Quick example of how to handle popup (dropdown) menus in Awesomium 1.7 RC2 with GDI on Windows.

popup_menu_gdi_sample_main.cc

#include <Awesomium/WebCore.h>
#include <Awesomium/BitmapSurface.h>
#include <Awesomium/STLHelpers.h>
#include <iostream>

#define MAX_LOADSTRING 100

using namespace Awesomium;

// Global Variables:
#define WIN_WIDTH 800
#define WIN_HEIGHT 600
HINSTANCE hInst;
const wchar_t szTitle[] = L"Awesomium GDI Sample";
const wchar_t szWindowClass[] = L"AwesomiumWinClass";
WebCore* core = 0;
WebView* view;

HDC context;
HBITMAP bitmap;
unsigned char* bitmap_buf = 0;
HWND hWnd;

// Forward declarations of functions included in this code module:
ATOM MyRegisterClass(HINSTANCE hInstance);
BOOL InitInstance(HINSTANCE, int);
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);

std::wstring ToWideString(const WebString& str) {
  std::string s = ToString(str);
  return std::wstring(s.begin(), s.end());
}

void GetWindowPos(HWND hWnd, int *x, int *y)
{
    HWND hWndParent = GetParent(hWnd);
    POINT p = {0};

    MapWindowPoints(hWnd, hWndParent, &p, 1);

    (*x) = p.x;
    (*y) = p.y;
}

class MenuHandler : public WebViewListener::Menu {
  virtual void OnShowPopupMenu(Awesomium::WebView* caller,
                               const WebPopupMenuInfo& menu_info) {
    // Generate the popup menu
    HMENU hPopupMenu = CreatePopupMenu();
    for (size_t i = 0; i < menu_info.items.size(); i++) {
      const WebMenuItem& item = menu_info.items.At(i);
      if (item.type == kWebMenuItemType_Option)
        InsertMenu(hPopupMenu, i, MF_STRING, 1000 + i, 
          ToWideString(item.label).c_str());
      else if (item.type == kWebMenuItemType_Group)
        InsertMenu(hPopupMenu, i, MF_DISABLED | MF_STRING, 1000 + i, 
          ToWideString(item.label).c_str());
    }

    // Display the menu and get the selected ID
    SetForegroundWindow(hWnd);
    int winX, winY;
    GetWindowPos(hWnd, &winX, &winY);
    int selected_id = TrackPopupMenu(hPopupMenu, TPM_TOPALIGN | 
      TPM_LEFTALIGN | TPM_RETURNCMD, winX + menu_info.bounds.x, 
      winY + menu_info.bounds.y + 20, 0, hWnd, NULL);

    // Handle the selected id
    if (selected_id >= 1000)
      caller->DidSelectPopupMenuItem(selected_id - 1000);
    else
      caller->DidCancelPopupMenu();
  }

  virtual void OnShowContextMenu(Awesomium::WebView *view,const Awesomium::WebContextMenuInfo &info) {
  }
};

int APIENTRY wWinMain(HINSTANCE hInstance, HINSTANCE, wchar_t*, int nCmdShow) {
  WNDCLASSEX wc;
  MSG msg;

  wc.cbSize        = sizeof(WNDCLASSEX);
  wc.style         = 0;
  wc.lpfnWndProc   = WndProc;
  wc.cbClsExtra    = 0;
  wc.cbWndExtra    = 0;
  wc.hInstance     = hInstance;
  wc.hIcon         = LoadIcon(NULL, IDI_APPLICATION);
  wc.hCursor       = LoadCursor(NULL, IDC_ARROW);
  wc.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);
  wc.lpszMenuName  = NULL;
  wc.lpszClassName = szWindowClass;
  wc.hIconSm       = LoadIcon(NULL, IDI_APPLICATION);

  if(!RegisterClassEx(&wc))
  {
      MessageBox(NULL, L"Window Registration Failed!", L"Error!",
          MB_ICONEXCLAMATION | MB_OK);
      return 0;
  }

  // Perform application initialization:
  if (!InitInstance (hInstance, nCmdShow)) {
    return FALSE;
  }

