sdk/docs/man/xhtml/eglMakeCurrent.html

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    <title>eglMakeCurrent</title>
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    <div class="refentry">
      <a id="eglMakeCurrent"></a>
      <div class="titlepage"></div>
      <div xmlns="" class="refnamediv">
        <h1>eglMakeCurrent</h1>
        <p>
            attach an EGL rendering context to EGL surfaces
        </p>
      </div>
      <div class="refsynopsisdiv">
        <h2>C Specification</h2>
        <div class="funcsynopsis">
          <table xmlns="" border="0" summary="Function synopsis" cellspacing="0" cellpadding="0">
            <tr valign="bottom">
              <td>
                <code xmlns="http://www.w3.org/1999/xhtml" class="funcdef">EGLBoolean <strong class="fsfunc">eglMakeCurrent</strong>(</code>
                <td>EGLDisplay  <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">display</var>, </td>
              </td>
            </tr>
            <tr valign="top">
              <td> </td>
              <td>EGLSurface  <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">draw</var>, </td>
            </tr>
            <tr valign="top">
              <td> </td>
              <td>EGLSurface  <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">read</var>, </td>
            </tr>
            <tr valign="top">
              <td> </td>
              <td>EGLContext  <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">context</var><code>)</code></td>
            </tr>
          </table>
        </div>
      </div>
      <div class="refsect1">
        <a id="parameters"></a>
        <h2>Parameters</h2>
        <div class="variablelist">
          <dl class="variablelist">
            <dt>
              <span class="term">
                <em class="parameter">
                  <code>display</code>
                </em>
              </span>
            </dt>
            <dd>
              <p>Specifies the <acronym class="acronym">EGL</acronym> display connection.</p>
            </dd>
            <dt>
              <span class="term">
                <em class="parameter">
                  <code>draw</code>
                </em>
              </span>
            </dt>
            <dd>
              <p>Specifies the <acronym class="acronym">EGL</acronym> draw surface.</p>
            </dd>
            <dt>
              <span class="term">
                <em class="parameter">
                  <code>read</code>
                </em>
              </span>
            </dt>
            <dd>
              <p>Specifies the <acronym class="acronym">EGL</acronym> read surface.</p>
            </dd>
            <dt>
              <span class="term">
                <em class="parameter">
                  <code>context</code>
                </em>
              </span>
            </dt>
            <dd>
              <p>Specifies the <acronym class="acronym">EGL</acronym> rendering context
                        to be attached to the surfaces.
                    </p>
            </dd>
          </dl>
        </div>
      </div>
      <div class="refsect1">
        <a id="description"></a>
        <h2>Description</h2>
        <p>
            <code class="function">eglMakeCurrent</code> binds <em class="parameter"><code>context</code></em>
            to the current rendering thread and to the <em class="parameter"><code>draw</code></em>
            and <em class="parameter"><code>read</code></em> surfaces. <em class="parameter"><code>draw</code></em>
            is used for all GL operations except for any pixel data read back
            (<a class="citerefentry" href="glReadPixels.html"><span class="citerefentry"><span class="refentrytitle">glReadPixels</span></span></a>,
            <a class="citerefentry" href="glCopyTexImage2D.html"><span class="citerefentry"><span class="refentrytitle">glCopyTexImage2D</span></span></a>, and
            <a class="citerefentry" href="glCopyTexSubImage2D.html"><span class="citerefentry"><span class="refentrytitle">glCopyTexSubImage2D</span></span></a>),
            which is taken from the frame buffer values of
            <em class="parameter"><code>read</code></em>.
        </p>
        <p>
            If the calling thread has already a current rendering context, that
            context is flushed and marked as no longer current.
        </p>
        <p>
            The first time that <em class="parameter"><code>context</code></em> is made current,
            the viewport and scissor dimensions are set to the size of the
            <em class="parameter"><code>draw</code></em> surface. The viewport and
            scissor are not modified when <em class="parameter"><code>context</code></em> is
            subsequently made current.
        </p>
        <p>
            To release the current context without assigning a new one, call
            <code class="function">eglMakeCurrent</code> with <em class="parameter"><code>draw</code></em>
            and <em class="parameter"><code>read</code></em> set to
            <code class="constant">EGL_NO_SURFACE</code> and <em class="parameter"><code>context</code></em>
            set to <code class="constant">EGL_NO_CONTEXT</code>.
        </p>
        <p>
            Use
            <a class="citerefentry" href="eglGetCurrentContext.html"><span class="citerefentry"><span class="refentrytitle">eglGetCurrentContext</span></span></a>,
            <a class="citerefentry" href="eglGetCurrentDisplay.html"><span class="citerefentry"><span class="refentrytitle">eglGetCurrentDisplay</span></span></a>, and
            <a class="citerefentry" href="eglGetCurrentSurface.html"><span class="citerefentry"><span class="refentrytitle">eglGetCurrentSurface</span></span></a>
            to query the current rendering context and associated display connection and surfaces.
        </p>
      </div>
      <div class="refsect1">
        <a id="errors"></a>
        <h2>Errors</h2>
        <p>
            <code class="constant">EGL_FALSE</code> is returned on failure,
            <code class="constant">EGL_TRUE</code> otherwise. If <code class="constant">EGL_FALSE</code>
            is returned, the previously current rendering context and
            surfaces (if any) remain unchanged.
