Previously the client would only learn the mime type of what was being
dropped on it once the drop occurred. To enable more sophisticated
filtering of drag & drop, we now pass along the list of mime types being
dragged to the client with each MouseMove event.
(Note that MouseMove is translated to the various Drag* events in LibGUI
on the client side.)
If a widget accept()'s a "drag enter" event, that widget now becomes
the application-wide "pending drop" widget. That state is cleared if
the drag moves over another widget (or leaves the window entirely.)
These events allow widgets to react when a drag enters/leaves their
rectangle. The enter event carries position + mime type, while the
leave event has no information.
Instead of each window having a bool flag that says whether that window
is currently active, have a pointer to the active window on the app
object instead.
It always felt a bit jarring that tooltips would pop in right away when
you hover over a toolbar button. This patch adds a 700ms delay before
they appear, and a 50ms delay before they disappear.
Once a tooltip is up, moving the cursor between two widgets that both
have tooltips will leave the tooltip on screen without delays.
We need to call waitpid until no more waitable children are available.
This is necessary because SIGCHLD signals may coalesce into one when
multiple children terminate almost simultaneously.
Also, switch to EventLoop's asynchronous signal handling mechanism,
which allows more complex operations in the signal handler.
Application::show_tooltip() now keeps track of the application's active
tooltip source widget so it can be updated while being shown when the
same widget updates its tooltip label.
Application::hide_tooltip() will unset the tooltip source widget,
respectively.
This is pretty useful for the ResourceGraph applet's tooltips!
Also re-use the Application::TooltipWindow's rect position in its
set_tooltip() method to avoid flickering from the window temporarily
being moved to 100, 100 and the position adjusted moments later.
During app teardown, the Application object may be destroyed before
something else, and so having Application::the() return a reference was
obscuring the truth about its lifetime.
This patch makes the API more honest by returning a pointer. While
this makes call sites look a bit more sketchy, do note that the global
Application pointer only becomes null during app teardown.
