Only redraw the canvas if something has changed.
Only redraw the canvas if something has changed.

Without this, leaving an Octo tab open can max out a CPU core. This
reduces CPU usage by 10-50x, depending on resolution and actual
framerate.

james0x0A/Octo,whoozle/Octo,JohnEarnest/Octo,JohnEarnest/Octo,whoozle/Octo,whoozle/Octo,whoozle/Octo,JohnEarnest/Octo,JohnEarnest/Octo,JohnEarnest/Octo,whoozle/Octo,james0x0A/Octo