Refactored gamepad polling to support dynamic sources

device/gamepad/gamepad_pad_state_provider.h

+// Copyright 2016 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.
+
+#ifndef DEVICE_GAMEPAD_GAMEPAD_PAD_STATE_PROVIDER_H_
+#define DEVICE_GAMEPAD_GAMEPAD_PAD_STATE_PROVIDER_H_
+
+#include <stdint.h>
+
+#include <limits>
+#include <memory>
+
+#include "device/gamepad/gamepad_export.h"
+#include "device/gamepad/gamepad_standard_mappings.h"
+#include "third_party/WebKit/public/platform/WebGamepad.h"
+
+namespace device {
+
+class GamepadDataFetcher;
+
+enum GamepadSource {
+  GAMEPAD_SOURCE_NONE = 0,
+  GAMEPAD_SOURCE_ANDROID,
+  GAMEPAD_SOURCE_LINUX_UDEV,
+  GAMEPAD_SOURCE_MAC_HID,
+  GAMEPAD_SOURCE_MAC_XBOX,
+  GAMEPAD_SOURCE_TEST,
+  GAMEPAD_SOURCE_WIN_XINPUT,
+  GAMEPAD_SOURCE_WIN_RAW,
+};
+
+enum GamepadActiveState {
+  GAMEPAD_INACTIVE = 0,
+  GAMEPAD_ACTIVE,
+  GAMEPAD_NEWLY_ACTIVE,
+};
+
+struct PadState {
+  // Which data fetcher provided this gamepad's data.
+  GamepadSource source;
+  // Data fetcher-specific identifier for this gamepad.
+  int source_id;
+
+  // Indicates whether or not the gamepad is actively being updated
+  GamepadActiveState active_state;
+
+  // Gamepad data, unmapped.
+  blink::WebGamepad data;
+
+  // Functions to map from device data to standard layout, if available. May
+  // be null if no mapping is available or needed.
+  GamepadStandardMappingFunction mapper;
+
+  // Sanitization masks
+  // axis_mask and button_mask are bitfields that represent the reset state of
+  // each input. If a button or axis has ever reported 0 in the past the
+  // corresponding bit will be set to 1.
+
+  // If we ever increase the max axis count this will need to be updated.
+  static_assert(blink::WebGamepad::axesLengthCap <=
+                    std::numeric_limits<uint32_t>::digits,
+                "axis_mask is not large enough");
+  uint32_t axis_mask;
+
+  // If we ever increase the max button count this will need to be updated.
+  static_assert(blink::WebGamepad::buttonsLengthCap <=
+                    std::numeric_limits<uint32_t>::digits,
+                "button_mask is not large enough");
+  uint32_t button_mask;
+};
+
+class DEVICE_GAMEPAD_EXPORT GamepadPadStateProvider {
+ public:
+  GamepadPadStateProvider();
+  virtual ~GamepadPadStateProvider();
+
+  // Gets a PadState object for the given source and id. If the device hasn't
+  // been encountered before one of the remaining slots will be reserved for it.
+  // If no slots are available will return NULL.
+  PadState* GetPadState(GamepadSource source, int source_id);
+
+ protected:
+  void ClearPadState(PadState& state);
+
+  void InitializeDataFetcher(GamepadDataFetcher* fetcher);
+
+  void MapAndSanitizeGamepadData(PadState* pad_state,
+                                 blink::WebGamepad* pad,
+                                 bool sanitize);
+
+  // Tracks the state of each gamepad slot.
+  std::unique_ptr<PadState[]> pad_states_;
+};
+
+}  // namespace device
+
+#endif  // DEVICE_GAMEPAD_GAMEPAD_PAD_STATE_PROVIDER_H_