layer at (0,0) size 800x600
  RenderCanvas at (0,0) size 800x600
layer at (0,0) size 800x600
  RenderBlock {HTML} at (0,0) size 800x600
    RenderBody {BODY} at (8,8) size 784x584
      RenderBlock {DIV} at (0,0) size 784x56 [border: (2px solid #FF0000)]
        RenderInline {SPAN} at (0,0) size 14x28
          RenderText {TEXT} at (14,14) size 14x28
            text run at (14,14) width 14: "f "
selection is CARET:
start:      position 2 of child 1 {TEXT} of child 2 {SPAN} of root {DIV}
upstream:   position 2 of child 1 {TEXT} of child 2 {SPAN} of root {DIV}
downstream: position 2 of child 1 {TEXT} of child 2 {SPAN} of root {DIV}