Mouse: guaranteed down/drag/up order, hover, canvas leave detection

[Auroriax]

A number of options:

• mouse_up is also triggered when the mouse leaves the canvas and the drag ends. Player needs to click before input is registered again.
• mouse_up is triggered when the mouse goes up outside of the canvas, on the currently hovered tile.
• New prelude flag mouse_left_canvas so games can decide for themselves what to do when the mouse leaves the canvas.

Hover should probably be straightforward to implement and explain.

[Auroriax]

(If there are multiple events triggered, they're resolved in this order)

mouse_up (L/R) - Triggered when button is released (inside or outside canvas, when outside canvas on the last hovered tile) or other mouse button press triggers.

mouse_down - Mouse click INSIDE canvas

mouse_hover - When mouse moves to a different tile INSIDE canvas. ONLY when no other buttons are held or released this turn. Doesn't work on mobile.

mouse_focus - Cursor moved into a different tile tile INSIDE canvas. Similar to mouse_hover except that it doesn't matter if the mouse is currently dragging (triggers for both L/R buttons), or not dragging at all. Only works on mobile when the mouse is down.

mouse_drag (L/R) - Only if the respective cursor is down, INSIDE or OUTSIDE (along border) different tile on the canvas, if there's more than one tile between last and current drag position, automatically trigger movement for each tile.

TODO:

• right mouse button (inside canvas) press ends left button press (with mouse_up) and vice verca
• mouse_up outside of canvas triggers end of press (with mouse_up), equivalent for right mouse button
• implementation of hover and focus
• ensure that events trigger in the correct order

click -> onlyTriggerWhenCursorIsInsideCanvas AlwaysAllow, OnlyInsideCanvas, ResolveAsPath, drag / click / release

[Auroriax]

The core problem is that mouse controls are inconsistent. Ideally I'd like there to be a guaranteed press/drag/release order, but in reality there are a lot of edge cases (both mouse buttons pressed, held mouse moving onto canvas, using CTRL to get right click behavior, etc). As for leaving the canvas, there should probably be a prelude flag so that the old behavior is still the default one, so that old games don't break.