Path vs GeometryDrawing - wpf

Just wondering what's lighter, I'm going to have a control that draws 280 * 4 my SegmentControl, which is a quarter of a circle, and I'm just wondering what's the way that takes least memory to draw said segment.
GeometryDrawing:
<Image>
<Image.Source>
<DrawingImage>
<DrawingImage.Drawing>
<GeometryDrawing Brush="LightBlue"
Geometry="M24.612317,0.14044853 C24.612317,0.14044853 33.499971,-0.60608719 41,7.0179795 48.37642,14.516393 47.877537,23.404541 47.877537,23.404541 L24.60978,23.401991 z" />
</DrawingImage.Drawing>
</DrawingImage>
</Image.Source>
</Image>
Or Path:
<Path Fill="LightBlue"
Stretch="Fill"
Stroke="#FF0DA17D"
Data="M24.612317,0.14044853 C24.612317,0.14044853 33.499971,-0.60608719 41,7.0179795 48.37642,14.516393 47.877537,23.404541 47.877537,23.404541 L24.60978,23.401991 z" />
Or if you know of an even better way, it'll be much appreciated.
Thanks!

Related

WPF use Canvas as ImageSource

I am new to WPF and trying to build a basic app with a toolbar and icons. I am testing XamRibbon from Infragistics and ButtonTool that shows on the Ribbon require ImageSource to show an image like so:
<igRibbon:ButtonTool Caption="Edit"
igRibbon:RibbonGroup.MaximumSize="ImageAndTextLarge"
LargeImage="{StaticResource stop}"
SmallImage="{StaticResource stop}" />
I have a XAML icon defined in my dictionary with key 'stop' but the icons I am using are all in Canvas form like this:
<Canvas Width="32" Height="32" Canvas.Left="0" Canvas.Top="0">
<Canvas Clip="M15.82,31.2118l2.0148,-3.8306l-0.0332,-0.0332l0.1068,-0.1068l0.5615,-1.0675l0.253,0.253l8.5884,-8.5885l-0.0112,-0.0111l1.6101,-1.5876c0.4557,-0.4557,0.923,-0.5523,1.234,-0.5523c0.311,0,0.7784,0.0967,1.239,0.5572l0.6169,0.6168V0H0v32h15.7137C15.656,31.7398,15.6889,31.4614,15.82,31.2118z">
<Canvas>
<Canvas.RenderTransform>
<TransformGroup>
<TranslateTransform X="-1" Y="-1"/>
</TransformGroup>
</Canvas.RenderTransform>
<Polygon Points="17,28 17,24.5 15,24.5 15,28 3,28 3,30 29,30 29,28" Fill="#4EA17E" StrokeLineJoin="Miter"/>
<Path Data="M18.475,31h-4.9c-0.3038,0,-0.575,-0.1962,-0.575,-0.5v-2.95c0,-0.3038,0.2712,-0.55,0.575,-0.55h4.9c0.3038,0,0.55,0.2462,0.55,0.55V30.5C19.025,30.8038,18.7788,31,18.475,31z" Fill="#797979"/>
<Path Data="M28,1H4c-0.5523,0,-1,0.4477,-1,1v5c0,0.5523,0.4477,1,1,1h24c0.5523,0,1,-0.4477,1,-1V2C29,1.4477,28.5523,1,28,1zM7,6H5V3h2V6zM28,9H4c-0.5523,0,-1,0.4477,-1,1v5c0,0.5523,0.4477,1,1,1h24c0.5523,0,1,-0.4477,1,-1v-5C29,9.4477,28.5523,9,28,9zM7,14H5v-3h2V14zM28,17H4c-0.5523,0,-1,0.4477,-1,1v5c0,0.5523,0.4477,1,1,1h24c0.5523,0,1,-0.4477,1,-1v-5C29,17.4477,28.5523,17,28,17zM7,22H5v-3h2V22z" Fill="#3E79B4"/>
<Path Data="M7,22H5v-3h2V22zM7,11H5v3h2V11zM7,3H5v3h2V3z" Fill="#FFFFFF"/>
</Canvas>
</Canvas>
<Canvas>
<Path Data="M19.2158,27.348l9.0199,-9.0199l2.1233,2.1233l-9.0199,9.0199L19.2158,27.348zM29.6123,16.9515c0.3525,-0.3525,0.7113,-0.3525,1.0638,0l1.0596,1.0596c0.3525,0.3525,0.3525,0.7113,0,1.0638l-0.8743,0.8743l-2.1388,-2.1202L29.6123,16.9515zM16.7052,31.677l2.0176,-3.8361l2.1233,2.1233l-3.8361,2.0176c-0.061,0.0321,-0.1358,0.0207,-0.1846,-0.028l-0.0923,-0.0923C16.6845,31.8128,16.6732,31.738,16.7052,31.677z" Fill="#3E79B4"/>
</Canvas>
