forked from minhngoc25a/freetype2
Minor fixes.
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Werner Lemberg
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docs/ft2faq.html
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docs/ft2faq.html
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@ -104,19 +104,19 @@
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<ul><p>
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<li>
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<a href="#other-color">How can I set the color of text rendered
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by FreeType ?</a>
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by FreeType?</a>
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</li>
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<li>
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<a href="#other-depth">Can I use FreeType to draw text on a pixmap
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with arbitrary depth ?</a>
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with arbitrary depth?</a>
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</li>
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<li>
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<a href="#other-size">I set the pixel size to 8x8, but the resulting
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glyphs are larger than that. Why ?</a>
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<a href="#other-size">I set the pixel size to 8x8, but the
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resulting glyphs are larger than that. Why?</a>
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</li>
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<li>
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<a href="#other-bbox">How can I compute the bounding box of a text
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string without loading its glyphs ?</a>
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string without loading its glyphs?</a>
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</li>
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<li>
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<a href="#other-antialias">Which anti-aliasing algorithm is
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@ -567,112 +567,111 @@
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<a name="other-depth">
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<h3>
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IV.1 Can I use FreeType to draw text on a pixmap with arbitratry depth ?
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IV.1 Can I use FreeType to draw text on a pixmap with arbitratry depth?
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</h3>
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<p>No directly, as FreeType is a font library, not a general purpose
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graphics library or text rendering service. However, note that the
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<p>Not directly, as FreeType is a font library, not a general purpose
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graphics library or text rendering service. However, note that the
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anti-aliased renderer allows you to convert a vectorial glyph outline
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into a list of "spans" (i.e. horizontal pixel segments with same coverage)
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that can be rendered through user-provided callbacks.</p>
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into a list of "spans" (i.e. horizontal pixel segments with same
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coverage) that can be rendered through user-provided callbacks.</p>
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<p>By providing the appropriate span callback, you can render anti-aliased
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text to any kind of surface. You can also use any color or fill
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pattern/image if you want to. This process is called
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<em>direct rendering</em>. For more information, please read the
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documentation contained in the following files:</p>
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<p>By providing the appropriate span callback, you can render
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anti-aliased text to any kind of surface. You can also use any color or
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fill pattern/image if you want to. This process is called <em>direct
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rendering</em>. For more information, please read the documentation
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contained in the following files:</p>
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<ul>
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<li><p>
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<b><tt><freetype/ftimage.h></tt></b> contains the definition
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of the <tt>FT_Raster_Params</tt> type used with direct rendering.
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</p></li>
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<li><p>
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<b><tt><freetype/ftoutln.h></tt></b> contains the definition
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of the <tt>FT_Outline_Render</tt> function that can be used to
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convert vectorial outlines to span lists.
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</p></li>
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</ul>
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<ul>
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<li>
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<p><tt><freetype/ftimage.h></tt> contains the definition of
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the <tt>FT_Raster_Params</tt> type used with direct rendering.</p>
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</li>
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<li>
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<p><tt><freetype/ftoutln.h></tt> contains the definition of
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the <tt>FT_Outline_Render()</tt> function that can be used to
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convert vectorial outlines to span lists.</p>
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</li>
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</ul>
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<p>Here's some code that uses them:</p>
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<font color="blue"><pre>
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<p>Here's some code that uses them:</p>
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<font color="blue"><pre>
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FT_Raster_Params params;
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FT_Outline outline;
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... load vectorial glyph in "outline" ...
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params.flags = ft_raster_flag_aa | ft_raster_flag_direct;
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params.gray_spans = (FT_Raster_Span_Func)your_own_span_function_here;
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params.user = your_own_data_pointer;
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error = FT_Outline_Render( library, &outline, &params );</pre>
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</font>
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FT_Raster_Params params;
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FT_Outline outline;
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.. load vectorial glyph in "outline"
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params.flags = ft_raster_flag_aa | ft_raster_flag_direct;
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params.gray_spans = (FT_Raster_Span_Func)your_own_span_function_here;
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params.user = your_own_data_pointer;
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error = FT_Outline_Render( library, &outline, &params );
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</pre></font>
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<p>Note that direct rendering is <em>not</em> available with monochrome
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output, as the current renderer uses a two-pass algorithm to generate
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glyphs with correct drop-out control.</p>
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<p>Note that direct rendering is <em>not</em> available with monochrome
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output, as the current renderer uses a two-pass algorithm to generate
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glyphs with correct drop-out control.</p>
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<hr>
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<a name="other-color">
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<h3>
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IV.2 How can I set the color of text rendered by FreeType ?
