Fix extended scancode of 0 not being processed correctly #2417
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On Windows, keyboard events with an extended 0 Windows scancode are now processed by mapping the virtual-key code to a Windows scancode using the Win32 MapVirtualKey function. Some keyboard scancodes (in particular, ones used for some non-typical keys) are not mapped to corresponding Windows scancodes, and are instead mapped to an extended 0 Windows scancode, with the distinction being only in the virtual-key code. This causes GLFW to report a 256 GLFW scancode (0x00 | 0x100, 0x100 being the extended bit bitmask) for any of those keys, which causes API consumers to be unable to distinguish between them. There exists, however, a Win32 function MapVirtualKey that maps those virtual key-codes to proper Windows scancodes. GLFW even appears to use this workaround, but after further inspection, it checks whether the Windows scancode is 0 (0x00), and not extended 0 (0x100). This change makes GLFW check for the extended 0 keycode instead, which seems to work correctly. I'm not sure if checking for the non-extended 0 Windows scancode was intentional, as I never seem to have encountered one during testing with multiple keyboards. Thus, the handling of the non-extended 0 Windows scancode was removed, but it can be brought back if necessary.
elmindreda
added
bug
kangzixiang
approved these changes
Mar 2, 2024
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On Windows, keyboard events with an extended 0 Windows scancode are now processed by mapping the virtual-key code to a Windows scancode using the Win32
MapVirtualKeyfunction.Some keyboard scancodes (in particular, ones used for some non-typical keys) are not mapped to corresponding Windows scancodes, and are instead mapped to an extended 0 Windows scancode, with the distinction being only in the virtual-key code.
This causes GLFW to report a 256 GLFW scancode (0x00 | 0x100, 0x100 being the extended bit bitmask) for any of those keys, which causes API consumers to be unable to distinguish between them.
There exists, however, a Win32 function
MapVirtualKeythat maps those virtual key-codes to proper Windows scancodes. GLFW even appears to use this workaround, but after further inspection, it checks whether the Windows scancode is 0 (0x00), and not extended 0 (0x100).This change makes GLFW check for the extended 0 keycode instead, which seems to work correctly. I'm not sure if checking for the non-extended 0 Windows scancode was intentional, as I never seem to have encountered one during testing with multiple keyboards. Thus, the handling of the non-extended 0 Windows scancode was removed, but it can be brought back if necessary.
I'd like to know if I'm correct in the assumption that it was not intentional, if I'm wrong I will add another commit to also have the old behavior.
Thanks to @muzikbike for providing help in testing this, including a Windows environment and various keyboards.