Custom Controls – Extending the TextBox

The good folks over at Silverlight Show have just put up my article about writing a custom control. One of my earliest posts was on using a UserControl to create a WatermarkedTextBox. I’ve been meaning to follow up on it for a while on how to achieve the same thing (but better) using a Custom Control. In the example below it’s wired up as a filter for the list box. You can check the “Styled” box to apply a different style to the whole app, including the WatermarkedTextBox.

Go over to Silverlight Show to grab the source and read the full article.

A Chrome and Glass Theme- Part 8

Introduction

In this post I’m going to show you how to make the radio buttons I blogged about previously. These buttons have gone through many iterations and I’m still not sure I’m quite happy with them just yet, but I’ll cover them anyway since they introduce a few interesting attached properties. Here is the sample I’ve been building up, now with the radio buttons:

You can grab the source here.

This post is the 8th in a series. If you are not familiar with styling controls in Blend, or working with Resource Dictionaries then I would recommend that you start at the beginning of the series.

The Radio Button

When I first attempted this button I ended up with horribly complicated arrangement of shapes to get it to scale properly. I had placeholders and spacers and grids within grids, with some of them having their height bound to their widths (which doesn’t work very well). And I had half circles on the ends with gradient blends merging seamlessly into the gradient blend on a rectangle in the middle. It was pretty awful.

The previous blog about Automatic Rectangle Radius X and Y should give you an idea of a simpler way to achieve the look. In the end I went with the attached properties since they work nicely both at run-time and design-time. If you grab the source from the link above, you may have to build it in Blend to get it to use the attached properties on the design surface.

The RadioButton inherits from the ToggleButton, as does the CheckBox. They all have a common theme of the button being checked, unchecked, or indeterminate; The radio button just has a different visual appearance, and adds the GroupName property. This style could be adapted for the ToggleButton too, but it wouldn’t really work as a style for a CheckBox.

The contents for this button are grouped in a grid with two columns; the left column contains the orb, the right column contains the ContentPresenter element.

Creating a custom style template for a radio button shouldn’t be difficult at all if you have been following along with the series, but I thought it might be worthwhile to look at some of the elements that make up this button.

Scalable Rounded Ends

A rectangle has the RadiusX and RadiusY properties that let you turn the sharp corners into rounded corners. For this button I want the rounded ends to stay rounded, at the right proportion, regardless of the size of the button. Unfortunately, there is no easy way to set those properties to be half of the height of the rectangle.

As mentioned in the post about Automatic Rectangle Radius X and Y I used an attached property to achieve the rounded ends since that gave me the best result when working with Blend. I use 3 rectangles in the button: one for the rim using the ChromeBorder resource brush, one for the main body using the ChromeFill resource brush, and one the same size that uses the ChromeDarkeningLinear resource brush to make the white text stand out better.

The ellipse is used on the right end of the button to add some dark shading to make the button look rounder, and the Orb grid uses the same principle as this post.

I created an attached property called IsRounded that, when true, uses another attached property called RoundCapsRatio (which defaults to 0.5 if unset) that it multiplies against height or width (whichever is smaller) and applies to the RadiusX and RadiusY properties of the rectangle it is attached to. You may have to build the solution once in Blend to have it applied properly, but then the corner radius automatically updates in blend as the rectangle it is applied to changes size.

Scalable Orb

The other attached properties I created are WidthRatio and HeightRatio (not used in this example). I use the WidthRatio attached property on the Orb grid to keep it perfectly square so the ellipses inside it stay round. I can’t have this happen without an attached property because there is no other way (that works in Blend) to set the width of an element to be relative to the height. I set the WidthRatio to the value “1” to achieve this. I could have just used a Boolean attached property, but having the ratio makes it more reusable.

