//
// Urho3D Engine
// Copyright (c) 2008-2011 Lasse Öörni
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
//

#pragma once

#include "UIElement.h"

class BorderImage;
class ScrollBar;

/// Scrollable UI element for showing a (possibly large) child element
class ScrollView : public UIElement
{
    OBJECT(ScrollView);
    
    using UIElement::SetStyle;
    
public:
    /// Construct
    ScrollView(Context* context);
    /// Destruct
    virtual ~ScrollView();
    /// Register object factory
    static void RegisterObject(Context* context);
    
    /// Set UI element style from XML data
    virtual void SetStyle(const XMLElement& element);
    /// React to mouse wheel
    virtual void OnWheel(int delta, int buttons, int qualifiers);
    /// React to a key press
    virtual void OnKey(int key, int buttons, int qualifiers);
    /// React to resize
    virtual void OnResize();
    
    /// Set content element
    void SetContentElement(UIElement* element);
    /// Set view offset from the top-left corner
    void SetViewPosition(const IntVector2& position);
    /// Set view offset from the top-left corner
    void SetViewPosition(int x, int y);
    /// Set scrollbars' visibility
    void SetScrollBarsVisible(bool horizontal, bool vertical);
    /// Set arrow key scroll step. Also sets it on the scrollbars
    void SetScrollStep(float step);
    /// Set arrow key page step
    void SetPageStep(float step);
    
    /// Return view offset from the top-left corner
    const IntVector2& GetViewPosition() const { return viewPosition_; }
    /// Return content element
    UIElement* GetContentElement() const { return contentElement_; }
    /// Return horizontal scroll bar
    ScrollBar* GetHorizontalScrollBar() const { return horizontalScrollBar_; }
    /// Return vertical scroll bar
    ScrollBar* GetVerticalScrollBar() const { return verticalScrollBar_; }
    /// Return scroll panel
    BorderImage* GetScrollPanel() const { return scrollPanel_; }
    /// Return arrow key scroll step
    float GetScrollStep() const;
    /// Return arrow key page step
    float GetPageStep() const { return pageStep_; }
    
protected:
    /// Update view size from the content element
    void UpdateViewSize();
    /// Update the scrollbars' ranges and positions
    void UpdateScrollBars();
    /// Limit and update the view with a new position
    void UpdateView(const IntVector2& position);
    
    /// Content element
    SharedPtr<UIElement> contentElement_;
    /// Horizontal scroll bar
    SharedPtr<ScrollBar> horizontalScrollBar_;
    /// Vertical scroll bar
    SharedPtr<ScrollBar> verticalScrollBar_;
    /// Scroll panel element
    SharedPtr<BorderImage> scrollPanel_;
    /// Current view offset from the top-left corner
    IntVector2 viewPosition_;
    /// Total view size
    IntVector2 viewSize_;
    /// Arrow key page step
    float pageStep_;
    /// Ignore scrollbar events flag. Used to prevent possible endless loop when setting position
    bool ignoreEvents_;
    
private:
    /// Handle scrollbar value changed
    void HandleScrollBarChanged(StringHash eventType, VariantMap& eventData);
    /// Handle scrollbar visibility changed
    void HandleScrollBarVisibleChanged(StringHash eventType, VariantMap& eventData);
    /// Handle content element resized
    void HandleElementResized(StringHash eventType, VariantMap& eventData);
};