All properties should accept a function and return null should be interpreted as use the default if possible.

[lestcape]

As an example of what i think should be good to have, i will provide the next timeTable definition:

timeTable: {
    renderer: [
        {
            selector: function(object, ctx) {
                return ctx.gantt.displayMode === 'showTasks';
            },
            text: function(activity, ctx) {
                var textRef = config["displayModes"][ctx.gantt.displayMode]["text"];
                return getData(activity, textRef);
            },
            textOverflow: 'noDisplay',
            background: {
                palette: function(activity, ctx) {
                    return ['#5aa8f8', '#4178bc', '#8cd211', '#c8f08f', '#ba8ff7', '#a6266e', '#ff7832'];
                },
                getValue: function(activity, ctx) {
                    var textRef = config["displayModes"][ctx.gantt.displayMode]["text"];
                    return getData(activity, textRef);
                },
            },
        },
    ]
}

In the example, return null for a palette should be interpreted as "use the default palette" instead of display an error, because this allow us to decide dynamically to use the default palette. We have not way to said "use the default palette" from a function right now.

palette: function(activity, ctx) {
    return null
},

Also for compatibility reasons the next definition should be interpreted also as "use the default palette":

palette: null

The next definition should be good to be accepted as a valid one, but right now is not working:

background: function(activity, ctx) {
    return {
        palette: function(activity, ctx) {
            return ['#5aa8f8', '#4178bc', '#8cd211', '#c8f08f', '#ba8ff7', '#a6266e', '#ff7832'];
        },
        getValue: function(activity, ctx) {
            var textRef = config["displayModes"][ctx.gantt.displayMode]["text"];
            return getData(activity, textRef);
        },
    },
},

Allow that background can be a function can simplify in some cases the code.

[delhoume]

I agree it would be nice to have this implemented.