path: root/man/waffle_error.3.xml

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<refentry
    id="waffle_init"
    xmlns:xi="http://www.w3.org/2001/XInclude">

  <!-- See http://www.docbook.org/tdg/en/html/refentry.html. -->

  <refmeta>
    <refentrytitle>waffle_init</refentrytitle>
    <manvolnum>3</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>waffle_error</refname>
    <refname>waffle_error_get_info</refname>
    <refname>waffle_error_get_code</refname>
    <refname>waffle_error_to_string</refname>
    <refpurpose>Thread-local error state</refpurpose>
  </refnamediv>

  <refentryinfo>
    <title>Waffle Manual</title>
    <productname>waffle</productname>
    <xi:include href="common/author-chad.versace.xml"/>
    <xi:include href="common/copyright.xml"/>
    <xi:include href="common/legalnotice.xml"/>
  </refentryinfo>

  <refsynopsisdiv>

    <funcsynopsis language="C">

      <funcsynopsisinfo>
#include &lt;waffle.h&gt;

enum waffle_error {...};

struct waffle_error_info {
    int32_t code;
    const char *message;
    size_t message_length;
};
      </funcsynopsisinfo>

      <funcprototype>
        <funcdef>const struct waffle_error_info* <function>waffle_error_get_info</function></funcdef>
        <void/>
      </funcprototype>

      <funcprototype>
        <funcdef>int32_t <function>waffle_error_get_code</function></funcdef>
        <void/>
      </funcprototype>

      <funcprototype>
        <funcdef>const char* <function>waffle_error_to_string</function></funcdef>
        <paramdef>int32_t <parameter>e</parameter></paramdef>
      </funcprototype>

    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para>
      Waffle functions usually return either a <type>bool</type>, in which false indicates failure, or a pointer, in
      which null indicates failure. In addition to returning a flag indicating failure, most functions also clear and
      then set some thread-local error state.
    </para>
    <para>
      The only functions that do not alter waffle's error state are listed here and are explicitly documented as such.
      All functions listed here can be called before waffle has been successfully initialized with
      <citerefentry><refentrytitle>waffle_init</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    </para>

    <variablelist>

      <varlistentry>
        <term><type>struct waffle_error_info</type></term>
        <listitem>
          <para>
            This struct contains the user-visible portion of waffle's thread-local error state.
          </para>
          <para>
            <structfield>code</structfield> may be any token from <type>enum waffle_error</type>.
          </para>
          <para>
            <structfield>message</structfield> often contains a descriptive message about the error.
            It is never null, though it may be the empty string.
          </para>
          <para>
            <structfield>message_length</structfield> is the length of <structfield>message</structfield> according to
            <citerefentry><refentrytitle>strlen</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
          </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><function>waffle_error_to_string()</function></term>
        <listitem>
          <para>
            Convert a <type>waffle_error</type> token to a string.
            For example, convert <constant>WAFFLE_ERROR_UNKNOWN</constant> to <code>"WAFFLE_ERROR_UNKNOWN"</code>.
            Return null if the token is not a valid error token.
          </para>
          <para>
            This function always sets the error code to <constant>WAFFLE_ERROR_NONE</constant>.
          </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><function>waffle_error_get_info()</function></term>
        <listitem>
          <para>
            Get information about the current thread's error state.
          </para>
          <para>
            This function never returns null. The returned pointer becomes invalid when the thread-local error state
            changes.
          </para>
          <para>
            This function does not alter waffle's error state.
          </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><function>waffle_error_get_code()</function></term>
        <listitem>
          <para>
            Get the current thread's error code. Calling this function is equivalent to obtaining the error code with
            <code>waffle_error_get_info()->code</code>.
          </para>
          <para>
            This function does not alter waffle's error state.
          </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><type>enum waffle_error</type></term>
        <listitem>
          <para>
            For reference, below is the complete list of waffle's error codes.

