Bug 1393467 - clip FreeType glyph bitmap to mask in Skia. r=jrmuizel (e1d3260e) · Commits · Tommy Webb / Tor Browser

gfx/skia/skia/src/ports/SkFontHost_FreeType_common.cpp

+83 −17

Original line number	Diff line number	Diff line
		@@ -395,8 +395,6 @@ void SkScalerContext_FreeType_Base::generateGlyphImage(
		switch ( face->glyph->format ) {
		case FT_GLYPH_FORMAT_OUTLINE: {
		FT_Outline* outline = &face->glyph->outline;
		FT_BBox bbox;
		FT_Bitmap target;

		int dx = 0, dy = 0;
		if (fRec.fFlags & SkScalerContext::kSubpixelPositioning_Flag) {
		@@ -405,36 +403,97 @@ void SkScalerContext_FreeType_Base::generateGlyphImage(
		// negate dy since freetype-y-goes-up and skia-y-goes-down
		dy = -dy;
		}
		FT_Outline_Get_CBox(outline, &bbox);
		/*
		what we really want to do for subpixel is
		offset(dx, dy)
		compute_bounds
		offset(bbox & !63)
		but that is two calls to offset, so we do the following, which
		achieves the same thing with only one offset call.
		*/
		FT_Outline_Translate(outline, dx - ((bbox.xMin + dx) & ~63),
		dy - ((bbox.yMin + dy) & ~63));

		memset(glyph.fImage, 0, glyph.rowBytes() * glyph.fHeight);

		if (SkMask::kLCD16_Format == glyph.fMaskFormat) {
		FT_Outline_Translate(outline, dx, dy);
		FT_Error err = FT_Render_Glyph(face->glyph, doVert ? FT_RENDER_MODE_LCD_V :
		FT_RENDER_MODE_LCD);
		if (err) {
		SK_TRACEFTR(err, "Could not render glyph.");
		sk_bzero(glyph.fImage, glyph.computeImageSize());
		return;
		}

		SkMask mask;
		glyph.toMask(&mask);
		#ifdef SK_SHOW_TEXT_BLIT_COVERAGE
		memset(mask.fImage, 0x80, mask.fBounds.height() * mask.fRowBytes);
		#endif
		FT_GlyphSlotRec& ftGlyph = *face->glyph;

		if (!SkIRect::Intersects(mask.fBounds,
		SkIRect::MakeXYWH( ftGlyph.bitmap_left,
		-ftGlyph.bitmap_top,
		ftGlyph.bitmap.width,
		ftGlyph.bitmap.rows)))
		{
		return;
		}

		// If the FT_Bitmap extent is larger, discard bits of the bitmap outside the mask.
		// If the SkMask extent is larger, shrink mask to fit bitmap (clearing discarded).
		unsigned char* origBuffer = ftGlyph.bitmap.buffer;
		// First align the top left (origin).
		if (-ftGlyph.bitmap_top < mask.fBounds.fTop) {
		int32_t topDiff = mask.fBounds.fTop - (-ftGlyph.bitmap_top);
		ftGlyph.bitmap.buffer += ftGlyph.bitmap.pitch * topDiff;
		ftGlyph.bitmap.rows -= topDiff;
		ftGlyph.bitmap_top = -mask.fBounds.fTop;
		}
		if (ftGlyph.bitmap_left < mask.fBounds.fLeft) {
		int32_t leftDiff = mask.fBounds.fLeft - ftGlyph.bitmap_left;
		ftGlyph.bitmap.buffer += leftDiff;
		ftGlyph.bitmap.width -= leftDiff;
		ftGlyph.bitmap_left = mask.fBounds.fLeft;
		}
		if (mask.fBounds.fTop < -ftGlyph.bitmap_top) {
		mask.fImage += mask.fRowBytes * (-ftGlyph.bitmap_top - mask.fBounds.fTop);
		mask.fBounds.fTop = -ftGlyph.bitmap_top;
		}
		if (mask.fBounds.fLeft < ftGlyph.bitmap_left) {
		mask.fImage += sizeof(uint16_t) * (ftGlyph.bitmap_left - mask.fBounds.fLeft);
		mask.fBounds.fLeft = ftGlyph.bitmap_left;
		}
		// Origins aligned, clean up the width and height.
		int ftVertScale = (doVert ? 3 : 1);
		int ftHoriScale = (doVert ? 1 : 3);
		if (mask.fBounds.height() * ftVertScale < SkToInt(ftGlyph.bitmap.rows)) {
		ftGlyph.bitmap.rows = mask.fBounds.height() * ftVertScale;
		}
		if (mask.fBounds.width() * ftHoriScale < SkToInt(ftGlyph.bitmap.width)) {
		ftGlyph.bitmap.width = mask.fBounds.width() * ftHoriScale;
		}
		if (SkToInt(ftGlyph.bitmap.rows) < mask.fBounds.height() * ftVertScale) {
		mask.fBounds.fBottom = mask.fBounds.fTop + ftGlyph.bitmap.rows / ftVertScale;
		}
		if (SkToInt(ftGlyph.bitmap.width) < mask.fBounds.width() * ftHoriScale) {
		mask.fBounds.fRight = mask.fBounds.fLeft + ftGlyph.bitmap.width / ftHoriScale;
		}
		if (fPreBlend.isApplicable()) {
		copyFT2LCD16<true>(face->glyph->bitmap, mask, doBGR,
		copyFT2LCD16<true>(ftGlyph.bitmap, mask, doBGR,
		fPreBlend.fR, fPreBlend.fG, fPreBlend.fB);
		} else {
		copyFT2LCD16<false>(face->glyph->bitmap, mask, doBGR,
		copyFT2LCD16<false>(ftGlyph.bitmap, mask, doBGR,
		fPreBlend.fR, fPreBlend.fG, fPreBlend.fB);
		}
		// Restore the buffer pointer so FreeType can properly free it.
		ftGlyph.bitmap.buffer = origBuffer;
		} else {
		FT_BBox bbox;
		FT_Bitmap target;
		FT_Outline_Get_CBox(outline, &bbox);
		/*
		what we really want to do for subpixel is
		offset(dx, dy)
		compute_bounds
		offset(bbox & !63)
		but that is two calls to offset, so we do the following, which
		achieves the same thing with only one offset call.
		*/
		FT_Outline_Translate(outline, dx - ((bbox.xMin + dx) & ~63),
		dy - ((bbox.yMin + dy) & ~63));

		target.width = glyph.fWidth;
		target.rows = glyph.fHeight;
		target.pitch = glyph.rowBytes();
		@@ -442,8 +501,15 @@ void SkScalerContext_FreeType_Base::generateGlyphImage(
		target.pixel_mode = compute_pixel_mode( (SkMask::Format)fRec.fMaskFormat);
		target.num_grays = 256;

		memset(glyph.fImage, 0, glyph.rowBytes() * glyph.fHeight);
		FT_Outline_Get_Bitmap(face->glyph->library, outline, &target);
		#ifdef SK_SHOW_TEXT_BLIT_COVERAGE
		for (int y = 0; y < glyph.fHeight; ++y) {
		for (int x = 0; x < glyph.fWidth; ++x) {
		uint8_t& a = ((uint8_t)glyph.fImage)[(glyph.rowBytes() y) + x];
		a = SkTMax<uint8_t>(a, 0x20);
		}
		}
		#endif
		}
		} break;