[Tcl-bugs] [ tktoolkit-Bugs-833606 ] mousewheel binding incorrect

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Bugs item #833606, was opened at 2003-10-31 13:06
Message generated for change (Comment added) made by vincentdarley
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Category: 18. [text]
Group: obsolete: 8.4.4
Status: Open
Resolution: None
Priority: 8
Submitted By: Vince Darley (vincentdarley)
Assigned to: Jeffrey Hobbs (hobbs)
Summary: mousewheel binding incorrect

Initial Comment:
The text.tcl binding:

bind Text <MouseWheel> {
    %W yview scroll [expr {- (%D / 120) * 4}] units
}

isn't right.  If '%D' is a smallish positive number
(e.g. 100), then the whole expression is rounded down
to zero and no scrolling takes place.  This is
different to the case where %D is a smallish negative
number, where the expression will always be rounded
down to -1 * 4, and scrolling will take place.

I believe we should use something like:

if {%D < 0} {
    %W yview scroll [expr {- (%D / 120) * 4}] units
} else {
    %W yview scroll [expr { (-%D / 120) * 4}] units
}

On a separate note, I believe the magnitudes of %D
between the Windows and MacOS X implementations of this
binding are totally different.  The documentation says
the smallest value on Windows is 120.  On MacOS X it
has a smallest value of 1, I believe.  This suggests
something like this would be correct:

	if {[tk windowingsystem] eq "aqua"} {
	    bind Alpha <MouseWheel> {
		%W yview scroll [expr {-%D * 4}] units
	    }
	} else {
	    bind Alpha <MouseWheel> {
		if {%D < 0} {
		    %W yview scroll [expr {- (%D / 120) * 4}] units
		} else {
		    %W yview scroll [expr { (-%D / 120) * 4}] units
		}
	    }
	}





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>Comment By: Vince Darley (vincentdarley)
Date: 2003-12-05 10:40

Message:
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See tkMacOSXMouseEvent.c in cvs HEAD, e.g.:
GenerateMouseWheelEvent


----------------------------------------------------------------------

Comment By: Jeffrey Hobbs (hobbs)
Date: 2003-11-27 01:51

Message:
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user_id=72656

I don't see the MouseWheel event triggering at all on aqua.  
Is there some extra magic there (or more recent than 8.4.4 
support for it)?

----------------------------------------------------------------------

Comment By: Jeffrey Hobbs (hobbs)
Date: 2003-11-11 18:39

Message:
Logged In: YES 
user_id=72656

This will need specific testing across platforms - delay to 8.5 
alpha release.

----------------------------------------------------------------------

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