If you use both the attached properties on a visual element, the handler will prefer the WidthRatio over the HeightRatio. Here is the method that applies the property values. It only applies the values if they have actually been set:

   1: private static void UpdateSizeRatio(FrameworkElement element)

   2: {

   3:     double ratio;

   4:     if (element.ReadLocalValue(WidthRatioProperty) != DependencyProperty.UnsetValue)

   5:     {

   6:         ratio = (double)element.GetValue(WidthRatioProperty);

   7:         double height = element.ActualHeight;

   8:         if (!double.IsNaN(height) && height > 0)

   9:         {

  10:             element.Width = height * ratio;

  11:         }

  12:     }

  13:     else if (element.ReadLocalValue(HeightRatioProperty) != DependencyProperty.UnsetValue)

  14:     {

  15:         ratio = (double)element.GetValue(HeightRatioProperty);

  16:         double width = element.ActualWidth;

  17:         if (!double.IsNaN(width) && width > 0)

  18:         {

  19:             element.Height = width * ratio;

  20:         }

  21:     }

  22: }

Conclusion

As far as radio buttons go, these are fairly limited in their application since they are so big. They are too big to use in the same way as you would normally use a radio button, but they do make quite good navigation buttons instead of using tabs.

The use of Attached Properties seems the best solution for adding behavior to a visual element that works at design time in Blend, but it’s not ideal – I would really rather have a way to do this using Blend that didn’t need me to swap into the XAML.

References:

The icons are from the Tango Desktop Project.

Capturing a Silverlight App Screen

Here's a demo Silverlight application that captures the application screen and uses it a couple of different ways.

You can grab the source here.

The “Swap” button uses a screen capture to create a fun transition between two different views. The “Capture Filmstrip” button starts a timer that captures the screen every second and shows a thumbnail view of it. The “Animate Background” button plays a supporting role for the “Capture Filmstrip” button; it animates the background so the filmstrip captures are different from each other even if you don’t interact with the controls. You can click on one of the captured thumbnails to save it to disk.

This article at the excellent Silverlight Show e-magazine has more details on how (and why) to do this.

Blog Administration

I've been using the new features of Blogger to update the theme for Silverlight Scratchpad. As a result a lot of the code samples have been messed up.

So this is a pre-apology that there may be some reposting of old articles as I go through and clean up the code.

Automatic Rectangle Radius X and Y

Introduction

I created a design for a radio button that looks like this:

I'm going to write a future post on how to do this button, but I want to refine it a bit first. In this post I’m going to describe the approach I used for the rounded end-caps in the hopes that someone will help me perfect it.

I have the following requirements for this radio button style:

• It must be re-sizable
• The rounded ends must stay perfect half circles in proportion to the height of the button
• It must behave correctly in Blend
• Optional Extra: It would be nice to not have to manually edit XAML in Blend

I have the first three ticked off but the best approach so far still requires editing the XAML by hand. Here is a simple graphic to illustrate the end result when applied to a Rectangle element. The RadiusX and RadiusY are set to half the height of the rectangle:

Having the RadiusX and RadiusY calculated automatically is crucial to this design since I want it to be fully scalable (within reason).

I’ve been through several different approaches trying to get the full 4 marks, but 3 is the best I can manage. If you can spot any improvements or alternative approaches I would welcome suggestions.

Attached Property: 3 out of 4

The winning approach so far is to use an Attached Property that calculates the radii when the rectangle changes size. I made the attached property a little more generic by adding another attached property for specifying a ratio; 0.5 (the default) would give the result above. I also made it work off the lesser of the height and width values to cater for rectangles that are longer than they are wide. Here is the code for the attached property:

   1: using System;

   2: using System.Windows;

   3: using System.Windows.Shapes;

   4:  

   5: /// <summary>

   6: /// Contains attached properties for specifiying rounded ends on a Rectangle

   7: /// </summary>

   8: public static class RoundCaps

   9: {

  10:     /// <summary>

  11:     /// Attached Dependency Property for the IsRounded property

  12:     /// </summary>

  13:     public static readonly DependencyProperty IsRoundedProperty = DependencyProperty.RegisterAttached(

  14:         "IsRounded",

  15:         typeof(bool),

  16:         typeof(RoundCaps),

  17:         new PropertyMetadata(false, IsRoundedChanged));

  18:  

  19:     /// <summary>

  20:     /// Attached Dependency Property for the RoundCapsRatio property

  21:     /// </summary>

  22:     public static readonly DependencyProperty RoundCapsRatioProperty = DependencyProperty.RegisterAttached(

  23:         "RoundCapsRatio",

  24:         typeof(double),

  25:         typeof(RoundCaps),

  26:         new PropertyMetadata(0.5, RoundCapsRatioChanged));

  27:  

  28:     /// <summary>

  29:     /// Gets a value indicating if the Rectangle is rounded.

