normalizing_input_filter_cros.cc | Explore in Territory

// Copyright 2015 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "remoting/client/input/normalizing_input_filter_cros.h"

#include "base/check.h"
#include "ui/events/keycodes/dom/dom_code.h"

namespace remoting {

namespace {

// Returns true for OSKey codes.
static bool IsOsKey(uint32_t code) { … }

// Returns true for codes generated by EventRewriter::RewriteFunctionKeys().
static bool IsRewrittenFunctionKey(uint32_t code) { … }

// Returns true for codes generated by EventRewriter::RewriteExtendedKeys().
static bool IsRewrittenExtendedKey(uint32_t code) { … }

// Returns true for codes generated by EventRewriter::Rewrite().
static bool IsRewrittenKey(uint32_t code) { … }

}  // namespace

// The input filter tries to avoid sending keydown/keyup events for OSKey
// (aka Search, WinKey, Cmd, Super) when it is used to rewrite other key events.
// Rewriting via other combinations is not currently handled.
//
// OSKey events can be categorised as one of three kinds:
// - Modifying - Holding the key down while executing other input modifies the
//     effect of that input, e.g. OSKey+L causes the workstation to lock, e.g.
//     OSKey + mouse-move performs an extended selection.
// - Rewriting (ChromeOS only) - Holding the key down while pressing certain
//     keys causes them to be treated as different keys, e.g. OSKey causes the
//     Down key to behave as PageDown.
// - Normal - Press & release of the key trigger an action, e.g. showing the
//     Start menu.
//
// The input filter has four states:
// 1. No OSKey has been pressed.
//    - When an OSKey keydown is received, the event is deferred, and we move to
//      State #2.
// 2. An OSKey is pressed, but may be Normal, Rewriting or Modifying.
//    - If the OSKey keyup is received, the key is Normal, both events are sent
//      and we return to State #1.
//    - If a Rewritten event is received we move to State #3.
//    - If a Modified event is received the OSKey keydown is sent and we enter
//      State #4.
// 3. An OSKey is pressed, and is being used to Rewrite other key events.
//    - If the OSKey keyup is received then it is suppressed, and we move to
//      State #1.
//    - If a Modified event is received the OSKey keydown is sent and we enter
//      State #4.
//    - If a Rewritten event is received then we stay in State #3.
// 4. An OSKey is pressed, and is Modifying.
//    - If the OSKey keyup is received then we send it and we move to State #1.
//    - All other key event pass through the filter unchanged.
//
// ChromeOS also maps Alt+LeftClick to RightClick (even for an external mouse).
// As with the OSKey remapping described above, this is fed into this filter
// as Alt followed by RightClick. However, because there are other ways to
// generate RightClick (two-finger tap, for example), rather than suppressing
// the Alt key as we do for the OSKey (which would allow Alt+LeftClick to be
// interpreted as interpreted as RightClick as per the ChromeOS idiom), the
// filter maps RightClick to LeftClick while LeftAlt is held, which allows
// Alt+LeftClick to be injected. The equivalent mapping using RightAlt is
// unchanged, allowing Alt+RightClick also to be injected, as long as the
// target application doesn't distinguish between left and right Alt keys.
//
// This file must be kept up to date with changes to
// ui/events/ash/event_rewriter_ash.cc

NormalizingInputFilterCros::NormalizingInputFilterCros(
    protocol::InputStub* input_stub)
    : … { … }

NormalizingInputFilterCros::~NormalizingInputFilterCros() = default;

void NormalizingInputFilterCros::InjectKeyEvent(
    const protocol::KeyEvent& event_arg) { … }

void NormalizingInputFilterCros::InjectMouseEvent(
    const protocol::MouseEvent& event) { … }

void NormalizingInputFilterCros::ProcessKeyDown(
    const protocol::KeyEvent& event) { … }

void NormalizingInputFilterCros::ProcessKeyUp(const protocol::KeyEvent& event) { … }

void NormalizingInputFilterCros::SwitchRewritingKeyToModifying() { … }

void NormalizingInputFilterCros::UndoAltKeyMapping(protocol::KeyEvent* event) { … }

}  // namespace remoting
chromium/remoting/client/input/normalizing_input_filter_cros.cc
