//-----------------------------------------------------------------------
// <copyright file="Placeholder.cs" company="Jeow Li Huan">
// Copyright (c) Jeow Li Huan. All rights reserved.
// </copyright>
//-----------------------------------------------------------------------
using System;
using System.Collections.Generic;
using System.Globalization;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Controls.Primitives;
using System.Windows.Documents;
using System.Windows.Media;
namespace TetonWhitewaterKayak.WinUI
{
/// <summary>
/// Represents an adorner that adds placeholder text to a <see cref="T:System.Windows.Controls.TextBox"/>,
/// <see cref="T:System.Windows.Controls.RichTextBox"/> or <see cref="T:System.Windows.Controls.PasswordBox"/>.
/// </summary>
public class Placeholder : Adorner
{
#region Dependency Property
/// <summary>
/// Identifies the <see cref="T:Huan.Windows.Documents.Placeholder" />.Text attached property.
/// </summary>
public static readonly DependencyProperty TextProperty = DependencyProperty.RegisterAttached(
"Text",
typeof(string),
typeof(Placeholder),
new FrameworkPropertyMetadata(string.Empty, OnTextChanged));
/// <summary>
/// Identifies the <see cref="T:Huan.Windows.Documents.Placeholder" />.HideOnFocus attached property.
/// </summary>
public static readonly DependencyProperty HideOnFocusProperty = DependencyProperty.RegisterAttached(
"HideOnFocus",
typeof(bool),
typeof(Placeholder),
new FrameworkPropertyMetadata(true, OnHideOnFocusChanged));
#endregion
/// <summary>
/// <see langword="true"/> when the placeholder text is visible, <see langword="false" /> otherwise.
/// Used to avoid calling <see cref="M:System.Windows.UIElement.InvalidateVisual"/> unnecessarily.
/// </summary>
private bool isPlaceholderVisible;
#region Constructors
/// <summary>
/// Initializes static members of the <see cref="T:Huan.Windows.Documents.Placeholder"/> class.
/// </summary>
static Placeholder()
{
IsHitTestVisibleProperty.OverrideMetadata(typeof(Placeholder), new FrameworkPropertyMetadata(false));
ClipToBoundsProperty.OverrideMetadata(typeof(Placeholder), new FrameworkPropertyMetadata(true));
}
/// <summary>
/// Initializes a new instance of the <see cref="T:Huan.Windows.Documents.Placeholder"/> class.
/// </summary>
/// <param name="adornedElement">
/// The element to bind the adorner to.
/// </param>
/// <exception cref="T:System.ArgumentNullException">
/// Raised when adornedElement is null.
/// </exception>
public Placeholder(PasswordBox adornedElement)
: this((Control)adornedElement)
{
if (!(adornedElement.IsFocused && (bool)adornedElement.GetValue(HideOnFocusProperty)))
adornedElement.PasswordChanged += this.AdornedElement_ContentChanged;
}
/// <summary>
/// Initializes a new instance of the <see cref="T:Huan.Windows.Documents.Placeholder"/> class.
/// </summary>
/// <param name="adornedElement">
/// The element to bind the adorner to.
/// </param>
/// <exception cref="T:System.ArgumentNullException">
/// Raised when adornedElement is null.
/// </exception>
public Placeholder(TextBoxBase adornedElement)
: this((Control)adornedElement)
{
if (!(adornedElement.IsFocused && (bool)adornedElement.GetValue(HideOnFocusProperty)))
adornedElement.TextChanged += this.AdornedElement_ContentChanged;
}
/// <summary>
/// Initializes a new instance of the <see cref="T:Huan.Windows.Documents.Placeholder"/> class.
/// </summary>
/// <param name="adornedElement">
/// The element to bind the adorner to.
/// </param>
/// <exception cref="T:System.ArgumentNullException">
/// Raised when adornedElement is null.
/// </exception>
protected Placeholder(Control adornedElement)
: base(adornedElement)
{
if ((bool)adornedElement.GetValue(HideOnFocusProperty))
{
adornedElement.GotFocus += this.AdornedElement_GotFocus;
adornedElement.LostFocus += this.AdornedElement_LostFocus;
}
}
#endregion
#region Attached Property Getters and Setters
/// <summary>
/// Gets the value of the <see cref="T:Huan.Windows.Documents.Placeholder" />.Text attached property for a specified element.
/// </summary>
/// <param name="adornedElement">
/// The element from which the property value is read.
