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| <title xmlns:xlink="http://www.w3.org/1999/xlink">eglIntro - EGL Reference Pages</title> |
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| <div class="refentry" id="eglIntro"> |
| <div class="titlepage"/> |
| <div class="refnamediv"> |
| <h2>Name</h2> |
| <p>eglIntro — |
| introduction to managing client API rendering through the |
| <abbr class="acronym">EGL</abbr> API. |
| </p> |
| </div> |
| <div class="refsect1" id="overview"> |
| <h2>Overview</h2> |
| <p> |
| The <em class="firstterm">Khronos Native Platform Graphics |
| Interface</em> (EGL) provides a means for rendering |
| using a <em class="firstterm">client API</em> such as OpenGL ES |
| (a 3D renderer for embedded systems), OpenGL (a functional |
| superset of OpenGL ES for desktop systems), and OpenVG (a 2D |
| vector graphics renderer) together with a |
| <em class="firstterm">platform</em>, such as Microsoft Windows or |
| the X Window System. |
| </p> |
| <p> |
| Depending on its implementation EGL might be more or less |
| tightly integrated into the platform. Most EGL |
| functions require an EGL display connection, which can be |
| obtained by calling |
| <a class="citerefentry" href="eglGetPlatformDisplay.xhtml"><span class="citerefentry"><span class="refentrytitle">eglGetPlatformDisplay</span></span></a> |
| or |
| <a class="citerefentry" href="eglGetDisplay.xhtml"><span class="citerefentry"><span class="refentrytitle">eglGetDisplay</span></span></a>. |
| To initialize and |
| query what EGL version is supported on the display |
| connection, call |
| <a class="citerefentry" href="eglInitialize.xhtml"><span class="citerefentry"><span class="refentrytitle">eglInitialize</span></span></a>. |
| </p> |
| <p> |
| The EGL specification does not define the set of platforms that |
| may be supported by an EGL implementation, nor does it specify |
| behavior specific to any platform. The set of supported |
| platforms and their behavior is defined by platform-specific |
| extensions. To detect if a particular platform is supported, |
| clients should query the <code class="constant">EGL_EXTENSIONS</code> |
| string of <code class="constant">EGL_NO_DISPLAY</code> using |
| <a class="citerefentry" href="eglQueryString.xhtml"><span class="citerefentry"><span class="refentrytitle">eglQueryString</span></span></a>. |
| </p> |
| <p> |
| Platforms supporting EGL make a subset of their |
| visuals (which may also referred to as pixel formats, frame |
| buffer configurations, or other similar terms) available for |
| client API rendering. Windows and pixmaps created with these |
| visuals may also be rendered into using the platform APIs. |
| </p> |
| <p> |
| An EGL <em class="firstterm">surface</em> extends a native |
| window or pixmap with additional <em class="firstterm">auxillary |
| buffers</em>. These buffers include a color buffer, a |
| depth buffer, a stencil buffer, and an alpha mask buffer. |
| Some or all of the buffers listed are included in each EGL |
| frame buffer configuration. |
| </p> |
| <p> |
| EGL supports rendering into three types of surfaces: |
| windows, pixmaps and pixel buffers (pbuffers). EGL window |
| and pixmap surfaces are associated with corresponding |
| resources of the platform. EGL pixel buffers are |
| EGL-only resources, and do not accept rendering through the |
| platform APIs. |
| </p> |
| <p> |
| To render using a client API into an EGL surface, you must |
| determine the appropriate EGL frame buffer configuration, |
| which supports the rendering features the application |
| requires. |
| <a class="citerefentry" href="eglChooseConfig.xhtml"><span class="citerefentry"><span class="refentrytitle">eglChooseConfig</span></span></a> |
| returns an <span class="type">EGLConfig</span> matching the required |
