GTK: slightly change how we display drag images.

We use a popup window for the drag because in many window managers it looks better.

Ideally we would implement the alpha-channel fading that some other WebKit ports use, but gtk_drag_set_icon_* don't seem to support transparency (dragged tabs can be transparent because they use a different approach that avoids this problem, but is more complicated in other ways).

BUG=none
TEST=manual

Review URL: http://codereview.chromium.org/1519019

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@43976 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 38 insertions, 40 deletions

diff --git a/chrome/browser/gtk/tab_contents_drag_source.cc b/chrome/browser/gtk/tab_contents_drag_source.cc
index fc5ffd5..8e285d1 100644
--- a/chrome/browser/gtk/tab_contents_drag_source.cc
+++ b/chrome/browser/gtk/tab_contents_drag_source.cc
@@ -31,7 +31,8 @@ TabContentsDragSource::TabContentsDragSource(
     TabContentsView* tab_contents_view)
     : tab_contents_view_(tab_contents_view),
       drag_failed_(false),
-      drag_widget_(NULL) {
+      drag_widget_(NULL),
+      drag_icon_(NULL) {
   drag_widget_ = gtk_invisible_new();
   g_signal_connect(drag_widget_, "drag-failed",
                    G_CALLBACK(OnDragFailedThunk), this);
@@ -162,7 +163,7 @@ void TabContentsDragSource::DidProcessEvent(GdkEvent* event) {
   }
 }
 
-void TabContentsDragSource::OnDragDataGet(
+void TabContentsDragSource::OnDragDataGet(GtkWidget* sender,
     GdkDragContext* context, GtkSelectionData* selection_data,
     guint target_type, guint time) {
   const int kBitsPerByte = 8;
@@ -268,7 +269,9 @@ void TabContentsDragSource::OnDragDataGet(
   }
 }
 
-gboolean TabContentsDragSource::OnDragFailed() {
+gboolean TabContentsDragSource::OnDragFailed(GtkWidget* sender,
+                                             GdkDragContext* context,
+                                             GtkDragResult result) {
   drag_failed_ = true;
 
   gfx::Point root = gtk_util::ScreenPoint(GetContentNativeView());
@@ -284,7 +287,8 @@ gboolean TabContentsDragSource::OnDragFailed() {
   return FALSE;
 }
 
-void TabContentsDragSource::OnDragBegin(GdkDragContext* drag_context) {
+void TabContentsDragSource::OnDragBegin(GtkWidget* sender,
+                                        GdkDragContext* drag_context) {
   if (!download_url_.is_empty()) {
     // Generate the file name based on both mime type and proposed file name.
     std::string download_mime_type = UTF16ToUTF8(wide_download_mime_type_);
@@ -313,15 +317,25 @@ void TabContentsDragSource::OnDragBegin(GdkDragContext* drag_context) {
 
   if (!drag_image_.isNull()) {
     GdkPixbuf* pixbuf = gfx::GdkPixbufFromSkBitmap(&drag_image_);
-    gtk_drag_set_icon_pixbuf(drag_context, pixbuf,
-                             image_offset_.x(), image_offset_.y());
-    // Let the drag take ownership.
+    GtkWidget* image = gtk_image_new_from_pixbuf(pixbuf);
+    gtk_widget_show(image);
     g_object_unref(pixbuf);
+    drag_icon_ = gtk_window_new(GTK_WINDOW_POPUP);
+    g_object_ref_sink(drag_icon_);
+    gtk_container_add(GTK_CONTAINER(drag_icon_), image);
+
+    gtk_drag_set_icon_widget(drag_context, drag_icon_,
+                             image_offset_.x(), image_offset_.y());
   }
 }
 
