Wayland: Fix missing damage event on window show

By definition a hidden window on Wayland does not have valid framebuffer
contents.

This adds a window damage (refresh) event when a window is shown, to
request an initial frame for the now visible window.

(cherry picked from commit 25c521cbe5)

README.md

@@ -129,6 +129,7 @@ information on what to include when reporting a bug.
  - [Wayland] Bugfix: Disable key repeat mechanism when window loses input focus
  - [Wayland] Bugfix: Window hiding and showing did not work (#1492,#1731)
  - [Wayland] Bugfix: A key being repeated was not released when window lost focus
+ - [Wayland] Bugfix: Showing a hidden window did not emit a window refresh event
 
 
 ## Contact

src/wl_window.c

@@ -1180,6 +1180,7 @@ void _glfwPlatformShowWindow(_GLFWwindow* window)
             createShellSurface(window);
 
         window->wl.visible = GLFW_TRUE;
+        _glfwInputWindowDamage(window);
     }
 }