Re: [XForms] Canvas / button interaction

[Clive Stubbings]

Ok,

Getting closer..

I changed the code so it paints the 'yellow' button as being the full size of 
the window (ie 300x200)..

Clicking the button, I get a strip 10 pixels high at the top of the window. So I 
moved the canvas from (10,10) to (10,25)... And I get a strip 25 pixels high...

So somewhere the the polygon fill is being clipped to the top edge of the 
canvas. Can't see it at the momet though.

If I create 2 canvases, its the top one that sets the limit - order doesn't 
seem to matter.

Cheers
Clive

On Sat, 11 Feb 2012, Clive Stubbings wrote:

> Jens,
>
> I've been having a bit more look at windows.
>
> What seems to happen is:
>
>         A main form window (id 1e00018) is created
>         GC get created on that
>         Then a pixmap is created (id 1e0003a)
>         The pixmap is used for some initial drawing of the objects
>         The canvas is created with a window (id 1e0003b)
>         some more drawing happens on the pixmap
>         the pixmap gets copied to the display
>
>         A click event on the checkbutton does its
>         object drawing on the original (id 1e00018) window
>
>         An expose seems to go via the pixmap.
>
> There may be something unstable here too. I'm sure that in the past an expose 
> event anywhere on the form was enough to cause the objects to be re-drawn. 
> However in my current build, which has -g enabled and some debug messages, 
> thats not true any more - expose the button and its displayed, but the expose 
> region has to include the object..
>
> Basically at the moment it seems to copy a pixmap to 1e00018 but not draw a 
> polygon on it....
>
> XCopyArea( flx->display, p->pixmap, p->win, flx->gc, 0, 0, p->w, p->h, p->x, 
> p->y );
>
> vs
>
> XFillPolygon( flx->display, flx->win, flx->gc, xp, n, Nonconvex, 
> CoordModeOrigin );
>
> Odd..
>
> Cheers
> Clive
>
> On Fri, 10 Feb 2012, Jens Thoms Toerring wrote:
>
> > Hi Clive,
> >
> > On Fri, Feb 10, 2012 at 01:37:46AM +0000, Clive Stubbings wrote:
> > > More bits of data..
> > >
> > > Adding XFlush() and XSync() calls after the polygon draw makes no 
> > > difference.
> > >
> > > A redraw as a result of an expose event - eg window raise does
> > > result in correct drawing.
> > >
> > > Interestingly, it can be any part of the window that is exposed - it
> > > doesn't have to be the bit with the button in it, or the bit with the
> > > canvas..
> > >
> > > Two things that are different in the 2 cases are the clipping calls and
> > > the value of flx->win, but it looks like they are not the problem.
> >
> > Mmm, the different flx->win values worry me a bit. can there
> > something be going wrong with double buffering?
> >
> > > Jens, any idea how to fake an expose event in Xforms? I'd like to
> > > see if what makes the difference is a real X-expose event or whether
> > > its something different in the xforms handling of expose vs draw.
> >
> > I guess you could use fl_XPutBackEvent() to stick an arti-
> > ficially created event into XForms' event queue...
> >
> >                               Best regards, Jens
> > --
> >  \   Jens Thoms Toerring  ________      address@hidden
> >   \_______________________________      http://toerring.de