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Erik Turner · Guest

I wrote an application to display logic analyzer trace files on the PC a
couple of months ago. At the time, we were all running WinNT4 SP6 and
this application was used extensively by several people with no problems.

Recently, my employer "upgraded" to XP Pro and now the application crashes
during a Polyline call. This is not a normal crash, it is catastrophic. The video
output completely stops (the monitor reports loss of signal). The machine is
unresponsively to anything but holding down the power button for 5+ seconds.

The problem seems to be triggered by the sequence of polyline calls which
can have up to 65300 points (TPoint). This works fine under Windows 2000
and Windows NT4. However, under XP, bad things happen.

There doesn't seem to be a stated limit for Polyline under WinNT,2K,XP but
I'm thinking that maybe there is one. Does anyone have any experience with
this problem? I can make the max size smaller and do more of them but what
is the real limit?

I'm using Delphi 5 SP1, my dataset consists of about 2000000 points drawn
12 times (the number of transitions is less). I'm using a TPaintBox to draw
the logic trace.

Thanks in advance,
Erik Turner

William · Guest

Erik Turner wrote:

Erik Turner · Guest

Good question.

I originally thought that it would be faster to collapse the zero-length
line segments so I spent some time optimizing this. However, when I
measured the elapsed time of the "optimized" method, it took longer.
So I went back to the simpler "unoptimized" method.

I've included the core drawing routine at the end of this email.
Basically, I add two new points every time the sample changes from
high to low or low to high. When I get to 65300 points (determined
empirically under Windows 2000/NT), I issue a PolyLine call and
reset the point vector. After the loop is finished, I issue a PolyLine
call to draw the remaining points.

When I was testing this under Windows 2000/NT, even failures didn't
crash the machine; they just failed to draw the requested PolyLine.

Erik Turner

************* DRAWING CODE ***********************

PointIdx := 0;
PointVec[PointIdx].X := StartSamplePixel + SamplePixel;
if SampleValue = 0
then PointVec[PointIdx].Y := SignalLowY
else PointVec[PointIdx].Y := SignalHighY;
Inc(PointIdx);
for SampleIdx := StartSampleIdx+1 to FDispRightSampleIdx do
begin
PrevSampleValue := SampleValue;
PrevSampleTime := SampleTime;
SampleValue := FLogicData.SampleSignal[SampleIdx,SignalIdx];
SampleTime := PrevSampleTime + FLogicData.SampleDeltaPsec;
SamplePixel := Round((SampleTime - StartSampleTime) / FDispPsecPerPixel);
PointVec[PointIdx].X := StartSamplePixel + SamplePixel;
if PrevSampleValue <> SampleValue then
begin
if PointIdx > 65300 then
begin
Windows.PolyLine(Canvas.Handle,PointVec,PointIdx-1);
PointVec[0] := PointVec[PointIdx-1];
PointVec[1] := PointVec[PointIdx];
PointIdx := 1;
end;
Inc(PointIdx);
PointVec[PointIdx].X := StartSamplePixel + SamplePixel;
if SampleValue = 0
then PointVec[PointIdx].Y := SignalLowY
else PointVec[PointIdx].Y := SignalHighY;
Inc(PointIdx);
PointVec[PointIdx] := PointVec[PointIdx-1];
end;
end;
Windows.PolyLine(Canvas.Handle,PointVec,PointIdx+1);

"William" <bill_meyer (AT) earthlink (DOT) net> wrote

David J Taylor · Guest

"Erik Turner" <erik (AT) spamless (DOT) turner.org> wrote

[]

quick · Guest

Erik Turner wrote: