Remove the requirement of D3D_FEATURE_LEVEL_11_0, but export the D3D_FEATURE_LEVEL through APIs

webrtc/modules/desktop_capture/win/dxgi_duplicator_controller.cc

Index: webrtc/modules/desktop_capture/win/dxgi_duplicator_controller.cc
diff --git a/webrtc/modules/desktop_capture/win/dxgi_duplicator_controller.cc b/webrtc/modules/desktop_capture/win/dxgi_duplicator_controller.cc
index 03dc15aa07f2a28d7da40f33a896a6be44ad872c..114053cfe91035930471ae99a76ea0203763bff2 100644
--- a/webrtc/modules/desktop_capture/win/dxgi_duplicator_controller.cc
+++ b/webrtc/modules/desktop_capture/win/dxgi_duplicator_controller.cc
@@ -44,6 +44,22 @@ bool DxgiDuplicatorController::IsSupported() {
   return Initialize();
 }
 
+bool DxgiDuplicatorController::SupportedFeatureLevels(
+    D3D_FEATURE_LEVEL* min_feature_level,
+    D3D_FEATURE_LEVEL* max_feature_level) {
+  rtc::CritScope lock(&lock_);
+  if (!Initialize()) {
+    return false;
+  }
+  if (min_feature_level != nullptr) {

[Sergey Ulanov, 2016/11/07 19:37:16]

nit: remove "!=nullptr" part.

[Hzj_jie, 2016/11/08 01:25:40]

Done.

+    *min_feature_level = min_feature_level_;
+  }
+  if (max_feature_level != nullptr) {
+    *max_feature_level = max_feature_level_;
+  }
+  return true;
+}
+
 DesktopVector DxgiDuplicatorController::dpi() {
   rtc::CritScope lock(&lock_);
   if (Initialize()) {
@@ -121,6 +137,11 @@ bool DxgiDuplicatorController::DoInitialize() {
   RTC_DCHECK(desktop_rect_.is_empty());
   RTC_DCHECK(duplicators_.empty());
 
+  // The maximum and minimum D3D_FEATURE_LEVEL supported by D3D11CreateDevice by
+  // default.
+  min_feature_level_ = D3D_FEATURE_LEVEL_11_0;
+  max_feature_level_ = D3D_FEATURE_LEVEL_9_1;

[Sergey Ulanov, 2016/11/07 19:37:16]

Maybe set these to -1 for initialization. Otherwise you have min > max, which
just doesn't look right.
Also this code won't work correctly if any of the devices has feature level
below 9.1 or above 11.

[Hzj_jie, 2016/11/08 01:25:39]

In D3dDevice::EnumDevices(), since we do not provide a D3D_FEATURE_LEVEL*, the
default feature levels is 9.1 to 11.0 (https://goo.gl/lcMhss). So here 11.0 and
9.1 is the largest and smallest possibilities.

But I do not think -1 is a safe value, considering Microsoft uses top 20 bits
for major version, middle 4 bits for minor version, low 8 bits as preserved
(https://goo.gl/tU4DoL). -1 means version 1048575.255.*(?). It looks like 0 is
not really possible, since there should be no 0.0.0(?).

+
   std::vector<D3dDevice> devices = D3dDevice::EnumDevices();
   if (devices.empty()) {
     return false;
@@ -131,6 +152,16 @@ bool DxgiDuplicatorController::DoInitialize() {
     if (!duplicators_.back().Initialize()) {
       return false;
     }
+
+    D3D_FEATURE_LEVEL feature_level =
+        devices[i].d3d_device()->GetFeatureLevel();
+    if (feature_level > max_feature_level_) {
+      max_feature_level_ = feature_level;
+    }
+    if (feature_level < min_feature_level_) {
+      min_feature_level_ = feature_level;
+    }
+
     if (desktop_rect_.is_empty()) {
       desktop_rect_ = duplicators_.back().desktop_rect();
     } else {