In Win32 programming, what is the difference between a window's parent and a window's owner? I thought I had it figured out, then I came across this code:
SetWindowLong(handle, GWL_HWNDPARENT, foo);
This actually sets the window's owner, not the parent - despite the GWL_HWNDPARENT being used. Are the terms parent/owner interchangeable, or is there actually a difference?
Owner is the Window* responsible for a control or dialog (for example, responsible for creating/destroying the window).
Parent is the next-senior window* to a control or dialog in the window chain, but isn't actually responsible for it (doesn't necessarily care about its lifecycle, etc). A window's parent can also be its owner.
*Window vs window: Window is an actual window displayed on the screen; window is any object with a HWND (includes buttons, panels, etc).
Ownership is a relationship between two top level windows while Parent is a relationship between a top level and a WS_CHILD, or a WS_CHILD and another WS_CHILD.
The parent of a button is the form it is on, while a message box is owned by the form that showed it.
Read this article from Microsoft Win32 Window Hierarchy and Styles to get a much clearer understanding of Ownership, Parenting, ZOrder, SetWindowLong, GetWindow and all the other nasty bits of the Win32 api for creating window relationships.