Repaint windows on screen unlock.

ui/views/win/hwnd_message_handler.cc

Index: ui/views/win/hwnd_message_handler.cc
diff --git a/ui/views/win/hwnd_message_handler.cc b/ui/views/win/hwnd_message_handler.cc
index c4a52976c3f8fda93a3c16828b6232e15db4fc1c..c333e8cdb1f53ccf32611189faab6bc90d14c2b1 100644
--- a/ui/views/win/hwnd_message_handler.cc
+++ b/ui/views/win/hwnd_message_handler.cc
@@ -6,6 +6,8 @@
 
 #include <dwmapi.h>
 #include <shellapi.h>
+#include <wtsapi32.h>
+#pragma comment(lib, "wtsapi32.lib")
 
 #include "base/bind.h"
 #include "base/debug/trace_event.h"
@@ -315,6 +317,21 @@ void AddScrollStylesToWindow(HWND window) {
   }
 }
 
+bool IsWorkstationLocked() {
+  bool is_locked = true;
+  HDESK input_desk = ::OpenInputDesktop(0, 0, GENERIC_READ);

[cpu_(ooo_6.6-7.5), 2014/01/19 20:52:45]

Opening the input desktop still has me confused. You want to know if your
process is attached to the desktop that has input right?

I see my previous idea does not work on XP, so you can use
http://www.experts-exchange.com/Programming/System/Windows__Programming/Q_235...

+  if (input_desk) {
+    wchar_t name[256] = {0};
+    DWORD needed = 0;
+    if (::GetUserObjectInformation(
+            input_desk, UOI_NAME, name, sizeof(name), &needed)) {
+      is_locked = lstrcmpi(name, L"default") != 0;
+    }
+    ::CloseDesktop(input_desk);
+  }
+  return is_locked;
+}
+
 }  // namespace
 
 // A scoping class that prevents a window from being able to redraw in response
@@ -1287,6 +1304,23 @@ void HWNDMessageHandler::RedrawLayeredWindowContents() {
   skia::EndPlatformPaint(layered_window_contents_->sk_canvas());
 }
 
+void HWNDMessageHandler::ForceRedrawWindow(int attempts) {
+  if (IsWorkstationLocked()) {
+    // Presents will continue to fail as long as the input desktop is
+    // unavailable.
+    if (--attempts <= 0)
+      return;
+    base::MessageLoop::current()->PostDelayedTask(
+        FROM_HERE,
+        base::Bind(&HWNDMessageHandler::ForceRedrawWindow,
+                   weak_factory_.GetWeakPtr(),
+                   attempts),
+        base::TimeDelta::FromMilliseconds(500));
+    return;
+  }
+  InvalidateRect(hwnd(), NULL, FALSE);
+}
+
 // Message handlers ------------------------------------------------------------
 
 void HWNDMessageHandler::OnActivateApp(BOOL active, DWORD thread_id) {
@@ -1386,11 +1420,14 @@ LRESULT HWNDMessageHandler::OnCreate(CREATESTRUCT* create_struct) {
 
   delegate_->HandleCreate();
 
+  WTSRegisterSessionNotification(hwnd(), NOTIFY_FOR_THIS_SESSION);
+
   // TODO(beng): move more of NWW::OnCreate here.
   return 0;
 }
 
 void HWNDMessageHandler::OnDestroy() {
+  WTSUnRegisterSessionNotification(hwnd());
   delegate_->HandleDestroying();
 }
 
@@ -2052,6 +2089,16 @@ LRESULT HWNDMessageHandler::OnScrollMessage(UINT message,
   return 0;
 }
 
+void HWNDMessageHandler::OnSessionChange(WPARAM status_code,
+                                         PWTSSESSION_NOTIFICATION session_id) {
+  // Direct3D presents are ignored while the screen is locked, so force the
+  // window to be redrawn on unlock.
+  if (status_code == WTS_SESSION_UNLOCK)
+    ForceRedrawWindow(10);
+
+  SetMsgHandled(FALSE);
+}
+
 LRESULT HWNDMessageHandler::OnSetCursor(UINT message,
                                         WPARAM w_param,
                                         LPARAM l_param) {