  WebConfig config;
  core = WebCore::Initialize(config);
  view = core->CreateWebView(WIN_WIDTH, WIN_HEIGHT);
  view->set_menu_listener(new MenuHandler());
  view->LoadURL(WebURL(WSLit("http://www.w3schools.com/tags/tryit.asp?filename=tryhtml_optgroup")));
  view->Focus();

  BITMAPINFOHEADER bih = {0};
  bih.biSize = sizeof(BITMAPINFOHEADER);
  bih.biBitCount = 32;
  bih.biCompression = BI_RGB;
  bih.biPlanes = 1;
  bih.biWidth = WIN_WIDTH;
  bih.biHeight = -(WIN_HEIGHT);
  context = CreateCompatibleDC(0);
  bitmap = CreateDIBSection(context, (BITMAPINFO*)&bih, DIB_RGB_COLORS, (void**)&(bitmap_buf), 0, 0);

  // Main message loop:
  while (GetMessage(&msg, NULL, 0, 0)) {
    TranslateMessage(&msg);
    DispatchMessage(&msg);
  }

  ReleaseDC(0, context);
  DeleteObject(bitmap);

  WebCore::Shutdown();

  return (int) msg.wParam;
}

BOOL InitInstance(HINSTANCE hInstance, int nCmdShow) {
  hInst = hInstance;

  hWnd = CreateWindow(szWindowClass, szTitle, WS_OVERLAPPEDWINDOW,
                      CW_USEDEFAULT, CW_USEDEFAULT, WIN_WIDTH + 20, WIN_HEIGHT + 40, 
                      NULL, NULL, hInstance, NULL);

  // Create our WebCore Update timer, renders at a max of 66 FPS
  UINT myTimer = SetTimer ( hWnd, 0, 15, NULL );

  if (!hWnd) {
    return FALSE;
  }

  ShowWindow(hWnd, nCmdShow);
  UpdateWindow(hWnd);

  return TRUE;
}

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam) {
  PAINTSTRUCT ps;
  HDC hdc;

  switch (message) {
  case WM_COMMAND:
    return DefWindowProc(hWnd, message, wParam, lParam);
    break;
  case WM_TIMER: {
    if (core) {
      core->Update();
      const BitmapSurface* surface =
        static_cast<const BitmapSurface*>(view->surface());
      if (surface) {
        if (surface->is_dirty()) {
          InvalidateRect (hWnd, NULL, FALSE);
          UpdateWindow (hWnd);
        }
      }
    }
  }
  break;
  case WM_PAINT: {
    hdc = BeginPaint(hWnd, &ps);

    if (view) {
      BitmapSurface* surface =
        static_cast<BitmapSurface*>(view->surface());
      if (surface) {
        surface->CopyTo(bitmap_buf, WIN_WIDTH * 4, 4, false, false);
        surface->set_is_dirty(false);
        SelectObject(context, bitmap);
        BitBlt(hdc, 0, 0, WIN_WIDTH, WIN_HEIGHT, context, 0, 0, SRCCOPY);
        ReleaseDC(hWnd, context);
      }
    }

    EndPaint(hWnd, &ps);
  }
  break;
  case WM_DESTROY:
    PostQuitMessage(0);
    break;
  case WM_MOUSEMOVE: {
    if (view)
      view->InjectMouseMove(LOWORD(lParam), HIWORD(lParam));
    break;
  }
  case WM_LBUTTONDOWN: {
    if (view)
      view->InjectMouseDown(kMouseButton_Left);
    break;
  }
  case WM_LBUTTONUP: {
    if (view)
      view->InjectMouseUp(kMouseButton_Left);
    break;
  }
  case WM_KEYDOWN:
  case WM_KEYUP:
  case WM_CHAR: {
    if (view)
      view->InjectKeyboardEvent(WebKeyboardEvent(message, wParam, lParam));
    break;
  }
  case WM_QUIT:

    break;
  default:
    return DefWindowProc(hWnd, message, wParam, lParam);
  }
  return 0;
}