How can I convert Canvas XAML to something that can be used as ImageSource like a DrawingImage for example? I hope this makes sense.
I don't use Infragistics controls, but I believe they follow the standard WPF controls.
I used image control and try to display your canvas path image.
define the Geometry from your canvas path in resource
<Geometry x:Key="StopGeometry">M13,11.3814v18.115c0.0083,0.2845,0.2134,0.5036,0.4896,0.5036h4c0.2807,0,0.5104,-0.2297,0.5104,-0.5104v-18.088l7.6585,7.6695c0.1259,0.1261,0.3415,0.0369,0.3415,-0.1413v-6.2525c0,-0.2125,-0.0845,-0.4162,-0.2349,-0.5663l-9.934,-9.9139c-0.2999,-0.2654,-0.4015,-0.2654,-0.6944,0.0157L5.235,12.0908c-0.1504,0.1501,-0.235,0.3539,-0.235,0.5664v6.2414c0,0.1782,0.2154,0.2674,0.3414,0.1414L13,11.3814z</Geometry>
in XAML
<Image Height="100" Width="100">
<Image.Source>
<DrawingImage >
<DrawingImage.Drawing>
<GeometryDrawing Brush="#3E79B4" Geometry="{StaticResource StopGeometry}"/>
</DrawingImage.Drawing>
</DrawingImage>
</Image.Source>
</Image>
I used the Blend for Visual studio to convert your Canvas as DrawingBrush. Now I can simply use what Blend Gave me. Only copy and paste I did.
<Image Height="32" Width="32">
<Image.Source>
<DrawingImage>
<DrawingImage.Drawing>
<DrawingGroup>
<DrawingGroup ClipGeometry="M15.82,31.2118L17.8348,27.3812 17.8016,27.348 17.9084,27.2412 18.4699,26.1737 18.7229,26.4267 27.3113,17.8382 27.3001,17.8271 28.9102,16.2395C29.3659,15.7838 29.8332,15.6872 30.1442,15.6872 30.4552,15.6872 30.9226,15.7839 31.3832,16.2444L32.0001,16.8612 32.0001,0 0,0 0,32 15.7137,32C15.656,31.7398,15.6889,31.4614,15.82,31.2118z">
<DrawingGroup>
<DrawingGroup.Transform>
<MatrixTransform Matrix="1,0,0,1,-1,-1" />
</DrawingGroup.Transform>
<GeometryDrawing Brush="#FF4EA17E" Geometry="M17,28 L17,24.5 15,24.5 15,28 3,28 3,30 29,30 29,28 z" />
<GeometryDrawing Brush="#FF797979" Geometry="M18.475,31L13.575,31C13.2712,31,13,30.8038,13,30.5L13,27.55C13,27.2462,13.2712,27,13.575,27L18.475,27C18.7788,27,19.025,27.2462,19.025,27.55L19.025,30.5C19.025,30.8038,18.7788,31,18.475,31z" />
<GeometryDrawing Brush="#FF3E79B4" Geometry="M28,1L4,1C3.4477,1,3,1.4477,3,2L3,7C3,7.5523,3.4477,8,4,8L28,8C28.5523,8,29,7.5523,29,7L29,2C29,1.4477,28.5523,1,28,1z M7,6L5,6 5,3 7,3 7,6z M28,9L4,9C3.4477,9,3,9.4477,3,10L3,15C3,15.5523,3.4477,16,4,16L28,16C28.5523,16,29,15.5523,29,15L29,10C29,9.4477,28.5523,9,28,9z M7,14L5,14 5,11 7,11 7,14z M28,17L4,17C3.4477,17,3,17.4477,3,18L3,23C3,23.5523,3.4477,24,4,24L28,24C28.5523,24,29,23.5523,29,23L29,18C29,17.4477,28.5523,17,28,17z M7,22L5,22 5,19 7,19 7,22z" />
<GeometryDrawing Brush="White" Geometry="M7,22L5,22 5,19 7,19 7,22z M7,11L5,11 5,14 7,14 7,11z M7,3L5,3 5,6 7,6 7,3z" />
</DrawingGroup>
</DrawingGroup>
<GeometryDrawing Brush="#FF3E79B4" Geometry="M19.2158,27.348L28.2357,18.3281 30.359,20.4514 21.3391,29.4713 19.2158,27.348z M29.6123,16.9515C29.9648,16.599,30.3236,16.599,30.6761,16.9515L31.7357,18.0111C32.0882,18.3636,32.0882,18.7224,31.7357,19.0749L30.8614,19.9492 28.7226,17.829 29.6123,16.9515z M16.7052,31.677L18.7228,27.8409 20.8461,29.9642 17.01,31.9818C16.949,32.0139,16.8742,32.0025,16.8254,31.9538L16.7331,31.8615C16.6845,31.8128,16.6732,31.738,16.7052,31.677z" />
</DrawingGroup>
</DrawingImage.Drawing>
</DrawingImage>
</Image.Source>
</Image>
I think this is the easiest solution.

