M11: document the canvas show entry point

crates/ui-egui/src/canvas.rs

@@ -190,6 +190,7 @@ pub fn fit(app: &mut VectorcraftApp, how: &str) {
     v.zoom = zoom;
 }
 
+/// Paint the document canvas, complete or cached artwork, navigation and tool overlays.
 pub fn show(app: &mut VectorcraftApp, ui: &mut Ui) {
     let t = Tokens::get(ui.ctx());
     let full = ui.available_rect_before_wrap();