drive Android rendering from the main thread via invalidate() calls

android/cpp/jni.cpp

@@ -30,6 +30,7 @@ std::string dataPath;
 std::string apkPath;
 std::string androidRelease;
 
+jmethodID onInvalidateId = nullptr;
 jmethodID onMapChangedId = nullptr;
 jmethodID onFpsChangedId = nullptr;
 
@@ -277,6 +278,13 @@ void JNICALL nativeUpdate(JNIEnv *env, jobject obj, jlong nativeMapViewPtr) {
     nativeMapView->getMap().update();
 }
 
+void JNICALL nativeOnInvalidate(JNIEnv *env, jobject obj, jlong nativeMapViewPtr) {
+    mbgl::Log::Debug(mbgl::Event::JNI, "nativeOnInvalidate");
+    assert(nativeMapViewPtr != 0);
+    NativeMapView *nativeMapView = reinterpret_cast<NativeMapView *>(nativeMapViewPtr);
+    nativeMapView->onInvalidate();
+}
+
 void JNICALL nativeResize(JNIEnv *env, jobject obj, jlong nativeMapViewPtr, jint width, jint height,
                           jfloat ratio, jint fbWidth, jint fbHeight) {
     mbgl::Log::Debug(mbgl::Event::JNI, "nativeResize");
@@ -805,6 +813,12 @@ extern "C" JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM *vm, void *reserved) {
         return JNI_ERR;
     }
 
+    onInvalidateId = env->GetMethodID(nativeMapViewClass, "onInvalidate", "()V");
+    if (onInvalidateId == nullptr) {
+        env->ExceptionDescribe();
+        return JNI_ERR;
+    }
+
     onMapChangedId = env->GetMethodID(nativeMapViewClass, "onMapChanged", "()V");
     if (onMapChangedId == nullptr) {
         env->ExceptionDescribe();
@@ -921,6 +935,7 @@ extern "C" JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM *vm, void *reserved) {
         {"nativePause", "(J)V", reinterpret_cast<void *>(&nativePause)},
         {"nativeResume", "(J)V", reinterpret_cast<void *>(&nativeResume)},
         {"nativeUpdate", "(J)V", reinterpret_cast<void *>(&nativeUpdate)},
+        {"nativeOnInvalidate", "(J)V", reinterpret_cast<void *>(&nativeOnInvalidate)},
         {"nativeResize", "(JIIFII)V",
          reinterpret_cast<void *>(static_cast<void JNICALL (
              *)(JNIEnv *, jobject, jlong, jint, jint, jfloat, jint, jint)>(&nativeResize))},
@@ -1092,6 +1107,7 @@ extern "C" JNIEXPORT void JNICALL JNI_OnUnload(JavaVM *vm, void *reserved) {
     latLngZoomLatitudeId = nullptr;
     latLngZoomZoomId = nullptr;
 
+    onInvalidateId = nullptr;
     onMapChangedId = nullptr;
     onFpsChangedId = nullptr;
 

android/cpp/native_map_view.cpp

@@ -125,13 +125,49 @@ void NativeMapView::deactivate() {
 }
 
 void NativeMapView::invalidate() {
-    mbgl::Log::Debug(mbgl::Event::Android, "NativeMapView::invalidate");
+    mbgl::Log::Debug(mbgl::Event::Android, "NativeMapView::invalidate()");
 
-    // TODO: inform the main thread that it must call map->renderSync();
+    clean.clear();
+
+    assert(vm != nullptr);
+    assert(obj != nullptr);
+
+    JavaVMAttachArgs args = {JNI_VERSION_1_2, "NativeMapView::invalidate()", NULL};
+
+    jint ret;
+    JNIEnv *env = nullptr;
+    bool detach = false;
+    ret = vm->GetEnv(reinterpret_cast<void **>(&env), JNI_VERSION_1_6);
+    if (ret != JNI_OK) {
+        if (ret != JNI_EDETACHED) {
+            mbgl::Log::Error(mbgl::Event::JNI, "GetEnv() failed with %i", ret);
+            throw new std::runtime_error("GetEnv() failed");
+        } else {
+            ret = vm->AttachCurrentThread(&env, &args);
+            if (ret != JNI_OK) {
+                mbgl::Log::Error(mbgl::Event::JNI, "AttachCurrentThread() failed with %i", ret);
+                throw new std::runtime_error("AttachCurrentThread() failed");
+            }
+            detach = true;
+        }
+    }
+
+    env->CallVoidMethod(obj, onInvalidateId);
+    if (env->ExceptionCheck()) {
+        env->ExceptionDescribe();
+    }
+
+    if (detach) {
+        if ((ret = vm->DetachCurrentThread()) != JNI_OK) {
+            mbgl::Log::Error(mbgl::Event::JNI, "DetachCurrentThread() failed with %i", ret);
+            throw new std::runtime_error("DetachCurrentThread() failed");
+        }
+    }
+    env = nullptr;
 }
 
 void NativeMapView::swap() {
-    mbgl::Log::Debug(mbgl::Event::Android, "NativeMapView::invalidate");
+    mbgl::Log::Debug(mbgl::Event::Android, "NativeMapView::swap");
 
     if ((display != EGL_NO_DISPLAY) && (surface != EGL_NO_SURFACE)) {
         if (!eglSwapBuffers(display, surface)) {
@@ -709,5 +745,14 @@ void NativeMapView::updateFps() {
     env = nullptr;
 }
 
+void NativeMapView::onInvalidate() {
+    mbgl::Log::Debug(mbgl::Event::Android, "NativeMapView::onInvalidate()");
+
+    const bool dirty = !clean.test_and_set();
+    if (dirty) {
+        map.renderSync();
+    }
+}
+
 }
 }