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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Hello, Harfbuzz: HarfBuzz Manual</title> <meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> <link rel="home" href="index.html" title="HarfBuzz Manual"> <link rel="up" href="pt01.html" title="Part I. User's manual"> <link rel="prev" href="building.html" title="Building"> <link rel="next" href="buffers-language-script-and-direction.html" title="Buffers, language, script and direction"> <meta name="generator" content="GTK-Doc V1.27.1 (XML mode)"> <link rel="stylesheet" href="style.css" type="text/css"> </head> <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> <table class="navigation" id="top" width="100%" summary="Navigation header" cellpadding="2" cellspacing="5"><tr valign="middle"> <td width="100%" align="left" class="shortcuts"></td> <td><a accesskey="h" href="index.html"><img src="home.png" width="16" height="16" border="0" alt="Home"></a></td> <td><a accesskey="u" href="pt01.html"><img src="up.png" width="16" height="16" border="0" alt="Up"></a></td> <td><a accesskey="p" href="building.html"><img src="left.png" width="16" height="16" border="0" alt="Prev"></a></td> <td><a accesskey="n" href="buffers-language-script-and-direction.html"><img src="right.png" width="16" height="16" border="0" alt="Next"></a></td> </tr></table> <div class="chapter"> <div class="titlepage"><div><div><h2 class="title"> <a name="hello-harfbuzz"></a>Hello, Harfbuzz</h2></div></div></div> <div class="toc"><dl class="toc"><dt><span class="section"><a href="hello-harfbuzz.html#what-harfbuzz-doesnt-do">What Harfbuzz doesn't do</a></span></dt></dl></div> <p> Here's the simplest Harfbuzz that can possibly work. We will improve it later. </p> <div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p> Create a buffer and put your text in it. </p></li></ol></div> <pre class="programlisting"> #include <hb.h> hb_buffer_t *buf; buf = hb_buffer_create(); hb_buffer_add_utf8(buf, text, strlen(text), 0, strlen(text)); </pre> <div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem" value="2"><p> Guess the script, language and direction of the buffer. </p></li></ol></div> <pre class="programlisting"> hb_buffer_guess_segment_properties(buf); </pre> <div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem" value="3"><p> Create a face and a font, using FreeType for now. </p></li></ol></div> <pre class="programlisting"> #include <hb-ft.h> FT_New_Face(ft_library, font_path, index, &face) hb_font_t *font = hb_ft_font_create(face); </pre> <div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem" value="4"><p> Shape! </p></li></ol></div> <pre class="programlisting"> hb_shape(font, buf, NULL, 0); </pre> <div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem" value="5"><p> Get the glyph and position information. </p></li></ol></div> <pre class="programlisting"> hb_glyph_info_t *glyph_info = hb_buffer_get_glyph_infos(buf, &glyph_count); hb_glyph_position_t *glyph_pos = hb_buffer_get_glyph_positions(buf, &glyph_count); </pre> <div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem" value="6"><p> Iterate over each glyph. </p></li></ol></div> <pre class="programlisting"> for (i = 0; i < glyph_count; ++i) { glyphid = glyph_info[i].codepoint; x_offset = glyph_pos[i].x_offset / 64.0; y_offset = glyph_pos[i].y_offset / 64.0; x_advance = glyph_pos[i].x_advance / 64.0; y_advance = glyph_pos[i].y_advance / 64.0; draw_glyph(glyphid, cursor_x + x_offset, cursor_y + y_offset); cursor_x += x_advance; cursor_y += y_advance; } </pre> <div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem" value="7"><p> Tidy up. </p></li></ol></div> <pre class="programlisting"> hb_buffer_destroy(buf); hb_font_destroy(hb_ft_font); </pre> <div class="section"> <div class="titlepage"><div><div><h2 class="title" style="clear: both"> <a name="what-harfbuzz-doesnt-do"></a>What Harfbuzz doesn't do</h2></div></div></div> <p> The code above will take a UTF8 string, shape it, and give you the information required to lay it out correctly on a single horizontal (or vertical) line using the font provided. That is the extent of Harfbuzz's responsibility. </p> <p> If you are implementing a text layout engine you may have other responsibilities, that Harfbuzz will not help you with: </p> <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> Harfbuzz won't help you with bidirectionality. If you want to lay out text with mixed Hebrew and English, you will need to ensure that the buffer provided to Harfbuzz has those characters in the correct layout order. This will be different from the logical order in which the Unicode text is stored. In other words, the user will hit the keys in the following sequence: </p> <pre class="programlisting"> A B C [space] ג ב א [space] D E F </pre> <p> but will expect to see in the output: </p> <pre class="programlisting"> ABC אבג DEF </pre> <p> This reordering is called <span class="emphasis"><em>bidi processing</em></span> ("bidi" is short for bidirectional), and there's an algorithm as an annex to the Unicode Standard which tells you how to reorder a string from logical order into presentation order. Before sending your string to Harfbuzz, you may need to apply the bidi algorithm to it. Libraries such as ICU and fribidi can do this for you. </p> </li> <li class="listitem"><p> Harfbuzz won't help you with text that contains different font properties. For instance, if you have the string "a <span class="emphasis"><em>huge</em></span> breakfast", and you expect "huge" to be italic, you will need to send three strings to Harfbuzz: <code class="literal">a</code>, in your Roman font; <code class="literal">huge</code> using your italic font; and <code class="literal">breakfast</code> using your Roman font again. Similarly if you change font, font size, script, language or direction within your string, you will need to shape each run independently and then output them independently. Harfbuzz expects to shape a run of characters sharing the same properties. </p></li> <li class="listitem"> <p> Harfbuzz won't help you with line breaking, hyphenation or justification. As mentioned above, it lays out the string along a <span class="emphasis"><em>single line</em></span> of, notionally, infinite length. If you want to find out where the potential word, sentence and line break points are in your text, you could use the ICU library's break iterator functions. </p> <p> Harfbuzz can tell you how wide a shaped piece of text is, which is useful input to a justification algorithm, but it knows nothing about paragraphs, lines or line lengths. Nor will it adjust the space between words to fit them proportionally into a line. If you want to layout text in paragraphs, you will probably want to send each word of your text to Harfbuzz to determine its shaped width after glyph substitutions, then work out how many words will fit on a line, and then finally output each word of the line separated by a space of the correct size to fully justify the paragraph. </p> </li> </ul></div> <p> As a layout engine implementor, Harfbuzz will help you with the interface between your text and your font, and that's something that you'll need - what you then do with the glyphs that your font returns is up to you. The example we saw above enough to get us started using Harfbuzz. Now we are going to use the remainder of Harfbuzz's API to refine that example and improve our text shaping capabilities. </p> </div> </div> <div class="footer"> <hr>Generated by GTK-Doc V1.27.1</div> </body> </html>