cast<QT_MANGLE_NAMESPACE(QCocoaView) *>(view) registerDragTypes];
+    NSWindow *win = qt_mac_window_for(q);
+    if (on) {
+        if ([win isKindOfClass:[QT_MANGLE_NAMESPACE(QCocoaWindow) class]])
+            [static_cast<QT_MANGLE_NAMESPACE(QCocoaWindow) *>(win) registerDragTypes];
+        else if ([win isKindOfClass:[QT_MANGLE_NAMESPACE(QCocoaPanel) class]])
+            [static_cast<QT_MANGLE_NAMESPACE(QCocoaPanel) *>(win) registerDragTypes];
     }
 #endif
 }