From: Dan Minor <dminor@mozilla.com>
Date: Tue, 17 Sep 2019 06:47:00 +0000
Subject: Bug 1581193 - Fix devicechange event on Windows; r=achronop

This restores the code for generating devicechange events that was
accidentally removed as part of updating the Windows video capture code
in Bug 1552755.

Differential Revision: https://phabricator.services.mozilla.com/D46033
Mercurial Revision: https://hg.mozilla.org/mozilla-central/rev/840c4edafa021eeac6a7e6ae0e828d0adcfea92e
---
 .../video_capture/windows/device_info_ds.cc   | 39 +++++++++++++++++++
 .../video_capture/windows/device_info_ds.h    |  3 ++
 2 files changed, 42 insertions(+)

diff --git a/modules/video_capture/windows/device_info_ds.cc b/modules/video_capture/windows/device_info_ds.cc
index d0d274cb02..460ef3b7b9 100644
--- a/modules/video_capture/windows/device_info_ds.cc
+++ b/modules/video_capture/windows/device_info_ds.cc
@@ -20,6 +20,29 @@
 namespace webrtc {
 namespace videocapturemodule {
 
+LRESULT CALLBACK WndProc(HWND hWnd, UINT uiMsg, WPARAM wParam, LPARAM lParam)
+{
+    DeviceInfoDS* pParent;
+    if (uiMsg == WM_CREATE)
+    {
+        pParent = (DeviceInfoDS*)((LPCREATESTRUCT)lParam)->lpCreateParams;
+        SetWindowLongPtr(hWnd, GWLP_USERDATA, (LONG_PTR)pParent);
+    }
+    else if (uiMsg == WM_DESTROY)
+    {
+        SetWindowLongPtr(hWnd, GWLP_USERDATA, NULL);
+    }
+    else if (uiMsg == WM_DEVICECHANGE)
+    {
+        pParent = (DeviceInfoDS*)GetWindowLongPtr(hWnd, GWLP_USERDATA);
+        if (pParent)
+        {
+            pParent->DeviceChange();
+        }
+    }
+    return DefWindowProc(hWnd, uiMsg, wParam, lParam);
+}
+
 // static
 DeviceInfoDS* DeviceInfoDS::Create() {
   DeviceInfoDS* dsInfo = new DeviceInfoDS();
@@ -77,6 +100,18 @@ DeviceInfoDS::DeviceInfoDS()
                         << rtc::ToHex(hr);
     }
   }
+
+  _hInstance = reinterpret_cast<HINSTANCE>(GetModuleHandle(NULL));
+  _wndClass = {0};
+  _wndClass.lpfnWndProc = &WndProc;
+  _wndClass.lpszClassName = TEXT("DeviceInfoDS");
+  _wndClass.hInstance = _hInstance;
+
+  if (RegisterClass(&_wndClass)) {
+    _hwnd = CreateWindow(_wndClass.lpszClassName, NULL, 0, CW_USEDEFAULT,
+                         CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, NULL,
+                         NULL, _hInstance, this);
+  }
 }
 
 DeviceInfoDS::~DeviceInfoDS() {
@@ -85,6 +120,10 @@ DeviceInfoDS::~DeviceInfoDS() {
   if (_CoUninitializeIsRequired) {
     CoUninitialize();
   }
+  if (_hwnd != NULL) {
+    DestroyWindow(_hwnd);
+  }
+  UnregisterClass(_wndClass.lpszClassName, _hInstance);
 }
 
 int32_t DeviceInfoDS::Init() {
diff --git a/modules/video_capture/windows/device_info_ds.h b/modules/video_capture/windows/device_info_ds.h
index 1b52645cde..dc7b9b1a24 100644
--- a/modules/video_capture/windows/device_info_ds.h
+++ b/modules/video_capture/windows/device_info_ds.h
@@ -93,6 +93,9 @@ class DeviceInfoDS : public DeviceInfoImpl {
   IEnumMoniker* _dsMonikerDevEnum;
   bool _CoUninitializeIsRequired;
   std::vector<VideoCaptureCapabilityWindows> _captureCapabilitiesWindows;
+  HWND _hwnd;
+  WNDCLASS _wndClass;
+  HINSTANCE _hInstance;
 };
 }  // namespace videocapturemodule
 }  // namespace webrtc