| attributes, if any. A complete list of EGL frame buffer |
| configurations can be obtained by calling |
| <a class="citerefentry" href="eglGetConfigs.xhtml"><span class="citerefentry"><span class="refentrytitle">eglGetConfigs</span></span></a>. |
| Attributes of a particular EGL frame buffer configuration |
| can be queried by calling |
| <a class="citerefentry" href="eglGetConfigAttrib.xhtml"><span class="citerefentry"><span class="refentrytitle">eglGetConfigAttrib</span></span></a>. |
| </p> |
| <p> |
| For EGL window and pixmap surfaces, a suitable native window |
| or pixmap with a matching native visual must be created |
| first. For a given EGL frame buffer configuration, the |
| native visual type and ID can be retrieved with a call to |
| <a class="citerefentry" href="eglGetConfigAttrib.xhtml"><span class="citerefentry"><span class="refentrytitle">eglGetConfigAttrib</span></span></a>. |
| For pixel buffers, no underlying native resource is |
| required. |
| </p> |
| <p> |
| To create an EGL window surface from a native window, call |
| <a class="citerefentry" href="eglCreateWindowSurface.xhtml"><span class="citerefentry"><span class="refentrytitle">eglCreateWindowSurface</span></span></a>. |
| To create an EGL pixmap surface from a native pixmap, call |
| <a class="citerefentry" href="eglCreatePixmapSurface.xhtml"><span class="citerefentry"><span class="refentrytitle">eglCreatePixmapSurface</span></span></a>. |
| To create a pixel buffer (pbuffer) surface (which has no |
| associated native buffer), call |
| <a class="citerefentry" href="eglCreatePbufferSurface.xhtml"><span class="citerefentry"><span class="refentrytitle">eglCreatePbufferSurface</span></span></a> |
| To create a pixel buffer (pbuffer) surface whose color |
| buffer is provided by an OpenVG <span class="type">VGImage</span>, call |
| <a class="citerefentry" href="eglCreatePbufferFromClientBuffer.xhtml"><span class="citerefentry"><span class="refentrytitle">eglCreatePbufferFromClientBuffer</span></span></a>. |
| Use |
| <a class="citerefentry" href="eglDestroySurface.xhtml"><span class="citerefentry"><span class="refentrytitle">eglDestroySurface</span></span></a> |
| to release previously allocated resources. |
| </p> |
| <p> |
| An EGL rendering context is required to bind client API |
| rendering to an EGL surface. An EGL surface and an EGL |
| rendering context must have compatible EGL frame buffer |
| configurations. To create an EGL rendering context, call |
| <a class="citerefentry" href="eglCreateContext.xhtml"><span class="citerefentry"><span class="refentrytitle">eglCreateContext</span></span></a>. |
| The type of client API context created (OpenGL ES, OpenVG, |
| etc.) can be changed by first calling |
| <a class="citerefentry" href="eglBindAPI.xhtml"><span class="citerefentry"><span class="refentrytitle">eglBindAPI</span></span></a>. |
| </p> |
| <p> |
| An EGL rendering context may be bound to one or two EGL |
| surfaces by calling |
| <a class="citerefentry" href="eglMakeCurrent.xhtml"><span class="citerefentry"><span class="refentrytitle">eglMakeCurrent</span></span></a>. |
| This context/surface(s) association specifies the |
| <em class="firstterm">current context</em> and |
| <em class="firstterm">current surface</em>, and is used by all |
| client API rendering commands for the bound context until |
| <a class="citerefentry" href="eglMakeCurrent.xhtml"><span class="citerefentry"><span class="refentrytitle">eglMakeCurrent</span></span></a> |
| is called with different arguments. |
| </p> |
| <p> |
| Both platform and client API commands may be used to operate |
| on certain surfaces. However, the two command streams are |
| not synchronized. Synchronization can be explicitly |
| specified using by calling |
| <a class="citerefentry" href="eglWaitClient.xhtml"><span class="citerefentry"><span class="refentrytitle">eglWaitClient</span></span></a>, |
