Scrolling Tabs

chrome/browser/ui/touch/tabs/touch_tab_strip.h

 // Copyright (c) 2011 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.
 
 #ifndef CHROME_BROWSER_UI_TOUCH_TABS_TOUCH_TAB_STRIP_H_
 #define CHROME_BROWSER_UI_TOUCH_TABS_TOUCH_TAB_STRIP_H_
 #pragma once
 
 #include "chrome/browser/ui/views/tabs/base_tab_strip.h"
 
 class TouchTab;
 
 ///////////////////////////////////////////////////////////////////////////////
 //
 // TouchTabStrip
 //
 //  A View that represents the TabStripModel. The TouchTabStrip has the
 //  following responsibilities:
 //    - It implements the TabStripModelObserver interface, and acts as a
 //      container for Tabs, and is also responsible for creating them.
 //
+// TODO(wyck): Use transformable views for scrolling.
 ///////////////////////////////////////////////////////////////////////////////
 class TouchTabStrip : public BaseTabStrip {
  public:
   explicit TouchTabStrip(TabStripController* controller);
   virtual ~TouchTabStrip();
 
   // AbstractTabStripView implementation:
   virtual bool IsPositionInWindowCaption(const gfx::Point& point);
   virtual void SetBackgroundOffset(const gfx::Point& offset);
 
   // BaseTabStrip implementation:
   virtual void PrepareForCloseAt(int model_index);
   virtual void StartHighlight(int model_index);
   virtual void StopAllHighlighting();
   virtual BaseTab* CreateTabForDragging();
   virtual void RemoveTabAt(int model_index);
   virtual void SelectTabAt(int old_model_index, int new_model_index);
   virtual void TabTitleChangedNotLoading(int model_index);
   virtual BaseTab* CreateTab();
   virtual void StartInsertTabAnimation(int model_index);
   virtual void AnimateToIdealBounds();
   virtual bool ShouldHighlightCloseButtonAfterRemove();
   virtual void GenerateIdealBounds();
   virtual void LayoutDraggedTabsAt(const std::vector<BaseTab*>& tabs,
                                    BaseTab* active_tab,
                                    const gfx::Point& location,
                                    bool initial_drag);
   virtual int GetSizeNeededForTabs(const std::vector<BaseTab*>& tabs);
 
+  // views::View overrides:
+  virtual bool OnMousePressed(const views::MouseEvent& event) OVERRIDE;
+  virtual bool OnMouseDragged(const views::MouseEvent& event) OVERRIDE;
+  virtual void OnMouseReleased(const views::MouseEvent& event,
+                               bool canceled) OVERRIDE;
+
   // Retrieves the Tab at the specified index. Remember, the specified index
   // is in terms of tab_data, *not* the model.
   TouchTab* GetTabAtTabDataIndex(int tab_data_index) const;
 
  private:
   void Init();
 
   // Overridden from views::View.
   virtual gfx::Size GetPreferredSize() OVERRIDE;
   virtual void PaintChildren(gfx::Canvas* canvas) OVERRIDE;
   virtual views::View::TouchStatus OnTouchEvent(
       const views::TouchEvent& event) OVERRIDE;
   virtual void ViewHierarchyChanged(bool is_add,
                                     View* parent,
                                     View* child) OVERRIDE;
 
+  // Adjusts the state of scroll interaction when a mouse press occurs at the
+  // given point.  Sets an appropriate |initial_scroll_offset_|.
+  void BeginScroll(const gfx::Point& point);
+
+  // Adjusts the state of scroll interaction when the mouse is dragged to the
+  // given point.  If the scroll is not beyond the minimum threshold, the tabs
+  // will not actually scroll.
+  void ContinueScroll(const gfx::Point& point);
+
+  // Adjusts the state of scroll interaction when the mouse is released.  Either
+  // scrolls to the final mouse release point or selects the current tab
+  // depending on whether the mouse was dragged beyone the minimum threshold.
+  void EndScroll(const gfx::Point& point);
+
+  // Adjust the positions of the tabs to perform a scroll of |delta_x| relative
+  // to the |initial_scroll_offset_|.
+  void ScrollTo(int delta_x);
+
   // True if PrepareForCloseAt has been invoked. When true remove animations
   // preserve current tab bounds.
   bool in_tab_close_;
 
   // Last time the tabstrip was tapped.
   base::Time last_tap_time_;
 
   // The view that was tapped last.
   View* last_tapped_view_;
 
+  // Records the mouse x coordinate at the start of a drag operation.
+  int initial_mouse_x_;
+
+  // Records the scroll offset at the time of the start of a drag operation.
+  int initial_scroll_offset_;
+
+  // The current offset of the view.  Positive scroll offsets move the icons to
+  // the left.  Negative scroll offsets move the icons to the right.
+  int scroll_offset_;
+
+  // State of the scrolling interaction.  Will be true once the drag has been
+  // displaced beyond the minimum dragging threshold.
+  bool scrolling_;
+
+  // Records the tab that was under the initial mouse press.  Must match the
+  // tab that was under the final mouse release in order for the tab to
+  // be selected.
+  TouchTab* initial_tab_;
+
+  // The minimum value that |scroll_offset_| can have.  Based on the total
+  // width of all the content to be scrolled, less the viewport size.
+  int min_scroll_offset_;
+
   DISALLOW_COPY_AND_ASSIGN(TouchTabStrip);
 };
 
 #endif  // CHROME_BROWSER_UI_TOUCH_TABS_TOUCH_TAB_STRIP_H_