Ubuntu Manpage: waffle_config, waffle_config_choose, waffle_config_destroy, waffle_config_get_native

NAME

       waffle_config, waffle_config_choose, waffle_config_destroy, waffle_config_get_native - class
       waffle_config

SYNOPSIS

       #include <waffle.h>

       struct waffle_config;

       struct waffle_config* waffle_config_choose(struct waffle_display *display, const int32_t attrib_list[]);

       bool waffle_config_destroy(struct waffle_config *self);

       union waffle_native_config* waffle_config_get_native(struct waffle_config *self);

DESCRIPTION

       struct waffle_config
           An opaque type.

       waffle_config_choose()
           Choose a config on display that satifisfies the set of attributes specified by attrib_list. The
           config can later be used to create surfaces and contexts with waffle_window_create(3) and
           waffle_context_create(3).

           attrib_list consists of a zero-terminated sequence of name/value pairs. If an attribute is absent
           from attrib_list, then it assumes its default value. If attrib_list is null, then it is intrepreted
           the same as the empty list, which is the list that contains only the terminal zero. See the section
           called “ATTRIBUTES” below for details on the set of attributes that may appear in attrib_list.

       waffle_config_destroy()
           Destroy the config and release its memory.

       waffle_config_get_native()
           Get the config's underlying native objects. Use free(3) to deallocate the returned pointer. See
           waffle_native(3) for the definition of union waffle_native_config.

DISCUSSION

       The context attributes (WAFFLE_CONTEXT_*) have quirks that are specific to the native platform. Waffle
       attempts to accomdate those quirks in a platform-neutral way as much as possible, but not all quirks can
       be eliminated through a platform abstraction layer. The quirks are documented below in detail.

       For example, one quirk that Waffle is able to accommodate is that some platforms require specification of
       context attributes at different times. GLX requires that the context attributes be specified at time of
       context creation [glXCreateContextAttribsARB(3)] but MacOS requires the attributes to be specified when
       choosing a config [CGLChoosePixelFormat]. Therefore, Waffle is constrained by MacOS to require the
       attributes at time of waffle_config_choose().

       For additional documentation on the behavior of context attributes on each platform, refer to the
       following:

           For GLX, refer to the GLX 1.4 Specification[1] and the specifications for extensions
           GLX_ARB_create_context_profile[2] and GLX_EXT_create_context_es2_profile[3].

           For EGL, refer to the EGL 1.4 Specification[4] and the specifications for extension
           EGL_KHR_create_context[5].

           For CGL, refer to the documentation of kCGLPFAOpenGLProfile in the CGL Reference[6].

ATTRIBUTES

WAFFLE_CONTEXT_API
This is a required attribute; it has no default value. It must be one of:
WAFFLE_CONTEXT_OPENGL
WAFFLE_CONTEXT_OPENGL_ES1
WAFFLE_CONTEXT_OPENGL_ES2
WAFFLE_CONTEXT_OPENGL_ES3

The actual set of supported values depends on the native platform. To check if the system supports a
given API, use waffle_display_supports_context_api(3). Invariants and expectations for each platform
are discussed below.

On Android, WAFFLE_CONTEXT_OPENGL_ES1 is always supported. Beginning with Ice Cream Sandwich (that
is, Android 4.0), WAFFLE_CONTEXT_OPENGL_ES2 is also supported. Use
waffle_display_supports_context_api(3) to check if additional APIs are supported.

On GLX, WAFFLE_CONTEXT_OPENGL is always supported. The system may optionally support additional APIs.

On EGL platforms other than Android, no API is guaranteed to be supported. One must use
waffle_display_supports_context_api(3) to check for supported APIs.

On MacOS, only WAFFLE_CONTEXT_OPENGL is supported. This may change in the future if Apple adds
support for additional APIs.

WAFFLE_CONTEXT_MAJOR_VERSION
WAFFLE_CONTEXT_MINOR_VERSION
This pair of attributes is optional. They specify the context version that waffle_context_create(3)
will request.

The pair's default value and set of accepted values depend on the value of WAFFLE_CONTEXT_API and the
native platform. Below is described in detail the rules by which waffle filters the set of accepted
values according to the value of WAFFLE_CONTEXT_API. Even if waffle_config_choose() accepts the
requested version and successfully returns a config, the native platform may later reject the
requested version when waffle_context_create(3) is called.

If the requested API is WAFFLE_CONTEXT_OPENGL_ES1, then the default value is 1.0. The only accepted
values are 1.0 and 1.1.

If the requested API is WAFFLE_CONTEXT_OPENGL_ES2, then the default value is 2.0. Waffle accepts any
value that is at least 2.0 and strictly less than 3.0.

If the requested API is WAFFLE_CONTEXT_OPENGL_ES3, then the default value is 3.0. Waffle accepts any
value that is at least 3.0 and strictly less than 4.0.

