Color binding doesn't support alpha for hex strings missing an alpha portion

[rcoopr]

When adding a binding with an initial value of a hex string with 3 or 6 digits (no alpha portion), the controller does not add an alpha slider.

const PARAMS = {
  tint: '#ff0',
};

pane.addBinding(PARAMS, 'tint', {
  view: 'color',
  color: { alpha: true },
});

I would expect declaring { alpha: true } to always add a supporting alpha slider. As a workaround, you can add the alpha portion to the hex string.

input	has alpha slider
'#fff'	❌
'#ffffff'	❌
'#fffc'	✅
'#ffffffcc'	✅
0xfff	✅
0xffffff	✅

[kitschpatrol]

I was initially confused about this as well, but the { alpha: true } option only applies to how number values are parsed into colors, not string values.

(See how options / input params are processed for numbers vs for strings.)

Similarly, the {type: 'float' | 'int'} option only applies to object color values.

It's kind of subtle, but this is consistent with how these options are explained and demonstrated in the docs.

[rcoopr]

I agree it's consistent, but it's very easy to think that the string input with alpha: true was just left out of the docs, because if you included every variation then nobody is going to read the 86 page long docs.

I see that it's not a bug. I think it's not very useful/confusing to have a specific flag to include alpha but not have it work in some scenarios.

[kitschpatrol]

Yeah for sure — or some kind of generic typing approach that would restrict the available options based on the type of the bound value might help.

I'm working on a Tweakpane plugin to expand color handling by using the ColorJS library to back the internal color representation. This will bring support for CSS 4 color strings / more modern syntax, along with support for additional object / tuple param types. Hoping that can help with more demanding color use cases. Should be released in a week or two.

(Update: An early version of the plugin is available here: https://github.com/kitschpatrol/tweakpane-plugin-color-plus)

[cocopon]

Basically, Tweakpane respects a bound value. I assume that parameters with initial values like '#ff0' might not support alpha.

Users need to specify the alpha option explicitly if the pane cannot determine wheather the parameter has an alpha field. For example, 0xff0055 (in decimal: 16711765) can be interpreted as either rgb(0xff, 0x00, 0x55) or rgba(0x00, 0xff, 0x00, 0x55 / 0xff).