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POCustom line drawing in WPF
 

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  1. POCustom line drawing in WPF
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    <p>I'm trying to manually draw a line in WPF by overriding the OnRender method of a control and calling the DrawLine method on the given DrawingContext. I read somewhere that this method call doesn't instantly draw the line, but I can't work out how to actually cause the line to appear.</p> <p>I've tried using a combination of PathGeometry, LineSegments, Line and Polyline controls. I could draw what I wanted then, but offsets weren't quite right (i.e. when drawing a line, it was fine, when drawing a polyline, everything became incorrectly offset).</p> <p>Any advice on this would be great.</p> <p><strong>EDIT</strong></p> <p><em>Pen Code</em></p> <pre><code> private static readonly Pen LinePen = new Pen(new SolidColorBrush(Colors.Green), 3.0d); private static readonly Pen WayPointPen = new Pen(new SolidColorBrush(Colors.Gray), 3.0d); </code></pre> <p><em>Render Code</em></p> <pre><code> protected override void OnRender(DrawingContext drawingContext) { // Draw way points this.DrawWayPoints(drawingContext); if (mDrawing) { // Draw current line this.DrawCurrentLine(drawingContext); } } private void DrawCurrentLine(DrawingContext context) { if(mStartPoint.HasValue &amp;&amp; mEndPoint.HasValue) { // Draw the line context.DrawLine(LinePen, mStartPoint.Value, mEndPoint.Value); } } private void DrawWayPoints(DrawingContext context) { if (mWayPoints.Count &lt; 2) { return; } // Draw all points for (int i = 0; i &lt; mWayPoints.Count - 1; i++) { var start = mWayPoints[i]; var end = mWayPoints[i + 1]; // Draw the line context.DrawLine(WayPointPen, start, end); } } </code></pre> <p><strong>EDIT</strong></p> <p>Test Project: <a href="http://dl.dropbox.com/u/12763956/DrawingTest.zip" rel="nofollow">http://dl.dropbox.com/u/12763956/DrawingTest.zip</a> (Test Project written in Visual Studio 2010)</p> <p>Usage: - Left click within the raised area to add points to the list. - Right click to end drawing and clear points.</p> <p>Note: Custom drawn lines (in OnRender override) do not appear.</p>
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    1. USSamuel Slade
    1. USSamuel Slade
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    1. COI draw lines with OnRender and they appear. Can you add sample code so I can see what you're doing wrong?
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      1. USEd Bayiates
    2. COI've added the render code I'm using. It's contained within a WPF control. I've tried having no content within the control and with a canvas element. I've also debugged to make sure the calls to DrawLine are actually hit, and they are.
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      1. USSamuel Slade
    3. COSorry for the delay answering -- was off on my motorcycle. Your code looks perfectly fine. Can you use Debug.WriteLine to get the specific points you are trying to draw lines to/from? If they are out of bounds, no line will appear.
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