How do I draw with coordinates in [0;1] instead of pixels in WPF?

My coordinates are relative to the control size, in the 0 to 1 range. I currently draw on my control using manual scaling by RenderSize, which works fine, but is surely the wrong way.
How can I draw directly in 0-1 coordinates instead?
You may use Path controls and scale their Data by applying an appropriate transform to the Geometry.Transform property, like in the trivial example shown below. This way you would scale the drawn shapes, but not their stroke thicknesses.
<Grid>
<Canvas>
<Canvas.Resources>
<ScaleTransform x:Key="transform"
ScaleX="{Binding Value, ElementName=scaleSlider}"
ScaleY="{Binding Value, ElementName=scaleSlider}"/>
</Canvas.Resources>
<Path Stretch="None" Stroke="Blue" StrokeThickness="2">
<Path.Data>
<RectangleGeometry Rect="0.1,0.1,0.8,0.4"
Transform="{StaticResource transform}"/>
</Path.Data>
</Path>
<Path Stretch="None" Stroke="Red" StrokeThickness="2">
<Path.Data>
<EllipseGeometry Center="0.6,0.5" RadiusX="0.3" RadiusY="0.3"
Transform="{StaticResource transform}"/>
</Path.Data>
</Path>
</Canvas>
<Slider x:Name="scaleSlider" HorizontalAlignment="Center" VerticalAlignment="Bottom"
Width="100" Minimum="100" Maximum="500"/>
</Grid>

