Hello,
I am trying to create a slider that will increase in value as the slider handle is dragged down (or left). There doesn't appear to be any property I can set to do this, so I'm wondering if I need to go ahead and extend the Slider class to do this behavior or if there is an easier way?
Thanks,
Jason
#ifndef SLIDER_REVERSE_H
#define SLIDER_REVERSE_H
class Slider_reverse : public JUCE_NAMESPACE::Slider
{
public:
Slider_reverse (const String& componentName): JUCE_NAMESPACE::Slider(componentName) {};
~Slider_reverse() {};
double proportionOfLengthToValue (double proportion) { return JUCE_NAMESPACE::Slider::proportionOfLengthToValue(1.0f-proportion);};
double valueToProportionOfLength (double value) { return 1.0f-(JUCE_NAMESPACE::Slider::valueToProportionOfLength(value)); };
};
#endif // SLIDER_REVERSE_H
what about rotating the Slider by Pi using an AffineTransform around its centre?
The derived class worked perfectly. I didn't noticed those methods when I was looking at the Slider class.
J
Rotating will make things such as text to look different. One wouldn’t want the text rotated…
You could also implement a custom lookandfeel for the Slider in which you change the way it paints. Benefit is that you don’t need to use a derived class.
Do you know where and how to implement this to a slider parameter listener?
Editor vs Processor side?
I ended up just throwing it in a custom slider class, works like a dream!
Thanks,
I have a few sliders, well knobs, which I would like to have reverse behavior, meaning dragging left will increase value, and dragging right will decrease.
I already have a custom LookandFeel class with a ‘drawRotarySlider’ function.
So looking at your above example code, which I can easily insert into my class or even function, but how do I actually specify that a particular knob/slider should behave in reverse?
As a side note, I am actually quite surprised that there seems not to be a JUCE reverse value option!?!
Since the NormalisableRange supports now lambdas for proportionForValue and vice versa, you can achieve that without overriding.
And if this is in a plugin, it’s best to specify that in the AudioProcessorParameter’s NormalisableRange, that you supply upon its creation. This will be propagated to the Slider via SliderAttachment to give a consistent behaviour in host views (automation/control surfaces) and the slider in your UI.
That wasn’t possible 2014, when this thread was created…
Ok great! Do you know of any online example of implementing this?
This is the constructor NormalisableRange.
auto range = NormalisableRange<double>(0.0, 100.0,
[] (auto rangeStart, auto rangeEnd, auto normalised)
{ return rangeStart + (1.0 - normalised) * (rangeEnd - rangeStart); },
[] (auto rangeStart, auto rangeEnd, auto value)
{ return 1.0 - (value - rangeStart) / (rangeEnd - rangeStart); },
[] (auto rangeStart, auto rangeEnd, auto value)
{ return roundToInt (value); });
slider.setNormalisableRange (range);
or use the range in the AudioParameterFloat constructor.
N.B. the AudioParameterFloat uses NormalisableRange<float>, vs. the Slider uses NormalisableRange<double>.
If I did it right, this slider should go from 100 to 0 in integer steps…
EDIT: actually much easier to use jmap:
auto range = NormalisableRange<double>(0.0, 100.0,
[] (auto rangeStart, auto rangeEnd, auto normalised)
{ return jmap (normalised, rangeEnd, rangeStart); },
[] (auto rangeStart, auto rangeEnd, auto value)
{ return jmap (value, rangeEnd, rangeStart, 0.0, 1.0); },
[] (auto rangeStart, auto rangeEnd, auto value)
{ return roundToInt (value); });
Thanks a bunch, I’ll try it out right away!
Still however, it seems to be that one should just be able to specify a “simple” reverse slider setting.
I thought to remember to set a negative step to achieve that, but I must have dreamed that… it will not pass the asserts…
Agreed, it is always a difficult trade off between user convenience and keep the API small…
Not my say luckily 
Your first example worked fine, but I had to setNumDecimalPlacesToDisplay(0), which I did not have to do before.
Now I’ll try your second solution.
Yep second example worked great too, still having to setNumDecimalPlacesToDisplay.
I had a look into the Slider code, the NormalisableRange has a member interval, that is used to figure out how many decimal places to display.
And I learned, that the snapToValue is optional, so you can simplify the example to
auto range = NormalisableRange<double>(0.0, 100.0,
[] (auto rangeStart, auto rangeEnd, auto normalised)
{ return jmap (normalised, rangeEnd, rangeStart); },
[] (auto rangeStart, auto rangeEnd, auto value)
{ return jmap (value, rangeEnd, rangeStart, 0.0, 1.0); });
range.interval = 1;
slider.setNormalisableRange (range);
That will display no numbers behind the decimal point.