| <a class="citerefentry" href="eglWaitNative.xhtml"><span class="citerefentry"><span class="refentrytitle">eglWaitNative</span></span></a>, |
| and possibly by calling other platform APIs. |
| </p> |
| </div> |
| <div class="refsect1" id="examples"> |
| <h2>Examples</h2> |
| <p> |
| Below is a minimal example of creating an RGBA-format window that |
| allows rendering with OpenGL ES. |
| The window is cleared to yellow when the program runs. For simplicity, |
| the program does not check for any errors. |
| </p> |
| <pre class="programlisting"> |
| #include <stdlib.h> |
| #include <unistd.h> |
| #include <GLES/egl.h> |
| #include <GLES/gl.h> |
| typedef ... NativeWindowType; |
| extern NativeWindowType createNativeWindow(void); |
| static EGLint const attribute_list[] = { |
| EGL_RED_SIZE, 1, |
| EGL_GREEN_SIZE, 1, |
| EGL_BLUE_SIZE, 1, |
| EGL_NONE |
| }; |
| int main(int argc, char ** argv) |
| { |
| EGLDisplay display; |
| EGLConfig config; |
| EGLContext context; |
| EGLSurface surface; |
| NativeWindowType native_window; |
| EGLint num_config; |
| /* get an EGL display connection */ |
| display = eglGetDisplay(EGL_DEFAULT_DISPLAY); |
| /* initialize the EGL display connection */ |
| eglInitialize(display, NULL, NULL); |
| /* get an appropriate EGL frame buffer configuration */ |
| eglChooseConfig(display, attribute_list, &config, 1, &num_config); |
| /* create an EGL rendering context */ |
| context = eglCreateContext(display, config, EGL_NO_CONTEXT, NULL); |
| /* create a native window */ |
| native_window = createNativeWindow(); |
| /* create an EGL window surface */ |
| surface = eglCreateWindowSurface(display, config, native_window, NULL); |
| /* connect the context to the surface */ |
| eglMakeCurrent(display, surface, surface, context); |
| /* clear the color buffer */ |
| glClearColor(1.0, 1.0, 0.0, 1.0); |
| glClear(GL_COLOR_BUFFER_BIT); |
| glFlush(); |
| eglSwapBuffers(display, surface); |
| sleep(10); |
| return EXIT_SUCCESS; |
| } |
| </pre> |
| </div> |
| <div class="refsect1" id="notes"> |
| <h2>Notes</h2> |
| <p> |
| Prior to EGL 1.5, platforms were referred to as the |
| <em class="firstterm">native window system</em>, and |
| platform-specific queries and APIs were not available. Only a |
| single native window system was supported. |
| </p> |
| </div> |
| <div class="refsect1" id="usingeglextensions"> |
| <h2>Using EGL Extensions</h2> |
| <p> |
| All supported EGL extensions will have a corresponding definition in |
| <code class="filename">egl.h</code> and a token in the extension strings returned |
| by |
| <a class="citerefentry" href="eglQueryString.xhtml"><span class="citerefentry"><span class="refentrytitle">eglQueryString</span></span></a>. |
| </p> |
| </div> |
| <div class="refsect1" id="futureeglversions"> |
| <h2>Future EGL Versions</h2> |
| <p> |
| <a class="citerefentry" href="eglInitialize.xhtml"><span class="citerefentry"><span class="refentrytitle">eglInitialize</span></span></a> |
| and |
| <a class="citerefentry" href="eglQueryString.xhtml"><span class="citerefentry"><span class="refentrytitle">eglQueryString</span></span></a> |
| can be used to determine at run-time what version of EGL is available. |
| To check the EGL version at compile-time, test whether |
| <code class="constant">EGL_VERSION_<em class="replaceable"><code>x</code></em>_<em class="replaceable"><code>y</code></em></code> |
| is defined, where <em class="replaceable"><code>x</code></em> and |
| <em class="replaceable"><code>y</code></em> are the major and minor version |
| numbers. |
| </p> |
| </div> |
| <div class="refsect1" id="files"> |
| <h2>Files</h2> |
| <div class="variablelist"> |
| <dl class="variablelist"> |
| <dt> |
| <span class="term"> |
| <code class="filename">GLES/egl.h</code> |
| </span> |
| </dt> |
