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Diffstat (limited to 'src/mbgl/text/local_glyph_rasterizer.hpp')
-rw-r--r-- | src/mbgl/text/local_glyph_rasterizer.hpp | 42 |
1 files changed, 42 insertions, 0 deletions
diff --git a/src/mbgl/text/local_glyph_rasterizer.hpp b/src/mbgl/text/local_glyph_rasterizer.hpp new file mode 100644 index 0000000000..c2bdbd2840 --- /dev/null +++ b/src/mbgl/text/local_glyph_rasterizer.hpp @@ -0,0 +1,42 @@ +#pragma once + +#include <mbgl/text/glyph.hpp> + +namespace mbgl { + +/* + Given a font stack and a glyph ID, platform-specific implementations of + LocalGlyphRasterizer will decide which, if any, local fonts to use and + then generate a matching glyph object with a greyscale rasterization of + the glyph and appropriate metrics. GlyphManager will then use TinySDF to + transform the rasterized bitmap into an SDF. + + The JS equivalent of this functionality will only generate glyphs in the + 'CJK Unified Ideographs' and 'Hangul Syllables' ranges, for which it can + get away with rendering a fixed 30px square image and GlyphMetrics of: + + width: 24, + height: 24, + left: 0, + top: -8, + advance: 24 + + The JS equivalent also uses heuristic evaluation of the font stack name + to control the font-weight it uses during rasterization. + + It is left to platform-specific implementation to decide how best to + map a FontStack to a particular rasterization. + + The default implementation simply refuses to rasterize any glyphs. +*/ + +class LocalGlyphRasterizer { +public: + virtual ~LocalGlyphRasterizer() = default; + + // virtual so that test harness can override platform-specific behavior + virtual bool canRasterizeGlyph(const FontStack&, GlyphID); + virtual Glyph rasterizeGlyph(const FontStack&, GlyphID); +}; + +} // namespace mbgl |