The `level.Canvas` is a widget that holds onto its Palette and Grid and
has interactions to allow scrolling and editing the grid using the
swatches available on the palette.
Thus all of the logic in the Editor Mode for drawing directly onto the
root SDL surface are now handled inside a level.Canvas instance.
The `level.Canvas` widget has the following properties:
* Like any widget it has an X,Y position and a width/height.
* It has a Scroll position to control which slice of its drawing will be
visible inside its bounding box.
* It supports levels having negative coordinates for their pixels. It
doesn't care. The default Scroll position is (0,0) at the top left
corner of the widget but you can scroll into the negatives and see the
negative pixels.
* Keyboard keys will scroll the viewport inside the canvas.
* The canvas draws only the pixels that are visible inside its bounding
box.
This feature will eventually pave the way toward:
* Doodads being dropped on top of your map, each Doodad being its own
Canvas widget.
* Using drawings as button icons for the user interface, as the Canvas
is a normal widget.
Implements the dev console in-game with various commands to start out
with.
Press the Enter key to show or hide the console. Commands supported:
new
Start a new map in Edit Mode.
save [filename.json]
Save the current map to disk. Filename is required unless you
have saved recently.
edit filename.json
Open a map from disk in Edit Mode.
play filename.json
Play a map from disk in Play Mode.
