public static unsafe void CompareMetricsWithStb(Font f, DrawableFontAtlas atlas, StbTrueType.stbtt_fontinfo stbFont)
{
var pc = new StbTrueType.stbtt_pack_context();
StbTrueType.stbtt_PackBegin(pc, (byte *)0, 512, 512, 512, 1, null);
var cd = new StbTrueType.stbtt_packedchar[f.LastCharIndex + 1];
StbTrueType.stbrp_rect[] rects;
fixed(StbTrueType.stbtt_packedchar *charDataPtr = &cd[0])
{
var range = new StbTrueType.stbtt_pack_range
{
first_unicode_codepoint_in_range = 0,
array_of_unicode_codepoints = null,
num_chars = (int)f.LastCharIndex + 1,
chardata_for_range = charDataPtr,
font_size = -atlas.FontSize
};
rects = new StbTrueType.stbrp_rect[f.LastCharIndex + 1];
fixed(StbTrueType.stbrp_rect *rectPtr = &rects[0])
{
int n = StbTrueType.stbtt_PackFontRangesGatherRects(pc, stbFont, &range, 1, rectPtr);
StbTrueType.stbtt_PackFontRangesPackRects(pc, rectPtr, n);
}
}
foreach ((char charIndex, DrawableGlyph atlasGlyph) in atlas.Glyphs)
{
FontGlyph glyph = atlasGlyph.FontGlyph;
var advance = 0;
var bearing = 0;
StbTrueType.stbtt_GetCodepointHMetrics(stbFont, charIndex, &advance, &bearing);
Assert.True(advance == glyph.AdvanceWidth);
Assert.True(bearing == glyph.LeftSideBearing || glyph.LeftSideBearing == 0); // stb has junk data beyond valid
var minX = 0;
var maxX = 0;
var minY = 0;
var maxY = 0;
StbTrueType.stbtt_GetCodepointBitmapBoxSubpixel(stbFont, charIndex, atlas.RenderScale, atlas.RenderScale, 0, 0, &minX, &minY, &maxX, &maxY);
Rectangle bbox = glyph.GetBBox(atlas.RenderScale);
Assert.Equal(minX, bbox.X);
Assert.Equal(minY, bbox.Y);
Assert.Equal(maxX, bbox.Width);
Assert.Equal(maxY, bbox.Height);
Rectangle drawBox = new Rectangle(0, 0, bbox.Width - bbox.X, bbox.Height - bbox.Y);
drawBox.Size += Vector2.One; // Add padding from stb
StbTrueType.stbrp_rect rect = rects[charIndex];
Assert.Equal(rect.w, drawBox.Width);
Assert.Equal(rect.h, drawBox.Height);
}
}