📄 bindings-surfaces.html
字号:
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"><title>Surfaces</title><meta name="generator" content="DocBook XSL Stylesheets V1.68.1"><link rel="start" href="index.html" title="Cairo: A Vector Graphics Library"><link rel="up" href="language-bindings.html" title="Appendix A. Creating a language binding for cairo"><link rel="prev" href="bindings-patterns.html" title="Patterns"><link rel="next" href="bindings-fonts.html" title="Fonts"><meta name="generator" content="GTK-Doc V1.6 (XML mode)"><link rel="stylesheet" href="style.css" type="text/css"><link rel="part" href="pt01.html" title="Part I. Tutorial"><link rel="part" href="pt02.html" title="Part II. Reference"><link rel="chapter" href="Drawing.html" title="Drawing"><link rel="chapter" href="Fonts.html" title="Fonts"><link rel="chapter" href="Surfaces.html" title="Surfaces"><link rel="chapter" href="Support.html" title="Utilities"><link rel="index" href="ix01.html" title="Index"><link rel="appendix" href="language-bindings.html" title="Appendix A. Creating a language binding for cairo"></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="2"><tr valign="middle"><td><a accesskey="p" href="bindings-patterns.html"><img src="left.png" width="24" height="24" border="0" alt="Prev"></a></td><td><a accesskey="u" href="language-bindings.html"><img src="up.png" width="24" height="24" border="0" alt="Up"></a></td><td><a accesskey="h" href="index.html"><img src="home.png" width="24" height="24" border="0" alt="Home"></a></td><th width="100%" align="center">Cairo: A Vector Graphics Library</th><td><a accesskey="n" href="bindings-fonts.html"><img src="right.png" width="24" height="24" border="0" alt="Next"></a></td></tr></table><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="bindings-surfaces"></a>Surfaces</h2></div></div></div><p> Like patterns, surfaces, which use only the <a href="cairo-cairo-surface-t.html#cairo-surface-t"><span class="type">cairo_surface_t</span></a> type in the C API should be broken up into a hierarchy of types in a language binding. </p><pre class="programlisting">cairo_surface_t cairo_image_surface_t cairo_atsui_surface_t cairo_win32_surface_t cairo_xlib_surface_t cairo_beos_surface_t </pre><p> Unlike patterns, the constructors and methods on these types are clearly named, and can be trivially associated with the appropriate subtype. Many language bindings will want to avoid binding the platform-specific subtypes at all, since the methods on these types are not useful without passing in native C types. Unless there is a language binding for Xlib available, there is no way to represent a XLib <span class="type">Display</span> * in that language. </p><p> This doesn't mean that platform-specific surface types can't be used in a language binding that doesn't bind the constructor. A very common situation is to use a cairo language binding in combination with a binding for a higher level system like the <a href="http://www.gtk.org/" target="_top">GTK+</a> widget toolkit. In such a situation, the higher level toolkit provides ways to get references to platform specific surfaces. </p><p> The <a href="cairo-cairo-surface-t.html#cairo-surface-set-user-data"><code class="function">cairo_surface_set_user_data()</code></a>, and <a href="cairo-cairo-surface-t.html#cairo-surface-get-user-data"><code class="function">cairo_surface_get_user_data()</code></a> methods are provided for use in language bindings, and should not be directly exposed to applications. One example of the use of these functions in a language binding is creating a binding for: </p><pre class="programlisting">cairo_surface_t *<a href="cairo-Image-Surfaces.html#cairo-image-surface-create-for-data"><code class="function">cairo_image_surface_create_for_data</code></a> (unsigned char *data, cairo_format_t format, int width, int height, int stride);</pre><p> The memory block passed in for <em class="parameter"><code>data</code></em> must be kept around until the surface is destroyed, so the language binding must have some way of determining when that happens. The way to do this is to use the <em class="parameter"><code>destroy</code></em> argument to <code class="function">cairo_surface_set_user_data()</code>. </p><p class="remark"><i><span class="remark"> Some languages may not have a suitable “pointer to a block of data” type to pass in for <em class="parameter"><code>data</code></em>. And even where a language does have such a type, the user will be frequently able to cause the backing store to be reallocated to a different location or truncated. Should we recommend a standard type name and binding for a buffer object here? </span></i></p></div></body></html>⌨️ 快捷键说明
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -