More comment changes

canvas.go

@@ -5,7 +5,7 @@ import "image/draw"
 import "image/color"
 
 // Canvas is like Image but also requires Set and SetRGBA methods. This
-// interface can be easily satisfied using an image.RGBA struct.
+// interface can be easily satisfied using a BasicCanvas struct.
 type Canvas interface {
 	draw.Image
 	Buffer () (data []color.RGBA, stride int)

layout.go

@@ -20,6 +20,8 @@ type Layout interface {
 	Arrange (entries []LayoutEntry, width, height int)
 
 	// MinimumSize returns the minimum width and height that the layout
-	// needs to properly arrange the given slice of layout entries.
+	// needs to properly arrange the given slice of layout entries, given a
+	// "suqeeze" width so that the height can be determined for elements
+	// fulfilling the Expanding interface.
 	MinimumSize (entries []LayoutEntry) (width, height int)
 }