[comp.windows.x] Position of the thumb on scrollbars

sanjay@mit-amt.MEDIA.MIT.EDU (Sanjay Manandhar) (02/22/90)

According to the documentation, one can place the thumb on arbitrary
position along the scrollbar. This is supposed to take a float between
0.0 and 1.0.

However, the best I can do is get the thumb at beginning of the bar.
I've tried placing the thumb midway (0.5), for instance, in R3 and R4.

XtSetArg(arg[7], XtNtop, 0.5);            # in R3
XtSetArg(arg[7], XtNtopOfThumb, 0.5);     # in R4

The R4 docs provide a portable way to do this, but that does not work
either. If someone has run into this problem, and found a fix, I'd
appreciate hearing it.

thanx,

sanjay

kit@EXPO.LCS.MIT.EDU (Chris D. Peterson) (02/23/90)

> However, the best I can do is get the thumb at beginning of the bar.
> I've tried placing the thumb midway (0.5), for instance, in R3 and R4.

> XtSetArg(arg[7], XtNtop, 0.5);            # in R3
> XtSetArg(arg[7], XtNtopOfThumb, 0.5);     # in R4

This will never work, since the 0.5 is truncated to 0 by the C compiler.

> The R4 docs provide a portable way to do this, but that does not work
> either. If someone has run into this problem, and found a fix, I'd
> appreciate hearing it.

That code works great for me, take a look at examples/Xaw/xscroll.c.  This
example program puts up a scrollbar with its thumb at .5, and works correctly on
all our machines.

						Chris D. Peterson     
						MIT X Consortium 

Net:	 kit@expo.lcs.mit.edu
Phone:   (617) 253 - 9608	
Address: MIT - Room NE43-213