ft2-base_interface.html

嵌入式freetype库的应用文档包含freetype的简要说明和应用example

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<p>A macro that returns true whenever a face object contains a font whose format is based on the SFNT storage scheme. This usually means: TrueType fonts, OpenType fonts, as well as SFNT-based embedded bitmap fonts.</p>
<p>If this macro is true, all functions defined in <a href="ft2-header_file_macros.html#FT_SFNT_NAMES_H">FT_SFNT_NAMES_H</a> and <a href="ft2-header_file_macros.html#FT_TRUETYPE_TABLES_H">FT_TRUETYPE_TABLES_H</a> are available.</p>
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<h4><a name="FT_IS_FIXED_WIDTH">FT_IS_FIXED_WIDTH</a></h4>
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#define <b>FT_IS_FIXED_WIDTH</b>( face ) \
          ( face-&gt;face_flags &amp; <a href="ft2-base_interface.html#FT_FACE_FLAG_XXX">FT_FACE_FLAG_FIXED_WIDTH</a> )

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<p>A macro that returns true whenever a face object contains a font face that contains fixed-width (or "monospace", "fixed-pitch", etc.) glyphs.</p>
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<h4><a name="FT_HAS_FIXED_SIZES">FT_HAS_FIXED_SIZES</a></h4>
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#define <b>FT_HAS_FIXED_SIZES</b>( face ) \
          ( face-&gt;face_flags &amp; <a href="ft2-base_interface.html#FT_FACE_FLAG_XXX">FT_FACE_FLAG_FIXED_SIZES</a> )

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<p>A macro that returns true whenever a face object contains some embedded bitmaps. See the `available_sizes' field of the <a href="ft2-base_interface.html#FT_FaceRec">FT_FaceRec</a> structure.</p>
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<h4><a name="FT_HAS_FAST_GLYPHS">FT_HAS_FAST_GLYPHS</a></h4>
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#define <b>FT_HAS_FAST_GLYPHS</b>( face ) \
          ( face-&gt;face_flags &amp; <a href="ft2-base_interface.html#FT_FACE_FLAG_XXX">FT_FACE_FLAG_FAST_GLYPHS</a> )

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<p>Deprecated; indicates that the face contains so-called "fast" glyph bitmaps.</p>
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<h4><a name="FT_HAS_GLYPH_NAMES">FT_HAS_GLYPH_NAMES</a></h4>
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#define <b>FT_HAS_GLYPH_NAMES</b>( face ) \
          ( face-&gt;face_flags &amp; <a href="ft2-base_interface.html#FT_FACE_FLAG_XXX">FT_FACE_FLAG_GLYPH_NAMES</a> )

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<p>A macro that returns true whenever a face object contains some glyph names that can be accessed through <a href="ft2-base_interface.html#FT_Get_Glyph_Name">FT_Get_Glyph_Name</a>.</p>
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<h4><a name="FT_HAS_MULTIPLE_MASTERS">FT_HAS_MULTIPLE_MASTERS</a></h4>
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#define <b>FT_HAS_MULTIPLE_MASTERS</b>( face ) \
          ( face-&gt;face_flags &amp; <a href="ft2-base_interface.html#FT_FACE_FLAG_XXX">FT_FACE_FLAG_MULTIPLE_MASTERS</a> )

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<p>A macro that returns true whenever a face object contains some multiple masters. The functions provided by <a href="ft2-header_file_macros.html#FT_MULTIPLE_MASTERS_H">FT_MULTIPLE_MASTERS_H</a> are then available to choose the exact design you want.</p>
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<h4><a name="FT_STYLE_FLAG_XXX">FT_STYLE_FLAG_XXX</a></h4>
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#define <a href="ft2-base_interface.html#FT_STYLE_FLAG_XXX">FT_STYLE_FLAG_ITALIC</a>  ( 1 &lt;&lt; 0 )
#define <a href="ft2-base_interface.html#FT_STYLE_FLAG_XXX">FT_STYLE_FLAG_BOLD</a>    ( 1 &lt;&lt; 1 )

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<p>A list of bit-flags used to indicate the style of a given face. These are used in the `style_flags' field of <a href="ft2-base_interface.html#FT_FaceRec">FT_FaceRec</a>.</p>
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<tr valign=top><td><b>FT_STYLE_FLAG_ITALIC</b></td><td>
<p>Indicates that a given face is italicized.</p>
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<tr valign=top><td><b>FT_STYLE_FLAG_BOLD</b></td><td>
<p>Indicates that a given face is bold.</p>
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<h4><a name="FT_Size_Internal">FT_Size_Internal</a></h4>
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  <span class="keyword">typedef</span> <span class="keyword">struct</span> FT_Size_InternalRec_*  <b>FT_Size_Internal</b>;

