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Both the TextArea gadget and ScrollList were outputting an unhelpful white rectangle and mysterious black rectangle when asked to plot the gadget prototype (eg. in the gadget palette in ResEd). The black rectangle turned out to represent a scroll bar, though it was the wrong width.
Changed to plot a 2D scrollbar (ala RISC OS 2) then overlay a virtual icon with the name of the gadget type.
main.c:
Relocate helper functions into glib.
Return 'Bad SWI' for unknown subreasons.
glib.c/glib3.c:
Remove various unused functions.
Added new function to plot a grey scrollbar from nested rectangles.
TextArea.c:
Add a vertical, or horixontal, or both, scrollbar plus the label "TextArea".
ScrollList.c:
Add a vertical scrollbar plus the label "ScrollList".

Requires Common-0_25 for the colour defines. Tested in !ResEd in various eigenfactor modes.

Version 0.40. Tagged as 'Gadgets-0_40'