Refactor intra-strip panel drags by introducing PanelDragController.

chrome/browser/ui/panels/detached_panel_strip.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/ui/panels/detached_panel_strip.h"
 
 #include <algorithm>
 #include "base/logging.h"
 #include "chrome/browser/ui/panels/panel_manager.h"
 
 DetachedPanelStrip::DetachedPanelStrip(PanelManager* panel_manager)
     : PanelStrip(PanelStrip::DETACHED),
-      panel_manager_(panel_manager) {
+      panel_manager_(panel_manager),
+      dragging_panel_(NULL) {
 }
 
 DetachedPanelStrip::~DetachedPanelStrip() {
   DCHECK(panels_.empty());
 }
 
 void DetachedPanelStrip::SetDisplayArea(const gfx::Rect& display_area) {
   if (display_area_ == display_area)
     return;
   display_area_ = display_area;
@@ skipping 48 matching lines @@
 void DetachedPanelStrip::MinimizePanel(Panel* panel) {
   DCHECK_EQ(this, panel->panel_strip());
   NOTIMPLEMENTED();
 }
 
 void DetachedPanelStrip::RestorePanel(Panel* panel) {
   DCHECK_EQ(this, panel->panel_strip());
   NOTIMPLEMENTED();
 }
 
+bool DetachedPanelStrip::CanDragPanel(Panel* panel) const {
+  // All detached panels are draggable.
+  return true;
+}
+
+void DetachedPanelStrip::StartDraggingPanel(Panel* panel) {
+  DCHECK(!dragging_panel_);
+
+  dragging_panel_ = panel;
+  dragging_panel_original_position_ = panel->GetBounds().origin();
+}
+
+void DetachedPanelStrip::DragPanel(int delta_x, int delta_y) {
+  DCHECK(dragging_panel_);
+
+  gfx::Rect new_bounds(dragging_panel_->GetBounds());
+  new_bounds.Offset(delta_x, delta_y);
+  dragging_panel_->SetPanelBounds(new_bounds);
+}
+
+void DetachedPanelStrip::EndDraggingPanel(bool cancelled) {
+  DCHECK(dragging_panel_);
+
+  if (cancelled) {
+    gfx::Rect new_bounds(dragging_panel_->GetBounds());
+    new_bounds.set_origin(dragging_panel_original_position_);
+    dragging_panel_->SetPanelBounds(new_bounds);
+  }

[Andrei, 2012/02/17 00:08:18]

It looks like cancelling the drag will happen very differently depending on
whether this panel changed strips during drag or not. If the drag was within one
strip, you simply call EndDraggingPanel() with cancelled=true. If strips were
changed, the controller has to remove/add it to where it started from, and to
use its own copy of dragging panel's original position. Is that so? Maybe we can
have the controller do the job in both cases?

[jianli, 2012/02/17 00:15:13]

Yes. Inter-strip drags are not included in this patch and I only assume the
drags are within this trip. When we add handling for inter-strip drags,
PanelDragController might do the job for both cases.

+
+  dragging_panel_ = NULL;
+}