windowCapture: return 1x1 frame to minimized winodw on Linux.

webrtc/modules/desktop_capture/window_capturer_x11.cc

Index: webrtc/modules/desktop_capture/window_capturer_x11.cc
diff --git a/webrtc/modules/desktop_capture/window_capturer_x11.cc b/webrtc/modules/desktop_capture/window_capturer_x11.cc
index ffe8a3ab9b463ac2ad10b7bc8590f6bdedac5e40..62c258ae85440b9a4609d0eb6be1ffc85d92a7ba 100644
--- a/webrtc/modules/desktop_capture/window_capturer_x11.cc
+++ b/webrtc/modules/desktop_capture/window_capturer_x11.cc
@@ -111,6 +111,9 @@ class WindowCapturerLinux : public DesktopCapturer,
   // Returns window title for the specified X |window|.
   bool GetWindowTitle(::Window window, std::string* title);
 
+  // Return WM_STATE property of the |window|.
+  int32_t GetWindowState(::Window window);
+
   Callback* callback_ = nullptr;
 
   rtc::scoped_refptr<SharedXDisplay> x_display_;
@@ -286,6 +289,14 @@ void WindowCapturerLinux::CaptureFrame() {
     return;
   }
 
+  if (GetWindowState(selected_window_) == IconicState) {
+    // Window is in minimized. Return a 1x1 frame as same as OSX/Win does.
+    std::unique_ptr<DesktopFrame> frame(
+        new BasicDesktopFrame(DesktopSize(1, 1)));
+    callback_->OnCaptureResult(Result::SUCCESS, std::move(frame));
+    return;
+  }
+
   std::unique_ptr<DesktopFrame> frame(
       new BasicDesktopFrame(x_server_pixel_buffer_.window_size()));
 
@@ -317,13 +328,7 @@ bool WindowCapturerLinux::HandleXEvent(const XEvent& event) {
 }
 
 ::Window WindowCapturerLinux::GetApplicationWindow(::Window window) {
-  // Get WM_STATE property of the window.
-  XWindowProperty<uint32_t> window_state(display(), window, wm_state_atom_);
-
-  // WM_STATE is considered to be set to WithdrawnState when it missing.
-  int32_t state = window_state.is_valid() ?
-      *window_state.data() : WithdrawnState;
-
+  int32_t state = GetWindowState(window);
   if (state == NormalState) {
     // Window has WM_STATE==NormalState. Return it.
     return window;
@@ -418,6 +423,14 @@ bool WindowCapturerLinux::GetWindowTitle(::Window window, std::string* title) {
   return result;
 }
 
+int32_t WindowCapturerLinux::GetWindowState(::Window window) {
+  // Get WM_STATE property of the window.
+  XWindowProperty<uint32_t> window_state(display(), window, wm_state_atom_);
+
+  // WM_STATE is considered to be set to WithdrawnState when it missing.
+  return window_state.is_valid() ? *window_state.data() : WithdrawnState;
+}
+
 }  // namespace
 
 // static