In Documentation Wiki, refering to undocking/docking, what is the 'panel chrome'?

In a Slicer Documentation Wiki I find the term ‘panel chrome’ in relation to re-docking the Welcome window after undocking it, when I am trying to see about expanding the 3D view to fill the screen.

I experimentally clicked the ‘restore’ button in the ‘Welcome To Slicer’ window, and the Welcome window undocks, and “SlicerApp-real” is added to the previously blank title bar of that window, and at that point that window has only a close window ‘X’ control. It surprises me that there isn’t a control present to re-dock the Welcome window. As I google around trying to figure out how to get it re-docked (having only the close window ‘X’ control present), I found at the following:

“The panel may be undocked (by left-clicking & dragging the panel chrome or by selecting its undock icon; hidden by selecting the hide (X) icon, or have its display toggled by selecting View->Module Panel. The panel can be re-docked by double-clicking on its chrome.”

What is the ‘panel chrome’?

I’ve never seen that phrase/term before.

I discover that double-clicking on the title bar of the Welcome window will re-dock the window, but why not just retain the ‘restore’ control in the title bar and make it toggle undock/redock?

Window chrome refers to nonclient area of a window. I’ve updated the wiki page to use simpler terms - window title bar and frame.

Qt’s default behavior is to show only a close button on undocked widgets. I agree that it could be useful to add a “dock” button in its title bar. This is already tracked here:

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