scroll-preserve-screen-position BROKEN when header line displayed

scroll-preserve-screen-position BROKEN when header line displayed

[Jens Lautenbacher]

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Hi all,

it seems that setting scroll-preserve-screen-position to t does not work
whenever a header line is displayed (e.g. Info mode, but also when using
the add-on elisp lib tabbar.el).

It manifests itself in moving the cursor one screen line down each
whenever page-up or page-down is pressed instead of having the cursor
stay fixed at current screen position. I tried to find the cause but
have not been able to locate it yet :-(

-- 
        jtl

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Re: scroll-preserve-screen-position BROKEN when header line displayed

[Richard Stallman]

This fixes it for me.  Do you get good results?

*** window.c	16 Oct 2004 01:47:10 -0400	1.480
--- window.c	31 Oct 2004 03:45:20 -0500	
***************
*** 4625,4641 ****
        w->force_start = Qt;
      }
  
    it.current_y = it.vpos = 0;
  
!   /* Preserve the screen position if we must.  */
    if (preserve_y >= 0)
      {
        move_it_to (&it, -1, -1, preserve_y, -1, MOVE_TO_Y);
        SET_PT_BOTH (IT_CHARPOS (it), IT_BYTEPOS (it));
      }
    else
      {
!       /* Move PT out of scroll margins.  */
        this_scroll_margin = max (0, scroll_margin);
        this_scroll_margin = min (this_scroll_margin, XFASTINT (w->total_lines) / 4);
        this_scroll_margin *= FRAME_LINE_HEIGHT (it.f);
--- 4625,4649 ----
        w->force_start = Qt;
      }
  
+   /* The rest of this function uses current_y in a nonstandard way,
+      not including the height of the header line if any.  */
    it.current_y = it.vpos = 0;
  
!   /* Preserve the screen position if we should.  */
    if (preserve_y >= 0)
      {
+       /* If we have a header line, take account of it.  */
+       if (WINDOW_WANTS_HEADER_LINE_P (w))
+ 	preserve_y -= CURRENT_HEADER_LINE_HEIGHT (w);
+ 
        move_it_to (&it, -1, -1, preserve_y, -1, MOVE_TO_Y);
        SET_PT_BOTH (IT_CHARPOS (it), IT_BYTEPOS (it));
      }
    else
      {
!       /* Move PT out of scroll margins.
! 	 This code wants current_y to be zero at the window start position
! 	 even if there is a header line.  */
        this_scroll_margin = max (0, scroll_margin);
        this_scroll_margin = min (this_scroll_margin, XFASTINT (w->total_lines) / 4);
        this_scroll_margin *= FRAME_LINE_HEIGHT (it.f);

Re: scroll-preserve-screen-position BROKEN when header line displayed

[Jens Lautenbacher]

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On Sun, 2004-10-31 at 04:42 -0500, Richard Stallman wrote:
> This fixes it for me.  Do you get good results?

yep, works like a charm. thanks a lot!

	jtl

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