This expands input events to represent sub-pixel mouse positions, devices responsible for generating events, and raw
device-oriented events. The X11 back end is refactored to make full use of the new expressiveness. Other backends have
had new functionality minimally stubbed out, save for the macos backend which already supports sub-pixel mouse
positions.
Making applications track modifier keys results in unnecessary work for
consumers, it's error prone, and it turns out to have unavoidable bugs.
For example, alt-tabbing with x11 results in the alt modifier state
getting stuck.
To resolve these problems, this patch adds a Mods value to the keyboard
input event.
Based on this patch: d287fa96e3
Depending on the platform and device, scroll deltas may either
be represented as pixel deltas specifying the amount
in pixels to scroll or they may be expressed in 'lines' or 'chunks'
for low resolution devices (eg. a traditional mouse wheel).
Pixel deltas are currently available on OS X. X11 currently
supports only integer line deltas, though pixel deltas
are available via XInput2. Windows supports fractional
line deltas.
Add a new api, window.set_cursor, for setting the cursor. The enum MouseCursor lists the possible cursors.
Only X11 is implemented. On OSX, Android, & Win32 the window.set_cursor function
either does nothing or calls the "unimplemented!" macro.
