Widgets can now set their favorite cursor using public API.
This is very necessary because all cursor-setting APIs are still
setting it on their GdkWindow, which by now is the toplevel - oops.
This will allow further cleanups and optimizations in capture/target/bubble
event delivery. For simplicity, ATM every widget will receive its own
GtkEventControllerLegacy, it could be desirable to add finer control over
this in the future, so widgets that fully use event controllers for input
management can do away without this legacy piece.
gtk_widget_draw_internal is now only used inside gtkwidget.c, so remove
the prototype from gtkwidgetprivate.h. And since all incovacations call
it with clip_to_size=TRUE, remove that parameter.
Since gtk+ draws more than the widget and allocates more size to it than
it knows about, this flag doesn't work anymore. Removing it (or setting
it to TRUE for widgets that used to set it to FALSE) fixes drawing
invalidation when these widgets get allocated a new size.
Since setting a clip is mandatory for almost all widgets, we can as well
change the size-allocate signature to include a out_clip parameter, just
like GtkCssGadget did. And since we now always propagate baselines, we
might as well pass that one on to size-allocate.
This way we can also make sure to transform the clip returned from
size-allocate to parent-coordinates, i.e. the same coordinate space
priv->allocation is in.
This function will be useful in other places, such as determining the
widgets that must receive crossing events after pointer picking points
to another widget.
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.
Add a new ::measure vfunc similar to GtkCssGadget's that widget
implementations have to override instead of the old get_preferred_width,
get_preferred_height, get_preferred_width_for_height,
get_preferred_height_for_width and
get_preferred_height_and_baseline_for_width.
GtkWidget.create_render_node() sets up a GskRenderNode appropriate for
rendering the contents of a widget, including its bounds,
transformation, and anchor point.
We need a virtual function to retrieve the GskRenderNode for each
widget, which is supposed to attach its own children's GskRenderNodes.
Additionally, we want to maintain the existing GtkWidget::draw mechanism
for widgets that do not implement get_render_node() — as well as widgets
that have handlers connected to the ::draw signal.