  30:     /// </summary>

  31:     /// <param name="d">The rectangle.</param>

  32:     /// <returns>true if the rectangle is rounded, else false</returns>

  33:     public static bool GetIsRounded(DependencyObject rectangle)

  34:     {

  35:         return (bool)rectangle.GetValue(IsRoundedProperty);

  36:     }

  37:  

  38:     /// <summary>

  39:     /// Sets a value indicating if the Rectangle is rounded.

  40:     /// </summary>

  41:     /// <param name="rectangle">The rectangle.</param>

  42:     /// <param name="value">true if the rectangle is rounded, else false.</param>

  43:     public static void SetIsRounded(DependencyObject rectangle, object value)

  44:     {

  45:         rectangle.SetValue(IsRoundedProperty, value);

  46:     }

  47:  

  48:     /// <summary>

  49:     /// Gets the roundedness ratio of the rectangle.

  50:     /// </summary>

  51:     /// <param name="rectangle">The ratio, relative to the lesser value of the rectangle's height and width.</param>

  52:     /// <returns>The ratio currently applied when calculating the roundedness</returns>

  53:     public static double GetRoundCapsRatio(DependencyObject rectangle)

  54:     {

  55:         return (double)rectangle.GetValue(RoundCapsRatioProperty);

  56:     }

  57:  

  58:     /// <summary>

  59:     /// Sets the roundedness ratio of the rectangle.

  60:     /// </summary>

  61:     /// <param name="rectangle">The ratio, relative to the lesser value of the rectangle's height and width.</param>

  62:     /// <returns>The ratio to be applied when calculating the roundedness</returns>

  63:     public static void SetRoundCapsRatio(DependencyObject d, object value)

  64:     {

  65:         d.SetValue(RoundCapsRatioProperty, value);

  66:     }

  67:  

  68:     private static void IsRoundedChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)

  69:     {

  70:         Rectangle rect = d as Rectangle;

  71:         if (null == d)

  72:             return;

  73:  

  74:         bool isRounded = (bool)e.NewValue == true;

  75:         if (isRounded)

  76:         {

  77:             rect.SizeChanged += RectSizeChanged;

  78:             UpdateRectangle(rect);

  79:         }

  80:         else

  81:         {

  82:             rect.SizeChanged -= RectSizeChanged;

  83:         }

  84:     }

  85:  

  86:     private static void RoundCapsRatioChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)

  87:     {

  88:         Rectangle rect = d as Rectangle;

  89:         if (null == rect)

  90:         {

  91:             return;

  92:         }

  93:  

  94:         UpdateRectangle(rect);

  95:     }

  96:  

  97:     private static void RectSizeChanged(object sender, SizeChangedEventArgs e)

  98:     {

  99:         Rectangle rect = sender as Rectangle;

 100:         if (null == rect)

 101:         {

 102:             return;

 103:         }

 104:  

 105:         UpdateRectangle(rect);

 106:     }

 107:  

 108:     private static void UpdateRectangle(Rectangle rect)

 109:     {

 110:         double ratio = (double)rect.GetValue(RoundCapsRatioProperty);

 111:  

 112:         rect.RadiusX = Math.Min(rect.ActualHeight, rect.ActualWidth) * ratio;

 113:         rect.RadiusY = rect.RadiusX;

 114:     }

 115: }

This is how the XAML looks (without the RoundedRatio property which defaults to 0.5 anyway):

<Rectangle x:Name="rectangle" local:RoundCaps.IsRounded="True" Fill="#FF2D2D2D"/>

This approach works nicely at both run time and design time (1 point each) and is fully scalable (1 point). Given the awkwardness of the other approaches I’ve tried, this is the winning solution so far.

Here are the two other approaches I’ve tried that didn’t fare so well.