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<p>An opaque handle to an FT_Size_InternalRec structure, used to model private data of a given FT_Size object.</p>
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<h4><a name="FT_Size_Metrics">FT_Size_Metrics</a></h4>
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  <span class="keyword">typedef</span> <span class="keyword">struct</span>  FT_Size_Metrics_
  {
    <a href="ft2-basic_types.html#FT_UShort">FT_UShort</a>  x_ppem;      /* horizontal pixels per EM               */
    <a href="ft2-basic_types.html#FT_UShort">FT_UShort</a>  y_ppem;      /* vertical pixels per EM                 */

    <a href="ft2-basic_types.html#FT_Fixed">FT_Fixed</a>   x_scale;     /* two scales used to convert font units  */
    <a href="ft2-basic_types.html#FT_Fixed">FT_Fixed</a>   y_scale;     /* to 26.6 frac. pixel coordinates        */

    <a href="ft2-basic_types.html#FT_Pos">FT_Pos</a>     ascender;    /* ascender in 26.6 frac. pixels          */
    <a href="ft2-basic_types.html#FT_Pos">FT_Pos</a>     descender;   /* descender in 26.6 frac. pixels         */
    <a href="ft2-basic_types.html#FT_Pos">FT_Pos</a>     height;      /* text height in 26.6 frac. pixels       */
    <a href="ft2-basic_types.html#FT_Pos">FT_Pos</a>     max_advance; /* max horizontal advance, in 26.6 pixels */

  } <b>FT_Size_Metrics</b>;

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<p>The size metrics structure returned scaled important distances for a given size object.</p>
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<tr valign=top><td><b>x_ppem</b></td><td>
<p>The character width, expressed in integer pixels. This is the width of the EM square expressed in pixels, hence the term `ppem' (pixels per EM).</p>
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<tr valign=top><td><b>y_ppem</b></td><td>
<p>The character height, expressed in integer pixels. This is the height of the EM square expressed in pixels, hence the term `ppem' (pixels per EM).</p>
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<tr valign=top><td><b>x_scale</b></td><td>
<p>A simple 16.16 fixed point format coefficient used to scale horizontal distances expressed in font units to fractional (26.6) pixel coordinates.</p>
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<tr valign=top><td><b>y_scale</b></td><td>
<p>A simple 16.16 fixed point format coefficient used to scale vertical distances expressed in font units to fractional (26.6) pixel coordinates.</p>
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<tr valign=top><td><b>ascender</b></td><td>
<p>The ascender, expressed in 26.6 fixed point pixels. Positive for ascenders above the baseline.</p>
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<tr valign=top><td><b>descender</b></td><td>
<p>The descender, expressed in 26.6 fixed point pixels. Negative for descenders below the baseline.</p>
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<tr valign=top><td><b>height</b></td><td>
<p>The text height, expressed in 26.6 fixed point pixels. Always positive.</p>
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<tr valign=top><td><b>max_advance</b></td><td>
<p>Maximum horizontal advance, expressed in 26.6 fixed point pixels. Always positive.</p>
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<p>For scalable fonts, the values of `ascender', `descender', and `height' are scaled versions of `face-&gt;ascender', `face-&gt;descender', and `face-&gt;height', respectively.</p>
<p>Unfortunately, due to glyph hinting, these values might not be exact for certain fonts. They thus must be treated as unreliable with an error margin of at least one pixel!</p>
<p>Indeed, the only way to get the exact pixel ascender and descender is to render <i>all</i> glyphs. As this would be a definite performance hit, it is up to client applications to perform such computations.</p>
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<h4><a name="FT_SizeRec">FT_SizeRec</a></h4>
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  <span class="keyword">typedef</span> <span class="keyword">struct</span>  FT_SizeRec_
  {
    <a href="ft2-base_interface.html#FT_Face">FT_Face</a>           face;      /* parent face object              */
    <a href="ft2-basic_types.html#FT_Generic">FT_Generic</a>        generic;   /* generic pointer for client uses */
    <a href="ft2-base_interface.html#FT_Size_Metrics">FT_Size_Metrics</a>   metrics;   /* size metrics                    */
    <a href="ft2-base_interface.html#FT_Size_Internal">FT_Size_Internal</a>  <span class="keyword">internal</span>;

  } <b>FT_SizeRec</b>;

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<p>FreeType root size class structure. A size object models the resolution and pointsize dependent data of a given face.</p>
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<tr valign=top><td><b>face</b></td><td>
<p>Handle to the parent face object.</p>
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<p>A typeless pointer, which is unused by the FreeType library or any of its drivers. It can be used by client applications to link their own data to each size object.</p>
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<tr valign=top><td><b>metrics</b></td><td>
<p>Metrics for this size object. This field is read-only.</p>
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<h4><a name="FT_SubGlyph">FT_SubGlyph</a></h4>
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  <span class="keyword">typedef</span> <span class="keyword">struct</span> FT_SubGlyphRec_*  <b>FT_SubGlyph</b>;

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<p>The subglyph structure is an internal objec