Appendix A: EGL Extensions

EGL_NV_system_time

Name	egl_nv_system_time
Name Strings	EGL_NV_system_time
Contact	NVIDIA Corporation (NVPerfHUDESDev@nvidia.com)
Dependencies	Requires EGL 1.2.
Overview	This extension exposes an alternative method of querying the system time from the driver instead of the operating system.
Issues	Add 64 bit types? Yes, EGL doesn't support any 64 bit types, so this extension adds `int64` and `uint64` types.
New Types	typedef long long int EGLint64NV; typedef unsigned long long int EGLEGLuint64NV;
New Procedures and Functions	EGLuint64NV eglGetSystemTimeFrequencyNV(void); EGLuint64NV eglGetSystemTimeNV(void);
New Tokens	None.
Description	The command: EGLuint64NV eglGetSystemTimeFrequencyNV(void); Returns the frequency of the system timer, in counts per second. The frequency will not change while the system is running. The command: EGLuint64NV eglGetSystemTimeNV(void); Returns the current value of the system timer. The system time in seconds can be calculated by dividing the returned value by the frequency returned by the `GetSystemTimeFrequencyNV` command. Multiple calls to `GetSystemTimeNV` may return the same values, applications need to be careful to avoid divide by zero errors when using the interval calculated from successive `GetSystemTimeNV` calls.
Usage Example	EGLuint64NV frequency = eglGetSystemTimeFrequencyNV(); loop { EGLuint64NV start = eglGetSystemTimeNV() / frequency; // draw EGLuint64NV end = eglGetSystemTimeNV() / frequency; EGLuint64NV interval = end - start; if (interval > 0) update_animation(interval); eglSwapBuffers(dpy, surface); }