Drawing Polyline with mouse events

Question

I'm trying to create a drawing application with WPF.

I use a Canvas and I draw Polyline on where the MouseMove event triggers. But some artifacts are created during the process :

StrokeThickness at 4 :

StrokeThickness at 15 :

The red points represent where the MouseMove triggered, and the gray line is, of course, the Polyline with all the red points.

Any ideas why I get this ?

Answer 1

If StrokeLineJoin=Miter then you can use StrokeMiterLimit to control how far out the miter extends.

( StrokeLineJoin=Mitre is the default on a PolyLine )

Alternatively, you can use StrokeLineJoin=Round to get a nice transition between segments.

Use StrokeStartLineCap and StrokeEndLineCap if you want different ends.

<Window x:Class="WpfApplication5.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="500" Width="500">
    <Window.Resources>
        <PointCollection x:Key="points">0,0 10,30 15,0 18,60 23,30 35,30 40,0 43,60 48,30 100,30</PointCollection>
    </Window.Resources>
<StackPanel VerticalAlignment="Center" HorizontalAlignment="Center">
    <StackPanel Orientation="Horizontal">
        <Polyline Stroke="Gray" StrokeThickness="4" Points="{StaticResource points}" />
        <Polyline Stroke="Gray" StrokeThickness="4" StrokeMiterLimit="10" Points="{StaticResource points}" />
        <Polyline Stroke="Gray" StrokeThickness="4" StrokeMiterLimit="5"  Points="{StaticResource points}" />
        <Polyline Stroke="Gray" StrokeThickness="4" StrokeMiterLimit="1"  Points="{StaticResource points}" />
    </StackPanel>
    <StackPanel Orientation="Horizontal" Margin="0,50,0,0">
        <Polyline Stroke="Gray" StrokeThickness="10" Points="{StaticResource points}" />
        <Polyline Stroke="Gray" StrokeThickness="10" StrokeMiterLimit="10" Points="{StaticResource points}" />
        <Polyline Stroke="Gray" StrokeThickness="10" StrokeMiterLimit="5"  Points="{StaticResource points}" />
        <Polyline Stroke="Gray" StrokeThickness="10" StrokeMiterLimit="1"  Points="{StaticResource points}" />
    </StackPanel>
        <StackPanel Orientation="Horizontal" Margin="0,50,0,0">
            <Polyline Stroke="Gray" StrokeThickness="10" StrokeLineJoin="Miter" StrokeStartLineCap="Round" StrokeEndLineCap="Round" Points="{StaticResource points}" />
            <Polyline Stroke="Gray" StrokeThickness="10" StrokeLineJoin="Bevel" StrokeStartLineCap="Round" StrokeEndLineCap="Round" Points="{StaticResource points}" />
            <Polyline Stroke="Gray" StrokeThickness="10" StrokeLineJoin="Round" StrokeStartLineCap="Round" StrokeEndLineCap="Round" Points="{StaticResource points}" />
        </StackPanel>
    </StackPanel>
</Window>