[Feature Request] Change opacity/color in "Objects" subwindow. And some `show_object()` improvements

[garywill]

Feature request:

1. UI allow to change opacity/color of showed objects, in "Objects" subwindow
2. Support default opacity setting
3. Support automatically give different color to objects, in a pre-set color list.

Currently we usually need to write

show_object(xxx, options={'alpha': 0.5} )

for every object.

Having to write many options={'alpha': 0.5} is tedious.

I've tried this workaround:

import cadquery as cq

box1 = cq.Workplane() .rect(10, 10) .extrude(10)

box2 = box1.val().moved((20, 0, 0))

def show(obj):
    show_object(obj, options={'alpha': 0.5})

show(box1)
show(box2)

But resulting in only box2 is showed, due to have same name. show_object() used obj as object name,

[jmwright]

Re: 1 - The Objects subwindow had a color control at one point, but I took it out because it did not work right. When I tried to fix it, I ran into a chicken-and-egg problem with the color specified by show_object() Which one takes precedence? You can end up with a situation where your code and what is displayed in the 3D viewer are different. This seems like it could be confusing for users.

Re: 2 - Do you mean a user-configurable default opacity setting? The implicit default is fully opaque now.

Re: 3 - What happens if you have so many objects that you run out of colors in the list? Do you loop back through the list, duplicating colors? Do you use procedural color generation instead so that you cannot run out of colors?

[garywill]

Do you mean a user-configurable default opacity setting?

We can do two: Built-in default opacity value (for example 0.5). Also allow user to configure default opacity value.

Do you use procedural color generation instead so that you cannot run out of colors?

Although I'm not UI designer, my gut feeling: procedural color generation would generate visually uncomfortable colors. I think a human-designed preset color list would be better. We can allow user to define their own color list, too.

What happens if you have so many objects that you run out of colors in the list? Do you loop back through the list, duplicating colors?

Yes

The Objects subwindow had a color control at one point, but I took it out because ... chicken-and-egg problem

Both color and opacity can run into chicken-and-egg problem. This is how I view:
If user specify a property value, then, use specified value and disable that property's GUI control on that object.
If user not specify, set the property to auto value, and enable that property's GUI control on that object.

That's my suggestion. Expecting further chat and discussion.