Hardware Keyboard: Windows

[dkwingsmt]

Description

This PR contains the Windows changes for the Hardware Keyboard project.

Classes has been adjusted as follows:

Before	After	Explain
KeyboardHookHandler	KeyboardHandlerBase	Abstract class for a handler to be added to FlutterWindowsView. Base class to KeyboardKeyHandler and TextInputPlugin.
KeyEventHandler	KeyboardKeyHandler	Handles redispatching and detects redispatched events.
	KeyboardKeyChannelHandler	Sends raw events through method channel and collect responses.
-	KeyboardKeyEmbedderHandler	Converts raw events to FlutterKeyEvent, sends them through embedder API and collect responses.

Other changes

The code for skipping VK_PROCESSKEY events have been moved from Win32Window to embedder delegates. This is because the key up events for these presses have normal virtual keys, but also need filtering, which requires more delicate key press tracking.

The logic for handling asynchronous event redispatching has been refactored to handle crashing in several cases. Now the two phases have different identifiers.

• Response phase:
  • Events are sent to platform, waiting for response.
  • Such events are stored in pending_responses_.
  • Such events are identified by self-incrementing sequence_ids.
• Redispatching phase:
  • Events are sent to the system, waiting for the redispatch.
  • Such events are stored in pending_redispatches_.
  • Such events are identified by hash.

The crash that lead to this refactor is explained in test KeyboardKeyHandlerTest/WithSlowFrameworkResponse.

Related Issues

• Umbrella: ☂️ Device-specific keyboard events should happen in the embedder flutter#44918

Tests

I added the following tests:

• keyboard_key_handler_unittests.cc
  • SingleDelegateWithAsyncResponds
  • SingleDelegateWithSyncResponds
  • WithTwoAsyncDelegates
  • WithSlowFrameworkResponse
• keyboard_key_embedder_handler_unittests.cc
  • BasicKeyPressingAndHolding
  • ToggleNumLockDuringNumpadPress
  • ImeEventsAreIgnored
  • ModifierKeysByExtendedBit
  • ModifierKeysByVirtualKey
  • AbruptRepeatIsConvertedtoDown
  • SynthesizeForDesyncPressingState
  • SynthesizeForDesyncToggledState
  • SynthesizeForDesyncToggledStateByItself
  • SynthesizeWithInitialTogglingState

Checklist

Before you create this PR confirm that it meets all requirements listed below by checking the relevant checkboxes ([x]). This will ensure a smooth and quick review process.

• I read the contributor guide and followed the process outlined there for submitting PRs.
• I signed the CLA.
• I read and followed the C++, Objective-C, Java style guides for the engine.
• I read the tree hygiene wiki page, which explains my responsibilities.
• I updated/added relevant documentation.
• All existing and new tests are passing.
• I am willing to follow-up on review comments in a timely manner.

Reviewer Checklist

• I have submitted any presubmit flakes in this PR using the engine presubmit flakes form before re-triggering the failure.

Breaking Change

Did any tests fail when you ran them? Please read handling breaking changes.

• No, no existing tests failed, so this is not a breaking change.
• Yes, this is a breaking change. If not, delete the remainder of this section.
  • I wrote a design doc: https://flutter.dev/go/template Replace this with a link to your design doc's short link
  • I got input from the developer relations team, specifically from: Replace with the names of who gave advice
  • I wrote a migration guide: https://flutter.dev/go/breaking-changes-template Replace this with a link to a pull request that adds the migration guide to https://flutter.dev/docs/release/breaking-changes

[clarkezone]

I can't see any conflicts but would appreicate it if you could take a look at #23573 to ensure this will work with / not break the forthcoming UWP embedder. Thx!

[dkwingsmt]

@gspencergoog @cbracken I've added the feature to synthesize events to keep synchronized with the true states from Win32's GetKeyState, as well as more tests. Can you make a full review? Thanks!

[chinmaygarde]

Ping @gspencergoog. This is also on @cbracken s backlog. But I know both are super busy ATM, so not sure this is will be reviewed immediately. Are there other reviewers we can find for this?

[dkwingsmt]

@gspencergoog I addressed all comments, PTAL

[gspencergoog]