Don't call Screen functions until app is ready

Fixes #907.

atom/common/api/atom_api_screen.cc

@@ -2,21 +2,41 @@
 // Use of this source code is governed by the MIT license that can be
 // found in the LICENSE file.
 
+#include "atom/browser/browser.h"
 #include "atom/common/native_mate_converters/gfx_converter.h"
 #include "atom/common/node_includes.h"
 
 namespace {
 
+const char* kRequireAppReadyMessage =
+    "APIs of \"screen\" module can only be used after the \"ready\" event of "
+    "\"app\" module gets emitted.";
+
+gfx::Point GetCursorScreenPoint(mate::Arguments* args) {
+  if (!atom::Browser::Get()->is_ready()) {
+    args->ThrowError(kRequireAppReadyMessage);
+    return gfx::Point();
+  }
+
+  gfx::Screen* screen = gfx::Screen::GetNativeScreen();
+  return screen->GetCursorScreenPoint();
+}
+
+gfx::Display GetPrimaryDisplay(mate::Arguments* args) {
+  if (!atom::Browser::Get()->is_ready()) {
+    args->ThrowError(kRequireAppReadyMessage);
+    return gfx::Display();
+  }
+
+  gfx::Screen* screen = gfx::Screen::GetNativeScreen();
+  return screen->GetPrimaryDisplay();
+}
+
 void Initialize(v8::Handle<v8::Object> exports, v8::Handle<v8::Value> unused,
                 v8::Handle<v8::Context> context, void* priv) {
-  gfx::Screen* screen = gfx::Screen::GetNativeScreen();
   mate::Dictionary dict(context->GetIsolate(), exports);
-  dict.SetMethod("getCursorScreenPoint",
+  dict.SetMethod("getCursorScreenPoint", &GetCursorScreenPoint);
-                 base::Bind(&gfx::Screen::GetCursorScreenPoint,
+  dict.SetMethod("getPrimaryDisplay", &GetPrimaryDisplay);
-                            base::Unretained(screen)));
-  dict.SetMethod("getPrimaryDisplay",
-                 base::Bind(&gfx::Screen::GetPrimaryDisplay,
-                            base::Unretained(screen)));
 }
 
 }  // namespace