This patch enables basic drag&drop between applications.
You initiate a drag by creating a GDragOperation object and calling
exec() on it. This creates a nested event loop in the calling program
that only returns once the drag operation has ended.
On the receiving side, you get a call to GWidget::drop_event() with
a GDropEvent containing information about the dropped data.
The only data passed right now is a piece of text that's also used
to visually indicate that a drag is happening (by showing the text in
a little box that follows the mouse cursor around.)
There are things to fix here, but we're off to a nice start. :^)
This patch converts the undo stack from GTextDocument into GUndoStack,
and GTextDocumentUndoCommand now inherits from GCommand.
Let's turn this into a generic mechanism that can be used to implement
undo/redo in any application. :^)
The idea here is to decouple the document from the editor widget so you
could have multiple editors being views onto the same document.
This doesn't work yet, since the document and editor are coupled in
various ways still (including a per-line back-pointer to the editor.)
Here's how you can use this to speed up startup time:
auto widget = GLazyWidget::construct();
widget->on_first_show = [](auto& self) {
self.set_layout(...);
...
};
Basically, it allows you to delay building the widget subtree until
it's shown for the first time.
Each GAbstractView now has a GModelSelection backed by a simple
HashTable<GModelIndex>. When the selection changes somehow, the view
gets notified via the notify_selection_changed() callback.
In the future it will probably make sense to move to using some kind of
ranges as the internal representation instead.
Instead of LibGUI and WindowServer building their own copies of the drawing
and graphics code, let's it in a separate LibDraw library.
This avoids building the code twice, and will encourage better separation
of concerns. :^)
