aux/android: Implement display metrics acquisition.

src/xrt/auxiliary/android/android_custom_surface.cpp

@@ -157,3 +157,50 @@ android_custom_surface_wait_get_surface(
 	return ANativeWindow_fromSurface(jni::env(),
 	                                 surf.object().makeLocalReference());
 }
+
+bool
+android_custom_surface_get_display_metrics(
+    struct _JavaVM *vm,
+    void *activity,
+    struct xrt_android_display_metrics *out_metrics)
+{
+	jni::init(vm);
+	try {
+		auto info = getAppInfo(XRT_ANDROID_PACKAGE, (jobject)activity);
+		if (info.isNull()) {
+			U_LOG_E(
+			    "Could not get application info for package '%s'",
+			    "org.freedesktop.monado.openxr_runtime");
+			return false;
+		}
+
+		auto clazz = loadClassFromPackage(info, (jobject)activity,
+		                                  FULLY_QUALIFIED_CLASSNAME);
+
+		if (clazz.isNull()) {
+			U_LOG_E("Could not load class '%s' from package '%s'",
+			        FULLY_QUALIFIED_CLASSNAME, XRT_ANDROID_PACKAGE);
+			return false;
+		}
+
+		// Teach the wrapper our class before we start to use it.
+		MonadoView::staticInitClass((jclass)clazz.object().getHandle());
+
+		jni::Object displayMetrics =
+		    MonadoView::getDisplayMetrics(Activity((jobject)activity));
+
+		*out_metrics = {
+		    .width_pixels = displayMetrics.get<int>("widthPixels"),
+		    .height_pixels = displayMetrics.get<int>("heightPixels"),
+		    .density_dpi = displayMetrics.get<int>("densityDpi"),
+		    .density = displayMetrics.get<float>("xdpi"),
+		    .scaled_density = displayMetrics.get<float>("ydpi"),
+		    .xdpi = displayMetrics.get<float>("density"),
+		    .ydpi = displayMetrics.get<float>("scaledDensity")};
+		return true;
+
+	} catch (std::exception const &e) {
+		U_LOG_E("Could not get display metrics: %s", e.what());
+		return false;
+	}
+}

src/xrt/auxiliary/android/android_custom_surface.h

@@ -23,6 +23,17 @@ extern "C" {
 struct _JNIEnv;
 struct _JavaVM;
 
+struct xrt_android_display_metrics
+{
+	int width_pixels;
+	int height_pixels;
+	int density_dpi;
+	float density;
+	float scaled_density;
+	float xdpi;
+	float ydpi;
+};
+
 /*!
  * Opaque type representing a custom surface added to an activity, and the async
  * operation to perform this adding.
@@ -77,6 +88,13 @@ android_custom_surface_destroy(
 ANativeWindow *
 android_custom_surface_wait_get_surface(
     struct android_custom_surface *custom_surface, uint64_t timeout_ms);
+
+bool
+android_custom_surface_get_display_metrics(
+    struct _JavaVM *vm,
+    void *activity,
+    struct xrt_android_display_metrics *out_metrics);
+
 #ifdef __cplusplus
 }
 #endif

src/xrt/auxiliary/android/org.freedesktop.monado.auxiliary.cpp

@@ -21,7 +21,10 @@ namespace org::freedesktop::monado::auxiliary {
 	      waitGetSurfaceHolder(classRef().getMethod(
 	          "waitGetSurfaceHolder", "(I)Landroid/view/SurfaceHolder;")),
 	      markAsDiscardedByNative(
-	          classRef().getMethod("markAsDiscardedByNative", "()V"))
+	          classRef().getMethod("markAsDiscardedByNative", "()V")),
+	      getDisplayMetrics(classRef().getStaticMethod(
+	          "getDisplayMetrics",
+	          "(Landroid/app/Activity;)Landroid/util/DisplayMetrics;"))
 	{}
 } // namespace org::freedesktop::monado::auxiliary
 } // namespace wrap

src/xrt/auxiliary/android/org.freedesktop.monado.auxiliary.hpp

@@ -83,6 +83,9 @@ namespace org::freedesktop::monado::auxiliary {
 		markAsDiscardedByNative();
 
 
+		static jni::Object
+		getDisplayMetrics(android::app::Activity const &activity);
+
 		/*!
 		 * Initialize the static metadata of this wrapper with a known
 		 * (non-null) Java class.
@@ -101,6 +104,7 @@ namespace org::freedesktop::monado::auxiliary {
 			jni::method_t attachToActivity;
 			jni::method_t waitGetSurfaceHolder;
 			jni::method_t markAsDiscardedByNative;
+			jni::method_t getDisplayMetrics;
 
 			/*!
 			 * Singleton accessor

src/xrt/auxiliary/android/org.freedesktop.monado.auxiliary.impl.hpp

@@ -40,5 +40,13 @@ namespace org::freedesktop::monado::auxiliary {
 		return object().call<void>(
 		    Meta::data().markAsDiscardedByNative);
 	}
+
+	inline jni::Object
+	MonadoView::getDisplayMetrics(android::app::Activity const &activity)
+	{
+		return Meta::data().clazz().call<jni::Object>(
+		    Meta::data().getDisplayMetrics, activity.object());
+	}
+
 } // namespace org::freedesktop::monado::auxiliary
 } // namespace wrap

src/xrt/auxiliary/android/src/main/java/org/freedesktop/monado/auxiliary/MonadoView.java

@@ -11,6 +11,7 @@ package org.freedesktop.monado.auxiliary;
 
 import android.app.Activity;
 import android.os.Build;
+import android.util.DisplayMetrics;
 import android.util.Log;
 import android.view.SurfaceHolder;
 import android.view.SurfaceView;
@@ -233,4 +234,12 @@ public class MonadoView extends SurfaceView implements SurfaceHolder.Callback, S
         Log.i(TAG, "surfaceRedrawNeeded");
     }
 
+    @NonNull
+    @Keep
+    public static DisplayMetrics getDisplayMetrics(Activity activity) {
+        DisplayMetrics displayMetrics = new DisplayMetrics();
+        activity.getWindowManager().getDefaultDisplay().getMetrics(displayMetrics);
+        return displayMetrics;
+    }
+
 }