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Fix oversized GDI glyph buffers

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gamer147
2026-08-16 11:24:07 -04:00
parent eef1225b56
commit 7b0987d9a6
4 changed files with 97 additions and 15 deletions
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19
engine/Age.Engine.Text.Windows/WindowsGdiGlyphMaskRasterizer.cs
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@@ -126,22 +126,31 @@ public sealed class WindowsGdiGlyphMaskRasterizer
int expectedBytes = checked(stride * height);
// CP932 0x8140 (U+3000 IDEOGRAPHIC SPACE) is a zero-ink spacing glyph. GDI reports
// its placement as a nominal 1x1 black box but returns a zero-byte required buffer.
// Preserve those metrics and materialize the implied transparent mask; a nonzero
// short/oversized payload still means that the bitmap contract is inconsistent.
if (size != 0 && size != expectedBytes)
// Preserve those metrics and materialize the implied transparent mask. GDI can also
// return storage beyond the metric-defined rows (for example, bold 24px MS Mincho 'p'
// reports 12x15 but requests 192 bytes rather than 180). Treat the queried size as the
// allocation contract and the GLYPHMETRICS box as the raster-consumption contract: read
// exactly the requested buffer, then retain only the rows described by the metrics. Bytes
// outside that box are not drawable coverage and are not required to be initialized to zero.
if (size != 0 && size < expectedBytes)
throw new InvalidOperationException(
$"GDI gray-4 buffer size {size} disagrees with {width}x{height}, stride {stride}.");
$"GDI gray-4 buffer size {size} for CP932 0x{code:x4} " +
$"('{request.FontFace}', {request.PixelHeight}px, width {request.RequestedWidth}, " +
$"weight {request.Weight}) is smaller than its {width}x{height} metric box, " +
$"stride {stride} ({expectedBytes} bytes).");
byte[] coverage = new byte[expectedBytes];
if (size > 0)
{
byte[] gdiBuffer = new byte[checked((int)size)];
identity = Mat2.Identity;
uint written = NativeMethods.GetGlyphOutlineA(
_displayIc.DangerousGetHandle(), code, GgoGray4Bitmap,
out GlyphMetrics secondMetrics, size, coverage, ref identity);
out GlyphMetrics secondMetrics, size, gdiBuffer, ref identity);
if (written == GdiError) ThrowWin32($"GetGlyphOutlineA read failed for CP932 0x{code:x4}");
if (written != size || !metrics.Equals(secondMetrics))
throw new InvalidOperationException("GDI glyph metrics changed between query and read.");
gdiBuffer.AsSpan(0, expectedBytes).CopyTo(coverage);
}
byte[] encoded = EncodeCp932Code(code);