// "Therefore those skilled at the unorthodox

// are infinite as heaven and earth,

// inexhaustible as the great rivers.

// When they come to an end,

// they begin again,

// like the days and months;

// they die and are reborn,

// like the four seasons."

//

// - Sun Tsu,

// "The Art of War"

using System.Windows;

using System.Windows.Controls;

using System.Windows.Controls.Primitives;

using System.Windows.Input;

using System.Windows.Media;

using TheArtOfDev.HtmlRenderer.Core.Entities;

using TheArtOfDev.HtmlRenderer.Core.Utils;

namespace TheArtOfDev.HtmlRenderer.WPF

{

/// <summary>

/// Provides HTML rendering using the text property.<br/>

/// WPF control that will render html content in it's client rectangle.<br/>

/// If the layout of the html resulted in its content beyond the client bounds of the panel it will show scrollbars (horizontal/vertical) allowing to scroll the content.<br/>

/// The control will handle mouse and keyboard events on it to support html text selection, copy-paste and mouse clicks.<br/>

/// </summary>

/// <remarks>

/// See <see cref="HtmlControl"/> for more info.

/// </remarks>

public class HtmlPanel : HtmlControl

{

#region Fields and Consts

/// <summary>

/// the vertical scroll bar for the control to scroll to html content out of view

/// </summary>

protected ScrollBar _verticalScrollBar;

/// <summary>

/// the horizontal scroll bar for the control to scroll to html content out of view

/// </summary>

protected ScrollBar _horizontalScrollBar;

#endregion

static HtmlPanel()

{

BackgroundProperty.OverrideMetadata(typeof(HtmlPanel), new FrameworkPropertyMetadata(SystemColors.WindowBrush));

TextProperty.OverrideMetadata(typeof(HtmlPanel), new PropertyMetadata(null, OnTextProperty_change));

}

/// <summary>

/// Creates a new HtmlPanel and sets a basic css for it's styling.

/// </summary>

public HtmlPanel()

{

_verticalScrollBar = new ScrollBar();

_verticalScrollBar.Orientation = Orientation.Vertical;

_verticalScrollBar.Width = 18;

_verticalScrollBar.Scroll += OnScrollBarScroll;

AddVisualChild(_verticalScrollBar);

AddLogicalChild(_verticalScrollBar);

_horizontalScrollBar = new ScrollBar();

_horizontalScrollBar.Orientation = Orientation.Horizontal;

_horizontalScrollBar.Height = 18;

_horizontalScrollBar.Scroll += OnScrollBarScroll;

AddVisualChild(_horizontalScrollBar);

AddLogicalChild(_horizontalScrollBar);

_htmlContainer.ScrollChange += OnScrollChange;

}

/// <summary>

/// Adjust the scrollbar of the panel on html element by the given id.<br/>

/// The top of the html element rectangle will be at the top of the panel, if there

/// is not enough height to scroll to the top the scroll will be at maximum.<br/>

/// </summary>

/// <param name="elementId">the id of the element to scroll to</param>

public virtual void ScrollToElement(string elementId)

{

ArgChecker.AssertArgNotNullOrEmpty(elementId, "elementId");

if (_htmlContainer != null)

{

var rect = _htmlContainer.GetElementRectangle(elementId);

if (rect.HasValue)

{

ScrollToPoint(rect.Value.Location.X, rect.Value.Location.Y);

_htmlContainer.HandleMouseMove(this, Mouse.GetPosition(this));

}

}

}

#region Private methods

protected override int VisualChildrenCount

{

get { return 2; }

}

protected override Visual GetVisualChild(int index)

{

if (index == 0)

return _verticalScrollBar;

else if (index == 1)

return _horizontalScrollBar;

return null;

}

/// <summary>

/// Perform the layout of the html in the control.

