By default the value of a scale widget is changed either by dragging the slider or by left-clicking in the trough. The increment by which the left-click changes is the same as the resolution, by default one unit. You can increase the increment by which a click moves by increasing the resolution value (which decreases the resolution in the normal sense). However, sometimes it is convenient to have a finer resolution available while also being able to move in larger increments. A solution is to bind to <B3>, which is by default unbound, a larger movement. This procedure moves by the specified multiplier k times the resolution of the scale.
proc ScaleMoveBigIncrement {w k x y} {
set part [$w identify $x $y]
switch -exact -- $part {
trough1 {
set dir -1;
}
trough2 {
set dir 1;
}
default {
return
}
}
set Resolution [$w cget -resolution]
set CurrentValue [$w get]
set Delta [expr $dir * $k * $Resolution]
$w set [expr $CurrentValue + $Delta]
}The coordinates x and y are supplied by Tk when the binding is triggered. w and k are, from the point of view of the individual binding, constants. They represent the scale widget and the desired resolution multiplier. You supply them when you create the bindng. A typical binding might look like this:
bind .play.vol <<B3>> {ScaleMoveBigIncrement .play.vol 5 %x %y}Of course you can bind to some other event if you wish to.
I think here is an unwanted behaviour of the scale widget! I want to use a scale to define values from 3 to 13 in increments of 2. So I define the scale like this:
pack [scale .s -orient hor] -fill x .s configure -from 3 -to 15 .s configure -tick 2 -resolution 2
What I get is a scale changing values from 4 to 14 in increments of 4. This is not what I expected. The reason is the -resolution option which causes the scale to change the -from value to a multiple of the resolution. Any comments? Is this a tk bug or can I do it another way?
WJP I would call this a bug since the observed behavior is not in agreement with the documentation and since the desired behavior is perfectly reasonable.