Implement mouse and monitor functionality for X11 & Mac OS

[drmfinlay]

Re: #8.

This PR implements mouse support for Linux and Mac OS via pynput.

I've moved all internal mouse event classes, flags and functions into modules under a new dragonfly/actions/mouse sub-package, similar to the keyboard sub-package. Windows functionality should be completely unaffected by these changes. From my testing, it seems to work just as it did before.

Mouse button and scroll events all work in X11. pynput doesn't seem to support scrolling or the "four"/"five" buttons on Mac OS. The "left", "right" and "middle" buttons seem to work properly though.

I won't merge this just yet because I want to get the Monitor class working on Linux so that relative mouse movements work correctly.

Mouse movements do not yet work properly on Mac OS because we don't have a Window class for that platform. That can wait for another day because I'm not very familiar with the Mac OS APIs.

[drmfinlay]

I've moved monitor code into some new modules, added boilerplate code for X11Monitor, removed mocking, adjusted imports and verified that the old Windows Monitor class still works perfectly (tested with two virtual monitors on Windows 7).

All I should have to do now is parse output from xrandr to get the info for X11. I think identifying connected monitors via the port ID should be good enough. For example, xrandr is showing my two monitors with input ports HDMI-1 and DP-1.

The monitors list will be updated whenever the rectangle is accessed. This is kind of hacky, but it works fine on Windows and xrandr seems to run quick enough that I doubt it will cause any noticeable latency.

[drmfinlay]

Getting the list of monitors seems to be pretty easy with AppKit on Mac OS: https://stackoverflow.com/questions/3129322/how-do-i-get-monitor-resolution-in-python/3129567#3129567
So I'll add a Monitor class for Mac OS too while I'm at it.

NSScreen.screens() doesn't update on monitor changes though. Not sure why.

[drmfinlay]

Monitor classes for Mac OS and X11 are now implemented:

• The Mac OS class requires the pyobjc package. I've added that to the dependencies for Mac OS. It can take a while to install.
• The X11 monitor class shells out to xrandr, which we should be able to rely on.

Like the Windows class, both of these implementations put the primary monitor first on the list. This affects where the mouse will move when using absolute movements (e.g. Mouse("[0, 0]")).

The monitors list currently gets updated, but only if a monitor's rectangle is retrieved, which is pretty hacky (I take full blame for that). A better way would be to change monitors into an object that acts like a list and updates when accessed. Caching updates for a few seconds should make that efficient. I'll implement that before merging.

[drmfinlay]

This is ready to be merged now. The monitors list is now an instance of a new MonitorList class. MonitorList does what I described above except for the caching, which doesn't really seem necessary. List updates can be avoided by taking a copy of the list: list(monitors).

There are two new class methods:

• get_all_monitors(cls) — Gets a list of all connected monitors. Replaces update_monitors_list().
• get_monitor(cls, handle, rectangle) — Gets a new or existing Monitor object depending on the handle. Updates the rectangle if reusing an object.

These are based on similar methods in Dragonfly's Window classes and have greatly simplified platform-specific code.

A FakeMonitor class has also been added to be consistent with the Window classes, rather than just using the base class.