Zack Middleton
The change to the keymap to use SDL_SCANCODE_TO_KEYCODE in SDL_x11keyboard.c causes all SDL scancodes without a Usc4 character to be XOR'd with SDLK_SCANCODE_MASK, but not all key code are suppose to be (as seen in include/SDL_keycodes.h). SDLK_BACKSPACE is not 0x4000002A.
I think the full list of keys affected are return, escape, backspace, tab, and delete.
Jacob Lee
If a user has a non-standard keyboard mapping -- say, their caps lock key has been mapped to Ctrl -- then SDL_GetModState() is no longer accurate: it only considers the unmapped keys. This is a regression from SDL 1.2.
I think there are two parts to this bug: first, GetModState should use keycodes, rather than scancodes, which is easy enough.
Unfortunately, on my system, SDL considers Caps Lock, even when mapped as Control, to be both SDL_SCANCODE_CAPSLOCK and SDLK_CAPSLOCK. The output from checkkeys for it is:
INFO: Key pressed : scancode 57 = CapsLock, keycode 0x40000039 = CapsLock modifiers: CAPS
Whereas the output for xev is:
KeyPress event, serial 41, synthetic NO, window 0x4a00001,
root 0x9a, subw 0x0, time 40218333, (144,177), root:(1458,222),
state 0x10, keycode 66 (keysym 0xffe3, Control_L), same_screen YES,
XKeysymToKeycode returns keycode: 37
XLookupString gives 0 bytes:
XmbLookupString gives 0 bytes:
XFilterEvent returns: False
I think the problem is that X11_UpdateKeymap in SDL_x11keyboard.c only builds a mapping for keycodes associated with a Unicode character (anything where X11_KeyCodeToUcs returns a value). In the case of caps lock, SDL scancode 57 becomes x11 keycode 66, which becomes x11 keysym 65507(Control_L), which does not have a unicode value.
To fix this, I suspect that SDL needs a mapping of the rest of the x11 keysyms to their corresponding SDL key codes.
An existing hint lets apps that don't need the timer resolution changed avoid
this, to save battery, etc, but this fixes several problems in timing, audio
callbacks not firing fast enough, etc.
Fixes Bugzilla #2944.
