Fix documentation for GtkCanvas: reveal doesn't actually redraw the…

… backing store.

docs/src/manual/canvas.md

@@ -24,7 +24,7 @@ win = GtkWindow(c, "Canvas")
 end
 ```
 This `draw` function will be called each time the window is resized or otherwise needs to refresh its display.
-If you need to force a redraw of the canvas, you can call `reveal` on the canvas widget.
+If you need to force a redraw of the canvas, you can call `draw(c)`.
 
 ![canvas](figures/canvas.png)
 
@@ -86,7 +86,7 @@ w = GtkWindow(canvas,"CairoMakie example")
 
 @guarded draw(canvas) do widget
     global f, ax, p = lines(1:10)
-    CairoMakie.autolimits!(ax) 	
+    CairoMakie.autolimits!(ax)
     screen = CairoMakie.Screen(f.scene, config, Gtk4.cairo_surface(canvas))
     CairoMakie.resize!(f.scene, Gtk4.width(widget), Gtk4.height(widget))
     CairoMakie.cairo_draw(screen, f.scene)

src/cairo.jl

@@ -79,6 +79,13 @@ mutable struct GtkCanvas <: GtkDrawingArea # NOT a GType
 end
 const GtkCanvasLeaf = GtkCanvas
 
+"""
+    resize(config::Function, widget::GtkCanvas)
+
+Set a function `config` to be called whenever the `GtkCanvas`'s size is changed and
+trigger a redraw. The `config` function should have a single argument, the `GtkCanvas`,
+from which the `CairoSurface` can be retrieved using [`getgc`](@ref).
+"""
 function resize(config::Function, widget::GtkCanvas)
     widget.resize = config
     if G_.get_realized(widget) && widget.is_sized
@@ -102,6 +109,11 @@ function draw(redraw::Function, widget::GtkCanvas)
     nothing
 end
 
+"""
+    draw(widget::GtkCanvas)
+
+Triggers a redraw of the canvas using a previously set `redraw` function.
+"""
 function draw(widget::GtkCanvas)
     if !isdefined(widget, :back)
         #@warn("backing store not defined")