/// </param>
/// <returns>
/// The placeholder text property value for the element.
/// </returns>
/// <exception cref="T:ArgumentNullException">
/// Raised when adornedElement is null.
/// </exception>
public static string GetText(Control adornedElement)
{
if (adornedElement == null)
throw new ArgumentNullException("adornedElement");
return (string)adornedElement.GetValue(TextProperty);
}
/// <summary>
/// Sets the value of the <see cref="T:Huan.Windows.Documents.Placeholder" />.Text attached property to a specified element.
/// </summary>
/// <param name="adornedElement">
/// The element to which the attached property is written.
/// </param>
/// <param name="placeholderText">
/// The needed placeholder text value.
/// </param>
/// <exception cref="T:ArgumentNullException">
/// Raised when adornedElement is null.
/// </exception>
/// <exception cref="T:InvalidOperationException">
/// Raised when adornedElement is not a <see cref="T:System.Windows.Controls.TextBox"/>,
/// <see cref="T:System.Windows.Controls.RichTextBox"/> or <see cref="T:System.Windows.Controls.PasswordBox"/>.
/// </exception>
public static void SetText(Control adornedElement, string placeholderText)
{
if (adornedElement == null)
throw new ArgumentNullException("adornedElement");
adornedElement.SetValue(TextProperty, placeholderText);
}
/// <summary>
/// Gets the value of the <see cref="T:Huan.Windows.Documents.Placeholder" />.HideOnFocus attached property for a specified element.
/// </summary>
/// <param name="adornedElement">
/// The element from which the property value is read.
/// </param>
/// <returns>
/// A value indicating whether the control will be hidden when the element is in focus.
/// </returns>
/// <exception cref="T:ArgumentNullException">
/// Raised when adornedElement is null.
/// </exception>
public static bool GetHideOnFocus(Control adornedElement)
{
if (adornedElement == null)
throw new ArgumentNullException("adornedElement");
return (bool)adornedElement.GetValue(HideOnFocusProperty);
}
/// <summary>
/// Sets the value of the <see cref="T:Huan.Windows.Documents.Placeholder" />.HideOnFocus attached property to a specified element.
/// </summary>
/// <param name="adornedElement">
/// The element to which the attached property is written.
/// </param>
/// <param name="hideOnFocus">
/// A value indicating whether to hide the placeholder text when the element is in focus.
/// </param>
/// <exception cref="T:ArgumentNullException">
/// Raised when adornedElement is null.
/// </exception>
/// <exception cref="T:InvalidOperationException">
/// Raised when adornedElement is not a <see cref="T:System.Windows.Controls.TextBox"/>,
/// <see cref="T:System.Windows.Controls.RichTextBox"/> or <see cref="T:System.Windows.Controls.PasswordBox"/>.
/// </exception>
public static void SetHideOnFocus(Control adornedElement, bool hideOnFocus)
{
if (adornedElement == null)
throw new ArgumentNullException("adornedElement");
adornedElement.SetValue(HideOnFocusProperty, hideOnFocus);
}
#endregion
/// <summary>
/// Draws the content of a <see cref="T:System.Windows.Media.DrawingContext" /> object during the render pass of a <see cref="T:Huan.Windows.Documents.Placeholder"/> element.
/// </summary>
/// <param name="drawingContext">
/// The <see cref="T:System.Windows.Media.DrawingContext" /> object to draw. This context is provided to the layout system.
/// </param>
protected override void OnRender(DrawingContext drawingContext)
{
Control adornedElement = this.AdornedElement as Control;
string placeholderText;
bool hideOnFocus = (bool)adornedElement.GetValue(HideOnFocusProperty);
if (adornedElement == null ||
(adornedElement.IsFocused && hideOnFocus) ||
!this.IsElementEmpty() ||
string.IsNullOrEmpty(placeholderText = (string)adornedElement.GetValue(TextProperty)))
this.isPlaceholderVisible = false;
else
{
this.isPlaceholderVisible = true;
Size size = adornedElement.RenderSize;
double maxHeight = size.Height - adornedElement.BorderThickness.Top - adornedElement.BorderThickness.Bottom - adornedElement.Padding.Top - adornedElement.Padding.Bottom;
double maxWidth = size.Width - adornedElement.BorderThickness.Left - adornedElement.BorderThickness.Right - adornedElement.Padding.Left - adornedElement.Padding.Right - 4.0;
if (maxHeight <= 0 || maxWidth <= 0)
return;
TextAlignment computedTextAlignment = this.ComputedTextAlignment();
// Foreground brush does not need to be dynamic. OnRender called when SystemColors changes.
