🚀 go-pugleaf

calder@NURB.JRC.FLINDERS.EDU.AU (Paul Calder) writes:

|Donn Cave writes ...

|>In 3.0.1, it sometimes seems that the actual size and position of
|>elements on the screen is slightly more variable than one would expect,
|>and I have been thinking that this is because of round-off errors between
|>InterViews' floating point coordinate system, and X's integer screen
|>coordinates.

| This behaviour is an unavoidable consequence of round-off; to call it
| an 'error' is a bit strong.  Mark Linton's paper on device-independent
| rendering addresses the issue in more detail.  (The paper was
| presented at XTech92 and is available from sgi.com as xconf92.ps.Z.)

| You can avoid the 'undulation' on scrolling if you always scroll by
| exact pixel-sized amounts.

Thanks, but most of the problem is that the buttons look funny even when
they're not scrolling.  I didn't mean 'error' in a deprecatory way, it's
simply a practical problem: if there are going to be narrow elements like
the bevels in an outset frame, those elements need to have a uniform size
or they will make for slightly distracting visual cues.

To put it more personally, if I show my colleagues an application with a row
of buttons, and one or two of the buttons seem oddly different because the
3-d decorations aren't uniform, they will laugh at me for using InterViews,
and we can't have that.

Someone helpfully sent a tip on Display::to_pixels()  (albeit with disclaimer
that he hadn't found it helpful), and I have been trying to think how to
make, say, a subclass of Center or something that would force alignment to
a non-fractional pixel coordinate, but I haven't gotten anywhere with it
yet.  I think I would have to overload draw()?, but I don't know how to
find non-relative coordinates for a glyph.

	Donn Cave, University Computing Services, University of Washington
	donn@cac.washington.edu