            <variablelist>

              <varlistentry>
                <term><constant>WAFFLE_NO_ERROR</constant> = 0x00</term>
                <listitem>
                  <para>
                    The function succeeded.
                  </para>
                </listitem>
              </varlistentry>

              <varlistentry>
                <term><constant>WAFFLE_ERROR_FATAL</constant> = 0x01</term>
                <listitem>
                  <para>
                    Waffle encountered a fatal error.  All future waffle calls result in
                    undefined behavior.
                  </para>
                </listitem>
              </varlistentry>

              <varlistentry>
                <term><constant>WAFFLE_ERROR_UNKNOWN</constant> = 0x02</term>
                <listitem>
                  <para>
                    Waffle encountered an error for which it lacks an error code.  This is
                    usually produced when an underlying native call, such as
                    <citerefentry><refentrytitle>XOpenDisplay</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
                    fails for an unknown reason.
                  </para>
                </listitem>
              </varlistentry>

              <varlistentry>
                <term><constant>WAFFLE_ERROR_INTERNAL</constant> = 0x03</term>
                <listitem>
                  <para>
                    You found a bug in waffle.  Please report it.  The error message, obtained by
                    <function>waffle_error_get_info()</function>, should contain a description of the bug.
                  </para>
                </listitem>
              </varlistentry>

              <varlistentry>
                <term><constant>WAFFLE_ERROR_BAD_ALLOC</constant> = 0x04</term>
                <listitem>
                  <para>
                    Waffle failed to allocate memory.
                  </para>
                </listitem>
              </varlistentry>

              <varlistentry>
                <term><constant>WAFFLE_ERROR_NOT_INITIALIZED</constant> = 0x05</term>
                <listitem>
                  <para>
                    The failed function requires waffle to be initialized with
                    <citerefentry><refentrytitle>waffle_init</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
                  </para>
                </listitem>
              </varlistentry>

              <varlistentry>
                <term><constant>WAFFLE_ERROR_ALREADY_INITIALIZED</constant> = 0x06</term>
                <listitem>
                  <para>
                    If waffle has already been initialized by a successful call to
                    <citerefentry><refentrytitle>waffle_init</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
                    then subsequent calls to <function>waffle_init()</function> produce this error.
                  </para>
                </listitem>
              </varlistentry>

              <varlistentry>
                <term><constant>WAFFLE_ERROR_BAD_ATTRIBUTE</constant> = 0x08</term>
                <listitem>
                  <para>
                    An unrecognized attribute name or attribute value was passed in an
                    attribute list.
                  </para>
                </listitem>
              </varlistentry>

              <varlistentry>
                <term><constant>WAFFLE_ERROR_BAD_PARAMETER</constant> = 0x10</term>
                <listitem>
                  <para>
                    The failed function was passed an invalid argument.
                  </para>
                </listitem>
              </varlistentry>

              <varlistentry>
                <term><constant>WAFFLE_ERROR_BAD_DISPLAY_MATCH</constant> = 0x11</term>
                <listitem>
                  <para>
                    The waffle objects passed to the failed function belong to different
                    displays.
                  </para>
                </listitem>
              </varlistentry>

              <varlistentry>
                <term><constant>WAFFLE_ERROR_UNSUPPORTED_ON_PLATFORM</constant> = 0x12</term>
                <listitem>
                  <para>
                    The requested action is unsupported on the current system or platform, but is otherwise valid.
                  </para>
                  <para>
                    For example, attempting to choose a <type>waffle_config</type> whose API is OpenGL ES1 on a system
                    that doesn't OpenGL ES1 will produce this error.
                  </para>
                </listitem>
              </varlistentry>

              <varlistentry>
                <term><constant>WAFFLE_ERROR_BUILT_WITHOUT_SUPPORT</constant> = 0x13</term>
                <listitem>
                  <para>
                    Waffle was built without support for the requested action.
                  </para>
                  <para>
                    For example, if waffle was built without support for GBM, then calling <code>waffle_init()</code>
                    with attribute <code>WAFFLE_PLATFORM=WAFFLE_PLATFORM_GBM</code> will produce this error.
                </para>
                </listitem>
              </varlistentry>

            </variablelist>
          </para>
        </listitem>
      </varlistentry>

    </variablelist>

  </refsect1>

  <refsect1>
    <title>See Also</title>
    <para>
      <citerefentry><refentrytitle>waffle</refentrytitle><manvolnum>7</manvolnum></citerefentry>
    </para>
  </refsect1>

</refentry>

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