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mono / libgdiplus

C-based implementation of the GDI+ API
http://www.mono-project.com/
MIT License
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Vertical text alignment and positioning fix #670

Open PreferLinux opened 3 years ago

PreferLinux commented 3 years ago

Before fix: Screenshot_20200908_152640 The vertical text is being drawn off-screen. Note the boxes (from measuring the string) for vertical left-to-right are correct, hence no test failures. GdipAddPathString() has much the same issue, so I've added a test there that has vertical text to detect the incorrect drawing location (fails without fix). I've also added tests for alignment when drawing at a point instead of in a box, and drawing with both vertical and right-to-left (which fail without the fix).

Here's a screenshot with only the changes to pango_DrawString applied, fixing the drawing location: Screenshot_20200908_154720 On vertical text the alignment is opposite what it should be, and on right-to-left it is also significantly offset horizontally. Hence there are also changes dealing with alignment.

With all changes: Screenshot_20200908_152509 .Net / Windows 8.1 as a comparison: screenshot-Windows-text-alignment

Test application: text-align.txt Compiles with mcs -r:System.Windows.Forms,System.Drawing text-align.txt -unsafe

Furthermore, as gdip_pango_setup_layout transforms the Cairo context on vertical text, GdipAddPathString() wasn't getting the correct path points. I've changed it to save and later restore the context to fix this.

PreferLinux commented 3 years ago

Nice, a test failure in CI that I don't get on my machine. Will have to add some debugging to that test, and then revert it...

PreferLinux commented 3 years ago

Actually, didn't need to. It is simply that the Linux testing uses Cairo text rendering (due to an old Pango version), and that can't handle the tests I added. Those tests have now been made conditional.