Brush foreground = SystemColors.GrayTextBrush.Clone();
foreground.Opacity = adornedElement.Foreground.Opacity;
Typeface typeface = new Typeface(adornedElement.FontFamily, FontStyles.Italic, adornedElement.FontWeight, adornedElement.FontStretch);
FormattedText formattedText = new FormattedText(
placeholderText,
CultureInfo.CurrentCulture,
adornedElement.FlowDirection,
typeface,
adornedElement.FontSize,
foreground);
formattedText.TextAlignment = computedTextAlignment;
formattedText.MaxTextHeight = maxHeight;
formattedText.MaxTextWidth = maxWidth;
double left;
double top = 0.0;
if (adornedElement.FlowDirection == FlowDirection.RightToLeft)
left = adornedElement.BorderThickness.Right + adornedElement.Padding.Right + 2.0;
else
left = adornedElement.BorderThickness.Left + adornedElement.Padding.Left + 2.0;
switch (adornedElement.VerticalContentAlignment)
{
case VerticalAlignment.Top:
case VerticalAlignment.Stretch:
top = adornedElement.BorderThickness.Top + adornedElement.Padding.Top;
break;
case VerticalAlignment.Bottom:
top = size.Height - adornedElement.BorderThickness.Bottom - adornedElement.Padding.Bottom - formattedText.Height;
break;
case VerticalAlignment.Center:
top = (size.Height + adornedElement.BorderThickness.Top - adornedElement.BorderThickness.Bottom + adornedElement.Padding.Top - adornedElement.Padding.Bottom - formattedText.Height) / 2.0;
break;
}
if (adornedElement.FlowDirection == FlowDirection.RightToLeft)
{
// Somehow everything got drawn reflected. Add a transform to correct.
drawingContext.PushTransform(new ScaleTransform(-1.0, 1.0, RenderSize.Width / 2.0, 0.0));
drawingContext.DrawText(formattedText, new Point(left, top));
drawingContext.Pop();
}
else
drawingContext.DrawText(formattedText, new Point(left, top));
}
}
/// <summary>
/// Adds a <see cref="T:Huan.Windows.Documents.Placeholder"/> to the adorner layer.
/// </summary>
/// <param name="adornedElement">
/// The adorned element.
/// </param>
private static void AddAdorner(Control adornedElement)
{
AdornerLayer adornerLayer = AdornerLayer.GetAdornerLayer(adornedElement);
if (adornerLayer == null)
return;
Adorner[] adorners = adornerLayer.GetAdorners(adornedElement);
if (adorners != null)
foreach (Adorner adorner in adorners)
if (adorner is Placeholder)
{
adorner.InvalidateVisual();
return;
}
TextBox textBox = adornedElement as TextBox;
if (textBox != null)
{
adornerLayer.Add(new Placeholder(textBox));
return;
}
RichTextBox richTextBox = adornedElement as RichTextBox;
if (richTextBox != null)
{
adornerLayer.Add(new Placeholder(richTextBox));
return;
}
PasswordBox passwordBox = adornedElement as PasswordBox;
if (passwordBox != null)
{
adornerLayer.Add(new Placeholder(passwordBox));
return;
}
// TextBox is hidden in template. Search for it.
TextBox templateTextBox = null;
templateTextBox = FindTextBox(adornedElement);
if (templateTextBox != null)
Placeholder.SetText(templateTextBox, (string)Placeholder.GetText(adornedElement));
}
/// <summary>
/// Finds a <see cref="T:System.Windows.Controls.TextBox"/> in the visual tree of the adorned element using a breadth first search.
/// </summary>
/// <param name="adornedElement">The adorned element which visual tree is searched for a <see cref="T:System.Windows.Controls.TextBox"/>.</param>
/// <returns>The <see cref="T:System.Windows.Controls.TextBox"/> if one is found, <see langword="null"/> if none exists.</returns>
private static TextBox FindTextBox(Control adornedElement)
{
TextBox templateTextBox = null;
Queue<DependencyObject> queue = new Queue<DependencyObject>();
queue.Enqueue(adornedElement);
while (queue.Count > 0)
{
DependencyObject element = queue.Dequeue();
templateTextBox = element as TextBox;
if (templateTextBox != null)
break;
for (int i = 0; i < VisualTreeHelper.GetChildrenCount(element); ++i)
queue.Enqueue(VisualTreeHelper.GetChild(element, i));
}
return templateTextBox;
}
/// <summary>
/// Event handler for AdornedElement.Loaded.
