Use the shifted version of the letter as the key name

SDL_Keycode is defined as the unshifted key on the keyboard, but the key name is defined as the letter printed on that key, which is usually the shifted capital letter.

Fixes https://github.com/libsdl-org/SDL/issues/5836

src/events/SDL_keymap.c

@@ -21,6 +21,7 @@
 #include "SDL_internal.h"
 
 #include "SDL_keymap_c.h"
+#include "SDL_keyboard_c.h"
 #include "../SDL_hashtable.h"
 
 struct SDL_Keymap
@@ -1006,12 +1007,22 @@ const char *SDL_GetKeyName(SDL_Keycode key)
     case SDLK_DELETE:
         return SDL_GetScancodeName(SDL_SCANCODE_DELETE);
     default:
-        /* Unaccented letter keys on latin keyboards are normally
-           labeled in upper case (and probably on others like Greek or
-           Cyrillic too, so if you happen to know for sure, please
-           adapt this). */
-        if (key >= 'a' && key <= 'z') {
-            key -= 32;
+        // SDL_Keycode is defined as the unshifted key on the keyboard,
+        // but the key name is defined as the letter printed on that key,
+        // which is usually the shifted capital letter.
+        if (key > 0x7F || (key >= 'a' && key <= 'z')) {
+            SDL_bool translated = SDL_FALSE;
+            SDL_Scancode scancode = SDL_GetScancodeFromKey(key, SDL_KMOD_NONE);
+            if (scancode != SDL_SCANCODE_UNKNOWN) {
+                SDL_Keycode capital = SDL_GetKeyFromScancode(scancode, SDL_KMOD_SHIFT);
+                if (capital > 0x7F || (capital >= 'A' && capital <= 'Z')) {
+                    key = capital;
+                    translated = SDL_TRUE;
+                }
+            }
+            if (!translated && key >= 'a' && key <= 'z') {
+                key = 'A' + (key - 'a');
+            }
         }
 
         end = SDL_UCS4ToUTF8(key, name);