[Development] Do we have some plans about the damage tracking of QtQuick's scene graphics?
giuseppe.dangelo at kdab.com
Thu Jun 2 14:25:57 CEST 2022
On 02/06/2022 12:53, Shawn Rutledge wrote:
> In Qt Quick the strategy has been to build a complete scene graph for
> all the contents of all visible items that you declared, and during
> rending, the SG nodes that are not visible get culled; so we didn’t have
> anything like QPaintEvent::region() to tell you what part of an Item is
I don't think that this is the problem here (i.e. partial updates within
_one_ Item); rather, the fact that if any item in a scene needs to
update, there's no damage-tracking mechanism to tell the underlying
graphics layers that only a specific screen region has been damaged.
... or is there? QSG_VISUALIZE=changes does (used to do) exactly this.
(I no longer remember if it shows an Item's bounding rectangle taking
transformations into account, or an Item's actual geometry -- how does
it do so in the presence of arbitrary vertex shaders?).
Properly signalling damage areas has a lot of interesting use cases,
from compositors to efficiently enable remoting solutions (frame
My 2 c,
Giuseppe D'Angelo | giuseppe.dangelo at kdab.com | Senior Software Engineer
KDAB (France) S.A.S., a KDAB Group company
Tel. France +33 (0)4 90 84 08 53, http://www.kdab.com
KDAB - The Qt, C++ and OpenGL Experts
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