Qt4-preview-feedback Archive, July 2007
A suggestion for Layout system for QGraphicsItems
Message 1 in thread
Hi, Andres/Girish,
In the "Dialog on the Canvas" blog post comment, you
mentioned that you guys are working on the layout
system for QGraphicsItems. Just wondering would you
consider delivering an additional notification via
QGraphicsItem::itemChange() to the item's parent to
tell it about the pending geometry change of its
child? This helps tremendously in the case of nested
layouts where a change in the child's geometry needs
to propagate upwards but using childrenBoundingRect()
is very costly. So it's better to let the child notify
its parent. A natural place to do the notification is
inside the prepareGeometryChange() - for it needs to
be called before people attempt to change the item's
geometry anyway. Of course, you may have a better
candidate in mind.
Why this interests me? Well, part of what we use Qt
for is to create graphical editors for all kinds of
data models. In Qt 4.1.x, we incorporated many ideas
from Eclipse's Draw2d/GEF to help us do that. Now I am
in the process of porting my libraries to
QGraphicsView. The lack of layout support in 4.3.0 is
an issue I immediately ran into.
That said, I am very interested in testing out the
layout system that you guys are working on. Is it
available in the daily snapshot already? I didn't find
it in the snapshot of 20070730, but again maybe I
didn't look at the right place in the snapshot. If
it's not available with the snapshot, could I get
access to it from somewhere?
Regards,
Pin-Yen
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