obeying the sheet protocol

• To: westy@freya.cs.umass.edu, clim@BBN.COM
• Subject: obeying the sheet protocol
• From: Scott McKay <swm@lyra.mystech.com>
• Date: Thu, 20 Jan 1994 10:02-0500
• In-Reply-To: <9401192213.AA08388@earhart.cs.umass.edu>

    Date: Wed, 19 Jan 1994 17:13 EST
    From: "David L. Westbrook" <westy%earhart@cs.umass.edu>


    CLIM 2.0
    Lispworks 3.2b and Allegro 4.2

    When I execute this code:

    (when (sheetp (frame-top-level-sheet *application-frame*))
      (dolist (kid (sheet-children window))
       ...))

SHEET-CHILDREN is not actually a hard-and-fast part of the sheet
protocol.  It's part of what was called the "sheet parent protocol" in
Silica.  Even if SHEET-CHILDREN were part of the sheet protocol, this
code would still not be correct since it assumes that all sheets
implement SHEET-CHILDREN using a list.

There is a function called MAP-OVER-SHEETS that maps over all of the
descendent sheets of a sheet.  There is no function that maps over just
the children ("direct descendents") of a sheet, probably because we
didn't need it ourselves and forgot to implement it.

    I get errors similar to this:

    Error: No applicable methods for #<STANDARD-GENERIC-FUNCTION SHEET-CHILDREN 10A4F9B0>
	   with args (#<SCROLL-BAR-PANE :VERTICAL 100A3368>)

    Is there some other way to insure that an object obeys the sheet protocol?

    David L. Westbrook
    westy@cs.umass.edu
  

• obeying the sheet protocol
• From: "David L. Westbrook" <westy%earhart@cs.umass.edu>

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