don't explicitly require LibOVR for android build

BUILD_ANDROID.md

@@ -7,10 +7,13 @@ You will need the following tools to build our Android targets.
 * [Android NDK](https://developer.android.com/tools/sdk/ndk/index.html) = r10c
 * [Android SDK](http://developer.android.com/sdk/installing/index.html) ~> 24.0.2
   * Be sure to install SDK Platform for API Level 19
-* [Oculus Mobile SDK](https://developer.oculus.com/downloads/#sdk=mobile) ~> 0.4.2
 
 You will also need to cross-compile the dependencies required for all platforms for Android, and help CMake find these compiled libraries on your machine.
 
+####Optional Components
+
+* [Oculus Mobile SDK](https://developer.oculus.com/downloads/#sdk=mobile) ~> 0.4.2
+
 ####ANDROID_LIB_DIR
 
 Since you won't be installing Android dependencies to system paths on your development machine, CMake will need a little help tracking down your Android dependencies. 
@@ -97,6 +100,8 @@ This will create the `lib` and `include` folders inside `ANDROID_LIB_DIR/soxr` t
 
 ####Oculus Mobile SDK
 
+The Oculus Mobile SDK is optional, for Gear VR support. It is not required to compile gvr-interface.
+
 Download the [Oculus Mobile SDK](https://developer.oculus.com/downloads/#sdk=mobile) and extract the archive inside your `ANDROID_LIB_DIR` folder. Rename the extracted folder to `libovr`.
 
 From the VrLib directory, use ndk-build to build VrLib. This will create the liboculus.a archive that our FindLibOVR module will look for when cmake is run.

gvr-interface/CMakeLists.txt

@@ -24,15 +24,18 @@ set(ANDROID_APK_VERSION_NAME "0.1")
 set(ANDROID_APK_VERSION_CODE 1)
 set(ANDROID_DEPLOY_QT_INSTALL "--install")
 
-find_package(LibOVR REQUIRED)
-target_link_libraries(${TARGET_NAME} ${LIBOVR_LIBRARIES} ${LIBOVR_ANDROID_LIBRARIES})
-include_directories(SYSTEM ${LIBOVR_INCLUDE_DIRS})
+find_package(LibOVR)
+if (LIBOVR_FOUND)
+  add_definitions(-DHAVE_LIBOVR)
+  target_link_libraries(${TARGET_NAME} ${LIBOVR_LIBRARIES} ${LIBOVR_ANDROID_LIBRARIES})
+  include_directories(SYSTEM ${LIBOVR_INCLUDE_DIRS})
 
-# we need VRLib, so add a project.properties to our apk build folder that says that
-file(RELATIVE_PATH RELATIVE_VRLIB_PATH ${ANDROID_APK_OUTPUT_DIR} "${LIBOVR_VRLIB_DIR}")
-file(WRITE "${ANDROID_APK_BUILD_DIR}/project.properties" "android.library.reference.1=${RELATIVE_VRLIB_PATH}")
-
-list(APPEND IGNORE_COPY_LIBS ${LIBOVR_ANDROID_LIBRARIES})
+  # we need VRLib, so add a project.properties to our apk build folder that says that
+  file(RELATIVE_PATH RELATIVE_VRLIB_PATH ${ANDROID_APK_OUTPUT_DIR} "${LIBOVR_VRLIB_DIR}")
+  file(WRITE "${ANDROID_APK_BUILD_DIR}/project.properties" "android.library.reference.1=${RELATIVE_VRLIB_PATH}")
+  
+  list(APPEND IGNORE_COPY_LIBS ${LIBOVR_ANDROID_LIBRARIES})
+endif ()
 
 # the presence of a HOCKEY_APP_ID means we are making a beta build
 if (HOCKEY_APP_ID)

gvr-interface/src/GVRInterface.cpp

@@ -15,11 +15,15 @@
 #include <qpa/qplatformnativeinterface.h>
 #include <QtWidgets/QMenuBar>
 
+#ifdef HAVE_LIBOVR
+
 #include <GlUtils.h>
 #include <VrApi/LocalPreferences.h>
 #include <VrApi/VrApi.h>
 #include <VrApi/VrApi_local.h>
 
+#endif
+
 #include "GVRMainWindow.h"
 #include "RenderingClient.h"
 
@@ -32,13 +36,16 @@ GVRInterface::GVRInterface(int argc, char* argv[]) :
     _client = new RenderingClient(this);
     
     connect(this, &QGuiApplication::applicationStateChanged, this, &GVRInterface::handleApplicationStateChange);
-    
+
+#ifdef HAVE_LIBOVR
     QAndroidJniEnvironment jniEnv;
     
     QPlatformNativeInterface* interface = QApplication::platformNativeInterface();
     jobject activity = (jobject) interface->nativeResourceForIntegration("QtActivity");
 
+
     ovr_RegisterHmtReceivers(&*jniEnv, activity);
+#endif
     
     // call our idle function whenever we can
     QTimer* idleTimer = new QTimer(this);
@@ -60,10 +67,12 @@ GVRInterface::GVRInterface(int argc, char* argv[]) :
 }
 
 void GVRInterface::idle() {
+#ifdef HAVE_LIBOVR
     if (!_inVRMode && ovr_IsHeadsetDocked()) {
         qDebug() << "The headset just got docked - assume we are in VR mode.";
         _inVRMode = true;
     } else if (_inVRMode) {
+
         if (ovr_IsHeadsetDocked()) {
             static int counter = 0;
             
@@ -90,6 +99,7 @@ void GVRInterface::idle() {
             _inVRMode = false;
         }
     } 
+#endif
 }
 
 void GVRInterface::handleApplicationStateChange(Qt::ApplicationState state) {

gvr-interface/src/GVRInterface.h

@@ -15,8 +15,11 @@
 #include <QtWidgets/QApplication>
 
 class RenderingClient;
+
+#ifdef HAVE_LIBOVR
 class ovrMobile;
 class ovrHmdInfo;
+#endif
 
 #if defined(qApp)
 #undef qApp
@@ -37,8 +40,10 @@ private:
     RenderingClient* _client;
     bool _inVRMode;
     
+#ifdef HAVE_LIBOVR
     ovrMobile* _ovr;
     ovrHmdInfo* _hmdInfo;
+#endif
 };
 
 #endif // hifi_GVRInterface_h

libraries/audio-client/src/AudioClient.cpp

@@ -328,7 +328,7 @@ bool sampleChannelConversion(const int16_t* sourceSamples, int16_t* destinationS
                              const QAudioFormat& sourceAudioFormat, const QAudioFormat& destinationAudioFormat) {
     if (sourceAudioFormat.channelCount() == 2 && destinationAudioFormat.channelCount() == 1) {
         // loop through the stereo input audio samples and average every two samples
-        for (int i = 0; i < numSourceSamples; i += 2) {
+        for (uint i = 0; i < numSourceSamples; i += 2) {
             destinationSamples[i / 2] = (sourceSamples[i] / 2) + (sourceSamples[i + 1] / 2);
         }
         
@@ -336,7 +336,7 @@ bool sampleChannelConversion(const int16_t* sourceSamples, int16_t* destinationS
     } else if (sourceAudioFormat.channelCount() == 1 && destinationAudioFormat.channelCount() == 2) {
         
         // loop through the mono input audio and repeat each sample twice
-        for (int i = 0; i < numSourceSamples; ++i) {
+        for (uint i = 0; i < numSourceSamples; ++i) {
             destinationSamples[i * 2] = destinationSamples[(i * 2) + 1] = sourceSamples[i];
         }