Conference bulova::decw_jan-89_to_nov-90

2191.0. "Problem moving graphics on screen." by EXLIB::DLUGOSZ (Open foot, Insert Mouth) Fri Feb 02 1990 13:34

I'm trying to include an area cut/copy/paste function into a program and I'd
like it to work in a way similar to DECpaint. 

My first attempt was to copy the selected area to a pixmap and then use
XCopyArea, and along with a GC with funcion = GXxor, to move it around
on the drawing canvas. It worked, and was fast - but you have the problem
of getting inconsistent results dragging around due to XOR'ing with 
different color backgounds.

I thought I had the problem licked yesterday. I scratched the above and
instead created a window widget, copied the selected area to the widget, 
and then used XtSetValues to move the widget. It worked great - on my
DECstation 3100. When I tryed in on my GPX/II this morning - what a dog! 
DECpaint runs circles around it (so would my daughter's pet snail).

Since I've tryed a few other things to speed it up, including setting the
widgets background pixmap to None to inherit the pixel data under the
window, using a window instead of a widget and moving it with XMoveWindow,
and even grabbing the server (getting desperate!). Can't get any
improvement in performance.

Does anybody have any ideas about this? DECpaint does it - and apparently
is using a window or window widget from watching its behavior. This is
the last piece in a program that I need to use as an example in a class
that I'm teaching - in a week... Any help would be appreciated (not to
mention benificial to my sanity!).

Ron

    Ron,
    
    You might try using a window and moving it with XMoveWindow rather
    than a window widget and XtSetValues. It will be faster, but perhaps
    not fast enough for a GPX.
    
    How is the underlying window's data being managed? If it's maintained
    in a pixmap, then I would allocate a new pixmap for the piece to be
    dragged, and try doing the dragging with XCopyArea and GXcopy, while
    restoring pixels in the wake of the dragged area with XCopyArea from
    the backing pixmap. 
    
    Dave
     

    Hi Dave,
    
    I was wondering if you were still out there. I already tried the
    first suggestion - still way too slow on the GPX. The second one
    sounds interesting...I'll give it a try Monday.
    
    Thanks,
    Ron