Light ImGUI GUI Style Themes Should Affet Default View Background Color Too?

[geringsj]

When setting a light UI theme, View backgrounds should also be affected? How could we make one single "view default bg color" work, which either the user or the UI can configure? How would this interact with project files which bring an explicit background color value for each view with them?

[moritz-h]

Idea:
Use a global theme color table. Define an enum of around 7-10 theme entries (quick idea: "background", "primary", "secondary", "highlight", "selection", "text", "interface/UI") and store a global theme color for each entry. A few presets for all colors could maybe be predefined, matching the imgui style bright or dark.

For access use a ThemedColorParam. UI of this param has a combobox with the enum entries. I.e. the view can then use this ThemeColorParam for the background and initialize it with ThemeColor::Background.
The color param only stores the enum value, not an actually color, just look it up in the global table when using getColor(). Therefore no event handling for changes is needed.
Further an "custom" option would be great in the combobox, to basically force the ThemedColorParam to be an classical one with fully custom color override.

(maybe we also do not really need a new ThemedColorParam and can add this kind of functionality to the regular ColorParam instead)