Bug 463088 - Tab tear off cursor needs to be constant on Windows. r=enndeakin.

browser/base/content/tabbrowser.xml

@@ -1924,6 +1924,9 @@
             // the tab by dropping it on the desktop would result in an
             // "internet shortcut"
             dt.mozSetDataAt("text/plain", spec, 0);
+            
+            // Set the cursor to an arrow during tab drags.
+            dt.mozCursor = "default";
 
             var canvas = tabPreviews.capture(target, false);
             dt.setDragImage(canvas, 0, 0);

content/events/src/nsDOMDataTransfer.cpp

@@ -76,7 +76,8 @@ nsDOMDataTransfer::nsDOMDataTransfer()
     mIsExternal(PR_FALSE),
     mUserCancelled(PR_FALSE),
     mDragImageX(0),
-    mDragImageY(0)
+    mDragImageY(0),
+    mCursorState(PR_FALSE)
 {
 }
 
@@ -297,6 +298,25 @@ nsDOMDataTransfer::GetMozItemCount(PRUint32* aCount)
   return NS_OK;
 }
 
+NS_IMETHODIMP
+nsDOMDataTransfer::GetMozCursor(nsAString& aCursorState)
+{
+  if (mCursorState)
+    aCursorState.AssignASCII("default");
+  else
+    aCursorState.AssignASCII("auto");
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDOMDataTransfer::SetMozCursor(const nsAString& aCursorState)
+{
+  // Lock the cursor to an arrow during the drag.
+  mCursorState = aCursorState.EqualsASCII("default");
+
+  return NS_OK;
+}
+
 NS_IMETHODIMP
 nsDOMDataTransfer::MozTypesAt(PRUint32 aIndex, nsIDOMDOMStringList** aTypes)
 {

content/events/src/nsDOMDataTransfer.h

@@ -167,6 +167,9 @@ protected:
   PRUint32 mDropEffect;
   PRUint32 mEffectAllowed;
 
+  // Indicates the behavior of the cursor during drag operations
+  PRPackedBool mCursorState;
+
   // readonly data transfers may not be modified except the drop effect and
   // effect allowed.
   PRPackedBool mReadOnly;

dom/interfaces/events/nsIDOMDataTransfer.idl

@@ -39,7 +39,7 @@
 
 interface nsIVariant;
 
-[scriptable, uuid(B5947DD0-8E86-4B9C-AA65-C86303EFCF94)]
+[scriptable, uuid(E4970BA1-9567-455C-8B4E-4607D7E741BB)]
 interface nsIDOMDataTransfer : nsISupports
 {
   /**
@@ -180,6 +180,16 @@ interface nsIDOMNSDataTransfer : nsISupports
    */
   readonly attribute unsigned long mozItemCount;
 
+  /**
+   * Sets the drag cursor state. Primarily used to control the cursor during
+   * tab drags, but could be expanded to other uses.
+   *
+   * Possible values:
+   *  auto - use default system behavior.
+   *  default - set the cursor to an arrow during the drag operation.
+   */
+  attribute DOMString mozCursor;
+
   /**
    * Holds a list of the format types of the data that is stored for an item
    * at the specified index. If the index is not in the range from 0 to

widget/src/windows/nsDragService.cpp

@@ -270,7 +270,7 @@ nsDragService::StartInvokingDragSession(IDataObject * aDataObj,
 {
   // To do the drag we need to create an object that
   // implements the IDataObject interface (for OLE)
-  nsNativeDragSource* nativeDragSource = new nsNativeDragSource();
+  nsNativeDragSource* nativeDragSource = new nsNativeDragSource(mDataTransfer);
   if (!nativeDragSource)
     return NS_ERROR_OUT_OF_MEMORY;
 

widget/src/windows/nsNativeDragSource.cpp

@@ -38,14 +38,17 @@
 #include "nsNativeDragSource.h"
 #include <stdio.h>
 #include "nsISupportsImpl.h"
-
+#include "nsString.h"
 
 /*
  * class nsNativeDragSource
  */
-nsNativeDragSource::nsNativeDragSource()
+nsNativeDragSource::nsNativeDragSource(nsIDOMDataTransfer* aDataTransfer) :
-  : m_cRef(0), mUserCancelled(PR_FALSE)
+  m_cRef(0),
+  mUserCancelled(PR_FALSE),
+  m_hCursor(nsnull)
 {
+  mDataTransfer = do_QueryInterface(aDataTransfer);
 }
 
 nsNativeDragSource::~nsNativeDragSource()
@@ -122,5 +125,23 @@ nsNativeDragSource::GiveFeedback(DWORD dwEffect)
 #ifdef DEBUG
   //printf("GiveFeedback\n");
 #endif
+  
+  // For drags involving tabs, we do some custom work with cursors. 
+  if (mDataTransfer) {
+    nsAutoString cursor;
+    mDataTransfer->GetMozCursor(cursor);
+    if (cursor.EqualsASCII("default")) {
+      m_hCursor = ::LoadCursor(0, IDC_ARROW);
+    } else {
+      m_hCursor =  nsnull;
+    }
+  }
+
+  if (m_hCursor) {
+    ::SetCursor(m_hCursor);
+    return S_OK;
+  }
+  
+  // Let the system choose which cursor to apply.
 	return ResultFromScode(DRAGDROP_S_USEDEFAULTCURSORS);
 }

widget/src/windows/nsNativeDragSource.h

@@ -38,6 +38,8 @@
 #define _nsNativeDragSource_h_
 
 #include "nscore.h"
+#include "nsIDOMDataTransfer.h"
+#include "nsCOMPtr.h"
 #include <ole2.h>
 #include <oleidl.h>
 
@@ -53,7 +55,7 @@ public:
 
   // construct an nsNativeDragSource referencing adapter
   // nsNativeDragSource(nsIDragSource * adapter);
-  nsNativeDragSource();
+  nsNativeDragSource(nsIDOMDataTransfer* aDataTransfer);
   ~nsNativeDragSource();
 
   // IUnknown methods - see iunknown.h for documentation
@@ -78,7 +80,14 @@ public:
   PRPackedBool UserCancelled() { return mUserCancelled; }
 
 protected:
-  ULONG        m_cRef;     // reference count
+  // Reference count
+  ULONG m_cRef;
+
+  // Data object, hold information about cursor state
+  nsCOMPtr<nsIDOMNSDataTransfer> mDataTransfer;
+
+  // Custom drag cursor
+  HCURSOR m_hCursor;
 
   // true if the user cancelled the drag by pressing escape
   PRPackedBool mUserCancelled;