/// </summary>
/// <param name="sender">
/// The AdornedElement where the event handler is attached.
/// </param>
/// <param name="e">
/// Provides data about the event.
/// </param>
private static void AdornedElement_Loaded(object sender, RoutedEventArgs e)
{
Control adornedElement = (Control)sender;
adornedElement.Loaded -= AdornedElement_Loaded;
AddAdorner(adornedElement);
}
/// <summary>
/// Invoked whenever <see cref="T:Huan.Windows.Documents.Placeholder" />.Text attached property is changed.
/// </summary>
/// <param name="sender">
/// The object where the event handler is attached.
/// </param>
/// <param name="e">
/// Provides data about the event.
/// </param>
private static void OnTextChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
{
if (((string)e.OldValue).Equals((string)e.NewValue, StringComparison.Ordinal))
return;
Control adornedElement = sender as Control;
if (adornedElement == null)
return;
if (adornedElement.IsLoaded)
AddAdorner(adornedElement);
else
adornedElement.Loaded += AdornedElement_Loaded;
}
/// <summary>
/// Invoked whenever <see cref="T:Huan.Windows.Documents.Placeholder" />.HideOnFocus attached property is changed.
/// </summary>
/// <param name="sender">
/// The object where the event handler is attached.
/// </param>
/// <param name="e">
/// Provides data about the event.
/// </param>
private static void OnHideOnFocusChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
{
bool hideOnFocus = (bool)e.NewValue;
if ((bool)e.OldValue == hideOnFocus)
return;
Control adornedElement = sender as Control;
if (!(adornedElement is TextBox || adornedElement is PasswordBox || adornedElement is RichTextBox))
{
if (!adornedElement.IsLoaded)
adornedElement.Loaded += ChangeHideOnFocus;
else
{
TextBox templateTextBox = FindTextBox(adornedElement);
if (templateTextBox != null)
Placeholder.SetHideOnFocus(templateTextBox, (bool)e.NewValue);
}
return;
}
Placeholder placeholder = null;
AdornerLayer adornerLayer = AdornerLayer.GetAdornerLayer(adornedElement);
if (adornerLayer == null)
return;
Adorner[] adorners = adornerLayer.GetAdorners(adornedElement);
if (adorners != null)
foreach (Adorner adorner in adorners)
{
placeholder = adorner as Placeholder;
if (placeholder != null)
break;
}
if (placeholder == null)
return;
if (adornedElement.IsLoaded)
{
if (hideOnFocus)
{
adornedElement.GotFocus += placeholder.AdornedElement_GotFocus;
adornedElement.LostFocus += placeholder.AdornedElement_LostFocus;
if (adornedElement.IsFocused && placeholder.isPlaceholderVisible)
placeholder.InvalidateVisual();
}
else
{
adornedElement.GotFocus -= placeholder.AdornedElement_GotFocus;
adornedElement.LostFocus -= placeholder.AdornedElement_LostFocus;
placeholder.AdornedElement_LostFocus(adornedElement, new RoutedEventArgs(UIElement.LostFocusEvent, placeholder));
}
}
else
adornedElement.Loaded += AdornedElement_Loaded;
}
/// <summary>
/// Changes the HideOnFocus property of the text box in the visual tree of the sender.
/// </summary>
/// <param name="sender">The object where the event handler is attached.</param>
/// <param name="e">Provides data about the event.</param>
private static void ChangeHideOnFocus(object sender, RoutedEventArgs e)
{
Control adornedElement = sender as Control;
if (adornedElement == null)
return;
TextBox templateTextBox = FindTextBox(adornedElement);
if (templateTextBox != null)
Placeholder.SetHideOnFocus(templateTextBox, Placeholder.GetHideOnFocus(adornedElement));
}
#region Event Handlers
/// <summary>
/// Event handler for AdornedElement.GotFocus.
/// </summary>
/// <param name="sender">
/// The AdornedElement where the event handler is attached.
/// </param>
/// <param name="e">
/// Provides data about the event.