-void TabContentsDragSource::OnDragEnd(GdkDragContext* drag_context,
-                                      GdkDragAction action) {
+void TabContentsDragSource::OnDragEnd(GtkWidget* sender,
+                                      GdkDragContext* drag_context) {
+  if (drag_icon_) {
+    g_object_unref(drag_icon_);
+    drag_icon_ = NULL;
+  }
+
   MessageLoopForUI::current()->RemoveObserver(this);
 
   if (!download_url_.is_empty()) {
@@ -337,7 +351,7 @@ void TabContentsDragSource::OnDragEnd(GdkDragContext* drag_context,
     if (tab_contents()->render_view_host()) {
       tab_contents()->render_view_host()->DragSourceEndedAt(
           client.x(), client.y(), root.x(), root.y(),
-          gtk_dnd_util::GdkDragActionToWebDragOp(action));
+          gtk_dnd_util::GdkDragActionToWebDragOp(drag_context->action));
     }
   }
 
diff --git a/chrome/browser/gtk/tab_contents_drag_source.h b/chrome/browser/gtk/tab_contents_drag_source.h
index 423f895..fbfaeee 100644
--- a/chrome/browser/gtk/tab_contents_drag_source.h
+++ b/chrome/browser/gtk/tab_contents_drag_source.h
@@ -7,6 +7,7 @@
 
 #include <gtk/gtk.h>
 
+#include "app/gtk_signal.h"
 #include "base/basictypes.h"
 #include "base/file_path.h"
 #include "base/message_loop.h"
@@ -43,36 +44,14 @@ class TabContentsDragSource : public MessageLoopForUI::Observer {
   virtual void DidProcessEvent(GdkEvent* event);
 
  private:
-  static gboolean OnDragFailedThunk(GtkWidget* widget,
-                                    GdkDragContext* drag_context,
-                                    GtkDragResult result,
-                                    TabContentsDragSource* handler) {
-    return handler->OnDragFailed();
-  }
-  gboolean OnDragFailed();
-  static void OnDragBeginThunk(GtkWidget* widget,
-                             GdkDragContext* drag_context,
-                             TabContentsDragSource* handler) {
-    handler->OnDragBegin(drag_context);
-  }
-  void OnDragBegin(GdkDragContext* drag_context);
-  static void OnDragEndThunk(GtkWidget* widget,
-                             GdkDragContext* drag_context,
-                             TabContentsDragSource* handler) {
-    handler->OnDragEnd(drag_context, drag_context->action);
-  }
-  void OnDragEnd(GdkDragContext* drag_context,
-                 GdkDragAction operation);
-  static void OnDragDataGetThunk(GtkWidget* drag_widget,
-                                 GdkDragContext* context,
-                                 GtkSelectionData* selection_data,
-                                 guint target_type,
-                                 guint time,
-                                 TabContentsDragSource* handler) {
-    handler->OnDragDataGet(context, selection_data, target_type, time);
-  }
-  void OnDragDataGet(GdkDragContext* context, GtkSelectionData* selection_data,
-                     guint target_type, guint time);
+  CHROMEGTK_CALLBACK_2(TabContentsDragSource, gboolean, OnDragFailed,
+                       GdkDragContext*, GtkDragResult);
+  CHROMEGTK_CALLBACK_1(TabContentsDragSource, void, OnDragBegin,
+                       GdkDragContext*);
+  CHROMEGTK_CALLBACK_1(TabContentsDragSource, void, OnDragEnd,
+                       GdkDragContext*);
+  CHROMEGTK_CALLBACK_4(TabContentsDragSource, void, OnDragDataGet,
+                       GdkDragContext*, GtkSelectionData*, guint, guint);
 
   gfx::NativeView GetContentNativeView() const;
 
@@ -109,6 +88,11 @@ class TabContentsDragSource : public MessageLoopForUI::Observer {
   // The URL to download from for a drag-out download.
   GURL download_url_;
 
+  // The widget that provides visual feedback for the drag. We use this instead
+  // of gtk_drag_set_icon_pixbuf() because some window managers will use shadows
+  // or other visual effects on top level windows.
+  GtkWidget* drag_icon_;
+
   DISALLOW_COPY_AND_ASSIGN(TabContentsDragSource);
 };