// Листинг 2.2. Оконная функция с полосами прокрутки

#include <commdlg.h>
#include <fstream>
#include <vector>
#include <string>

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM
	lParam)
{
	PAINTSTRUCT ps;
	HDC hdc;
	static TCHAR name[256] = _T("");;
	static OPENFILENAME file;
	std::ifstream in;
	std::ofstream out;
	static std::vector<std::string> v;
	std::vector<std::string>::iterator it;
	std::string st;
	int y, k;
	static int n,length,sx,sy,cx,iVscrollPos,iHscrollPos,COUNT,MAX_WIDTH;
	static SIZE size = {8, 16}; //Ширина и высота символа
	switch (message)
	{
	case WM_CREATE:
		file.lStructSize = sizeof(OPENFILENAME);
        file.hInstance = hInst;
		file.lpstrFilter = _T("Text\0*.txt");
		file.lpstrFile = name;
		file.nMaxFile = 256;
		file.lpstrInitialDir = _T(".\\");
		file.lpstrDefExt = _T("txt");
        break;
	case WM_SIZE:
	   sx = LOWORD(lParam);
	   sy = HIWORD(lParam);
	   k = n - sy/size.cy;
	   if (k > 0) COUNT = k; else COUNT = iVscrollPos = 0;
	   SetScrollRange(hWnd, SB_VERT, 0, COUNT, FALSE);
	   SetScrollPos (hWnd, SB_VERT, iVscrollPos, TRUE);
	   k = length - sx/size.cx;
	   if (k > 0) MAX_WIDTH = k; else MAX_WIDTH = iHscrollPos = 0;
	   SetScrollRange(hWnd, SB_HORZ, 0, MAX_WIDTH, FALSE);
	   SetScrollPos (hWnd, SB_HORZ, iHscrollPos, TRUE);
	   break;
	case WM_VSCROLL :
	   switch (LOWORD(wParam))
	   {
	                case SB_LINEUP   : iVscrollPos--; break; 
			case SB_LINEDOWN : iVscrollPos++; break;
			case SB_PAGEUP   : iVscrollPos -= sy / size.cy; break;
			case SB_PAGEDOWN : iVscrollPos += sy / size.cy; break;
			case SB_THUMBPOSITION : iVscrollPos = HIWORD(wParam); break;
	   }
	   iVscrollPos = max(0, min(iVscrollPos, COUNT));
	   if (iVscrollPos != GetScrollPos(hWnd, SB_VERT))
	   {
		   SetScrollPos (hWnd, SB_VERT, iVscrollPos, TRUE);
		   InvalidateRect(hWnd, NULL, TRUE);
	   }
       break;
	case WM_HSCROLL :
	   switch (LOWORD(wParam))
	   {
	   case SB_LINEUP   : iHscrollPos--; break;
	   case SB_LINEDOWN : iHscrollPos++; break;
	   case SB_PAGEUP   : iHscrollPos -= 8; break;
           case SB_PAGEDOWN : iHscrollPos += 8; break;
	   case SB_THUMBPOSITION : iHscrollPos = HIWORD(wParam); break;
	   }
	   iHscrollPos = max(0, min(iHscrollPos, MAX_WIDTH));
	   if (iHscrollPos != GetScrollPos(hWnd, SB_HORZ))
	   {
		   SetScrollPos (hWnd, SB_HORZ, iHscrollPos, TRUE);
		   InvalidateRect(hWnd, NULL, TRUE);
	   }
       break;
	case WM_COMMAND:
		switch (LOWORD(wParam))
		{
		  case ID_FILE_NEW :
			if (!v.empty()) std::vector<std::string>().swap(v);
			n = length = 0;
			SendMessage(hWnd, WM_SIZE, 0, sy << 16 | sx);
			InvalidateRect(hWnd, NULL, TRUE);
			break;
		  case ID_FILE_OPEN :
			  file.lpstrTitle = _T("Открыть файл для чтения");
			  file.Flags = OFN_HIDEREADONLY;
			  if (!GetOpenFileName(&file)) return 1;
			  in.open(name);
			  while (getline(in,st))
			  {
				  if (length < st.length()) length = st.length();
                  v.push_back(st);
			  }
			  in.close();
			  n = v.size();
			  SendMessage(hWnd, WM_SIZE, 0, sy << 16 | sx);
			  InvalidateRect(hWnd, NULL, TRUE);
			  break;
		  case ID_FILE_SAVE :
			  file.lpstrTitle = _T("Открыть файл для записи");
			  file.Flags = OFN_NOTESTFILECREATE;
			  if (!GetSaveFileName(&file)) return 1;
			  out.open(name);
			  for (it = v.begin(); it != v.end(); ++it) out << *it << '\n';
			  out.close();
			  break;
		  case IDM_EXIT: DestroyWindow(hWnd); break;
          default: return DefWindowProc(hWnd, message, wParam, lParam);
	      }
		  break;
	case WM_PAINT:
		hdc = BeginPaint(hWnd, &ps);
		for (y=0,it=v.begin()+iVscrollPos;it!=v.end()&&y<sy;++it,y+=size.cy)
			if (iHscrollPos < it->length())
			   TabbedTextOutA(hdc,0,y,it->data()+iHscrollPos,it->length()-
			     iHscrollPos,0,NULL,0);
		EndPaint(hWnd, &ps);
		break;
	case WM_DESTROY:
	   PostQuitMessage(0);
	   break;
	default: return DefWindowProc(hWnd, message, wParam, lParam);
	}
	return 0;
}