The Windows overlay badge rendered as a black square because GDI drawing
functions do not write the alpha channel — all pixels stay at A=0, causing
Windows to fall back to the opaque monochrome mask and draw corner pixels
as solid black.
Fix: after all GDI calls, iterate the pixel buffer and set alpha=0xFF for
every non-zero pixel; corner pixels (zero) retain A=0 and composite as
transparent, giving a proper circular badge.
Also increased bitmap size 16→20 and font height 11→14 for better
legibility, especially for two-digit mention counts.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
jared
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