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diff --git a/docs/MESA_swap_frame_usage.spec b/docs/MESA_swap_frame_usage.spec new file mode 100644 index 00000000000..38cf51a2092 --- /dev/null +++ b/docs/MESA_swap_frame_usage.spec @@ -0,0 +1,201 @@ +Name + + MESA_swap_frame_usage + +Name Strings + + GLX_MESA_swap_frame_usage + +Contact + + Ian Romanick, IBM, idr at us.ibm.com + +Status + + Deployed in DRI drivers post-XFree86 4.3. + +Version + + Date: 5/1/2003 Revision: 1.1 + +Number + + ??? + +Dependencies + + GLX_SGI_swap_control affects the definition of this extension. + GLX_MESA_swap_control affects the definition of this extension. + GLX_OML_sync_control affects the definition of this extension. + + Based on WGL_I3D_swap_frame_usage version 1.3. + +Overview + + This extension allows an application to deterine what portion of the + swap period has elapsed since the last swap operation completed. The + "usage" value is a floating point value on the range [0,max] which is + calculated as follows: + + td + percent = ---- + tf + + where td is the time measured from the last completed buffer swap (or + call to enable the statistic) to when the next buffer swap completes, tf + is the entire time for a frame which may be multiple screen refreshes + depending on the swap interval as set by the GLX_SGI_swap_control or + GLX_OML_sync_control extensions. + + The value, percent, indicates the amount of time spent between the + completion of the two swaps. If the value is in the range [0,1], the + buffer swap occurred within the time period required to maintain a + constant frame rate. If the value is in the range (1,max], a constant + frame rate was not achieved. The value indicates the number of frames + required to draw. + + This definition of "percent" differs slightly from + WGL_I3D_swap_frame_usage. In WGL_I3D_swap_frame_usage, the measurement + is taken from the completion of one swap to the issuance of the next. + This representation may not be as useful as measuring between + completions, as a significant amount of time may pass between the + issuance of a swap and the swap actually occuring. + + There is also a mechanism to determine whether a frame swap was + missed. + +New Procedures and Functions + + int glXGetFrameUsageMESA(Display *dpy, + GLXDrawable drawable, + float *usage) + + int glXBeginFrameTrackingMESA(Display *dpy, + GLXDrawable drawable) + + int glXEndFrameTrackingMESA(Display *dpy, + GLXDrawable drawable) + + int glXQueryFrameTrackingMESA(Display *dpy, + GLXDrawable drawable, + int64_t *swapCount, + int64_t *missedFrames, + float *lastMissedUsage) + +New Tokens + + None + +Additions to Chapter 2 of the 1.4 GL Specification (OpenGL Operation) + + None + +Additions to Chapter 3 of the 1.4 GL Specification (Rasterization) + + None + +Additions to Chapter 4 of the 1.4 GL Specification (Per-Fragment Operations +and the Framebuffer) + + None + +Additions to Chapter 5 of the 1.4 GL Specification (Special Functions) + + None + +Additions to Chapter 6 of the 1.4 GL Specification (State and State Requests) + + None + +Additions to the GLX 1.3 Specification + + The frame usage is measured as the percentage of the swap period elapsed + between two buffer-swap operations being commited. In unextened GLX the + swap period is the vertical refresh time. If SGI_swap_control or + MESA_swap_control are supported, the swap period is the vertical refresh + time multiplied by the swap interval (or one if the swap interval is set + to zero). + + If OML_sync_control is supported, the swap period is the vertical + refresh time multiplied by the divisor parameter to + glXSwapBuffersMscOML. The frame usage in this case is less than 1.0 if + the swap is commited before target_msc, and is greater than or equal to + 1.0 otherwise. The actual usage value is based on the divisor and is + never less than 0.0. + + int glXBeginFrameTrackingMESA(Display *dpy, + GLXDrawable drawable, + float *usage) + + glXGetFrameUsageMESA returns a floating-point value in <usage> + that represents the current swap usage, as defined above. + + Missed frame swaps can be tracked by calling the following function: + + int glXBeginFrameTrackingMESA(Display *dpy, + GLXDrawable drawable) + + glXBeginFrameTrackingMESA resets a "missed frame" count and + synchronizes with the next frame vertical sync before it returns. + If a swap is missed based in the rate control specified by the + <interval> set by glXSwapIntervalSGI or the default swap of once + per frame, the missed frame count is incremented. + + The current missed frame count and total number of swaps since + the last call to glXBeginFrameTrackingMESA can be obtained by + callling the following function: + + int glXQueryFrameTrackingMESA(Display *dpy, + GLXDrawable drawable, + int64_t *swapCount, + int64_t *missedFrames, + float *lastMissedUsage) + + The location pointed to by <swapCount> will be updated with the + number of swaps that have been commited. This value may not match the + number of swaps that have been requested since swaps may be + queued by the implementation. This function can be called at any + time and does not synchronize to vertical blank. + + The location pointed to by <missedFrames> will contain the number + swaps that missed the specified frame. The frame usage for the + last missed frame is returned in the location pointed to by + <lastMissedUsage>. + + Frame tracking is disabled by calling the function + + int glXEndFrameTrackingMESA(Display *dpy, + GLXDrawable drawable) + + This function will not return until all swaps have occurred. The + application can call glXQueryFrameTrackingMESA for a final swap and + missed frame count. + + If these functions are succesful, zero is returned. If the context + associated with dpy and drawable is not a direct context, + GLX_BAD_CONTEXT is returned. + +Errors + + If the function succeeds, zero is returned. If the function + fails, one of the following error codes is returned: + + GLX_BAD_CONTEXT The current rendering context is not a direct + context. + +GLX Protocol + + None. This extension only extends to direct rendering contexts. + +New State + + None + +New Implementation Dependent State + + None + +Revision History + + 1.1, 5/1/03 Added contact information. + 1.0, 3/17/03 Initial version based on WGL_I3D_swap_frame_usage. |