Compass with an arrow wpf

I have to show a compass with an arrow inside a circle
I have the following code:
<Page xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<Page.Resources>
<Pen x:Key="BlackPen1" Thickness="1" Brush="Black"></Pen>
</Page.Resources>
<Grid>
<!-- Image for the Circle -->
<Image>
<Image.Source>
<DrawingImage>
<DrawingImage.Drawing>
<GeometryDrawing Pen="{StaticResource BlackPen1}" >
<GeometryDrawing.Geometry>
<GeometryGroup>
<EllipseGeometry RadiusX="50" RadiusY="50"></EllipseGeometry>
</GeometryGroup>
</GeometryDrawing.Geometry>
</GeometryDrawing>
</DrawingImage.Drawing>
</DrawingImage>
</Image.Source>
</Image>
<Path Grid.Row="1" Data="M15,0 L30,40 L0,40Z" Stroke="Black" Fill="Black" StrokeThickness="1" HorizontalAlignment="Center" />
<Line Grid.Row="0" Y1="40" Y2="400" X1="0" X2="0" Stroke="Black" StrokeThickness="5" HorizontalAlignment="Center" />
</Grid>
</Page>
Now I have to transform this whole compass based on the input angle.
One thing I know is If I move my arrow shape into Image type I can tans form this using the following
<Image.RenderTransform>
<RotateTransform Angle="{Binding ElementName=root, Path=Angle}"/>
</Image.RenderTransform>
But I am not able to draw this geometry inside the Image tag.
How to achieve this?
Why would you need to rotate the Ellipse? Surely only the arrow moves in a compass. In order to make that job easier, why don't you create the arrow in just one Path, instead of additionally using a Line element? You could define the same arrow with rotation like this:
<Path Grid.Row="1" Data="M15,0 30,40 18,40 18,400 12,400 12,40 0,40Z" Stroke="Black"
Fill="Black" StrokeThickness="1" HorizontalAlignment="Center"
RenderTransformOrigin="0.5,0.5">
<Path.RenderTransform>
<RotateTransform Angle="{Binding Angle, ElementName=root}" />
</Path.RenderTransform>
</Path>
You can apply the rotation to the whole Grid That contains all of your controls. Don't forget to set RenderTransformOrigin="0.5,0.5" on the element you rotate so it rotates arround the center and not the top left corner.
Or you could add a RotationTransform to each of the elements Path, Line and Ellipse. However in this case Rotation centers will probably be different for each one and it makes it more complicated.

Problems drawing an "x" in the center of a circle using XAML

I am trying to create a red circle with a black x through it using XAML.
My problem is that they aren't aligned correctly.
What is the right way to do this?
This is what I've got so far:
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<Image>
<Image.Source>
<DrawingImage>
<DrawingImage.Drawing>
<DrawingGroup>
<GeometryDrawing Brush="Red">
<GeometryDrawing.Pen>
<Pen Brush="Transparent" Thickness="0"/>
</GeometryDrawing.Pen>
<GeometryDrawing.Geometry>
<EllipseGeometry Center="8,8" RadiusX="8" RadiusY="8"/>
</GeometryDrawing.Geometry>
</GeometryDrawing>
<GeometryDrawing>
<GeometryDrawing.Pen>
<Pen Brush="Black" Thickness="2.5"/>
</GeometryDrawing.Pen>
<GeometryDrawing.Geometry>
<PathGeometry>