| <dd> |
| <p> |
| EGL header file |
| </p> |
| </dd> |
| </dl> |
| </div> |
| </div> |
| <div class="refsect1" id="seealso"> |
| <h2>See Also</h2> |
| <p> |
| |
| <a class="citerefentry" href="eglBindAPI.xhtml"><span class="citerefentry"><span class="refentrytitle">eglBindAPI</span></span></a>, |
| <a class="citerefentry" href="eglChooseConfig.xhtml"><span class="citerefentry"><span class="refentrytitle">eglChooseConfig</span></span></a>, |
| <a class="citerefentry" href="eglCreateContext.xhtml"><span class="citerefentry"><span class="refentrytitle">eglCreateContext</span></span></a>, |
| <a class="citerefentry" href="eglCreatePbufferFromClientBuffer.xhtml"><span class="citerefentry"><span class="refentrytitle">eglCreatePbufferFromClientBuffer</span></span></a>, |
| <a class="citerefentry" href="eglCreatePbufferSurface.xhtml"><span class="citerefentry"><span class="refentrytitle">eglCreatePbufferSurface</span></span></a>, |
| <a class="citerefentry" href="eglCreatePixmapSurface.xhtml"><span class="citerefentry"><span class="refentrytitle">eglCreatePixmapSurface</span></span></a>, |
| <a class="citerefentry" href="eglCreateWindowSurface.xhtml"><span class="citerefentry"><span class="refentrytitle">eglCreateWindowSurface</span></span></a>, |
| <a class="citerefentry" href="eglDestroyContext.xhtml"><span class="citerefentry"><span class="refentrytitle">eglDestroyContext</span></span></a>, |
| <a class="citerefentry" href="eglDestroySurface.xhtml"><span class="citerefentry"><span class="refentrytitle">eglDestroySurface</span></span></a>, |
| <a class="citerefentry" href="eglGetConfigs.xhtml"><span class="citerefentry"><span class="refentrytitle">eglGetConfigs</span></span></a>, |
| <a class="citerefentry" href="eglGetDisplay.xhtml"><span class="citerefentry"><span class="refentrytitle">eglGetDisplay</span></span></a>, |
| <a class="citerefentry" href="eglGetPlatformDisplay.xhtml"><span class="citerefentry"><span class="refentrytitle">eglGetPlatformDisplay</span></span></a>, |
| <a class="citerefentry" href="eglInitialize.xhtml"><span class="citerefentry"><span class="refentrytitle">eglInitialize</span></span></a>, |
| <a class="citerefentry" href="eglMakeCurrent.xhtml"><span class="citerefentry"><span class="refentrytitle">eglMakeCurrent</span></span></a>, |
| <a class="citerefentry" href="eglQueryString.xhtml"><span class="citerefentry"><span class="refentrytitle">eglQueryString</span></span></a>, |
| <a class="citerefentry" href="eglSwapBuffers.xhtml"><span class="citerefentry"><span class="refentrytitle">eglSwapBuffers</span></span></a>, |
| <a class="citerefentry" href="eglTerminate.xhtml"><span class="citerefentry"><span class="refentrytitle">eglTerminate</span></span></a>, |
| <a class="citerefentry" href="eglWaitGL.xhtml"><span class="citerefentry"><span class="refentrytitle">eglWaitGL</span></span></a>, |
| <a class="citerefentry" href="eglWaitNative.xhtml"><span class="citerefentry"><span class="refentrytitle">eglWaitNative</span></span></a> |
| </p> |
| </div> |
| <p> |
| </p> |
| <div class="refsect3" id="copyright"> |
| <img src="KhronosLogo.jpg"/> |
| <p> |
| Copyright © 2003-2014 The Khronos Group Inc. |
| Permission is hereby granted, free of charge, to any person obtaining a |
| copy of this software and/or associated documentation files (the |
| "Materials"), to deal in the Materials without restriction, including |
| without limitation the rights to use, copy, modify, merge, publish, |
| distribute, sublicense, and/or sell copies of the Materials, and to |
| permit persons to whom the Materials are furnished to do so, subject to |
| the condition that this copyright notice and permission notice shall be included |
| in all copies or substantial portions of the Materials. |
| </p> |
| </div> |
| <p> |
| </p> |
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