Re: Re xt5250 and 132 column issues....

On Thu, 18 Dec 2008, Scott Klement wrote:

>> This is where I experience about a 3 – 5 second wait before the 132
>> column screen is displayed, but with only 84 columns and 25 rows. The
>> rest is cut-off.
>
> I run FreeBSD, and have not encountered this symptom.  However, I can
> explain to you how things work, and maybe that'll give you some ideas of
> how to solve the problem.

[Snip very good explanation of the problem]

> Have you tried x5250?  You might have better luck with that.  x5250 is a
> true X11 program, it's not a console program running in an xterm.  If my
> theories are correct, that SHOULD make a big difference.

I experimented with x5250 and while on my system it doesn't exhibit the 
problematic behaviour described for xt5250 it still doesn't fill the 
window with content when maximized.  That's because x5250 chooses window 
size based on how much space is required to draw the contents in the font 
specified.  Maximizing simply gives more room to x5250 to draw in.  But 
since it doesn't need that room you just end up with a bunch of blank 
space along the right and bottom edges of the window (this is the same 
behaviour I get with xt5250 maximized).  Switching from 80 to 132 columns 
and back is completely free of any problems, but of course it resizes the 
window to the size it needs and no more.  So a maximized window becomes 
unmaximized (at least it does on my system running WindowMaker).

A nice feature to add to x5250 would be font resizing based on window 
size.  This is a tough problem because of the difficulty of finding an 
approriate font on the system that fits the dimensions of an arbitrary 
window.  I think that is why IBM iSeries Access snaps windows to specific 
dimensions and doesn't allow windows of any arbitrary size.  I don't even 
know how to go about finding a list of fonts in X11 that look like that 
same but are different sizes programmatically.  Indeed, there is a chance 
that appropriate fonts don't even exist beyond a certain range of sizes. 
The current way fonts are loaded and screen sizes determined goes 
something like this:

1. look for the font the user specified (either on the command line or in 
an X11 resource).
2. if found, load that font.
3. determine the maximum width in pixels that would be required to fit 80 
or 132 characters in that font on the screen.  Do the same for the font 
height and number of rows.
4. create or resize the window using the found dimensions.

In order for the window content to fill an arbitrary sized window there 
would have to be some mechanism for finding fonts that when rendered with 
their widest/tallest character fit the window size.  There is probably a 
way to find a list of fonts (xfontsel shows such a list).  Figuring out 
which of those fonts would fit the required dimensions would be a 
challenge.  I think x5250 would have to load each font and check one by 
one.  Of course you would also want a way to use only fixed width fonts 
and that might be hard to do.

The entire above discussion is based around using bitmapped fonts.  There 
might be another solution:  use scalable fonts.  Not all scalable fonts 
are created equal.  More recent X11 apps use pango or some other font 
rendering library to acheive good looking scalable fonts.  I avoided that 
in x5250 in order to minimize the number of dependancies on other 
software.  But perhaps adding pango support or something like it would be 
a nice option.

James Rich

if you want to understand why that is, there are many good books on
the design of operating systems. please pass them along to redmond
when you're done reading them :)
 	- Paul Davis on ardour-dev

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