And use this to cull widgets and gadgets that are completely outside the
clip region.
A potential optimization is to apply this clip region to cairo contexts
created with gtk_snapshot_append_cairo_node(), but for that we'd need to
apply the inverse matrix to the clip region, and that causes rounding
errors.
Plus, I hope that cairo drawing becomes exceedingly rare so it won't be
used for the whole widget factory like today (which might also explain
why no culling happens in the widget factory outside the header bar.
The equivalent to cairo_matrix_multiply (a, b, c) is
graphene_matrix_multiply (c, b, a).
graphene_matrix_multiply (a, b, c) may not be called with b and c being
the same matrix.
We do no longer bind textures to a renderer, instead they are a way for
applications to provide texture data.
For now, that's it. We've reverted to uploading it from scratch every
frame.
and gtk_snapshot_render_frame() to be direct replacements for the
old gtk_render_*() functions.
Use them to replace Cairo usage completely in gtk_window_snapshot().
We now try to emulate cairo_t:
We keep a stack of nodes via push/pop and a transform matrix.
So whenever a new node is added to the snapshot, we transform it
by the current transform matrix and append it to the current node.