Value Converter: 1 Out Of 4

One approach was to bind the RadiusX and RadiusY properties of the rectangle to itself and use an IValueConverter to calculate the values based off the height and width of the rectangle. In case you’re interested, here is the code for the value converter:

   1: public class RatioConverter : IValueConverter

   2: {

   3:  

   4:     public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)

   5:     {

   6:         FrameworkElement element = (FrameworkElement)value;

   7:         double height = element.ActualHeight;

   8:         double number = height;

   9:         double ratio = double.Parse((string)parameter);

  10:         return number * ratio;

  11:     }

  12:  

  13:     public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)

  14:     {

  15:         throw new NotSupportedException();

  16:     }

  17: }

The converter doesn’t work at all at run time because it evaluates during the Measure and Arrange cycle for the visual tree, which means that ActualHeight and ActualWidth haven’t actually been calculated and are still 0. I will give it half a point because if I explicitly set the height rather than use “Auto” it does work; but having to explicitly set the height is not good if I’m using this approach inside a resizable Button’s control template.

I will also give it 0.5 for working in Blend – almost. Again, if I explicitly set the height it works in Blend. Blend does somehow manage to apply it correctly for Auto height but only when I build the project (no extra points).

I tried a couple of variations around this, such as binding against the width and height of a sibling element (or cousin) but it started getting a little bit ridiculous and the code-smell was pretty terrible.

Attached Behavior: The Wrong 3 Out Of 4

Another thing I tried was writing an attached behavior for a Rectangle that would automatically set the corner radius values based on the dimensions of the rectangle. That works fine for a running application, but behaviors don't execute in Blend, so the design-time experience is ruined since the corners remain square.

This is the code for the behavior:

   1: public class RoundCapsBehavior : Behavior<Rectangle>

   2: {

   3:     public static readonly DependencyProperty RoundedRatioProperty = DependencyProperty.Register(

   4:         "RoundedRatio", typeof(double), typeof(RoundCapsBehavior), new PropertyMetadata(0.5, RoundedRatioChanged));

   5:  

   6:     public double RoundedRatio

   7:     {

   8:         get { return (double)this.GetValue(RoundedRatioProperty); }

   9:         set { this.SetValue(RoundedRatioProperty, value); }

  10:     }

  11:  

  12:     protected override void OnAttached()

  13:     {

  14:         base.OnAttached();

  15:         this.AssociatedObject.SizeChanged += AssociatedObjectSizeChanged;

  16:     }

  17:  

  18:     protected override void OnDetaching()

  19:     {

  20:         base.OnDetaching();

  21:         this.AssociatedObject.SizeChanged -= AssociatedObjectSizeChanged;

  22:     }

  23:  

  24:     void AssociatedObjectSizeChanged(object sender, SizeChangedEventArgs e)

  25:     {

  26:         this.UpdateRadiusXY();

  27:     }

  28:  

  29:     private void UpdateRadiusXY()

  30:     {

  31:         this.AssociatedObject.RadiusX =

  32:             Math.Min(this.AssociatedObject.ActualHeight, this.AssociatedObject.ActualWidth)

  33:             * this.RoundedRatio;

  34:         this.AssociatedObject.RadiusY = this.AssociatedObject.RadiusX;

  35:     }

  36:  

  37:     private static void RoundedRatioChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)

  38:     {

  39:         RoundCapsBehavior behavior = d as RoundCapsBehavior;

  40:         if (null == behavior)

  41:             return;

  42:         behavior.UpdateRadiusXY();

  43:     }

  44: }

It’s pretty simple – it just attaches a handler to the SizeChanged event and recalculates the corners when the event fires. It uses a property on the behavior that you can change the ratio with; the default 0.5 so the radius values will be half the height or width (whichever is larger).

It gets 1 point for working perfectly at run time, and 1 point for being scalable. It also gets the bonus point for not requiring any direct editing of the XAML, which gives it 3 out of 4, but one of those 3 was optional and it missed the third required point.

This one is probably the most frustrating because it feels like it should work. Behaviors, after all, were created as a convenience for the design surface – attached properties can do everything a behavior can – but the OnAttached and OnDetached methods are not called when the behaviors are used inside Blend.

Summary

So the Attached Dependency Property is currently winning the race, and unless someone comes up with a better solution, it will be the method-of-choice for the radio button style at the top. I just wish that Blend exposed a visual mechanism for adding custom attached properties to elements. Attached Behaviors were meant to give us that, but the OnAttached and OnDetached don’t get called so the behavior is not applied in the design surface.