Gamepad API for Android

content/browser/gamepad/gamepad_platform_data_fetcher_android.cc

+// Copyright 2014 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 "content/browser/gamepad/gamepad_platform_data_fetcher_android.h"
+
+#include "base/android/jni_array.h"
+#include "base/android/jni_string.h"
+#include "base/debug/trace_event.h"
+#include "base/strings/string16.h"
+#include "jni/GamepadAdapter_jni.h"
+#include "third_party/WebKit/public/platform/WebGamepad.h"
+
+namespace content {
+
+namespace {
+
+void CopyJavaStringToWebUCharArray(
+    JNIEnv* env, jstring src, blink::WebUChar* array, size_t array_length) {
+  COMPILE_ASSERT(sizeof(base::string16::value_type) == sizeof(blink::WebUChar),
+                 string16_and_WebUChar_are_same_size);
+  base::string16 data;
+  base::android::ConvertJavaStringToUTF16(env, src, &data);
+  CHECK(array_length > 0);
+  const size_t bytes_to_copy = std::min(data.size(), array_length - 1);
+  memcpy(array, data.data(), bytes_to_copy);
+  array[bytes_to_copy] = 0;
+}
+
+}
+
+using base::android::AttachCurrentThread;
+using blink::WebGamepad;
+using blink::WebGamepads;

[jdduke (slow), 2014/03/07 23:16:39]

Please move the using statements above the initial nameespace declaration.

[kbalazs, 2014/03/12 00:17:36]

Done.

+
+GamepadPlatformDataFetcherAndroid::GamepadPlatformDataFetcherAndroid() {
+  j_gamepad_adapter_.Reset(

[jdduke (slow), 2014/03/07 23:16:39]

If the GamePadAdapter is a singleton in practice, we don't need to hold a
reference to it.   Just make getGamepadData and setFetched static methods on the
GamepadAdapter class that redirect to the proper instance.

[kbalazs, 2014/03/12 00:17:36]

Done.

+      Java_GamepadAdapter_attach(AttachCurrentThread(),
+                                 reinterpret_cast<intptr_t>(this)));
+}
+
+GamepadPlatformDataFetcherAndroid::~GamepadPlatformDataFetcherAndroid() {
+}
+
+void GamepadPlatformDataFetcherAndroid::GetGamepadData(
+    blink::WebGamepads* pads,
+    bool devices_changed_hint) {
+  TRACE_EVENT0("GAMEPAD", "GetGamepadData");
+  data_ = pads;
+  data_->length = WebGamepads::itemsLengthCap;

[jdduke (slow), 2014/03/07 23:16:39]

Rather than storing |data_| and assuming we'll get a callback, pass |pads| to
Java, and have Java call a static |RefreshGamepadData()| function, similar to
the one below but with the |pads| object as an argument.  Then populate the
|pads| object there, and GamePadAdapter no longer needs a
GamepadPlatformDataFetcherAndroid reference (no need to Attach()).

[jdduke (slow), 2014/03/07 23:33:27]

I see now, you definitely still need attach in some fashion, but you could
probably just re-use the |setFetched()| function for that.

[kbalazs, 2014/03/12 00:17:36]

Done.

+  Java_GamepadAdapter_getGamepadData(
+      AttachCurrentThread(), j_gamepad_adapter_.obj());
+  data_ = NULL;
+}
+
+void GamepadPlatformDataFetcherAndroid::PauseHint(bool paused) {
+  Java_GamepadAdapter_setFetched(

[jdduke (slow), 2014/03/07 23:16:39]

Same with the other function, make this a static call on the Java side that
redirects to the appropriate instance.

[kbalazs, 2014/03/12 00:17:36]

Done.

+        AttachCurrentThread(), j_gamepad_adapter_.obj(), !paused);
+}
+
+void GamepadPlatformDataFetcherAndroid::RefreshDevice(

[jdduke (slow), 2014/03/07 23:16:39]

This function can be made static (and local to this .cc file), see above
comments.

+    JNIEnv* env,
+    jobject obj,
+    int index,
+    bool connected,
+    jstring id,
+    jstring mapping,
+    long timestamp,
+    jfloatArray axes,
+    jfloatArray buttons) {
+  CHECK(data_);
+  WebGamepad& pad = data_->items[index];
+  pad.connected = connected;
+  if (!connected)
+    return;
+  CopyJavaStringToWebUCharArray(env, id, pad.id, WebGamepad::idLengthCap);
+  CopyJavaStringToWebUCharArray(env, mapping, pad.mapping,
+                                WebGamepad::mappingLengthCap);
+  pad.timestamp = timestamp;
+  std::vector<float> axes_data;
+  base::android::JavaFloatArrayToFloatVector(env, axes, &axes_data);
+  pad.axesLength = std::min(axes_data.size(), WebGamepad::axesLengthCap);
+  memcpy(pad.axes, axes_data.begin(), pad.axesLength * sizeof(float));

[jdduke (slow), 2014/03/07 23:16:39]

Could you add a line space in between each logical vector copy grouping here?

[kbalazs, 2014/03/12 00:17:36]

Done.

+  std::vector<float> buttons_data;
+  base::android::JavaFloatArrayToFloatVector(env, buttons, &buttons_data);
+  pad.buttonsLength =
+      std::min(buttons_data.size(), WebGamepad::buttonsLengthCap);
+  for (unsigned i = 0; i < pad.buttonsLength; ++i) {
+    float value = buttons_data[i];
+    pad.buttons[i].pressed = value;
+    pad.buttons[i].value = value;
+  }
+}
+
+bool GamepadPlatformDataFetcherAndroid::RegisterGamepadAdapter(JNIEnv* env) {
+  return RegisterNativesImpl(env);
+}
+
+}