The focus flag follows the main window's WM_SETFOCUS and WM_KILLFOCUS.
Across a video driver restart that keeps the window - loading content,
a change of geometry - nothing is sent to the window, and a flag left
saying unfocused stayed so: every key and mouse button was dropped
until an Alt-Tab sent the window its focus again.
When the flag says unfocused, the poll now asks whether the main window
is the foreground window and goes by that for its frame. The flag
itself is still written only by the window procedure, so a loss it is
about to store is not overwritten. Nothing is asked while the window
has the focus.
winraw_poll_test checks that a stale flag with the main window in
front still reads the keys, and that a main window not in front does
not.
LibretroAdmin
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