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IV.2 How can I set the color of text rendered by FreeType?
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</h3>
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<p>Basically, you can't do that, because FreeType is simply a font
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library. In general, you'll need to use your favorite graphics library
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to draw the FreeType glyphs with the appropriate color.</p>
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library. In general, you will need to use your favorite graphics
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library to draw the FreeType glyphs with the appropriate color.</p>
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<p>Note that for anti-aliased glyphs, you can "set the color" by using
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<em>direct rendering</em> as described in <a href="#other-depth">this
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answer</a></p>
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answer</a>.</p>
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<hr>
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<a name="other-size">
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<h3>
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IV.3 I set the pixel size to 8x8, but the resulting glyphs are larger
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(or smaller) than that. Why ??
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(or smaller) than that. Why?
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</h3>
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<p>A lot of people have a hard time understanding this topic, because
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they think of glyphs as fixed-width/height "cells", like those of
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fonts used in terminals/consoles. This assumption is simply not valid
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with most "modern" font formats, even bitmapped-based ones like
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PCF or BDF.</p>
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<p>A lot of people have difficulties to understand this topic, because
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they think of glyphs as fixed-width resp. fixed-height "cells", like
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those of fonts used in terminals/consoles. This assumption is simply
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not valid with most "modern" font formats, even bitmapped-based ones
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like <tt>PCF</tt> or <tt>BDF</tt>.</p>
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<p>Be aware that the <em>character size</em> that is set either through
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<tt>FT_Set_Char_Size</tt> or <tt>FT_Set_Pixel_Sizes</tt> isn't directly
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related to the dimension of the glyph bitmaps generated.</p>
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<tt>FT_Set_Char_Size()</tt> or <tt>FT_Set_Pixel_Sizes()</tt> isn't
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directly related to the dimension of the glyph bitmaps generated.</p>
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<p>Rather, the character size is indeed the size of
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<em>an abstract square</em>, called the <em>EM</em>, used by typographers
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to design fonts. Scaling two distinct fonts to the same character size, be
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it expressed in points or pixels, will generally result in bitmaps with
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<em>distinct dimensions</em> !</p>
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<p>Rather, the character size is indeed the size of <em>an abstract
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square</em>, called the <em>EM</em>, used by typographers to design
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fonts. Scaling two distinct fonts to the same character size, be it
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expressed in points or pixels, will generally result in bitmaps with
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<em>distinct dimensions</em>!</p>
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<p>Note that historically, the EM corresponded to the width of a capital
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"M" in Latin typefaces. However, later improvements in typography led to
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the designs that greatly detract from this rule. Today, it is not possible
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to connect the EM size to a specific font "feature" in a reliable way.</p>
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"M" in Latin typefaces. However, later improvements in typography led
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to designs that greatly detract from this rule. Today, it is not
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possible to connect the EM size to a specific font "feature" in a
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reliable way.</p>
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<hr>
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<a name="other-bbox">
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<h3>
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IV.4 How can I compute the bounding box of a given string of text without
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loading its glyphs before ?
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IV.4 How can I compute the bounding box of a given string of text
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without loading its glyphs before?
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</h3>
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<p>A lot of people want to be able to compute the size in pixels of a simple
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string of text with minimal overhead. For example, that can be useful to
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draw centered text within a button.</p>
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<p>A lot of people want to be able to compute the size in pixels of a
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simple string of text with minimal overhead. For example, that can be
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useful to draw centered text within a button. (to be continued...)</p>
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<hr>
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<a name="other-antialias">
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<h3>
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IV.1 Which anti-aliasing algorithm is used by FreeType 2?</h3>
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IV.5 Which anti-aliasing algorithm is used by FreeType 2?</h3>
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<p>The algorithm has been specifically designed for FreeType. It is
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based on ideas that were originally found in the implementation of the
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@ -699,7 +698,7 @@
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<hr>
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<a name="other-opentype">
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<h3>
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IV.2 When will FreeType 2 support OpenType?
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IV.6 When will FreeType 2 support OpenType?
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</h3>
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<p>Well, the engine already reads OpenType/CFF files perfectly. What it
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@ -707,7 +706,7 @@
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<p>FreeType 1 comes with a set of extensions that are used to load
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and manage OpenType Layout tables. It even has a demonstration program
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named "<tt>ftstrtto</tt>" to show its capabilities.</p>
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named <tt>ftstrtto</tt> to show its capabilities.</p>
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<p>For FreeType 2, we have decided that the layout operations
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provided through these tables are better placed in a specific
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