AskMinMax adds 3 to both minimum dimensions and 16 to both default
dimensions, assigns both maxima MUI_MAXMAX and returns zero. Draw calls
Area, handles full/update flags, fills the content rectangle and returns
zero. A local -1 pen draws a shadow/background pattern. A referenced pen
is read as an index; Get status is ignored with index initially zero,
and a Pendisplay getter's 65535 failure value does not select the local
-1 pattern path. Use references with compatible screen/color-map
resources.
DragQuery refuses self and accepts a successful Pendisplay_Spec getter,
or an Imagedisplay_Spec string longer than two bytes starting with "2:".
DragDrop prefers Pendisplay_Spec, otherwise passes the image string
after its two-byte prefix to the Spec setter. It returns zero and does
not repeat the query checks. The setter copies a complete MUI_PenSpec,
so the source must provide 32 readable bytes at that address, not just a
short NUL-terminated pen string.