<PathFigure StartPoint="4,4">
<LineSegment Point="12,12"/>
</PathFigure>
<PathFigure StartPoint="4,12">
<LineSegment Point="12,4"/>
</PathFigure>
</PathGeometry>
</GeometryDrawing.Geometry>
</GeometryDrawing>
</DrawingGroup>
</DrawingImage.Drawing>
</DrawingImage>
</Image.Source>
</Image>
</Grid>
Simply putting an ellipse in the same grid with a black X the X isn't quite centered on the ellipse because the coordinates of each line you draw are really coordinates within the space allotted for it.
I think they needed to be in some sort of geometry or drawing aggregate to give them the same coordinate system. The geometry group and path are aggregators but both require their contents to have the same fill and stroke and the stroke and fill is different for the red circle (no stroke) and the black X (no fill).
The only aggregator that gives common coordinate systems and allows different fills & strokes for its members that I could find was the DrawingGroup.
The string shortcuts that work for creating a Path via its Data property don't appear to work for creating a PathGeometry so all had to be filled in by hand.
OK, so three hundred ways to skin a cat. Without fully understanding your use case I just came up with the fastest way to draw what you requested.
<Grid HorizontalAlignment="Left"
Height="80"
Margin="80,80,0,0"
VerticalAlignment="Top"
Width="80">
<Ellipse Fill="Red"
HorizontalAlignment="Stretch"
VerticalAlignment="Stretch" />
<Path Data="M40,53 L48,69 62,69 49,46 61,24 48,24 C48,24 40,39 40,39 40,39 32,24 32,24 L18,24 30,46 17,69 31,69 z"
Fill="Black"
Margin="15"
Stretch="Fill"
HorizontalAlignment="Center"
VerticalAlignment="Center"
/>
</Grid>
This is probably outside what exactly you're looking for, but hopefully it at least gives you another way to think about it.
I had the same issue when trying to center text within an ellipse. The problem with using something like a TextBlock is that the kerning and escapement of each character is slightly different and so while the TextBlock element itself might be technically centered within the ellipse, this does not mean that the character will be centered in the ellipse. The character always appears to be too low and to the right of center in most situations.
I have had some success by wrapping the TextBlock in a ViewBox. While I am not fully versed in the technical implementation of the ViewBox, the ViewBox appears to wrap the visual rendering of the content which allows me to center that rendering more easily than trying to center to layout elements together.
I also seem to have better luck using an outer element that is of odd width/height rather than even width and height.
<Grid Width="19"
Height="19">
<Ellipse Fill="#FFB1413F"
StrokeThickness="0"
HorizontalAlignment="Stretch"
VerticalAlignment="Stretch" />
<Viewbox HorizontalAlignment="Center"
VerticalAlignment="Stretch">
<TextBlock Text="X"
Margin="1"
FontWeight="Bold"
Foreground="White"
HorizontalAlignment="Center"
VerticalAlignment="Center" />
</Viewbox>
</Grid>

