DROPDOWN LISTBOX (WIN32)

#define _WIN32_WINNT 0x0501
#define _WIN32_IE 0x0501
#include <windows.h>

HINSTANCE g_hInst;
HWND g_hWnd, g_hListbox;
char g_szAppName[] = "DropDown";
BOOL g_bCapture = FALSE;

WNDPROC defListboxProc;

#define MAX_ITEMS  10

int __fastcall bnatoi(const char* psz)
{
  __asm
  {
    xor   eax, eax
    push  ebx
    xor   edx, edx
    xor   ebx, ebx
    cmp   byte ptr[ecx], '-'
    jne   short L1
    inc   ecx
    mov   edx, 0xFFFFFFFF
L1:
    mov   bl, byte ptr[ecx]
    cmp   bl, '0'
    jb    short L2
    cmp   bl, '9'
    ja    short L2
    lea   eax, dword ptr[eax + 4 * eax]
    sub   bl, '0'
    add   eax, eax
    inc   ecx
    add   eax, ebx
    jmp   short L1
L2:
    add   eax, edx
    pop   ebx
    xor   eax, edx
  }
}

LRESULT ListBox_OnLButtonDown(HWND hWnd, WPARAM wParam, LPARAM lParam)
{
  POINT pt = {LOWORD(lParam), HIWORD(lParam)};
  RECT clientRect, screenRect;
  POINT screenMousePos;
  GetCursorPos(&screenMousePos);
  GetWindowRect(hWnd, &screenRect);
  GetClientRect(hWnd, &clientRect);
  LRESULT l = 0;
  if(PtInRect(&screenRect, screenMousePos))
  {
    if(pt.x > clientRect.right)
    {
      // Clic dans la fenêtre, mais en dehors de la zone client
      // Donc sur la scollbar
      g_bCapture = TRUE; // Car la ListBox va recevoir WM_CAPTURECHANGED, mais il ne faut pas la fermer
      // On enlève temporairement la capture
      ReleaseCapture();
      l = CallWindowProc((WNDPROC)GetWindowLongPtr(hWnd, GWL_WNDPROC),
        hWnd,
        WM_NCLBUTTONDOWN,
        HTVSCROLL,
        MAKELPARAM(screenMousePos.x, screenMousePos.y));
      SetCapture(hWnd);
      g_bCapture = FALSE;
    }
    return l;
  }
  else DestroyWindow(hWnd); // Clic à coté de la fenêtre
  return 0;
}

LRESULT ListBox_OnMouseMove(HWND hWnd, WPARAM wParam, LPARAM lParam)
{
  int sel, count;
  POINT pt;
  RECT rect;
  pt.x = (short)LOWORD(lParam);
  pt.y = (short)HIWORD(lParam);
  GetClientRect(hWnd, &rect);
  if(PtInRect(&rect, pt) || (wParam & MK_LBUTTON))
  {
    // On prend les mouvements de la souris quand on est au dessus de la listBox,
    // ou quand le bouton gauche de la souris est enfoncé
    if(pt.y < 0)
      PostMessage(hWnd, WM_VSCROLL, SB_LINEUP, 0);
    if(pt.y > rect.bottom)
      PostMessage(hWnd, WM_VSCROLL, SB_LINEDOWN, 0);
    sel = LOWORD(SendMessage(hWnd, LB_ITEMFROMPOINT, 0, lParam));
    SendMessage(hWnd, LB_SELITEMRANGE, TRUE, MAKELPARAM(0, sel));
    count = (int)SendMessage(hWnd, LB_GETCOUNT, 0, 0);
    if(sel != count - 1)
      SendMessage(hWnd, LB_SELITEMRANGE, FALSE, MAKELPARAM(sel + 1, count - 1));
  }
  return 0;
}

LRESULT CALLBACK ListboxProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
  int sel;
  switch(uMsg)
  {
  case WM_MOUSEMOVE:
    return ListBox_OnMouseMove(hWnd, wParam, lParam);
  case WM_LBUTTONDOWN:
    return ListBox_OnLButtonDown(hWnd, wParam, lParam);
  case WM_KEYDOWN:
    switch(wParam)
    {
    case VK_DOWN:
      sel = (int)SendMessage(hWnd, LB_GETSELCOUNT, 0, 0);
      SendMessage(hWnd, LB_SETSEL, 1, sel);
      break;
    case VK_UP:
      sel = (int)SendMessage(hWnd, LB_GETSELCOUNT, 0, 0);
      SendMessage(hWnd, LB_SETSEL, 1, sel - 1);
      SendMessage(hWnd, LB_SETSEL, 0, sel - 1);
      break;
    case VK_RETURN:
      goto ok;
    case VK_ESCAPE:
      DestroyWindow(hWnd);
      break;
    }
    break;
  case WM_LBUTTONUP:
ok:
  case WM_CAPTURECHANGED:
    if(!g_bCapture)
    {
      DestroyWindow(hWnd);
      g_hListbox = 0;
    }
  }
  return CallWindowProc(defListboxProc, hWnd, uMsg, wParam, lParam);
}

