[no subject]

[PGS@MIT-AI]

CC: (BUG LISPM) at MIT-AI
Hi, Richard:

I've found what causes the clipping of the vectors drawn by the window
version of draw-line when it is drawing on a pane. It seems to be an
incompatibility between the code for ":margins-for" in LISPM2; FRAME
35 and the code for ":draw-line" in LISPM2; WINDOW 177.

":margins-for" defines a pane's margins as the difference of its edges
and those of the frame it is in:

(defmethod (window-frame-class :margins-for) (pane &aux pane-edges)
    (cond ((memq pane panes)
	   (setq pane-edges (<- pane ':edges))
	   (list (- (first pane-edges) left)
		 (- (second pane-edges) top)
		 (- right (third pane-edges))
		 (- bottom (fourth pane-edges))))
	  (t (ferror nil "~S is not a pane of ~S" pane self))))

But ":draw-line", when it determines what arguments to give to
TV-DRAW-LINE-CLIPPED, subtracts the values given for the margins from
the corresponding edges of the window, not of the frame:

(DEFMETHOD (WINDOW-CLASS :DRAW-LINE) (XO YO X Y &OPTIONAL (TV-ALU TV-ALU-IOR))
  (LET ((MARGINS (<- SELF ':MARGINS)))
    (LET ((LLIM (+ LEFT (CAR MARGINS))) (TLIM (+ TOP (CADR MARGINS)))
	  (RLIM (- RIGHT (CADDR MARGINS))) (BLIM (- BOTTOM (CADDDR MARGINS))))
      (TV-DRAW-LINE-CLIPPED (+ XO LLIM) (+ YO TLIM) (+ X LLIM) (+ Y TLIM)
			    TV-ALU SCREEN LLIM TLIM RLIM BLIM))))

So the limits it ends up with are sort of overdone.


							Pat