From 143a8203bdfef86cf174309e701f51f82df8fe42 Mon Sep 17 00:00:00 2001
From: Dimitri Schoolwerth <dimitri@schoolwerth.com>
Date: Wed, 27 May 2015 19:44:36 +0400
Subject: [PATCH] Fix dragging always resulting in wxDragLink on OS X

Commit f40e8bf uncovered a problem with dragging where when the
NSDragOperationLink bit is set in the drag mask (which by default always
is the case) the result is a wxDragLink operation instead of wxDragCopy
or wxDragMove. To fix this give priority to move and copy instead when
converting the drag mask to a wxDrag result.

This fixes copying through DND in wxRichTextCtrl.

See #13819.
---
 src/osx/cocoa/window.mm | 50 ++++++++++++++++++++++++++++++++---------
 1 file changed, 39 insertions(+), 11 deletions(-)

diff --git a/src/osx/cocoa/window.mm b/src/osx/cocoa/window.mm
index e4eabe8eea..d98cd3a682 100644
--- a/src/osx/cocoa/window.mm
+++ b/src/osx/cocoa/window.mm
@@ -1173,6 +1173,23 @@ unsigned int wxOnDraggingEnteredOrUpdated(wxWidgetCocoaImpl* viewImpl,
 {
     id <NSDraggingInfo>sender = (id <NSDraggingInfo>) s;
     NSPasteboard *pboard = [sender draggingPasteboard];
+    /*
+    sourceDragMask contains a flag field with drag operations permitted by
+    the source:
+    NSDragOperationCopy = 1,
+    NSDragOperationLink = 2,
+    NSDragOperationGeneric = 4,
+    NSDragOperationPrivate = 8,
+    NSDragOperationMove = 16,
+    NSDragOperationDelete = 32
+
+    By default, pressing modifier keys changes sourceDragMask:
+    Control ANDs it with NSDragOperationLink (2)
+    Option ANDs it with NSDragOperationCopy (1)
+    Command ANDs it with NSDragOperationGeneric (4)
+
+    The end result can be a mask that's 0 (NSDragOperationNone).
+    */
     NSDragOperation sourceDragMask = [sender draggingSourceOperationMask];
 
     wxWindow* wxpeer = viewImpl->GetWXPeer();
@@ -1183,16 +1200,26 @@ unsigned int wxOnDraggingEnteredOrUpdated(wxWidgetCocoaImpl* viewImpl,
     if ( target == NULL )
         return NSDragOperationNone;
 
-    wxDragResult result = wxDragNone;
     NSPoint nspoint = [viewImpl->GetWXWidget() convertPoint:[sender draggingLocation] fromView:nil];
     wxPoint pt = wxFromNSPoint( viewImpl->GetWXWidget(), nspoint );
 
-    if ( sourceDragMask & NSDragOperationLink )
-        result = wxDragLink;
-    else if ( sourceDragMask & NSDragOperationCopy )
-        result = wxDragCopy;
-    else if ( sourceDragMask & NSDragOperationMove )
+    /*
+    Convert the incoming mask to wxDragResult. This is a lossy conversion
+    because wxDragResult contains a single value and not a flag field.
+    When dragging the bottom part of the DND sample ("Drag text from here!")
+    sourceDragMask contains copy, link, generic, and private flags. Formerly
+    this would result in wxDragLink which is not what is expected for text.
+    Give precedence to the move and copy flag instead.
+    */
+    wxDragResult result = wxDragNone;
+
+    if (sourceDragMask & NSDragOperationMove)
         result = wxDragMove;
+    else if ( sourceDragMask & NSDragOperationCopy
+        || sourceDragMask & NSDragOperationGeneric)
+        result = wxDragCopy;
+    else if (sourceDragMask & NSDragOperationLink)
+        result = wxDragLink;
 
     PasteboardRef pboardRef;
     PasteboardCreate((CFStringRef)[pboard name], &pboardRef);
@@ -1276,12 +1303,13 @@ bool wxWidgetCocoaImpl::performDragOperation(void* s, WXWidget WXUNUSED(slf), vo
     NSPoint nspoint = [m_osxView convertPoint:[sender draggingLocation] fromView:nil];
     wxPoint pt = wxFromNSPoint( m_osxView, nspoint );
 
-    if ( sourceDragMask & NSDragOperationLink )
-        result = wxDragLink;
-    else if ( sourceDragMask & NSDragOperationCopy )
-        result = wxDragCopy;
-    else if ( sourceDragMask & NSDragOperationMove )
+    if (sourceDragMask & NSDragOperationMove)
         result = wxDragMove;
+    else if ( sourceDragMask & NSDragOperationCopy
+        || sourceDragMask & NSDragOperationGeneric)
+        result = wxDragCopy;
+    else if (sourceDragMask & NSDragOperationLink)
+        result = wxDragLink;
 
     PasteboardRef pboardRef;
     PasteboardCreate((CFStringRef)[pboard name], &pboardRef);