blob: 14603b6b98e38088a1c8e1bb54442ea6eec61f6c [file] [log] [blame]
Name Strings
Brian Nguyen, NVIDIA, brnguyen at
James Jones, NVIDIA, jajones at
Ian Romanick, Intel, idr at
Jesse Barnes, Intel, jbarnes at
Aaron Plattner, NVIDIA, aplattner at
Brian Nguyen, NVIDIA, brnguyen at
Version 8 (November 8, 2011)
This specification is written against the GLX 1.3 specification, but
only GLX 1.1 or greater with the ARB_get_proc_address extension is
required, for glXQueryExtensionString and glXGetProcAddressARB
This specification affects the GLX_SGI_swap_control extension.
Based on GLX_MESA_swap_control version 1.1, GLX_SGI_swap_control
version 1.9, and WGL_EXT_swap_control version 1.5.
This extension allows an application to specify a minimum
periodicity of color buffer swaps, measured in video frame periods,
for a particular drawable. It also allows an application to query
the swap interval and the implementation-dependent maximum swap
interval of a drawable.
IP Status
There are no known IP issues.
1. Should implementations that export GLX_EXT_swap_control also
export GL_EXT_swap_control?
RESOLVED: No. GL_EXT_swap_control is exported by WGL_EXT_swap_control
because of shortcomings in the WGL extension querying mechanisms. GLX
has no such shortcomings, so exporting only a GLX extension is
2. How should the swap interval interact with non-visible drawables?
RESOLVED: The definition of the swap interval does not make sense
when applied to drawables that are not visible on a display device,
so it makes no sense to modify or query the swap interval of such
drawables. BadWindow should be returned if the <drawable> argument
of glXSwapIntervalEXT is not a window, and the result of querying
the swap interval of a non-window drawable should be undefined.
3. How should the implementations maximum swap interval and current
swap interval be exposed?
RESOVLED: These are both properties of a GLX drawable, so they are
exposed through glXQueryDrawable.
New Procedures and Functions
void glXSwapIntervalEXT(Display *dpy,
GLXDrawable drawable,
int interval);
New Tokens
Additions to Chapter 2 of the OpenGL 1.2.1 Specification (OpenGL
Additions to Chapter 3 of the OpenGL 1.2.1 Specification (Rasterization)
Additions to Chapter 4 of the OpenGL 1.2.1 Specification (Per-Fragment
Operations and the Frame Buffer)
Additions to Chapter 5 of the OpenGL 1.2.1 Specification (Special
Additions to Chapter 6 of the OpenGL 1.2.1 Specification (State and
State Requests)
Additions to the GLX 1.3 Specification
[Add the following to Section 3.3.10 of the GLX specification
(Double Buffering)]
glXSwapIntervalEXT specifies the minimum number of video frame
periods per buffer swap for a particular GLX drawable (e.g. a value
of two means that the color buffers will be swapped at most every
other video frame). The interval takes effect when glXSwapBuffers
is first called on the drawable subsequent to the glXSwapIntervalEXT
A video frame period is the time required by the monitor to display
a full frame of video data. In the case of an interlaced monitor,
this is typically the time required to display both the even and odd
fields of a frame of video data.
If <interval> is set to a value of 0, buffer swaps are not
synchronized to a video frame. The <interval> value is silently
clamped to the maximum implementation-dependent value supported
before being stored.
The current swap interval and implementation-dependent max swap
interval for a particular drawable can be obtained by calling
glXQueryDrawable with the attributes GLX_SWAP_INTERVAL_EXT and
GLX_MAX_SWAP_INTERVAL_EXT respectively. The value returned by
glXQueryDrawable is undefined if the drawable is not a GLXWindow
and these attributes are given.
Calling glXSwapIntervalSGI is equivalent to calling
glXSwapIntervalEXT on the current drawable, if one exists.
GLX Protocol
One new GLX protocol command is added.
1 CARD8 opcode (X assigned)
1 16 GLX opcode (glXVendorPrivate)
2 5 request length
4 1416 vendor-specific opcode
4 CARD32 unused
4 GLX_DRAWABLE drawable
4 INT32 interval
glXSwapIntervalEXT generates BadValue if parameter <interval> is
less than zero.
glXSwapIntervalEXT generates BadWindow if parameter <drawable> is
not a GLXWindow or Window XID.
Usage Examples
Example 1: Set swap interval for the current drawable
Display *dpy = glXGetCurrentDisplay();
GLXDrawable drawable = glXGetCurrentDrawable();
const int interval = 1;
if (drawable) {
glXSwapIntervalEXT(dpy, drawable, interval);
Example 2: Query current drawable for swap interval and max swap
Display *dpy = glXGetCurrentDisplay();
GLXDrawable drawable = glXGetCurrentDrawable();
unsigned int swap, maxSwap;
if (drawable) {
glXQueryDrawable(dpy, drawable, GLX_SWAP_INTERVAL_EXT, &swap);
glXQueryDrawable(dpy, drawable, GLX_MAX_SWAP_INTERVAL_EXT,
printf("The swap interval is %u and the max swap interval is "
"%u\n", swap, maxSwap);
Version History
8. 8 Nov 2011 - BrianN
- Added missing GLX protocol
7. 22 Aug 2011 - BrianN
- Fixed example code and spec to reflect glXSwapIntervalEXT
has void return value
6. 26 Jan 2010 - AaronP
- Fixed and simplified the example code.
- Removed temporary tags from enum values.
5. 08 Oct 2009 - Jon Leech
-Fixed typos and removed temporary label on token values
4. 28 Sep 2009 - JamesJ
-Added extension number
-Corrected token values
3. 08 Sep 2009 - JamesJ
-Marked complete.
2. 20 Jul 2009 - BrianN
-Fixed formatting issues
-Modified proposed error values of glXSwapIntervalEXT
1. 20 Jul 2009 - BrianN
-Initial version