I think I have written almost the simplest line-drawing test program
that is possible, like 6-8 lines of relevant code, total.
The whole short project is here: http://bubbler.net/TestRB/home
(this address is case sensitive, and does NOT end in .html)
Description:
There is a canvas in a window that has two variables: previousX and previousY.
MouseDown fills these variables with current x and y, and returns True.
MouseDrag draws small circles at x,y.
Just for further confirmation of this problem I'm having, I have a
checkbox. When its value is True, the program draws lines between
previousX, previousY and current x,y, and then sets previousX to x,
and previousY to y.
All works fine on a Mac.
PROBLEM on a PC
On a somewhat old PC, however, performance is weird, i.e., terrible.
Most of the lines or dots suggest that the computer is having to work
very hard; the lines have bad jaggies, or the dots are ~1/2 inch
apart. It is easy to drag the pen far ahead of where the lines/dots
are appearing on the canvas.
But every so often, at irregular, unpredictable times, a smooth line
or much closer set of dots will stream forth. Fast, flowing, smooth
drawing THAT is what I want, consistently.
I am not drawing to an off-screen buffer or doing anything else. No
color, no penThickness, no threads, nothing extra.
It's on a Gateway Motion Tablet PC with a Pentium III 933 MHz and
256MB of RAM. Nothing else is running.
The exact same problem show when I use a Wacom tablet instead of the
touch screen on this PC.
It can't be just the old CPU, because of the occasional good performance.
I vaguely understand that Windows' approach to drawing is complex;
but I am not using any of that.
Can anyone think of an explanation? Is the Windows OS doing
something? Can I turn something off? Why so inconsistent?
I invite interested NUG folk to try my little program and see for
yourself IF you have a somewhat old PC to test on.
Thanks...
Jeb Eddy
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