[Tcl-bugs] [ tktoolkit-Bugs-842952 ] scrollbar dragging too slow (absolute when should be rel.)

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Bugs item #842952, was opened at 2003-11-16 01:09
Message generated for change (Tracker Item Submitted) made by Item Submitter
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=112997&aid=842952&group_id=12997

Category: 16. [scrollbar]
Group: develop: 8.5a0
Status: Open
Resolution: None
Priority: 5
Submitted By: Vince Darley (vincentdarley)
Assigned to: Jim Ingham (wolfsuit)
Summary: scrollbar dragging too slow (absolute when should be rel.)

Initial Comment:
When dragging the TkAqua scrollbar, the new scrollbar
position is calculated based upon the mouse's absolute
position within the scrollbar-control.

This is not how scrollbars should work, however.  The
position should be calculated as if the user were
actually dragging the bar physically with the mouse --
i.e. a pixel offset should be calculated of the current
mouse position relative to the original mouse-click
position, and that pixel offset should then be
reflected onto the scrollbar's coordinate system and
applied directly.  Then a range-check should be made to
ensure the value remains within [0,1.0]

Furthermore, the moment the mouse strays a pixel
outside the scrollbar control, the scrollbar position
is reset!!  This is totally against the HIG. In fact
the way Aqua works is to allow the mouse to be anywhere
on screen at all, and still maniplate the scrollbar as
long as the button is still held down (WinXP is
slightly different and provides about an inch of leeway
around the control).

The first of these problems is quite clear, here:

                if (scrollPtr->vertical == true) {
                    newFirstFraction =  (1.0 -
thumbWidth) *
                        ((double) (currentPoint.v -
trackBarPin) / trackBarSize);
                } else {
                    newFirstFraction =  (1.0 -
thumbWidth) *
                        ((double) (currentPoint.h -
trackBarPin) / trackBarSize);
                }

But I'm not really knowledgeable enough to fix it.


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