X11: Preserve unrelated values in WM_NORMAL_HINTS

This stops GLFW overwriting the whole WM_NORMAL_HINTS property every
time it updates size-related parts of it.

src/x11_window.c

@@ -270,6 +270,11 @@ static void updateNormalHints(_GLFWwindow* window, int width, int height)
 {
     XSizeHints* hints = XAllocSizeHints();
 
+    long supplied;
+    XGetWMNormalHints(_glfw.x11.display, window->x11.handle, hints, &supplied);
+
+    hints->flags &= ~(PMinSize | PMaxSize | PAspect);
+
     if (!window->monitor)
     {
         if (window->resizable)
@@ -306,9 +311,6 @@ static void updateNormalHints(_GLFWwindow* window, int width, int height)
         }
     }
 
-    hints->flags |= PWinGravity;
-    hints->win_gravity = StaticGravity;
-
     XSetWMNormalHints(_glfw.x11.display, window->x11.handle, hints);
     XFree(hints);
 }
@@ -696,7 +698,28 @@ static GLFWbool createNativeWindow(_GLFWwindow* window,
         XFree(hints);
     }
 
-    updateNormalHints(window, width, height);
+    // Set ICCCM WM_NORMAL_HINTS property
+    {
+        XSizeHints* hints = XAllocSizeHints();
+        if (!hints)
+        {
+            _glfwInputError(GLFW_OUT_OF_MEMORY, "X11: Failed to allocate size hints");
+            return GLFW_FALSE;
+        }
+
+        if (!wndconfig->resizable)
+        {
+            hints->flags |= (PMinSize | PMaxSize);
+            hints->min_width  = hints->max_width  = width;
+            hints->min_height = hints->max_height = height;
+        }
+
+        hints->flags |= PWinGravity;
+        hints->win_gravity = StaticGravity;
+
+        XSetWMNormalHints(_glfw.x11.display, window->x11.handle, hints);
+        XFree(hints);
+    }
 
     // Set ICCCM WM_CLASS property
     {