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 784x18
        RenderText {TEXT} at (0,0) size 21x18
          text run at (0,0) width 21: "test"
      RenderBlock {DIV} at (0,18) size 784x18
        RenderText {TEXT} at (0,0) size 8x18
          text run at (0,0) width 8: "x"
selection is CARET:
start:      position 1 of child 1 {TEXT} of child 2 {DIV} of root {BODY}
upstream:   position 1 of child 1 {TEXT} of child 2 {DIV} of root {BODY}
downstream: position 1 of child 1 {TEXT} of child 2 {DIV} of root {BODY}