cocoa devdraw: drawing fix

Devdraw now waits for the image: this means that
there is no more blank image when toggling
fullscreen, when unminimizing, or at startup; this
also means that we can live resize, but we only
enable live resizing with Page, because it seems
useless for other apps, and Acme and Sam bug with
it. The tradeoff is that bottom corners are
sometimes automatically rounded. There is a way to
prevent the rounding here:
http://parmanoir.com/Custom_NSThemeFrame
but this would obfuscate the code. Instead, we
make sure that the corners are always rounded.

Closing the window while its content is updated
causes an exception, without this patch. This
seems to happen regularly with stats(1).

This patch avoids a possible deadlock at startup,
which I never experienced. If I recollect right,
there is little chance that this happens on a
multi-core CPU.

Minimizing now activates next app in line, and
Devdraw now stops drawing while minimized.

[rsc, 2012-01-16 22:19:11]

There are multiple things going on here.  I am not sure
that all are worth doing.  For example, the bottom corners
often have useful pixels in them in Plan 9 apps.  My inclination
would be not to go to any extra effort to round them on Lion.
In fact, I was going to send you mail asking how we can disable
the resizer in the bottom left corner.  Right now in acme it is
nearly impossible, if you end up with a tag in the bottom of the
left column, to grab it.  You usually end up resizing the window
instead.  I would be plenty happy if only the bottom right corner
had a resizer, and if both corners stayed square.

As far as live resizing goes, that's really a whole nest of bugs all
to itself.  Is there a compelling reason to bother?  I especially
dislike having to change the sam and acme resizing code to
make up for it.

Can we drop live resizing, square the corners, and maybe get
rid of the resizer in the bottom left on Lion?

Thanks.

[djeannot24, 2012-01-18 15:54:01]

(I have pulled plan9port in between, so
Codereview's "Delta from patch set" between 4 and
3 is meaningless: a problem I had not foreseen. We
must use "Side-by-side diffs" instead.)

Live resizing is now disabled. (The funny thing is
that, without live resizing, Acme suffers from a
bug when we shrink it vertically: its windows in
the lower part of the old image vanish from the
new one. Also, with live resizing this time, when
we expand Acme vertically, tags stay group
together, except when we are really fast, but,
then, a little shrinking agglutinates them again.
I suspect that Acme has been designed with live
resizing in mind.)

The resizer in the bottom left corner annoys me
too, but I found no solution. Maybe there is one
at a lower level than Cocoa, I don't know.

Regarding the bottom corners, OS X will
automatically round them each time it wants an
image (after resizing or unminimizing for
example), and this rounding will remain so until
the app updates the corner zone. If you want the
corners to be always rounded, you can apply the
5th patch set; if you want the corners to be
sometimes rounded, sometimes squared, you can
apply the 4th patch set. The corner radius is 3
pixels. This rounding has never annoyed me so far,
but I only use Acme and Page. (Maybe there is a
way to disable this automatic rounding, but I am
ignorant of it.)

[djeannot24, 2012-03-05 20:54:17]

(I don't know if you are interested by this patch,
but I have updated its description.)

[rsc, 2012-03-05 20:54:33]

Thanks very much for the fix.

[rsc, 2012-03-05 20:55:34]

*** Submitted as http://code.google.com/p/plan9port/source/detail?r=b7f9f63245ee
***

Devdraw now waits for the image: this means that
there is no more blank image when toggling
fullscreen, when unminimizing, or at startup; this
also means that we can live resize, but we only
enable live resizing with Page, because it seems
useless for other apps, and Acme and Sam bug with
it. The tradeoff is that bottom corners are
sometimes automatically rounded. There is a way to
prevent the rounding here:
http://parmanoir.com/Custom_NSThemeFrame
but this would obfuscate the code. Instead, we
make sure that the corners are always rounded.

Closing the window while its content is updated
causes an exception, without this patch. This
seems to happen regularly with stats(1).

This patch avoids a possible deadlock at startup,
which I never experienced. If I recollect right,
there is little chance that this happens on a
multi-core CPU.

Minimizing now activates next app in line, and
Devdraw now stops drawing while minimized.

R=rsc
CC=plan9port.codebot
http://codereview.appspot.com/5499043

Committer: Russ Cox <rsc@swtch.com>