Scrolling the area view change drawing transparency

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What steps will reproduce the problem?
1. Draw a shape with an alpha value less than 1.0.
2. Scroll the drawing area.
3. The shape is drawn with a complete opaque stroke (alpha = 1.0). Draw another 
shape and the transparency gets back to normal.

What is the expected output? What do you see instead?

Transparency should not be changed while scrolling. Seems that repaint() method 
is not using drawing properties.

Original issue reported on code.google.com by sebastian.treu on 17 Mar 2011 at 8:46