BUG: GetGlyphOutline() with GGO_BITMAP Fails with Large Scale

• Microsoft Windows Software Development Kit (SDK) for Windows version 3.1

SYMPTOMS

Calling GetGlyphOutline() for a bitmap and passing a large X or Y scaling factor in the transformation matrix causes the return value to not properly track the bitmap size.

For example, Times New Roman Regular 72 point "1", with a scaling factor of 4.0 in eM11 of the transformation matrix, returns a black box of 100,64. This requires a bitmap of at least 800 bytes but GetGlyphOutline() only returns 256. The native buffer is returned with no problems.

CAUSE

A 12-point font on a VGA is marked to use the rasterizer's scan converter. However, if the scaling indicated in the transform exceeds the outline threshold, GDI's "external" scan converter should be used. Unfortunately, that condition is not detected.

NOTE: This problem occurs only with bitmaps; outlines are fine with all transformation matrices.

STATUS

Microsoft has confirmed this to be a bug in Windows version 3.1. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.