STR #702: Fl_Scrollbar increments incorrectly in specific situation

STR #702

Application:	FLTK Library
Status:	5 - New
Priority:	2 - Low, e.g. a documentation error or undocumented side-effect
Scope:	3 - Applies to all machines and operating systems
Subsystem:	Core Library
Summary:	Fl_Scrollbar increments incorrectly in specific situation
Version:	1.4-feature
Created By:	andhow.gmail
Assigned To:	matt
Fix Version:	Unassigned
Update Notification:	Receive EMails Don't Receive EMails

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#1	andhow.gmail 20:16 Jan 14, 2005

The undesirable behavior is that the scrollbar increments .value() by increasing values (as opposed to a smooth linear increment) which makes the scrollbar appear to scroll too fast. It only does it in a specific situation though: while in the middle of dragging the scroll bar (before releasing the mouse), calling the Fl_Scrollbar::value(int,int,int,int) function using a changing "min" (parameter 3) number. While not letting go of the scrollbar, the increment added to the .value() will increase until the scroll bar is released. Now if dragged again, the increment will be at its normal value, and increase as it is dragged more. For this reason, I believe that some internal value used by the Fl_Scrollbar is not being set when value() is called during a drag. Due to the way scrollbars are usually used, this doesn't come up often, but I have a program where it can be observed very clearly. I can provide the .exe and source if needed.

#2	mike 11:16 Feb 05, 2005

I don't see any way for us to detect or "fix" this behavior, so I am closing this report out. The widget is just not designed to handle this behavior or scenario. You can propose a change to this for FLTK 2.0, but it will not be fixed or changed in 1.1.x.

#3	greg.ercolano 20:05 Nov 01, 2017

This was never actually closed, and since I'm working on scrollbar related stuff I noticed this STR. Matt owns it and someone bumped it to 1.4, so apparently it's thought to still be "active". I'm not sure I understand the problem really; I've read comment #1 a few times, esp. that first sentence, and just don't get it. Can this be replicated with the test/valuator demo? Or include a simple compilable code example (code, no .exe's).