        </p>
        <p>
            <code class="constant">EGL_BAD_DISPLAY</code> is generated if
            <em class="parameter"><code>display</code></em> is not an EGL display connection.
        </p>
        <p>
            <code class="constant">EGL_NOT_INITIALIZED</code> is generated if
            <em class="parameter"><code>display</code></em> has not been initialized.
        </p>
        <p>
            <code class="constant">EGL_BAD_SURFACE</code> is generated if
            <em class="parameter"><code>draw</code></em> or <em class="parameter"><code>read</code></em> is not an
            EGL surface.
        </p>
        <p>
            <code class="constant">EGL_BAD_CONTEXT</code> is generated if
            <em class="parameter"><code>context</code></em> is not an EGL rendering context.
        </p>
        <p>
            <code class="constant">EGL_BAD_MATCH</code> is generated if
            <em class="parameter"><code>draw</code></em> or
            <em class="parameter"><code>read</code></em>
            are not compatible with
            <em class="parameter"><code>context</code></em>, or if
            <em class="parameter"><code>context</code></em> is set to
            <code class="constant">EGL_NO_CONTEXT</code> and
            <em class="parameter"><code>draw</code></em> or
            <em class="parameter"><code>read</code></em>
            are not set to
            <code class="constant">EGL_NO_SURFACE</code>, or if
            <em class="parameter"><code>draw</code></em> or
            <em class="parameter"><code>read</code></em> are set to
            <code class="constant">EGL_NO_SURFACE</code> and
            <em class="parameter"><code>context</code></em> is not set to
            <code class="constant">EGL_NO_CONTEXT</code>.
        </p>
        <p>
            <code class="constant">EGL_BAD_ACCESS</code> is generated if
            <em class="parameter"><code>context</code></em>
            is current to some other thread.
        </p>
        <p>
            <code class="constant">EGL_BAD_NATIVE_PIXMAP</code> may be generated if
            a native pixmap underlying either
            <em class="parameter"><code>draw</code></em> or
            <em class="parameter"><code>read</code></em>
            is no longer valid.
        </p>
        <p>
            <code class="constant">EGL_BAD_NATIVE_WINDOW</code> may be generated if
            a native window underlying either
            <em class="parameter"><code>draw</code></em> or
            <em class="parameter"><code>read</code></em>
            is no longer valid.
        </p>
        <p>
            <code class="constant">EGL_BAD_CURRENT_SURFACE</code> is generated if
            the previous context has unflushed commands and the previous surface
            is no longer valid.
        </p>
        <p>
            <code class="constant">EGL_BAD_ALLOC</code> may be generated if
            allocation of ancillary buffers for <em class="parameter"><code>draw</code></em> or
            <em class="parameter"><code>read</code></em> were delayed until
            <code class="function">eglMakeCurrent</code> is called, and there are not
            enough resources to allocate them.
        </p>
        <p>
            <code class="constant">EGL_CONTEXT_LOST</code> is generated if a power management
            event has occurred. The application must destroy all contexts and
            reinitialise OpenGL ES state and objects to continue rendering.
        </p>
      </div>
      <div class="refsect1">
        <a id="seealso"></a>
        <h2>See Also</h2>
        <p>
            <a class="citerefentry" href="glReadPixels.html"><span class="citerefentry"><span class="refentrytitle">glReadPixels</span></span></a>,
            <a class="citerefentry" href="glCopyTexImage2D.html"><span class="citerefentry"><span class="refentrytitle">glCopyTexImage2D</span></span></a>,
            <a class="citerefentry" href="glCopyTexSubImage2D.html"><span class="citerefentry"><span class="refentrytitle">glCopyTexSubImage2D</span></span></a>,
            <a class="citerefentry" href="eglCreateContext.html"><span class="citerefentry"><span class="refentrytitle">eglCreateContext</span></span></a>,
            <a class="citerefentry" href="eglCreatePbufferSurface.html"><span class="citerefentry"><span class="refentrytitle">eglCreatePbufferSurface</span></span></a>,
            <a class="citerefentry" href="eglCreatePixmapSurface.html"><span class="citerefentry"><span class="refentrytitle">eglCreatePixmapSurface</span></span></a>,
            <a class="citerefentry" href="eglCreateWindowSurface.html"><span class="citerefentry"><span class="refentrytitle">eglCreateWindowSurface</span></span></a>,
            <a class="citerefentry" href="eglGetCurrentContext.html"><span class="citerefentry"><span class="refentrytitle">eglGetCurrentContext</span></span></a>,
            <a class="citerefentry" href="eglGetCurrentDisplay.html"><span class="citerefentry"><span class="refentrytitle">eglGetCurrentDisplay</span></span></a>,
            <a class="citerefentry" href="eglGetCurrentSurface.html"><span class="citerefentry"><span class="refentrytitle">eglGetCurrentSurface</span></span></a>,
            <a class="citerefentry" href="eglGetDisplay.html"><span class="citerefentry"><span class="refentrytitle">eglGetDisplay</span></span></a>,
            <a class="citerefentry" href="eglInitialize.html"><span class="citerefentry"><span class="refentrytitle">eglInitialize</span></span></a>
        </p>
      </div>
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