| Name |
| |
| EXT_swap_control |
| |
| Name Strings |
| |
| GLX_EXT_swap_control |
| |
| Contributors |
| |
| Brian Nguyen, NVIDIA, brnguyen at nvidia.com |
| James Jones, NVIDIA, jajones at nvidia.com |
| Ian Romanick, Intel, idr at freedesktop.org |
| Jesse Barnes, Intel, jbarnes at virtuousgeek.org |
| Aaron Plattner, NVIDIA, aplattner at nvidia.com |
| |
| Contact |
| |
| Brian Nguyen, NVIDIA, brnguyen at nvidia.com |
| |
| Status |
| |
| Completed. |
| |
| Version |
| |
| Version 8 (November 8, 2011) |
| |
| Number |
| |
| 375 |
| |
| Dependencies |
| |
| 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 |
| respectively. |
| |
| 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. |
| |
| Overview |
| |
| 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. |
| |
| 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 |
| sufficient. |
| |
| 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 |
| |
| GLX_SWAP_INTERVAL_EXT 0x20F1 |
| GLX_MAX_SWAP_INTERVAL_EXT 0x20F2 |
| |
| Additions to Chapter 2 of the OpenGL 1.2.1 Specification (OpenGL |
| Operation) |
| |
| None. |
| |
| Additions to Chapter 3 of the OpenGL 1.2.1 Specification (Rasterization) |
| |
| None. |
| |
| Additions to Chapter 4 of the OpenGL 1.2.1 Specification (Per-Fragment |
| Operations and the Frame Buffer) |
| |
| None. |
| |
| Additions to Chapter 5 of the OpenGL 1.2.1 Specification (Special |
| Functions) |
| |
| None. |
| |
| Additions to Chapter 6 of the OpenGL 1.2.1 Specification (State and |
| State Requests) |
| |
| None. |
| |
| 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 |
| call. |
| |
| 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. |
| |
| SwapIntervalEXT |
| 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 |
| |
| Errors |
| |
| 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 |
| interval |
| |
| 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, |
| &maxSwap); |
| 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 |
