Anthony Petrov wrote:
Hi Dmitri,
On 01/21/2009 10:23 PM Anthony Petrov wrote:
Yeah, I see the point. Another option is to make the field private,
create a final package-private getter (though why? we have a lovely
public one already), and private setter. The setter would be invoked
through the sun.awt.AWTAccessor by the toplevel window whenever its
own GC gets changed (holding the TreeLock and traversing the whole
hierarchy). It will also be assigned when adding a component to a
container (by using the container's local copy of the gc - which we
assume correct). This way we ensure there's only one value of gc in
every single component in the given toplevel window at any moment of
time. I guess changing the GC is not quite frequent operation to worry
much about the performance of this approach?
By the way, Canvases may be created with a non-default GC. How should
these be treated then if we think we should have the same GC for every
component in a Window?
Hmm. Indeed, forgot about that.
Canvas is pretty much a toplevel from this perspective.
For Canvas it wasn't really meant to specify a location
(like, which screen it appears on), but the visual of the
window (or pixel format on windows).
So we can modify our original suggestion, and treat Canvas
as toplevel - allow it to have its own GC.
But it's not clear what to do if its toplevel containing
a canvas created with non-default GC is moved onto a different
screen (or if a display change event happened which
re-created all GCs).
The only sensible option I see is to change it to the
new default GC.
This stuff was designed when there were no multiple
screens, and it shows - at least, you couldn't move a
window from one screen to another (windows didn't
have multiscreen up until Win2k/WinXP, and xinerama
was a rare beast back then).
The bulk of multiscreen and display change support in Java
was retrofitted later.
Thanks,
Dmitri