LRESULT CALLBACK AppWndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
  static HWND hEdit;
  switch(uMsg)
  {
  case WM_KEYDOWN:
  case WM_MOUSEWHEEL:
    if(g_hListbox) PostMessage(g_hListbox, uMsg, wParam, lParam);
    break;
  case WM_CREATE:
    hEdit = CreateWindowEx(WS_EX_CLIENTEDGE, "EDIT", 0, WS_VISIBLE | WS_CHILD, 0, 0, 200, 25,
      hWnd, (HMENU)1000, g_hInst, 0);
    CreateWindowEx(0, "Button", "Test", WS_VISIBLE | WS_CHILD, 200, 0, 100, 25,
      hWnd, (HMENU)1001, g_hInst, 0);
    break;
  case WM_COMMAND:
    if(LOWORD(wParam) == 1001)
    {
      char szitems[32];
      GetWindowText(hEdit, szitems, 32);
      int nItems = bnatoi(szitems);
      if(nItems < 1) return 0;

      POINT pt = {200, 25}; // Coordonnées dans la fenêtre mère
      // Comme on va mettre le bureau en fenêtre mère, il faut transformer les coordonnées
      MapWindowPoints(hWnd, HWND_DESKTOP, &pt, 1);
      g_hListbox = CreateWindowEx(WS_EX_TOOLWINDOW, "Listbox", 0, 
        WS_VSCROLL | WS_BORDER | LBS_HASSTRINGS | LBS_MULTIPLESEL |WS_VISIBLE | WS_CHILD,
        pt.x, pt.y, 100, 100, hWnd, 0, g_hInst, 0);
      int height = (int)SendMessage(g_hListbox, LB_GETITEMHEIGHT, 0, 0);
      if(nItems > MAX_ITEMS) height *= MAX_ITEMS;
      else height *= nItems;

      SetWindowPos(g_hListbox, 0, 0, 0, 100, height, SWP_NOZORDER | SWP_NOACTIVATE | SWP_NOMOVE);
      SetParent(g_hListbox, HWND_DESKTOP);
      for(int i = 0; i < nItems; i++)
        SendMessage(g_hListbox, LB_ADDSTRING, 0, (LPARAM)"Chaine d'exemple");

      // Donne le focus à la fenêtre principale, pour qu'elle puisse rediriger les
      // message vers la listbox (WM_KEYDOWN, WM_WOUSEWHEEL...)
      SetFocus(hWnd);
      SetCapture(g_hListbox);
      defListboxProc = (WNDPROC)SetWindowLongPtr(g_hListbox, GWL_WNDPROC, (LONG_PTR)ListboxProc);
    }
    break;
  case WM_DESTROY:
    PostQuitMessage(0);
    return 0;
  }
  return DefWindowProc(hWnd, uMsg, wParam, lParam);
}

#ifdef _DEBUG
int main()
#else
#pragma comment(linker, "/entry:myWinMain")
int __stdcall myWinMain()
#endif
{
  MSG msg;
  g_hInst = GetModuleHandle(0);
  WNDCLASSEX wcex;

  memset(&wcex, 0, sizeof wcex);
  wcex.cbSize         = sizeof wcex;
  wcex.lpfnWndProc    = AppWndProc;
  wcex.style          = CS_HREDRAW | CS_VREDRAW;
  wcex.hInstance      = g_hInst;
  wcex.lpszClassName  = g_szAppName;
  wcex.hbrBackground  = GetSysColorBrush(COLOR_WINDOW);
  wcex.hCursor        = LoadCursor(0, IDC_ARROW);

  if(!RegisterClassEx(&wcex)) return 1;

  g_hWnd = CreateWindowEx(0, g_szAppName, g_szAppName, WS_OVERLAPPED | WS_VISIBLE | WS_SYSMENU,
    CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, 0, 0, g_hInst, 0);
  if(!g_hWnd) return 1;

  ShowWindow(g_hWnd, SW_NORMAL);
  while(GetMessage(&msg, NULL, 0, 0))
  {
    TranslateMessage(&msg);
    DispatchMessage(&msg);
  }
#ifdef _DEBUG
  return (int)msg.wParam;
#else
  ExitProcess(msg.wParam);
#endif
}