If the requested API is WAFFLE_CONTEXT_OPENGL, then the default and minimum accepted value is 1.0.

WAFFLE_CONTEXT_PROFILE
This attributes is optional. It specifies the context profile that waffle_context_create(3) will
request.

The attribute's default value and set of accepted values depend on the values of WAFFLE_CONTEXT_API,
WAFFLE_CONTEXT_MAJOR_VERSION, WAFFLE_CONTEXT_MINOR_VERSION, and the native platform. Below is
described in detail the rules by which waffle decides the default value and the set of accepted
values. Even if waffle_config_choose() accepts the requested profile and successfully returns a
config, the native platform may later reject the requested profile when waffle_context_create(3) is
called.

If the requested API is WAFFLE_CONTEXT_OPENGL_ES1, WAFFLE_CONTEXT_OPENGL_ES2, or
WAFFLE_CONTEXT_OPENGL_ES3, then the default and only accepted value is WAFFLE_NONE.

If the requested API is WAFFLE_CONTEXT_OPENGL and the requested version is less than 3.2, then the
default and only accepted value is WAFFLE_NONE.

If the requested API is WAFFLE_CONTEXT_OPENGL and the requested version is at least 3.2, then default
value is WAFFLE_CONTEXT_CORE_PROFILE. The set of accepted values is WAFFLE_CONTEXT_CORE_PROFILE and
WAFFLE_CONTEXT_COMPATIBILITY_PROFILE.

WAFFLE_CONTEXT_FORWARD_COMPATIBLE
This attribute, if true, instructs waffle_context_create(3) to create a forward-compatible context.
However, even if waffle_config_choose() successfully returns a config for a forward-compatible
context, the native platform may later reject it when waffle_context_create(3) is called.

Forward-compatible contexts do not support functionality marked as deprecated by that version of the
API. A non-forward-compatible context supports all functionality in that version, deprecated or not.

This attribute is optional and its default value is false(0). Valid values are true(1), false(0), and
WAFFLE_DONT_CARE. However, true(1) is valid only if the requested context API is
WAFFLE_CONTEXT_OPENGL and its version is at least 3.0.

WAFFLE_CONTEXT_DEBUG
This attribute, if true, instructs waffle_context_create(3) to create a debug context. However, even
if waffle_config_choose() successfully returns a config for a debug context, the native platform may
later reject it when waffle_context_create(3) is called.

Debug contexts are intended for use during application development, to provide additional runtime
checking, validation, and logging functionality while possibly incurring performance penalties. The
additional functionality provided by debug contexts may vary according to the implementation. In some
cases a debug context may be identical to a non-debug context.

This attribute is optional and its default value is false(0). Valid values are true(1), false(0), and
WAFFLE_DONT_CARE.

WAFFLE_CONTEXT_ROBUST_ACCESS
This attribute, if true, instructs waffle_context_create(3) to create a robust access context.

Robust access contexts can implement additional runtime checks, such as bounds checks for various
operations.

This attribute is optional and its default value is false(0). Valid values are true(1), false(0), and
WAFFLE_DONT_CARE.

WAFFLE_RED_SIZE
WAFFLE_GREEN_SIZE
WAFFLE_BLUE_SIZE
WAFFLE_ALPHA_SIZE
WAFFLE_DEPTH_SIZE
WAFFLE_STENCIL_SIZE
The default value for each size attribute is 0. Valid values are the non-negative integers and
WAFFLE_DONT_CARE. If the requested size for a channel is 0, then any surface created with the config
will lack that channel. If the requested size for a channel is positive, then the number of bits in
that channel for any surface created with the config will be at least the requested size.

WAFFLE_SAMPLE_BUFFERS
WAFFLE_SAMPLES
The default value of WAFFLE_SAMPLE_BUFFERS is false(0). Valid values are true(1), false(0), and
WAFFLE_DONT_CARE. The attribute specifies if a surface created with this config is double-buffered.
If false, then any surface created with the config will not be multisampled. If true, the any surface
created with the config will be multisampled, where the number of samples will be at least
WAFFLE_SAMPLES.

The default value of WAFFLE_SAMPLES is 0. Valid values are the non-negative integers and
WAFFLE_DONT_CARE.

WAFFLE_DOUBLE_BUFFERED
The default value is true(1). Valid values are true(1), false(0), and WAFFLE_DONT_CARE. This
attribute specifies if a surface created with this config is double-buffered.

WAFFLE_ACCUM_BUFFER
The default value is false(0). Valid values are true(1), false(0), and WAFFLE_DONT_CARE. This
attribute specifies if a surface created with this config possesses an accumulation buffer.

RETURN VALUE

       Functions whose return type is bool return true on success and false on failure. Functions whose return
       type is a pointer return NULL on failure. Use waffle_error_get_info(3) to get information about any
       errors.

