I was looking on how to replicate a Google button's shadow on hover effect in my WPF document and came across this: https://stackoverflow.com/a/53031057/12299798, which answers my problem exactly, but the only issue I have is that I normally do all the frontend things in XAML and so I am not quite experienced in the styling in C#. My problem is that I want to 'Bind' my foreground colour to the shadow colour, this is because in the code it only sets it to a greyish colour which would mean I would have to do a whole other class for each colour that I want to set it for. Here is my code now:
MainWindow.xaml:
<Button Content="shadow">
<Button.Style>
<Style TargetType="Button">
<Style.Triggers>
<Trigger Property="IsMouseOver" Value="True">
<Setter Property="local:UI.Elevation" Value="10"/>
</Trigger>
<Trigger Property="IsMouseOver" Value="False">
<Setter Property="local:UI.Elevation" Value="0"/>
</Trigger>
</Style.Triggers>
</Style>
</Button.Style>
</Button>
UI.cs:
public static class UI
{
public static readonly DependencyProperty ElevationProperty = DependencyProperty.RegisterAttached("Elevation", typeof(double), typeof(UI), new FrameworkPropertyMetadata(default(double), FrameworkPropertyMetadataOptions.AffectsRender, null, OnRedElevationChanged));
public static double GetElevation(this UIElement element) => element.GetValue(ElevationProperty) as double? ?? default;
public static void SetElevation(this UIElement element, double elevation) => element.SetValue(ElevationProperty, elevation);
private static object OnRedElevationChanged(DependencyObject d, object value)
{
if (d is UIElement element && value is double elevation)
if (elevation == 0)
element.Effect = null;
else
{
Effect e = CreateElevation(elevation, element.Effect);
if (e != null)
element.Effect = e;
}
return value;
}
private static Effect CreateElevation(double elevation, Effect source)
{
void MixShadows(DropShadowEffect nearest, DropShadowEffect matched, double balance)
{
matched.BlurRadius = matched.BlurRadius * (1 - balance) + nearest.BlurRadius * balance;
matched.ShadowDepth = matched.ShadowDepth * (1 - balance) + nearest.ShadowDepth * balance;
}
DropShadowEffect[] shadows = new DropShadowEffect[]
{
new DropShadowEffect()
{
BlurRadius = 5,
ShadowDepth = 1
},
new DropShadowEffect()
{
BlurRadius = 8,
ShadowDepth = 1.5
},
new DropShadowEffect()
{
BlurRadius = 14,
ShadowDepth = 4.5
},
new DropShadowEffect()
{
BlurRadius = 25,
ShadowDepth = 8
},
new DropShadowEffect()
{
BlurRadius = 35,
ShadowDepth = 13
}
};
elevation = Math.Max(0, elevation / 12 * shadows.Length - 1);
int prevIndex = (int)Math.Floor(elevation), index = (int)elevation, nextIndex = (int)Math.Ceiling(elevation);
double approx = elevation - index;
DropShadowEffect shadow = shadows[index];
if (approx != 0)
MixShadows(approx < 0 ? shadows[prevIndex] : shadows[nextIndex], shadow, Math.Abs(approx));
bool modify = false;
if (source is DropShadowEffect sourceShadow)
{
sourceShadow.BlurRadius = shadow.BlurRadius;
sourceShadow.ShadowDepth = shadow.ShadowDepth;
shadow = sourceShadow;
modify = true;
}
shadow.Direction = 270;
shadow.Color = Colors.Red;
shadow.Opacity = .42;
shadow.RenderingBias = RenderingBias.Performance;
return modify ? null : shadow;
}
}
And to get what I want in XAML I would do something like this:
<Button Content="shadow">
<Button.Style>
<Style TargetType="Button">
<Style.Triggers>
<Trigger Property="IsMouseOver" Value="True">
<Setter Property="local:UI.Elevation" Value="10"/>
<Setter Property="local:UI.Elevation.Foreground" Value="Blue"/>
</Trigger>
<Trigger Property="IsMouseOver" Value="False">
<Setter Property="local:UI.Elevation" Value="0"/>
<Setter Property="local:UI.Elevation.Foreground" Value="Blue"/>
</Trigger>
</Style.Triggers>
</Style>
</Button.Style>
</Button>
But I don't quite know how to link up the local:UI.Elevation.Foreground to change the shadow colour, I would have to change this line here from UI.cs: shadow.Color = Colors.Red; and bind it to the Elevation.Foreground, but I am having difficulties. Can anyone help?
All you need to do is updated the UI class with a new attached property named something like Color of type Color and give it a default color you like.
Then, in its OnColorChanged handler, call OnElevationChanged so that the shadow gets recreated.
#region Color (Attached Property)
public static readonly DependencyProperty ColorProperty =
DependencyProperty.RegisterAttached(
"Color",
typeof(Color),
typeof(UI),
new PropertyMetadata(Colors.Black, OnColorChanged));
public static Color GetColor(DependencyObject obj)
{
return (Color)obj.GetValue(ColorProperty);
}
public static void SetColor(DependencyObject obj, Color value)
{
obj.SetValue(ColorProperty, value);
}
private static void OnColorChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
OnElevationChanged(d, GetElevation((UIElement)d));
}
#endregion
In the CreateElevation method, add a new parameter for the color, so you can set it.
private static Effect CreateElevation(double elevation, Effect source, Color color)
{
...
shadow.Color = color;
...
}
Finally, in OnElevationChanged update it so it to call GetColor so it can pass in the new Color property.
private static object OnElevationChanged(DependencyObject d, object value)
{
if (d is UIElement element && value is double elevation)
if (elevation == 0)
element.Effect = null;
else
{
Effect e = CreateElevation(elevation, element.Effect, GetColor(element));
if (e != null)
element.Effect = e;
}
return value;
}
Example XAML
<Button
Width="100"
Height="20"
Content="shadow">
<Button.Style>
<Style TargetType="Button">
<Style.Triggers>
<Trigger Property="IsMouseOver" Value="True">
<Setter Property="local:UI.Elevation" Value="10" />
<Setter Property="local:UI.Color" Value="Blue" />
</Trigger>
<Trigger Property="IsMouseOver" Value="False">
<Setter Property="local:UI.Elevation" Value="5" />
<Setter Property="local:UI.Color" Value="Red" />
</Trigger>
</Style.Triggers>
</Style>
</Button.Style>
</Button>
NOTE: There is some refactoring you could do to make all this cleaner, but hopefully this will get your started.