Gamepad API support for chrome on android

content/browser/gamepad/gamepad_platform_data_fetcher_android.cc

+// Copyright (c) 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_android.h"
+#include "base/android/jni_array.h"
+#include "base/android/jni_string.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_util.h"
+#include "base/strings/utf_string_conversions.h"
+
+#include "jni/GamepadList_jni.h"
+
+#include "third_party/WebKit/public/platform/WebGamepads.h"
+
+using base::android::AttachCurrentThread;
+using base::android::CheckException;
+using base::android::ClearException;
+using base::android::ConvertJavaStringToUTF8;
+using base::android::ScopedJavaLocalRef;
+using blink::WebGamepad;
+using blink::WebGamepads;
+
+namespace content {
+
+bool
+GamepadPlatformDataFetcherAndroid::RegisterGamepadPlatformDataFetcherAndroid(
+    JNIEnv* env) {
+  return RegisterNativesImpl(env);
+}
+
+GamepadPlatformDataFetcherAndroid::GamepadPlatformDataFetcherAndroid() {
+  PauseHint(false);
+}
+
+GamepadPlatformDataFetcherAndroid::~GamepadPlatformDataFetcherAndroid() {
+}
+
+void GamepadPlatformDataFetcherAndroid::GetGamepadData(blink::WebGamepads* pads,
+                                                       bool) {
+  JNIEnv* env = AttachCurrentThread();
+  if (!env)
+    return;
+
+  pads->length = WebGamepads::itemsLengthCap;

[jdduke (slow), 2014/03/19 09:44:58]

Hmm, are we guaranteed to always populate |itemLengthCap| number of elements?

What you might do is set this to 0, then in |SetGamepadData| you can increase
|pads->length| to include the index, something like:

SetGamepadData(...) {
  DCHECK(jgamepads);
  blink::WebGamepads* gamepads = reinterpret_cast<WebGamepads*>(jgamepads);
  DCHECK_EQ(gamepads->length, index); 
  DCHECK_LT(index, WebGamepads::itemsLengthCap);
  ++gamepads->length;
   ....
}

Then at least we have some validation that we're filling the required fields (in
order).

[SaurabhK, 2014/03/19 13:15:52]

On 2014/03/19 09:44:58, jdduke wrote:

Yes, incorporating this in next patchset,

+  Java_GamepadList_getGamepadData(env, reinterpret_cast<intptr_t>(pads));
+}
+
+void GamepadPlatformDataFetcherAndroid::PauseHint(bool isaccesspaused) {
+  JNIEnv* env = AttachCurrentThread();
+  if (!env)
+    return;
+
+  Java_GamepadList_notifyForGamepadsAccess(env, isaccesspaused);
+}
+
+static void SetGamepadData(JNIEnv* env,
+                           jobject obj,
+                           jlong gamepads,
+                           jint index,
+                           jstring mapping,
+                           jboolean connected,
+                           jstring devicename,
+                           jlong timestamp,
+                           jfloatArray jaxes,
+                           jfloatArray jbuttons) {
+
+  blink::WebGamepad& pad =
+      reinterpret_cast<WebGamepads*>(gamepads)->items[index];
+  pad.connected = connected;
+
+  pad.timestamp = timestamp;
+
+  // Do not set gamepad parameters for all the gamepad devices that are not
+  // attached.
+  if (!connected)
+    return;
+
+  // Map the Gamepad DeviceName String to the WebGamepad Id. Ideally it should
+  // be mapped to vendor and product information but it is only available at
+  // kernel level and it can not be queried using class
+  // android.hardware.input.InputManager.
+
+  base::string16 device_name;
+  base::android::ConvertJavaStringToUTF16(env, devicename, &device_name);
+  const size_t name_to_copy =
+      std::min(device_name.size(), WebGamepad::idLengthCap - 1);
+  memcpy(pad.id, device_name.data(), name_to_copy);
+  pad.id[name_to_copy] = 0;
+
+  base::string16 mapping_name;
+  base::android::ConvertJavaStringToUTF16(env, devicename, &mapping_name);
+  const size_t mapping_to_copy =
+      std::min(mapping_name.size(), WebGamepad::mappingLengthCap - 1);
+  memcpy(pad.mapping, mapping_name.data(), mapping_to_copy);
+  pad.mapping[mapping_to_copy] = 0;
+
+  pad.timestamp = timestamp;
+
+  std::vector<float> axes;
+  base::android::JavaFloatArrayToFloatVector(env, jaxes, &axes);
+
+  // Set WebGamepad axeslength to total number of axes on the gamepad device.
+  // Only return the first axesLengthCap if axeslength captured by GamepadList
+  // is larger than axesLengthCap.
+  pad.axesLength = std::min(axes.size(), WebGamepad::axesLengthCap);
+
+  memcpy(pad.axes, axes.begin(), pad.axesLength * sizeof(float));
+
+  std::vector<float> buttons;
+  base::android::JavaFloatArrayToFloatVector(env, jbuttons, &buttons);
+
+  // Set WebGamepad buttonslength to total number of axes on the gamepad
+  // device. Only return the first buttonsLengthCap if axeslength captured by
+  // GamepadList is larger than buttonsLengthCap.
+  pad.buttonsLength = std::min(buttons.size(), WebGamepad::buttonsLengthCap);
+
+  // Copy buttons state to the WebGamepad buttons[].
+  for (unsigned int j = 0; j < pad.buttonsLength; j++) {
+    pad.buttons[j].pressed = buttons[j];
+    pad.buttons[j].value = buttons[j];
+  }
+}
+
+}  // namespace content