win32 (fullscreen) borderless window overlapping taskbar

Raymond Chen explained how to switch in and out of full screen mode rather simply by changing the window style with SetWindowLong(Ptr), using SetWindowPlacement to resize the window, and SetWindowPos to make sure the frame redraws.

The Task Bar detects when a window is trying to be full screen and automatically gets out of the way.

Use the SetWindowPos function to set your window TOPMOST. When you get a message saying you lost the focus, make it non-topmost again so the other window you switched to can appear.