/// </param>
private void AdornedElement_GotFocus(object sender, RoutedEventArgs e)
{
TextBoxBase textBoxBase = AdornedElement as TextBoxBase;
if (textBoxBase != null)
textBoxBase.TextChanged -= this.AdornedElement_ContentChanged;
else
{
PasswordBox passwordBox = AdornedElement as PasswordBox;
if (passwordBox != null)
passwordBox.PasswordChanged -= this.AdornedElement_ContentChanged;
}
if (this.isPlaceholderVisible)
this.InvalidateVisual();
}
/// <summary>
/// Event handler for AdornedElement.LostFocus.
/// </summary>
/// <param name="sender">
/// The AdornedElement where the event handler is attached.
/// </param>
/// <param name="e">
/// Provides data about the event.
/// </param>
private void AdornedElement_LostFocus(object sender, RoutedEventArgs e)
{
TextBoxBase textBoxBase = AdornedElement as TextBoxBase;
if (textBoxBase != null)
textBoxBase.TextChanged += this.AdornedElement_ContentChanged;
else
{
PasswordBox passwordBox = AdornedElement as PasswordBox;
if (passwordBox != null)
passwordBox.PasswordChanged += this.AdornedElement_ContentChanged;
}
if (!this.isPlaceholderVisible && this.IsElementEmpty())
this.InvalidateVisual();
}
/// <summary>
/// Event handler for AdornedElement.ContentChanged.
/// </summary>
/// <param name="sender">
/// The AdornedElement where the event handler is attached.
/// </param>
/// <param name="e">
/// Provides data about the event.
/// </param>
private void AdornedElement_ContentChanged(object sender, RoutedEventArgs e)
{
if (this.isPlaceholderVisible ^ this.IsElementEmpty())
this.InvalidateVisual();
}
#endregion
/// <summary>
/// Checks if the content of the adorned element is empty.
/// </summary>
/// <returns>
/// Returns <see langword="true" /> if the content is empty, <see langword="false" /> otherwise.
/// </returns>
private bool IsElementEmpty()
{
UIElement adornedElement = AdornedElement;
TextBox textBox = adornedElement as TextBox;
if (textBox != null)
return string.IsNullOrEmpty(textBox.Text);
PasswordBox passwordBox = adornedElement as PasswordBox;
if (passwordBox != null)
return string.IsNullOrEmpty(passwordBox.Password);
RichTextBox richTextBox = adornedElement as RichTextBox;
if (richTextBox != null)
{
BlockCollection blocks = richTextBox.Document.Blocks;
if (blocks.Count == 0)
return true;
if (blocks.Count == 1)
{
Paragraph paragraph = blocks.FirstBlock as Paragraph;
if (paragraph == null)
return false;
if (paragraph.Inlines.Count == 0)
return true;
if (paragraph.Inlines.Count == 1)
{
Run run = paragraph.Inlines.FirstInline as Run;
return run != null && string.IsNullOrEmpty(run.Text);
}
}
return false;
}
return false;
}
/// <summary>
/// Computes the text alignment of the adorned element.
/// </summary>
/// <returns>
/// Returns the computed text alignment.
/// </returns>
private TextAlignment ComputedTextAlignment()
{
Control adornedElement = AdornedElement as Control;
TextBox textBox = adornedElement as TextBox;
if (textBox != null)
{
if (DependencyPropertyHelper.GetValueSource(textBox, TextBox.HorizontalContentAlignmentProperty)
.BaseValueSource != BaseValueSource.Local ||
DependencyPropertyHelper.GetValueSource(textBox, TextBox.TextAlignmentProperty)
.BaseValueSource == BaseValueSource.Local)
// TextAlignment dominates
return textBox.TextAlignment;
}
RichTextBox richTextBox = adornedElement as RichTextBox;
if (richTextBox != null)
{
BlockCollection blocks = richTextBox.Document.Blocks;
TextAlignment textAlignment = richTextBox.Document.TextAlignment;
if (blocks.Count == 0)
return textAlignment;
if (blocks.Count == 1)
{
Paragraph paragraph = blocks.FirstBlock as Paragraph;
if (paragraph == null)
return textAlignment;
return paragraph.TextAlignment;
}
return textAlignment;
}
switch (adornedElement.HorizontalContentAlignment)
{
case HorizontalAlignment.Left:
return TextAlignment.Left;
case HorizontalAlignment.Right:
return TextAlignment.Right;
case HorizontalAlignment.Center:
return TextAlignment.Center;
case HorizontalAlignment.Stretch:
return TextAlignment.Justify;
}
return TextAlignment.Left;
}
}
}
