Multiple clipping regions on a PDF page not working

Question

I'm using SkiaSharp to print labels to PDF (and other things). Each page of the PDF can have multiple rows and columns. I need to clip each label to the correct size so it's doesn't trash neighbouring labels.

For testing, each label has a rectangle that extends too far plus 7 lines of text and a circle near the vertical middle.

My code is like:

using (var region = new SKRegion())
{
   region.SetRect(_labelClipRect);
   _currentCanvas.ClipRegion(region, SKClipOperation.Intersect);
   _labelView.Draw(_currentCanvas, _printRequest.Device.DPI, xOffsetPX, yOffsetPX);
}

The result is: The first label on each page looks correct but the rest are funky. The rectangle and circle are missing and the text is not clipped at all.

Anyone seen/got a sample of something like this?

Thanks

One idea I had was to paint a white(?) rectangle over the area outside the labels - rather than clipping it. However, labels may not have a white background so that could be an issue. — Jonesie, May 28 '18 at 12:58

score 0 · Answer 1 · answered Feb 13 '21 at 20:37

Each call to _currentCanvas.ClipRegion intersects passed region with the current one, it's not setting the clip to this region.

Try saving canvas state and restore after the label was drawn:

using (var region = new SKRegion())
{
   region.SetRect(_labelClipRect);
   _currentCanvas.Save();
   _currentCanvas.ClipRegion(region, SKClipOperation.Intersect);
   _labelView.Draw(_currentCanvas, _printRequest.Device.DPI, xOffsetPX, yOffsetPX);
   _currentCanvas.Restore();
}

Multiple clipping regions on a PDF page not working

1 Answers1