Mail Archives: djgpp/1999/04/12/14:30:51
Jonathan Gross <jgross AT ort DOT org DOT il> asked:
> I am building an MS-DOS windowing system with DJGPP.
> I need a way to draw all windows without drawing them one on
> top of the other but only where needed.
> any help is very appreciated!
Well, the solution depends on your architecture. Here is more or less what
Turbo Vision does:
For each character of a window that will be drawed TVision checks in the list
of windows (that's Z axis sorted) if any other window overlaps, if no overlap
then the content of this window is used. To speed up the things Turbo Vision
does it with lines and uses a recursive methode to break the lines in
segments when other window overlap partially.
The mechanism is relative complex and to make it worst windows have shadows
;-). As the original algorithm was in assembler the Robert's adaptation is
just a mess. I have an implementation in C++ that does the work for one
character in the screen, I use it for other class called TViewPlus, but you
can see how the line optimization works in this example.
Basically the optimization looks if other object is over the line, it can
hide the whole line (not drawing) or: the left part or the right part or just
be in the middle, in any of these cases the routine is called recursivelly to
solve the part/s that can be hided by the next object. When you reach the top
off the list of objects the recursion ends and you start drawing.
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