Index: third_party/freetype/include/ftcffdrv.h |
diff --git a/third_party/freetype/include/ftcffdrv.h b/third_party/freetype/include/ftcffdrv.h |
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index 0000000000000000000000000000000000000000..f7031bc8832543732c21ad8c86c47a427014fe73 |
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+/***************************************************************************/ |
+/* */ |
+/* ftcffdrv.h */ |
+/* */ |
+/* FreeType API for controlling the CFF driver (specification only). */ |
+/* */ |
+/* Copyright 2013, 2014 by */ |
+/* David Turner, Robert Wilhelm, and Werner Lemberg. */ |
+/* */ |
+/* This file is part of the FreeType project, and may only be used, */ |
+/* modified, and distributed under the terms of the FreeType project */ |
+/* license, LICENSE.TXT. By continuing to use, modify, or distribute */ |
+/* this file you indicate that you have read the license and */ |
+/* understand and accept it fully. */ |
+/* */ |
+/***************************************************************************/ |
+ |
+ |
+#ifndef __FTCFFDRV_H__ |
+#define __FTCFFDRV_H__ |
+ |
+#include <ft2build.h> |
+#include FT_FREETYPE_H |
+ |
+#ifdef FREETYPE_H |
+#error "freetype.h of FreeType 1 has been loaded!" |
+#error "Please fix the directory search order for header files" |
+#error "so that freetype.h of FreeType 2 is found first." |
+#endif |
+ |
+ |
+FT_BEGIN_HEADER |
+ |
+ |
+ /************************************************************************** |
+ * |
+ * @section: |
+ * cff_driver |
+ * |
+ * @title: |
+ * The CFF driver |
+ * |
+ * @abstract: |
+ * Controlling the CFF driver module. |
+ * |
+ * @description: |
+ * While FreeType's CFF driver doesn't expose API functions by itself, |
+ * it is possible to control its behaviour with @FT_Property_Set and |
+ * @FT_Property_Get. The list below gives the available properties |
+ * together with the necessary macros and structures. |
+ * |
+ * The CFF driver's module name is `cff'. |
+ * |
+ * *Hinting* *and* *antialiasing* *principles* *of* *the* *new* *engine* |
+ * |
+ * The rasterizer is positioning horizontal features (e.g., ascender |
+ * height & x-height, or crossbars) on the pixel grid and minimizing the |
+ * amount of antialiasing applied to them, while placing vertical |
+ * features (vertical stems) on the pixel grid without hinting, thus |
+ * representing the stem position and weight accurately. Sometimes the |
+ * vertical stems may be only partially black. In this context, |
+ * `antialiasing' means that stems are not positioned exactly on pixel |
+ * borders, causing a fuzzy appearance. |
+ * |
+ * There are two principles behind this approach. |
+ * |
+ * 1) No hinting in the horizontal direction: Unlike `superhinted' |
+ * TrueType, which changes glyph widths to accommodate regular |
+ * inter-glyph spacing, Adobe's approach is `faithful to the design' in |
+ * representing both the glyph width and the inter-glyph spacing |
+ * designed for the font. This makes the screen display as close as it |
+ * can be to the result one would get with infinite resolution, while |
+ * preserving what is considered the key characteristics of each glyph. |
+ * Note that the distances between unhinted and grid-fitted positions at |
+ * small sizes are comparable to kerning values and thus would be |
+ * noticeable (and distracting) while reading if hinting were applied. |
+ * |
+ * One of the reasons to not hint horizontally is antialiasing for LCD |
+ * screens: The pixel geometry of modern displays supplies three |
+ * vertical sub-pixels as the eye moves horizontally across each visible |
+ * pixel. On devices where we can be certain this characteristic is |
+ * present a rasterizer can take advantage of the sub-pixels to add |
+ * increments of weight. In Western writing systems this turns out to |
+ * be the more critical direction anyway; the weights and spacing of |
+ * vertical stems (see above) are central to Armenian, Cyrillic, Greek, |
+ * and Latin type designs. Even when the rasterizer uses greyscale |
+ * antialiasing instead of color (a necessary compromise when one |
+ * doesn't know the screen characteristics), the unhinted vertical |
+ * features preserve the design's weight and spacing much better than |
+ * aliased type would. |
+ * |
+ * 2) Aligment in the vertical direction: Weights and spacing along the |
+ * y~axis are less critical; what is much more important is the visual |
+ * alignment of related features (like cap-height and x-height). The |
+ * sense of alignment for these is enhanced by the sharpness of grid-fit |
+ * edges, while the cruder vertical resolution (full pixels instead of |
+ * 1/3 pixels) is less of a problem. |
+ * |
+ * On the technical side, horizontal alignment zones for ascender, |
+ * x-height, and other important height values (traditionally called |