/// </summary>

protected override Size MeasureOverride(Size constraint)

{

Size size = PerformHtmlLayout(constraint);

// to handle if scrollbar is appearing or disappearing

bool relayout = false;

var htmlWidth = HtmlWidth(constraint);

var htmlHeight = HtmlHeight(constraint);

if ((_verticalScrollBar.Visibility == Visibility.Hidden && size.Height > htmlHeight) ||

(_verticalScrollBar.Visibility == Visibility.Visible && size.Height <= htmlHeight))

{

_verticalScrollBar.Visibility = _verticalScrollBar.Visibility == Visibility.Visible ? Visibility.Hidden : Visibility.Visible;

relayout = true;

}

if ((_horizontalScrollBar.Visibility == Visibility.Hidden && size.Width > htmlWidth) ||

(_horizontalScrollBar.Visibility == Visibility.Visible && size.Width <= htmlWidth))

{

_horizontalScrollBar.Visibility = _horizontalScrollBar.Visibility == Visibility.Visible ? Visibility.Hidden : Visibility.Visible;

relayout = true;

}

if (relayout)

PerformHtmlLayout(constraint);

if (double.IsPositiveInfinity(constraint.Width) || double.IsPositiveInfinity(constraint.Height))

constraint = size;

return constraint;

}

/// <summary>

/// After measurement arrange the scrollbars of the panel.

/// </summary>

protected override Size ArrangeOverride(Size bounds)

{

var scrollHeight = HtmlHeight(bounds) + Padding.Top + Padding.Bottom;

scrollHeight = scrollHeight > 1 ? scrollHeight : 1;

var scrollWidth = HtmlWidth(bounds) + Padding.Left + Padding.Right;

scrollWidth = scrollWidth > 1 ? scrollWidth : 1;

_verticalScrollBar.Arrange(new Rect(System.Math.Max(bounds.Width - _verticalScrollBar.Width - BorderThickness.Right, 0), BorderThickness.Top, _verticalScrollBar.Width, scrollHeight));

_horizontalScrollBar.Arrange(new Rect(BorderThickness.Left, System.Math.Max(bounds.Height - _horizontalScrollBar.Height - BorderThickness.Bottom, 0), scrollWidth, _horizontalScrollBar.Height));

if (_htmlContainer != null)

{

if (_verticalScrollBar.Visibility == Visibility.Visible)

{

_verticalScrollBar.ViewportSize = HtmlHeight(bounds);

_verticalScrollBar.SmallChange = 25;

_verticalScrollBar.LargeChange = _verticalScrollBar.ViewportSize * .9;

_verticalScrollBar.Maximum = _htmlContainer.ActualSize.Height - _verticalScrollBar.ViewportSize;

}

if (_horizontalScrollBar.Visibility == Visibility.Visible)

{

_horizontalScrollBar.ViewportSize = HtmlWidth(bounds);

_horizontalScrollBar.SmallChange = 25;

_horizontalScrollBar.LargeChange = _horizontalScrollBar.ViewportSize * .9;

_horizontalScrollBar.Maximum = _htmlContainer.ActualSize.Width - _horizontalScrollBar.ViewportSize;

}

// update the scroll offset because the scroll values may have changed

UpdateScrollOffsets();

}

return bounds;

}

/// <summary>

/// Perform html container layout by the current panel client size.

/// </summary>

protected Size PerformHtmlLayout(Size constraint)

{

if (_htmlContainer != null)

{

_htmlContainer.MaxSize = new Size(HtmlWidth(constraint), 0);

_htmlContainer.PerformLayout();

return _htmlContainer.ActualSize;

}

return Size.Empty;

}

/// <summary>

/// Handle minor case where both scroll are visible and create a rectangle at the bottom right corner between them.

/// </summary>

protected override void OnRender(DrawingContext context)

{

base.OnRender(context);

// render rectangle in right bottom corner where both scrolls meet

if (_horizontalScrollBar.Visibility == Visibility.Visible && _verticalScrollBar.Visibility == Visibility.Visible)

context.DrawRectangle(SystemColors.ControlBrush, null, new Rect(BorderThickness.Left + HtmlWidth(RenderSize), BorderThickness.Top + HtmlHeight(RenderSize), _verticalScrollBar.Width, _horizontalScrollBar.Height));

}

/// <summary>

/// Handle mouse up to set focus on the control.

/// </summary>

protected override void OnMouseUp(MouseButtonEventArgs e)

{

base.OnMouseUp(e);

Focus();

}

/// <summary>

/// Handle mouse wheel for scrolling.

