Unify key name string handling

This makes key names per-key static strings for all supported platforms.

Fixes #1200.

include/GLFW/glfw3.h

@@ -4190,9 +4190,11 @@ GLFWAPI int glfwRawMouseMotionSupported(void);
  *  @errors Possible errors include @ref GLFW_NOT_INITIALIZED and @ref
  *  GLFW_PLATFORM_ERROR.
  *
+ *  @remark The contents of the returned string may change when a keyboard
+ *  layout change event is received.
+ *
  *  @pointer_lifetime The returned string is allocated and freed by GLFW.  You
- *  should not free it yourself.  It is valid until the next call to @ref
- *  glfwGetKeyName, or until the library is terminated.
+ *  should not free it yourself.  It is valid until the library is terminated.
  *
  *  @thread_safety This function must only be called from the main thread.
  *

src/cocoa_platform.h

@@ -139,7 +139,7 @@ typedef struct _GLFWlibraryNS
     id                  keyUpMonitor;
     id                  nibObjects;
 
-    char                keyName[64];
+    char                keynames[GLFW_KEY_LAST + 1][17];
     short int           keycodes[256];
     short int           scancodes[GLFW_KEY_LAST + 1];
     char*               clipboardString;

src/cocoa_window.m

@@ -1503,8 +1503,10 @@ const char* _glfwPlatformGetScancodeName(int scancode)
 {
     @autoreleasepool {
 
+    const int key = _glfw.ns.keycodes[scancode];
+
     UInt32 deadKeyState = 0;
-    UniChar characters[8];
+    UniChar characters[4];
     UniCharCount characterCount = 0;
 
     if (UCKeyTranslate([(NSData*) _glfw.ns.unicodeData bytes],
@@ -1529,12 +1531,12 @@ const char* _glfwPlatformGetScancodeName(int scancode)
                                                             characterCount,
                                                             kCFAllocatorNull);
     CFStringGetCString(string,
-                       _glfw.ns.keyName,
-                       sizeof(_glfw.ns.keyName),
+                       _glfw.ns.keynames[key],
+                       sizeof(_glfw.ns.keynames[key]),
                        kCFStringEncodingUTF8);
     CFRelease(string);
 
-    return _glfw.ns.keyName;
+    return _glfw.ns.keynames[key];
 
     } // autoreleasepool
 }

src/x11_platform.h

@@ -228,7 +228,7 @@ typedef struct _GLFWlibraryX11
     // Clipboard string (while the selection is owned)
     char*           clipboardString;
     // Key name string
-    char            keyName[5];
+    char            keynames[GLFW_KEY_LAST + 1][5];
     // X11 keycode to GLFW key LUT
     short int       keycodes[256];
     // GLFW key to X11 keycode LUT

src/x11_window.c

@@ -2792,6 +2792,7 @@ const char* _glfwPlatformGetScancodeName(int scancode)
     if (!_glfw.x11.xkb.available)
         return NULL;
 
+    const int key = _glfw.x11.keycodes[scancode];
     const KeySym keysym = XkbKeycodeToKeysym(_glfw.x11.display,
                                              scancode, _glfw.x11.xkb.group, 0);
     if (keysym == NoSymbol)
@@ -2801,12 +2802,12 @@ const char* _glfwPlatformGetScancodeName(int scancode)
     if (ch == -1)
         return NULL;
 
-    const size_t count = encodeUTF8(_glfw.x11.keyName, (unsigned int) ch);
+    const size_t count = encodeUTF8(_glfw.x11.keynames[key], (unsigned int) ch);
     if (count == 0)
         return NULL;
 
-    _glfw.x11.keyName[count] = '\0';
-    return _glfw.x11.keyName;
+    _glfw.x11.keynames[key][count] = '\0';
+    return _glfw.x11.keynames[key];
 }
 
 int _glfwPlatformGetKeyScancode(int key)