If multiple nested widgets have drag sources on them, both using bubble
phase, we need to reliably pick the inner one. Both of them will try to
start dragging, and we need to make sure there are no situations where the
outer widget starts drag earlier and cancels the inner one.
Currently, this can easily happen via integer rounding: start and current
coordinates passed into gtk_drag_check_threshold() are initially doubles
(other than in GtkNotebook and GtkIconView), and are casted to ints. Then
those rounded values are used to calculate deltas to compare to the drag
threshold, losing quite a lot of precision along the way, and often
resulting in the outer widget getting larger deltas.
To avoid it, just don't round it. Introduce a variant of the function that
operates on doubles: gtk_drag_check_threshold_double() and use it instead
of the original everywhere.
This commit handles complicated cases where we selections.
We handle this by adding extend and modify parameters to
the ::move-cursor signals, and adjust the bindings
accordingly.
This is a huge reorganization of GtkDropTarget. I did not know how to
split this up, so it's unfortunately all one commit.
Highlights:
- Split GtkDropTarget into GtkDropTarget and GtkDropTargetAsync
GtkDropTarget is the simple one that only works with GTypes and offers
a synchronous interface.
GtkDropTargetAsync retains the full old functionality and allows
handling mime types.
- Drop events are handled differently
Instead of picking a single drop target and sending all DND events to
it, every event is sent to every drop target. The first one to handle
the event gets to call gdk_drop_status(), further handlers do not
interact with the GdkDrop.
Of course, for the ultimate GDK_DROP_STARTING event, only the first
one to accept the drop gets to handle it.
This allows stacking DND event controllers that aren't necessarily
interested in handling the event or that might decide later to drop
it.
- Port all widgets to either of those
Both have a somewhat changed API due to the new event handling.
For the ones who should use the sync version, lots of cleanup was
involved to operate on a sync API.
Instead of just returning the last allocated numbers, we now compute the
proper sizes from scratch. This is a bit less trivial, but it results in
proper height-for-width handling.
This is a huge quest to remove all caching from GtkIconview to simplify
the code. As it turns out, iconview performance is a joke, so the caches
are kinda unnecessary.
If we need caching, we can add it in a useful way later.
If we use
&item->cell_area
instead of
(GdkRectangle *) item
there is no need anymore to keep the cell_area as the first member of
the the item. And we cget compile-time checks for changes to the item
struct.
