Cache DeviceDisplayInfo data in shared structure on native side to avoid frequent JNI calls.

ui/gfx/android/shared_device_display_info.cc

+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ui/gfx/android/shared_device_display_info.h"
+
+#include "base/android/jni_android.h"
+#include "base/android/jni_string.h"
+#include "base/logging.h"
+#include "jni/DeviceDisplayInfo_jni.h"
+
+using base::android::AttachCurrentThread;
+
+namespace gfx {
+
+// static JNI call
+static void UpdateSharedDeviceDisplayInfo(JNIEnv* env,
+                                   jobject obj,

[Alexei Svitkine (slow), 2013/10/22 21:01:54]

Nit: Align params.

[ostap, 2013/10/22 21:40:42]

Done.

+                                   jint display_height,
+                                   jint display_width,
+                                   jint bits_per_pixel,
+                                   jint bits_per_component,
+                                   jdouble dip_scale,
+                                   jint smallest_dip_width) {
+  SharedDeviceDisplayInfo::GetInstance()->InvokeUpdate(env, obj,
+      display_height, display_width, bits_per_pixel, bits_per_component,
+      dip_scale, smallest_dip_width);
+}
+
+SharedDeviceDisplayInfo* SharedDeviceDisplayInfo::GetInstance() {

[Alexei Svitkine (slow), 2013/10/22 21:01:54]

Nit: Add "// static" above this.

[ostap, 2013/10/22 21:40:42]

Done.

+  return Singleton<SharedDeviceDisplayInfo>::get();
+}
+
+int SharedDeviceDisplayInfo::GetDisplayHeight() {
+  base::AutoLock autolock(lock_);
+  return display_height_;
+}
+
+int SharedDeviceDisplayInfo::GetDisplayWidth() {
+  base::AutoLock autolock(lock_);
+  return display_width_;
+}
+
+int SharedDeviceDisplayInfo::GetBitsPerPixel() {
+  base::AutoLock autolock(lock_);
+  return bits_per_pixel_;
+}
+
+int SharedDeviceDisplayInfo::GetBitsPerComponent() {
+  base::AutoLock autolock(lock_);
+  return bits_per_component_;
+}
+
+double SharedDeviceDisplayInfo::GetDIPScale() {
+  base::AutoLock autolock(lock_);
+  return dip_scale_;
+}
+
+int SharedDeviceDisplayInfo::GetSmallestDIPWidth() {
+  base::AutoLock autolock(lock_);
+  return smallest_dip_width_;

[Alexei Svitkine (slow), 2013/10/22 21:01:54]

Can you add a DCHECK_NE(0, smallest_dip_width_); here and similarly to the other
functions above? (This way, it will detect if this gets called before the values
got initialized through JNI.)

[ostap, 2013/10/22 21:40:42]

Done.

+}
+
+bool SharedDeviceDisplayInfo::RegisterSharedDeviceDisplayInfo(JNIEnv* env) {

[Alexei Svitkine (slow), 2013/10/22 21:01:54]

Nit: Add "// static" above this.

[ostap, 2013/10/22 21:40:42]

Done.

+  return RegisterNativesImpl(env);
+}
+
+void SharedDeviceDisplayInfo::InvokeUpdate(JNIEnv* env,
+                                           jobject obj,
+                                           jint display_height,
+                                           jint display_width,
+                                           jint bits_per_pixel,
+                                           jint bits_per_component,
+                                           jdouble dip_scale,
+                                           jint smallest_dip_width) {
+  base::AutoLock autolock(lock_);
+
+  UpdateDisplayInfo(env, obj, display_height,
+      display_width, bits_per_pixel, bits_per_component, dip_scale,
+      smallest_dip_width);
+}
+
+SharedDeviceDisplayInfo::SharedDeviceDisplayInfo()
+    : display_height_(0),
+      display_width_(0),
+      bits_per_pixel_(0),
+      bits_per_component_(0),
+      dip_scale_(0),
+      smallest_dip_width_(0)
+

[Alexei Svitkine (slow), 2013/10/22 21:01:54]

Nit: Remove empty line.

[ostap, 2013/10/22 21:40:42]

Done.

+{
+  JNIEnv* env = base::android::AttachCurrentThread();
+  j_device_info_.Reset(
+      Java_DeviceDisplayInfo_createWithListener(env,
+          base::android::GetApplicationContext()));
+  UpdateDisplayInfo(env, j_device_info_.obj(),
+      Java_DeviceDisplayInfo_getDisplayHeight(env, j_device_info_.obj()),
+      Java_DeviceDisplayInfo_getDisplayWidth(env, j_device_info_.obj()),
+      Java_DeviceDisplayInfo_getBitsPerPixel(env, j_device_info_.obj()),
+      Java_DeviceDisplayInfo_getBitsPerComponent(env, j_device_info_.obj()),
+      Java_DeviceDisplayInfo_getDIPScale(env, j_device_info_.obj()),
+      Java_DeviceDisplayInfo_getSmallestDIPWidth(env, j_device_info_.obj()));
+}
+
+void SharedDeviceDisplayInfo::UpdateDisplayInfo(JNIEnv* env,
+                                                jobject jobj,
+                                                jint display_height,
+                                                jint display_width,
+                                                jint bits_per_pixel,
+                                                jint bits_per_component,
+                                                jdouble dip_scale,
+                                                jint smallest_dip_width) {
+  display_height_ = static_cast<int>(display_height);
+  display_width_ = static_cast<int>(display_width);
+  bits_per_pixel_ = static_cast<int>(bits_per_pixel);
+  bits_per_component_ = static_cast<int>(bits_per_component);
+  dip_scale_ = static_cast<double>(dip_scale);
+  smallest_dip_width_ = static_cast<int>(smallest_dip_width);
+}
+
+}  // namespace gfx