BadNote/windows/runner/pen_channel.cpp

#include "pen_channel.h"

#include <flutter/encodable_value.h>
#include <flutter/event_channel.h>
#include <flutter/event_stream_handler_functions.h>
#include <flutter/flutter_engine.h>
#include <flutter/standard_method_codec.h>

#include <memory>

namespace {

std::unique_ptr<flutter::EventSink<flutter::EncodableValue>> g_pen_sink;

std::unique_ptr<flutter::EventChannel<flutter::EncodableValue>> g_pen_channel;

}  // namespace

void RegisterPenChannel(flutter::FlutterEngine* engine) {
  g_pen_channel =
      std::make_unique<flutter::EventChannel<flutter::EncodableValue>>(
          engine->messenger(), "badnote/pen",
          &flutter::StandardMethodCodec::GetInstance());

  auto handler = std::make_unique<
      flutter::StreamHandlerFunctions<flutter::EncodableValue>>(
      [](const flutter::EncodableValue* arguments,
         std::unique_ptr<flutter::EventSink<flutter::EncodableValue>>&&
             events)
          -> std::unique_ptr<
              flutter::StreamHandlerError<flutter::EncodableValue>> {
        g_pen_sink = std::move(events);
        return nullptr;
      },
      [](const flutter::EncodableValue* arguments)
          -> std::unique_ptr<
              flutter::StreamHandlerError<flutter::EncodableValue>> {
        g_pen_sink = nullptr;
        return nullptr;
      });

  g_pen_channel->SetStreamHandler(std::move(handler));
}

void ObservePenMessage(UINT message, WPARAM wparam, LPARAM lparam) {
  if (message != WM_POINTERENTER && message != WM_POINTERDOWN &&
      message != WM_POINTERUPDATE && message != WM_POINTERUP) {
    return;
  }

  if (!g_pen_sink) {
    return;
  }

  UINT32 pointerId = GET_POINTERID_WPARAM(wparam);

  POINTER_INPUT_TYPE type = PT_POINTER;
  if (!GetPointerType(pointerId, &type) || type != PT_PEN) {
    return;
  }

  POINTER_PEN_INFO ppi{};
  if (!GetPointerPenInfo(pointerId, &ppi)) {
    return;
  }

  int flags = 0;
  if (ppi.penFlags & PEN_FLAG_BARREL)   flags |= 1;
  if (ppi.penFlags & PEN_FLAG_INVERTED) flags |= 2;
  if (ppi.penFlags & PEN_FLAG_ERASER)   flags |= 4;

  flutter::EncodableMap payload{
      {flutter::EncodableValue("flags"),  flutter::EncodableValue(flags)},
      {flutter::EncodableValue("tiltX"),  flutter::EncodableValue(static_cast<double>(ppi.tiltX))},
      {flutter::EncodableValue("tiltY"),  flutter::EncodableValue(static_cast<double>(ppi.tiltY))},
  };

  g_pen_sink->Success(flutter::EncodableValue(payload));

  // On pointer up, send a cleared flags event to signal lift-off.
  if (message == WM_POINTERUP) {
    flutter::EncodableMap clear{
        {flutter::EncodableValue("flags"),  flutter::EncodableValue(0)},
        {flutter::EncodableValue("tiltX"),  flutter::EncodableValue(0.0)},
        {flutter::EncodableValue("tiltY"),  flutter::EncodableValue(0.0)},
    };
    g_pen_sink->Success(flutter::EncodableValue(clear));
  }
}