/*
  SCREENGetFlipInfo.c

  AUTHORS:

  mario.kleiner.de@gmail.com    mk

  PLATFORMS:    All

  HISTORY:

  5.09.2011     mk  Created.

  DESCRIPTION:

  Returns information about execution of flips of a specific window.

*/

#include "Screen.h"

static char useString[] = "info = Screen('GetFlipInfo', windowPtr [, infoType=0] [, auxArg1]);";
static char synopsisString[] = 
    "Returns a struct with miscellaneous info about finished flips on the specified onscreen window.\n"
    "\n"
    "This function is currently only supported on Linux X11/GLX with the free graphics drivers,\n"
    "and on Linux/Wayland with support for the presentation_feedback extension.\n\n"
    "The function allows you to enable logging of timestamps and other status information "
    "about all completed bufferswaps, as triggered via Screen('Flip'), Screen('AsyncFlipBegin') etc. "
    "Whenever a flip completes, a little info struct is stored in a internal queue. This function "
    "allows you to fetch these info structs from the queue. It allows you to enable and disable "
    "logging of these info structs. Logging is disabled by default.\n\n"
    "\"windowPtr\" is the handle of the onscreen window for which info should be returned.\n"
    "\"infoType\" If left out or set to zero, the flip handle for the last invocation of flip is returned. "
    "E.g., if a value of 53 is returned, then the info struct with a info.SwapbuffersCount field of 53 "
    "will contain the info for that last invocation of flip.\n"
    "This allows to associate specific flips with the returned logged timestamps and other info.\n"
    "If set to 1, logging of flip completion info is enabled.\n"
    "If set to 2, logging of flip completion info is disabled.\n"
    "If set to 3, the oldest stored flip completion info is returned in a struct 'info'.\n\n"
    "The info struct contains the following fields:\n"
    "----------------------------------------------\n\n"
    "OnsetTime: Visual stimulus onset time of the completed Screen('Flip') operation.\n"
    "OnsetVBLCount: Video refresh cycle count when the flip completed.\n"
    "SwapbuffersCount: Serial number of this info struct. Corresponds to the handle returned for 'infoType' zero.\n"
    "SwapType: How was the flip executed? Low level info about strategy chosen by GPU.\n"
    "BackendFeedbackString: A string with more info, which is specific to a display backend, e.g., GLX vs. Wayland.\n"
    "Note: Currently only flips with a 'SwapType' field containing the (sub-)string 'Pageflip' are considered to "
    "have reliable timing and trustworthy timestamps. On Wayland dislay servers a 'SwapType' of 'ImpreciseCopy' "
    "also has good timing, although likely with less precise and accurate onset timestamps. 'ImprecisePageflip' "
    "is also considered having slightly less precise and accurate onset timestamps. Other types of 'Pageflip's "
    "should be high quality in the time domain.\n\n";

static char seeAlsoString[] = "OpenWindow, Flip, NominalFrameRate";

PsychError SCREENGetFlipInfo(void) 
{
#if PSYCH_SYSTEM == PSYCH_LINUX
    PsychWindowRecordType *windowRecord;
    int infoType = 0;
#endif

    // All subfunctions should have these two lines.
    PsychPushHelp(useString, synopsisString, seeAlsoString);
    if(PsychIsGiveHelp()){PsychGiveHelp();return(PsychError_none);};

#if PSYCH_SYSTEM == PSYCH_LINUX

    PsychErrorExit(PsychCapNumInputArgs(2));     //The maximum number of inputs
    PsychErrorExit(PsychRequireNumInputArgs(1)); //The required number of inputs
    PsychErrorExit(PsychCapNumOutputArgs(1));    //The maximum number of outputs

    PsychAllocInWindowRecordArg(kPsychUseDefaultArgPosition, TRUE, &windowRecord);
    if (!PsychIsOnscreenWindow(windowRecord)) PsychErrorExitMsg(PsychError_user, "Invalid 'windowPtr' specified. Not an onscreen window!");

    // Query infoType flag: Defaults to zero.
    PsychCopyInIntegerArg(2, FALSE, &infoType);
    if (infoType < 0 || infoType > 3) PsychErrorExitMsg(PsychError_user, "Invalid 'infoType' argument specified! Valid are 0, 1, 2, 3.");

    // Type 0: Return SBC handle of last scheduled flip:
    if (infoType == 0) {
        PsychCopyOutDoubleArg(1, FALSE, (double) windowRecord->target_sbc);
        return(PsychError_none);
    }

    // Type 1: Enable logging of swap completion events:
    if (infoType == 1) {
        PsychOSSwapCompletionLogging(windowRecord, 1, 0);
        return(PsychError_none);
    }

    // Type 2: Disable logging of swap completion events:
    if (infoType == 2) {
        PsychOSSwapCompletionLogging(windowRecord, 0, 0);
        return(PsychError_none);
    }

    // Type 3: Fetch logged swap completion events:
    if (infoType == 3) {
        PsychOSSwapCompletionLogging(windowRecord, 3, 1);
        return(PsychError_none);
    }
#else
    PsychErrorExitMsg(PsychError_unimplemented, "Sorry, this function is only supported on Linux.");
#endif

    // Done.
    return(PsychError_none);
}
