[cscore] Add USB camera change event (#3123)

cscore/src/main/native/windows/UsbCameraListener.cpp

@@ -0,0 +1,72 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#include "UsbCameraListener.h"
+
+#include "Notifier.h"
+#include "WindowsMessagePump.h"
+
+#include <dbt.h>  // NOLINT(build/include_order)
+
+#define IDT_TIMER1 1001
+
+using namespace cs;
+
+class UsbCameraListener::Impl {
+ public:
+  explicit Impl(Notifier& notifier) : m_notifier{notifier} {}
+
+  void Start() {
+    m_messagePump = std::make_unique<WindowsMessagePump>(
+        [this](HWND hwnd, UINT uiMsg, WPARAM wParam, LPARAM lParam) {
+          return this->PumpMain(hwnd, uiMsg, wParam, lParam);
+        });
+  }
+
+  void Stop() { m_messagePump = nullptr; }
+
+  LRESULT PumpMain(HWND hwnd, UINT uiMsg, WPARAM wParam, LPARAM lParam) {
+    switch (uiMsg) {
+      case WM_CLOSE:
+        KillTimer(hwnd, IDT_TIMER1);
+        break;
+      case WM_TIMER:
+        if (wParam == IDT_TIMER1) {
+          KillTimer(hwnd, IDT_TIMER1);
+          m_notifier.NotifyUsbCamerasChanged();
+        }
+        break;
+      case WM_DEVICECHANGE:
+        PDEV_BROADCAST_HDR parameter =
+            reinterpret_cast<PDEV_BROADCAST_HDR>(lParam);
+        if (wParam == DBT_DEVICEARRIVAL &&
+            parameter->dbch_devicetype == DBT_DEVTYP_DEVICEINTERFACE) {
+          SetTimer(hwnd, IDT_TIMER1, 200, nullptr);
+        } else if (wParam == DBT_DEVICEREMOVECOMPLETE &&
+                   parameter->dbch_devicetype == DBT_DEVTYP_DEVICEINTERFACE) {
+          SetTimer(hwnd, IDT_TIMER1, 200, nullptr);
+        }
+        break;
+    }
+    return 0;
+  }
+
+  Notifier& m_notifier;
+  std::unique_ptr<cs::WindowsMessagePump> m_messagePump;
+};
+
+UsbCameraListener::UsbCameraListener(wpi::Logger& logger, Notifier& notifier)
+    : m_impl{std::make_unique<Impl>(notifier)} {}
+
+UsbCameraListener::~UsbCameraListener() {
+  Stop();
+}
+
+void UsbCameraListener::Start() {
+  m_impl->Start();
+}
+
+void UsbCameraListener::Stop() {
+  m_impl->Stop();
+}