fix(win-llhook): restore MapVirtualKeyA for default kanata.exe

The commit fab0d89 intended to fix the functionality of keypad enter.
It worked for the US layout but broke other OS layouts. It turns out
MapVirtualKeyA **was** needed to translate to the appropriate scancode
output. The fix for keypad enter is done by attempting `osc_to_u16` if
MapVirtualKeyA fails, which it should for a nonexistent VK that kanata
uses for keypad enter.

src/oskbd/windows/mod.rs

@@ -128,8 +128,39 @@ fn send_key_sendinput(code: u16, is_key_up: bool) {
 
             let code_u32 = code as u32;
             kb_input.dwFlags |= KEYEVENTF_SCANCODE;
-            kb_input.wScan =
-                osc_to_u16(code.into()).unwrap_or_else(|| MapVirtualKeyA(code_u32, 0) as u16);
+            #[cfg(not(feature = "win_llhook_read_scancodes"))]
+            {
+                // This MapVirtualKeyA is needed to translate back to the proper scancode
+                // associated with with the virtual key.
+                // E.g. take this example:
+                //
+                // - KEY_A is the code here
+                // - OS layout is AZERTY
+                // - No remapping, e.g. active layer is:
+                //   - (deflayermap (active-layer) a a)
+                //
+                // This means kanata received a key press at US-layout position Q. However,
+                // translating KEY_A via osc_to_u16 will result in the scancode assocated with
+                // US-layout position A, but we want to output the position Q scancode. It is
+                // MapVirtualKeyA that does the correct translation for this based on the user's OS
+                // layout.
+                kb_input.wScan = MapVirtualKeyA(code_u32, 0) as u16;
+                if kb_input.wScan == 0 {
+                    // The known scenario for this is VK_KPENTER_FAKE which isn't a real VK so
+                    // MapVirtualKeyA is expected to return 0. This fake VK is used to
+                    // distinguish the key within kanata since in Windows there is no output VK for
+                    // the enter key at the numpad.
+                    //
+                    // The osc_to_u16 function knows the scancode for keypad enter though, and it
+                    // isn't known to change based on language layout so this seems fine to do.
+                    kb_input.wScan = osc_to_u16(code.into()).unwrap_or(0);
+                }
+            }
+            #[cfg(feature = "win_llhook_read_scancodes")]
+            {
+                kb_input.wScan =
+                    osc_to_u16(code.into()).unwrap_or_else(|| MapVirtualKeyA(code_u32, 0) as u16);
+            }
             if kb_input.wScan == 0 {
                 kb_input.dwFlags &= !KEYEVENTF_SCANCODE;
                 kb_input.wVk = code;