Re: GSK review and ideas

On Thu, Dec 15, 2016 at 10:26 AM, Alexander Larsson <alexl redhat com> wrote:

Also related to clipping, we're currently not doing any culling at
all. I think we need to make gtk_container_snapshot_child() take the
current clip into consideration when recursing. Right now we're
creating nodes for children that are not visible.

Of course, such culling relies on the fact that the children don't
draw outside their allocation. Culling seems quite important to be
able to handle 10000s of rows in a listbox. So maybe we need to
actually clip every widget.

The above kinda contradicts each other, so we need to decide what to
do here. My hunch is that the natural approach is a bit of both, where
we always repaint the entire window (ignoring the damage region), but
clip each widget to the allocation. That means clipping becomes a
simple int-rect intersection (not a full region_t) which can be done
fast (and maybe on the GPU) while still allowing highlevel culling on
the widget allocation level. Does that seem right?

Note that we do have a clip rect for widgets that can be larger than
the allocation. So we can have the best of both worlds: widgets can
opt in to drawing outside their alllocation by setting a clip, and we
can still cull everything whose clip rect doesn't intersect the (gsk)

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