setAttribute for strokeOpacity

[Wigand Rathmann]

Hello,

If I try to change the strokeOpacity of a line, it does not work usging line.setAttribute('strokeOpacity:0.1') 

but using 

line.visProp.strokeopacity=0.1;

The fiddle at setAttribute Examples demonstrates the behavior. 

To change the attribute strokeWidth by setAttribute works fine.

Regards,

Wigand

[ampwi...@gmail.com]

Hey Wigand! So I saw a couple things,  but you can look at this one here:

https://jsfiddle.net/kgtenzpd/

Which is based upon yours. The few changes:

• When setting up the line you can just equate the strokeOpacity to the slider value. No listeners needed!
• But if you wanted to add a listener you can. 
• The function of changeOpac that runs the setAttribute.. the parameter you pass is an object, like {strokeColor: JXG.palette.blue} so it needs to have the curly braces around the parameter parts. I would avoid creating it using text, just update the value you want to changed

Hope that helps!

-Colin

[Alfred Wassermann]

Oops, this is a missing feature! 

A quick workaround in Wigand's example would be to set

   linetest.setAttribute({strokeOpacity: slider.Value()});

instead of

    let txt = 'strokeopacity: ' + slider.Value().toFixed(1);
    linetest.setAttribute(txt);

The latter approach fails, because at the time being JSXGraph does not cast

the received value of strokeOpacity - which is a string - to floating point. That is,

in an expression like 

    el.setAttribute('key:value');

the type of value is always a string. 

In contrast, in

    el.setAttribute({key:value});

value keeps its type.

We have to check if this can be repaired without side effects.

Best wishes,

Alfred

[Wigand Rathmann]

Hello,

Thanks for the help! I used this to update a legend, where I need to change the opacity.
May be, this is a bit sophisticated, and it is possible to pass list of opacities to the legend object.

This is the result: Contour lines in 3d https://jsfiddle.net/WigandR/re9jg1wa/

A legend containing the levels of a function.

Best,

Wigand

[Alfred Wassermann]

Dear Wigand,

your contour line example is very tasteful!

One small problem remains to be solved: if the sliders are changed, new legend elements are created above the old ones.

Best wishes,

Alfred

[Wigand Rathmann]

Dear Alfred,

Right! I simply forgot to save the fix. Now that works too.

Best wishes,
Wigand