gui: Check if a node is on the current canvas when modifying its appearance.
gui: Check if a node is on the current canvas when modifying its appearance.

This also fixes a bug where a node's name would not be correctly
updated if it was on the current canvas.

Adapted from a patch by Yueli Yang.
coreemu/core,hakiri/core,hakiri/core,coreemu/core,hakiri/core,coreemu/core,coreemu/core