+ * `blue zones') as defined in the font are positioned independently, |
+ * each being rounded to the nearest pixel edge, taking care of |
+ * overshoot suppression at small sizes, stem darkening, and scaling. |
+ * |
+ * Hstems (this is, hint values defined in the font to help align |
+ * horizontal features) that fall within a blue zone are said to be |
+ * `captured' and are aligned to that zone. Uncaptured stems are moved |
+ * in one of four ways, top edge up or down, bottom edge up or down. |
+ * Unless there are conflicting hstems, the smallest movement is taken |
+ * to minimize distortion. |
+ * |
+ * @order: |
+ * hinting-engine |
+ * no-stem-darkening |
+ * darkening-parameters |
+ * |
+ */ |
+ |
+ |
+ /************************************************************************** |
+ * |
+ * @property: |
+ * hinting-engine |
+ * |
+ * @description: |
+ * Thanks to Adobe, which contributed a new hinting (and parsing) |
+ * engine, an application can select between `freetype' and `adobe' if |
+ * compiled with CFF_CONFIG_OPTION_OLD_ENGINE. If this configuration |
+ * macro isn't defined, `hinting-engine' does nothing. |
+ * |
+ * The default engine is `freetype' if CFF_CONFIG_OPTION_OLD_ENGINE is |
+ * defined, and `adobe' otherwise. |
+ * |
+ * The following example code demonstrates how to select Adobe's hinting |
+ * engine (omitting the error handling). |
+ * |
+ * { |
+ * FT_Library library; |
+ * FT_UInt hinting_engine = FT_CFF_HINTING_ADOBE; |
+ * |
+ * |
+ * FT_Init_FreeType( &library ); |
+ * |
+ * FT_Property_Set( library, "cff", |
+ * "hinting-engine", &hinting_engine ); |
+ * } |
+ * |
+ * @note: |
+ * This property can be used with @FT_Property_Get also. |
+ * |
+ */ |
+ |
+ |
+ /************************************************************************** |
+ * |
+ * @enum: |
+ * FT_CFF_HINTING_XXX |
+ * |
+ * @description: |
+ * A list of constants used for the @hinting-engine property to select |
+ * the hinting engine for CFF fonts. |
+ * |
+ * @values: |
+ * FT_CFF_HINTING_FREETYPE :: |
+ * Use the old FreeType hinting engine. |
+ * |
+ * FT_CFF_HINTING_ADOBE :: |
+ * Use the hinting engine contributed by Adobe. |
+ * |
+ */ |
+#define FT_CFF_HINTING_FREETYPE 0 |
+#define FT_CFF_HINTING_ADOBE 1 |
+ |
+ |
+ /************************************************************************** |
+ * |
+ * @property: |
+ * no-stem-darkening |
+ * |
+ * @description: |
+ * By default, the Adobe CFF engine darkens stems at smaller sizes, |
+ * regardless of hinting, to enhance contrast. This feature requires |
+ * a rendering system with proper gamma correction. Setting this |
+ * property, stem darkening gets switched off. |
+ * |
+ * Note that stem darkening is never applied if @FT_LOAD_NO_SCALE is set. |
+ * |
+ * { |
+ * FT_Library library; |
+ * FT_Bool no_stem_darkening = TRUE; |
+ * |
+ * |
+ * FT_Init_FreeType( &library ); |
+ * |
+ * FT_Property_Set( library, "cff", |
+ * "no-stem-darkening", &no_stem_darkening ); |
+ * } |
+ * |
+ * @note: |
+ * This property can be used with @FT_Property_Get also. |
+ * |
+ */ |
+ |
+ |
+ /************************************************************************** |
+ * |
+ * @property: |
+ * darkening-parameters |
+ * |
+ * @description: |
+ * By default, the Adobe CFF engine darkens stems as follows (if the |
+ * `no-stem-darkening' property isn't set): |
+ * |
+ * { |
+ * stem width <= 0.5px: darkening amount = 0.4px |
+ * stem width = 1px: darkening amount = 0.275px |
+ * stem width = 1.667px: darkening amount = 0.275px |
+ * stem width >= 2.333px: darkening amount = 0px |
+ * } |
+ * |
+ * and piecewise linear in-between. At configuration time, these four |
+ * control points can be set with the macro |
+ * `CFF_CONFIG_OPTION_DARKENING_PARAMETERS'. At runtime, the control |
+ * points can be changed using the `darkening-parameters' property, as |
+ * the following example demonstrates. |
+ * |
+ * { |
+ * FT_Library library; |
+ * FT_Int darken_params[8] = { 500, 300, // x1, y1 |
+ * 1000, 200, // x2, y2 |
+ * 1500, 100, // x3, y3 |
+ * 2000, 0 }; // x4, y4 |
+ * |
+ * |
+ * FT_Init_FreeType( &library ); |
+ * |
+ * FT_Property_Set( library, "cff", |
+ * "darkening-parameters", darken_params ); |
+ * } |
+ * |
+ * The x~values give the stem width, and the y~values the darkening |
+ * amount. The unit is 1000th of pixels. All coordinate values must be |
+ * positive; the x~values must be monotonically increasing; the |
+ * y~values must be monotonically decreasing and smaller than or |
+ * equal to 500 (corresponding to half a pixel); the slope of each |
+ * linear piece must be shallower than -1 (e.g., -.4). |
+ * |
+ * @note: |
+ * This property can be used with @FT_Property_Get also. |
+ * |
+ */ |
+ |
+ /* */ |
+ |
+ |
+FT_END_HEADER |
+ |
+ |
+#endif /* __FTCFFDRV_H__ */ |
+ |
+ |
+/* END */ |