Precise OpacityMask

Suppose I need to set an opacity mask on a WPF control that highlights a portion of it in precise position (suppose a 50x50 square at (50;50) position). To do that I create a DrawingGroup containing 2 GeometryDrawing objects: 1 semi-transparent rectangle for the whole actual size of the control and 1 opaque rectangle for highlighted area. Then I create a DrawingBrush from this DrawingGroup, set it's Stretch property to None and set this brush as OpacityMask of the control that needs to be masked.
All this works fine while nothing is "sticking" out of bounds of said control. But if control draws something outside of it's bounds the outer point becomes a starting point from where opacity mask is applied (if the brush is aligned to that side) and the whole mask shifts by that distance resulting in unexpected behavior.
I can't seem to find a way to force mask to be applied from control's bounds or at least get the actual bounds of the control (including sticking parts) so I can adjust my mask accordingly.
Any ideas highly appreciated!
Update: Here's a simple test-case XAML and screenshots demonstrating the issue:
We have 2 nested Borders and Canvas in the last one with the above mentioned square:
<Border Padding="20" Background="DarkGray" Width="240" Height="240">
<Border Background="LightBlue">
<Canvas>
<Rectangle Canvas.Left="50" Canvas.Top="50" Width="50" Height="50"
Stroke="Red" StrokeThickness="2"
Fill="White"
/>
</Canvas>
</Border>
</Border>
Here's how it looks:
(source: ailon.org)
Now we add an OpacityMask to the second border so that every part of it except our square is semi-transparent:
<Border.OpacityMask>
<DrawingBrush Stretch="None" AlignmentX="Left" AlignmentY="Top">
<DrawingBrush.Drawing>
<DrawingGroup>
<GeometryDrawing Brush="#30000000">
<GeometryDrawing.Geometry>
<RectangleGeometry Rect="0,0,200,200" />
</GeometryDrawing.Geometry>
</GeometryDrawing>
<GeometryDrawing Brush="Black">
<GeometryDrawing.Geometry>
<RectangleGeometry Rect="50,50,50,50" />
</GeometryDrawing.Geometry>
</GeometryDrawing>
</DrawingGroup>
</DrawingBrush.Drawing>
</DrawingBrush>
</Border.OpacityMask>
Everything looks as expected:
(source: ailon.org)
And now we add a line to the canvas that sticks 10 pixels out on the left of our border:
<Line X1="-10" Y1="150" X2="120" Y2="150"
Stroke="Red" StrokeThickness="2"
/>
And the mask shifts 10 pixels to the left:
(source: ailon.org)
Update2: As a workaround I add a ridiculously large transparent rectangle outside of bounds and adjust my mask accordingly but that is a really nasty workaround.
Update3: Note: The canvas with rectangle and line is there just as an example of some object that has something outside of it bounds. In context of this sample it should be treated as some sort of a black box. You can't change it's properties to solve the general issue. This would be the same as just moving the line so it doesn't stick out.
Interesting issue indeed - here's what I've figured: The effect you are experiencing seems to be determined by the Viewport concept/behavior of TileBrush (see Viewbox too for the complete picture). Apparently the implicit bounding box of a FrameworkElement (i.e. the Canvas in your case) is affected/expanded by elements sticking out of bounds in a subtle way, that is, the dimensions of the box expand but the coordinate system of the box does not scale, rather expands too into the out of bounds direction.
It might be easier to illustrate that graphically, but due to time constraints I'll just offer a solution first and will explain the steps I've taken for the moment in order to get you started:
Solution:
<Border Background="LightBlue" Width="198" Height="198">
<Border.OpacityMask>
<DrawingBrush Stretch="None" AlignmentX="Center" AlignmentY="Center"
Viewport="-10,0,222,202" ViewportUnits="Absolute">
<DrawingBrush.Drawing>
<DrawingGroup>
<GeometryDrawing Brush="#30000000">
<GeometryDrawing.Geometry>
<RectangleGeometry Rect="-10,0,220,200" />
</GeometryDrawing.Geometry>
</GeometryDrawing>
<GeometryDrawing Brush="Black">...</GeometryDrawing>
</DrawingGroup>
</DrawingBrush.Drawing>
</DrawingBrush>
</Border.OpacityMask>
<Canvas x:Name="myGrid">...</Canvas>
</Border>
Please note that I've adjusted units by +/- 2 pixels here and there for pixel precision without knowing where the offset originates, but I think this can be ignored for the purpose of the example and resolved later if need be.
Explanation:
To simplify the illustration one should usually make all related implied/auto properties explicit first.
The inner border receives auto dimensions of 198 from the outer border (240 - 20 padding - 2 pixels deduced by experiment; don't know their origin, but ignorable right now), that is if you specify this as follows nothing should change, while using other values yields graphical changes:
<Border Background="LightBlue" Width="198" Height="198">...</Border>
Further the default implied Viewport and ViewportUnits like so:
<DrawingBrush Stretch="None" AlignmentX="Left" AlignmentY="Top"
