[OpenJDK 2D-Dev] [PATCH] JDK-8146035: Windows - With LCD antialiasing, some glyphs are not rendered correctly

Dmitry Batrak dmitry.batrak at jetbrains.com
Thu Apr 7 12:26:28 UTC 2016


I'd like to propose a fix for JDK-8146035. I am not a committer,
so I hope someone can sponsor this fix.
I work at Jetbrains, which has signed a company-level contributor
so, from a legal perspective, I believe, there are no obstacles.

My investigation shows that the issue is caused by incorrect determination
of bitmap size, prepared for glyph rendering, so only part of glyph
becomes visible due to cropping. This seems to happen because
compatible bitmap is not selected into memory device context (DC)
before calling GetTextMetrics. Documentation for CreateCompatibleDC call

says compatible bitmap needs to be selected into DC before any drawing
Even though GetTextMetrics is not a drawing operation, it turns out
to be affected by selected bitmap's type too (by default a monochrome
is selected in a memory DC). This behaviour was also mentioned in the
MSDN blog post comment:

The proposed fix is to select a temporary 1x1 compatible bitmap
into memory DC before GetTextMetrics call.
Here's webrev link - http://adm-12504.intellij.net/
I didn't create a test case, as it would require a specific font file
(I couldn't reproduce the issue for fonts bundled with Windows).

Best regards,
Dmitry Batrak
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