ERRORS

       See waffle_error(3) for the complete list of waffle's error codes.

       Listed below are the errors specific to the waffle_config functions.

       waffle_config_choose()

           WAFFLE_ERROR_BAD_ATTRIBUTE
               An item in attrib_list is unrecognized or has an invalid value, or a required attribute is
               missing.

           WAFFLE_ERROR_UNSUPPORTED_ON_PLATFORM
               If the native platform does not expose the necessary functionality to create a context with the
               properties specified by config or if waffle can predetermine that the native platform will reject
               the config at context creation, but otherwise the requested attributes are valid, then
               WAFFLE_ERROR_UNSUPPORTED_ON_PLATFORM is emitted.

               For example,

               •   GLX supports creation of an OpenGL ES2 context only if libGLESv2.so.2 is installed and if
                   GLX_EXT_create_context_es2_profile is exposed as both a server and client extension.

               •   MacOS does not support the OpenGL 3.2 Compatibility Profile, and it supports the OpenGL 3.2
                   Core Profile only for MacOS >= 10.7 on select GPU's.

EXAMPLES

   Example 1
       Choose a config for an OpenGL legacy context that has at least 8 bits in each of the RGBA channels.

           #include <stdlib.h>
           #include <waffle.h>

           static const int32_t init_attrib_list[] = {
               WAFFLE_PLATFORM, WAFFLE_PLATFORM_GLX,
               0,
           };

           static const int32_t config_attrib_list[] = {
               WAFFLE_CONTEXT_API, WAFFLE_CONTEXT_OPENGL,

               WAFFLE_RED_SIZE,    8,
               WAFFLE_GREEN_SIZE,  8,
               WAFFLE_BLUE_SIZE,   8,
               WAFFLE_ALPHA_SIZE,  8,

               0,
           };

           int
           main()
           {
               struct waffle_display *display;
               struct waffle_config *config;
               bool ok;

               ok = waffle_init(init_attrib_list);
               if (!ok)
                 exit(EXIT_FAILURE);

               display = waffle_display_connect(NULL);
               if (!display)
                 exit(EXIT_FAILURE);

               config = waffle_config_choose(config_attrib_list);
               if (!config)
                 exit(EXIT_FAILURE);

               // Now clean up.
               waffle_config_destroy(config);
               waffle_display_disconnect(display);
               return EXIT_SUCCESS;
           }

   Example 2
       An attribute list for creating an OpenGL 3.2 Core Profile context that has depth and stencil buffers and
       some non-zero number of bits in each of the RGB channels. Since the default value of WAFFLE_ALPHA_SIZE is
       WAFFLE_DONT_CARE, the config may not have an alpha channel.

           const int32_t attrib_list[] = {
               WAFFLE_CONTEXT_API,             WAFFLE_CONTEXT_OPENGL,
               WAFFLE_CONTEXT_MAJOR_VERSION,   3,
               WAFFLE_CONTEXT_MINOR_VERSION,   2,
               WAFFLE_CONTEXT_PROFILE,         WAFFLE_CONTEXT_CORE_PROFILE,

               WAFFLE_RED_SIZE,                1,
               WAFFLE_GREEN_SIZE,              1,
               WAFFLE_BLUE_SIZE,               1,

               WAFFLE_DEPTH_SIZE,             24,
               WAFFLE_STENCIL_SIZE,            8,

               0,
           };

ISSUES

       Please report bugs or and feature requests to https://gitlab.freedesktop.org/mesa/waffle/issues.

AUTHOR

       Chad Versace <chad.versace@linux.intel.com>
           Former maintainer

COPYRIGHT

       Copyright © 2013 Intel

       This manual page is licensed under the Creative Commons Attribution-ShareAlike 3.0 United States License
       (CC BY-SA 3.0). To view a copy of this license, visit http://creativecommons.org.license/by-sa/3.0/us.

NOTES

        1. GLX 1.4 Specification
           http://www.opengl.org/registry/doc/glx1.4.pdf

        2. GLX_ARB_create_context_profile
           http://www.opengl.org/registry/specs/ARB/glx_create_context.txt

        3. GLX_EXT_create_context_es2_profile
           http://www.opengl.org/registry/specs/EXT/glx_create_context_es2_profile.txt

        4. EGL 1.4 Specification
           http://www.khronos.org/registry/egl/specs/eglspec.1.4.20110406.pdf

        5. EGL_KHR_create_context
           http://www.khronos.org/registry/egl/extensions/KHR/EGL_KHR_create_context.txt

        6. CGL Reference
           https://developer.apple.com/library/mac/#documentation/graphicsimaging/reference/CGL_OpenGL/Reference/reference.html

waffle                                             08/09/2024                                   WAFFLE_CONFIG(3)