This gives us flexibility to add others hints to control keyboard grab behavior
without having to touch all of the backends. It also allows us to possibly
expose keyboard grab separately from mouse grab for applications that want to
manage those independently.
First: disable d'n'd events by default; most apps don't need these at all, and
if an app doesn't explicitly handle these, each drop on the window will cause
a memory leak if the events are enabled. This follows the guidelines we have
for SDL_TEXTINPUT events already.
Second: when events are enabled or disabled, signal the video layer, as it
might be able to inform the OS, causing UI changes or optimizations (for
example, dropping a file icon on a Cocoa app that isn't accepting drops will
cause macOS to show a rejection animation instead of the drop operation just
vanishing into the ether, X11 might show a different cursor when dragging
onto an accepting window, etc).
Third: fill in the drop event details in the test library and enable the
events in testwm.c for making sure this all works as expected.
- Cache the _NET_FRAME_EXTENTS data locally, so we don't have to query
the X server for them (instead, we update our cached data when PropertyNotify
events alert us to a change).
- Use our cached extents for X11_GetWindowBordersSize(), so it's a fast call.
- Window position was meant to refer to the client area, not the window
decorations, so adjust appropriately when getting/setting the position.
This is currently implemented for X11, Cocoa, Windows, and DirectFB.
This patch is based on work in Unreal Engine 4's fork of SDL,
compliments of Epic Games.
The internal function SDL_EGL_LoadLibrary() did not delete and remove a mostly
uninitialized data structure if loading the library first failed. A later try to
use EGL then skipped initialization and assumed it was previously successful
because the data structure now already existed. This led to at least one crash
in the internal function SDL_EGL_ChooseConfig() because a NULL pointer was
dereferenced to make a call to eglBindAPI().
