tboxlibs wimp_update_window wanting wrong struct?

I’ve just been reading up about Wimp_UpdateWindow and found an oddity when trying to test it.

wimp.h (Export.APCS-32.Lib.tboxlibs.h.wimp) defines a struct called WimpRedrawWindowBlock, with a comment that it’s for Wimp_RedrawWindow, and another struct called WimpUpdateWindowBlock, with a comment that it’s for Wimp_UpdateWindow. Both of them set up their blocks appropriately (PRM pages 3-126 and 3-128 respectively). No problems so far.

On the other hand, wimplib.h (Export.APCS-32.Lib.tboxlibs.h.wimplib) has two lines of interest.

_kernel_oserror *wimp_redraw_window     (WimpRedrawWindowBlock *block, int *more);
_kernel_oserror *wimp_update_window     (WimpRedrawWindowBlock *block, int *more);

Shouldn’t wimp_update_window expect a WimpUpdateWindowBlock? Can someone please double-check that I’m not just going crazy? :)

To be fair, using a WimpRedrawWindowBlock does work (it just ignores its additional variables), but should this be fixed?

Yes it should be WimpRedrawWindowBlock WimpUpdateWindowBlock which the underlying swi will use regardless of the name of the structure passed to wimp_redraw_window.

Edit: Typo

Edit: Typo

Hah, you had me totally confused there at first! I decided to leave it and see whether it made any more sense when I came back… lo and behold :)

Just to further complicate things, the latest Acorn C/C++ manual says that wimp_update_window expects a WimpRedrawWindowBlock. If tboxlibs is changed then the documentation will become wrong!

WimpRedrawWindowBlock is correct. The window_handle and visible_area are used on entry to wimp_update_window and wimp_update window returns with the WimpRedrawWindow block filled in with WimpRedrawWindoblock information. After updating the window you call wimp_get_rectangle with the WimpRedrawWindow block like this:

int more;
WimpRedrawWindowBlock blk;
blk.window_handle = whatever;
blk.visible_area = window area to update;
wimp_update_window(&blk, &more)
while (more != 0)
{
    ...update window rectangle using values returned in blk
    wimp_get_rectangle(&blk, &more);
}

Aha! Yes, that would indeed explain it :)

So the only thing that’s actually wrong is the comment in wimp.h that says that WimpUpdateWindowBlock is for Wimp_UpdateWindow… and that may be valid in some cases too.

Thanks for investigating :)

I suppose if you were that way inclined you could use WimpUpdateWindowBlock to make what you are doing more readable/understandable like this:

WimpRedrawWindowBlock blk;
WimpUpdateWindowBlock* ublk = (void*)&blk;
ublk->window_handle = whatever;
ublk->update_area.xmin = 0;
ublk->update_area.ymin = 0;
ublk->update_area.xmax = 512;
ublk->update_area.ymax = 512;
wimp_update_window(&blk, &more);

then when you look at the code again some time later you can see you are filling in WimpUpdateWindowBlock details.