Fixed bug 4709 - incorrect (not) handling of windows on-screen cursor keys

Alex Denisov

When using Win10 on-screen keyboard (tooltip.exe), the left and right cursor keys in it do not produce SDLK_LEFT and SDLK_RIGHT events.

Windows messages generated by the on-screen keyboard, for some reason, have their scancodes set to zeroes. Here is the log from Spy++:

WM_KEYDOWN nVirtKey:VK_LEFT cRepeat:1 ScanCode:00 fExtended:0 fAltDown:0 fRepeat:0 fUp:0
WM_KEYUP nVirtKey:VK_LEFT cRepeat:1 ScanCode:00 fExtended:0 fAltDown:0 fRepeat:1 fUp:1

Regular physical keyboard produces VK_LEFT (ScanCode:4B) and VK_RIGHT (ScanCode:4D) which are interpreted correctly.

With on-screen keyboard, the switch statement in VKeytoScancode() does not check for VK_LEFT and VK_RIGHT, returning SDL_SCANCODE_UNKNOWN, which in turn does not get mapped to anything (because the scan codes are zeroes).

src/video/windows/SDL_windowsevents.c

@@ -86,6 +86,11 @@ VKeytoScancode(WPARAM vkey)
 /* Windows generates this virtual keycode for Keypad 5 when NumLock is off.
     case VK_CLEAR: return SDL_SCANCODE_CLEAR;
 */
+    case VK_LEFT: return SDL_SCANCODE_LEFT;
+    case VK_UP: return SDL_SCANCODE_UP;
+    case VK_RIGHT: return SDL_SCANCODE_RIGHT;
+    case VK_DOWN: return SDL_SCANCODE_DOWN;
+
     case VK_MODECHANGE: return SDL_SCANCODE_MODE;
     case VK_SELECT: return SDL_SCANCODE_SELECT;
     case VK_EXECUTE: return SDL_SCANCODE_EXECUTE;