[patch] cosmetic fix for KPlotWidget

[Jason Harris]

Hello,

The attached one-liner patch makes horizontal and vertical lines drawn in 
KPlotWidget much sharper, compare before[1] and after[2].

The issue: With antialiasing on, a line drawn with integer pixel values is 
regarded as being halfway between the bracketing pixels, so a line defined 
like:

	painter.drawLine( 1.0, 10.0, 1.0, 20.0 );

will look wide and fuzzy, whereas this line:

	painter.drawLine( 1.5, 10.0, 1.5, 20.0 );

looks narrow and sharp, because it doesn't "spill" into neighboring pixels.

The attached patch modifies the QPainter translate() coordinates by 0.5 
pixels, so that integer pixel values look sharp.

OK to commit? 

Jason

[1]: http://www.30doradus.org/kstars/kplottest_blurry.png
[2]: http://www.30doradus.org/kstars/kplottest_sharp.png

-- 
KStars: KDE Desktop Planetarium
kstars at 30doradus.org
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