Windows: Implement Refresh event (#454)

Fixes #180

CHANGELOG.md

@@ -4,6 +4,7 @@
 - Fixed SIGSEGV/SIGILL crashes on macOS caused by stabilization of the `!` (never) type.
 - Implement `WindowEvent::HiDPIFactorChanged` for macOS
 - On X11, input methods now work completely out of the box, no longer requiring application developers to manually call `setlocale`. Additionally, when input methods are started, stopped, or restarted on the server end, it's correctly handled.
+- Implemented `Refresh` event on Windows.
 
 # Version 0.12.0 (2018-04-06)
 

src/platform/windows/events_loop.rs

@@ -367,6 +367,15 @@ pub unsafe extern "system" fn callback(window: HWND, msg: UINT,
             1
         },
 
+        winuser::WM_PAINT => {
+            use events::WindowEvent::Refresh;
+            send_event(Event::WindowEvent {
+                window_id: SuperWindowId(WindowId(window)),
+                event: Refresh,
+            });
+            winuser::DefWindowProcW(window, msg, wparam, lparam)
+        },
+
         winuser::WM_SIZE => {
             use events::WindowEvent::Resized;
             let w = LOWORD(lparam as DWORD) as u32;