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tiennm99
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User report on v0.1.14: text appears semi-transparent, desktop wallpaper
bleeds through glyph pixels.
Root cause: GDI's DrawTextW writes only RGB into 32bpp BI_RGB DIBs — the
"reserved" alpha byte (byte 3) is not preserved per the BITMAPINFOHEADER
contract. When UpdateLayeredWindow later composites with AC_SRC_ALPHA, it
reads alpha=0 at every glyph pixel and shows them as fully transparent.
The pre-v0.1.13 pipeline worked around this with an apply_alpha_mask
post-pass that OR'd 0xFF000000 into every pixel inside the rounded rect.
The stadium-shape rewrite (526786b) removed it on the false assumption
that tiny-skia's per-pixel alpha would "stick" through subsequent GDI
writes — but GDI runs *after* tiny-skia in the pipeline, so any pixel
GDI text writes to loses the alpha that tiny-skia set.
Fix: re-stamp the alpha channel from the original Pixmap after the GDI
text overlay. This restores tiny-skia's exact alpha values (255 in the
stadium interior, partial on the AA curved perimeter, 0 outside),
including the AA fade at the stadium's rounded ends.
Implementation:
- new helper `restore_alpha_from_pixmap(pixmap, dst)` next to the
existing `copy_pixmap_to_dib`
- hoist `pixmap` out of the if-let arm in render() so it survives until
after `paint_bubble_text`
- call `restore_alpha_from_pixmap` post-text
Two parallel reviewers (debugger + code-reviewer) converged on the same
diagnosis; the debugger preferred this approach for its simplicity and
because it's robust to any GDI behavior (whether alpha is zeroed,
untouched, or scribbled on, we overwrite with the known-good value).
Build clean.