/// </summary>

protected override void OnMouseWheel(MouseWheelEventArgs e)

{

base.OnMouseWheel(e);

if (_verticalScrollBar.Visibility == Visibility.Visible)

{

_verticalScrollBar.Value -= e.Delta;

UpdateScrollOffsets();

e.Handled = true;

}

}

/// <summary>

/// Handle key down event for selection, copy and scrollbars handling.

/// </summary>

protected override void OnKeyDown(KeyEventArgs e)

{

base.OnKeyDown(e);

if (_verticalScrollBar.Visibility == Visibility.Visible)

{

if (e.Key == Key.Up)

{

_verticalScrollBar.Value -= _verticalScrollBar.SmallChange;

UpdateScrollOffsets();

e.Handled = true;

}

else if (e.Key == Key.Down)

{

_verticalScrollBar.Value += _verticalScrollBar.SmallChange;

UpdateScrollOffsets();

e.Handled = true;

}

else if (e.Key == Key.PageUp)

{

_verticalScrollBar.Value -= _verticalScrollBar.LargeChange;

UpdateScrollOffsets();

e.Handled = true;

}

else if (e.Key == Key.PageDown)

{

_verticalScrollBar.Value += _verticalScrollBar.LargeChange;

UpdateScrollOffsets();

e.Handled = true;

}

else if (e.Key == Key.Home)

{

_verticalScrollBar.Value = 0;

UpdateScrollOffsets();

e.Handled = true;

}

else if (e.Key == Key.End)

{

_verticalScrollBar.Value = _verticalScrollBar.Maximum;

UpdateScrollOffsets();

e.Handled = true;

}

}

if (_horizontalScrollBar.Visibility == Visibility.Visible)

{

if (e.Key == Key.Left)

{

_horizontalScrollBar.Value -= _horizontalScrollBar.SmallChange;

UpdateScrollOffsets();

e.Handled = true;

}

else if (e.Key == Key.Right)

{

_horizontalScrollBar.Value += _horizontalScrollBar.SmallChange;

UpdateScrollOffsets();

e.Handled = true;

}

}

}

/// <summary>

/// Get the width the HTML has to render in (not including vertical scroll iff it is visible)

/// </summary>

protected override double HtmlWidth(Size size)

{

var width = base.HtmlWidth(size) - (_verticalScrollBar.Visibility == Visibility.Visible ? _verticalScrollBar.Width : 0);

return width > 1 ? width : 1;

}

/// <summary>

/// Get the width the HTML has to render in (not including vertical scroll iff it is visible)

/// </summary>

protected override double HtmlHeight(Size size)

{

var height = base.HtmlHeight(size) - (_horizontalScrollBar.Visibility == Visibility.Visible ? _horizontalScrollBar.Height : 0);

return height > 1 ? height : 1;

}

/// <summary>

/// On HTML container scroll change request scroll to the requested location.

/// </summary>

private void OnScrollChange(object sender, HtmlScrollEventArgs e)

{

ScrollToPoint(e.X, e.Y);

}

/// <summary>

/// Set the control scroll offset to the given values.

/// </summary>

private void ScrollToPoint(double x, double y)

{

_horizontalScrollBar.Value = x;

_verticalScrollBar.Value = y;

UpdateScrollOffsets();

}

/// <summary>

/// On scrollbar scroll update the scroll offsets and invalidate.

/// </summary>

private void OnScrollBarScroll(object sender, ScrollEventArgs e)

{

UpdateScrollOffsets();

}

/// <summary>

/// Update the scroll offset of the HTML container and invalidate visual to re-render.

/// </summary>

private void UpdateScrollOffsets()

{

var newScrollOffset = new Point(-_horizontalScrollBar.Value, -_verticalScrollBar.Value);

if (!newScrollOffset.Equals(_htmlContainer.ScrollOffset))

{

_htmlContainer.ScrollOffset = newScrollOffset;

InvalidateVisual();

}

}

/// <summary>

/// On text property change reset the scrollbars to zero.

/// </summary>

private static void OnTextProperty_change(DependencyObject d, DependencyPropertyChangedEventArgs e)

{

var panel = d as HtmlPanel;

if (panel != null)

panel._horizontalScrollBar.Value = panel._verticalScrollBar.Value = 0;

}

#endregion

}

}