Viewport="0,0,1,1" ViewportUnits="RelativeToBoundingBox">...</DrawingBrush>
You are enforcing the DrawingBrush size by overriding Stretch with None, while keeping the position and dimension of the base tile at default and relative to its bounding box. In addition you (understandably) are overriding AlignmentX/AlignmentY, which determine the placement within the base tile, that is within its bounding box. Resetting those to their defaults of Center is already telling: The mask shifts accordingly, meaning it has to be smaller than the bounding box, else their would be nothing to center within.
This can be taken further by changing ViewportUnits to Absolute, which will yield no graphics at all until the units are properly adjusted of course; again, by experiment the following explicit values are matching the auto ones, while using other values yields graphical changes:
<DrawingBrush Stretch="None" AlignmentX="Center" AlignmentY="Center"
Viewport="0,0,202,202" ViewportUnits="Absolute">...</DrawingBrush>
Now the opacity mask already aligns properly with the control. Obviously there is one problem left though, as the mask is clipping the line now, which is no surprise given its size and the absence of any Stretch effect. Adjusting its size and position accordingly resolves this:
<RectangleGeometry Rect="-10,0,220,200" />
and
<DrawingBrush Stretch="None" AlignmentX="Center" AlignmentY="Center"
Viewport="-10,0,222,202" ViewportUnits="Absolute">...</DrawingBrush>
Finally the opacity mask matches the control bounds as desired!
Supplement:
The required offsets determined by deduction and experiment in the explanation above can be retrieved at runtime by means of the VisualTreeHelper Class:
Rect descendantBounds = VisualTreeHelper.GetDescendantBounds(myGrid);
Depending on your visual element composition and needs you may need to factor in the LayoutInformation Class and build the union of both to get the all-encompassing bounding box:
Rect descendantBounds = VisualTreeHelper.GetDescendantBounds(myGrid);
Rect layoutSlot = LayoutInformation.GetLayoutSlot(myGrid);
Rect boundingBox = descendantBounds;
boundingBox.Union(layoutSlot);
See the following links for more details on both topics:
Windows Presentation Foundation
Graphics Rendering Overview,
especially VisualTreeHelper
Class
The Layout System, especially
Element Bounding Boxes
On your Canvas object add ClipToBounds="True".
<Canvas ClipToBounds="True">
<Rectangle Canvas.Left="50" Canvas.Top="50" Width="50" Height="50"
Stroke="Red" StrokeThickness="2"
Fill="White" />
<Line X1="-10" Y1="150" X2="120" Y2="150"
Stroke="Red" StrokeThickness="2"/>
</Canvas>
One workaround that may be more ideal than your current one would be to simply apply the OpacityMask at a higher level. Using this demo code for example, you could remove the mask from the Border and apply it to the Window instead. With a bit of tweaking it fits properly:
<Window.OpacityMask>
<DrawingBrush AlignmentX="Left" AlignmentY="Top" Stretch="None">
<DrawingBrush.Drawing>
<DrawingGroup>
<GeometryDrawing Brush="#30000000">
<GeometryDrawing.Geometry>
<RectangleGeometry Rect="0,0,300,300"/>
</GeometryDrawing.Geometry>
</GeometryDrawing>
<GeometryDrawing Brush="Black">
<GeometryDrawing.Geometry>
<RectangleGeometry Rect="92,82,50,50"/>
</GeometryDrawing.Geometry>
</GeometryDrawing>
</DrawingGroup>
</DrawingBrush.Drawing>
</DrawingBrush>
</Window.OpacityMask>
You would have to write some code to move the mask when the Window is resized, and for that reason you may be better off generating the mask dynamically in the code-behind.
My question for you is, why do you need to handle geometries that go outside the bounds of your Canvas?
Since you have parts that stick out from the control, one idea is to separate control image from the control mask.
<Window x:Class="WpfApplication1.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Window1" Height="300" Width="300">
<Border Padding="20" Background="DarkGray" Width="240" Height="240"> <!-- user container -->
<Grid> <!-- the control -->
<Border Background="LightBlue" HorizontalAlignment="Stretch"> <!-- control mask-->
<Canvas>
<Rectangle Canvas.Left="50" Canvas.Top="50" Width="50" Height="50"
Stroke="Red" StrokeThickness="2"
Fill="White"
/>
<Canvas.OpacityMask>
<DrawingBrush Stretch="None" AlignmentX="Left" AlignmentY="Top" TileMode="None">
<DrawingBrush.Drawing>
<DrawingGroup>
<GeometryDrawing Brush="#30000000">
<GeometryDrawing.Geometry>
<RectangleGeometry Rect="0,0,200,200" />
</GeometryDrawing.Geometry>
</GeometryDrawing>
<GeometryDrawing Brush="Black">
<GeometryDrawing.Geometry>
<RectangleGeometry Rect="50,50,50,50" />
</GeometryDrawing.Geometry>
</GeometryDrawing>
</DrawingGroup>
</DrawingBrush.Drawing>
</DrawingBrush>
</Canvas.OpacityMask>
</Canvas>
</Border>
<Canvas> <!-- control image-->
<Line X1="-10" Y1="150" X2="120" Y2="150" Stroke="Red" StrokeThickness="2"/>
</Canvas>
</Grid>
</Border>
</Window>

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