Just to avoid having to do NULL checks when calling
widget_class->snapshot. We were crashing with drawing areas who don't
have a draw or a snapshot vfunc (woot!).
We need so subtract the allocation from the clip to get the clip offset,
not the other way around.
This was screwing in particular with marks on GtkScale, because GtkScale
mark clip computation is broken and always returns (0,0) which makes
scales have a waaaaay too large clip.
But that's another bug.
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.
Grips have long been unused in GTK, so remove all support for them.
This removes the GTK_STYLE_CLASS_GRIP and the special
gtk_render_handle() code for drawing those grips.
This allows renderers (or anyone really) to attach "render data" to
textures. Only the first render data sticks.
You can gsk_texture_set_render_data() with the key you will use to
look the data up again, and if no data has been set yet, yours will be
set.
You can retrieve this data via gsk_texture_get_render_data() later on.
If your data has been cleared, NULL will be returned.
When gsk_texture_clear_render_data() is called (which the texture will
call when it is finalized), your destory notify will be called and you
have to release your render data.
The GL driver uses this to attach texture ids to GskTextures.
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.
The snapshot vfuncs must only append at most a single node,
otherwise things are going to break if the widget is the root node.
Unfortunately there is no code that can check this in a generic fashion,
so we'll have to debug this on a case-by-case basis.
