《windows程序设计》获取文本尺寸（04）

代码如下：

program Project2;

{$APPTYPE CONSOLE}

{$R *.res}

uses
  System.SysUtils,
  windows,
  Winapi.Messages,
  Vcl.Dialogs;

var
  swndClass: tagWNDCLASS;
  message: MSG;
  mHwnd: hwnd;
  cxChar, cyChar: Integer;

function WindowProc(hwnd: hwnd; uMsg: UINT; wParam: wParam; lParam: lParam): LRESULT; stdcall;
var
  uHdc: HDC;
  ps: tagPAINTSTRUCT;
  tm: tagTEXTMETRIC;
begin
  case uMsg of
    WM_CREATE:
      begin
        {获取文本尺寸}
        uHdc := GetDC(hwnd);
        GetTextMetrics(uHdc, tm);
        ReleaseDC(hwnd, uHdc);
        cxChar := tm.tmAveCharWidth;
        cyChar := tm.tmHeight + tm.tmExternalLeading;
      end;
    WM_PAINT:
      begin
        uHdc := BeginPaint(hwnd, ps);
        TextOut(uHdc, 0, 0, PWideChar(format('文字高度：%d 文字宽度：%d', [cxChar, cyChar])), Length(format('文字高度：%d 文字宽度：%d', [cxChar, cyChar])));
        EndPaint(hwnd, ps);
      end;
  end;
  result := DefWindowProc(hwnd, uMsg, wParam, lParam);
end;

begin
  swndClass.cbClsExtra := 0; //窗口类扩展，无
  swndClass.cbWndExtra := 0; //窗口实例扩展
  swndClass.hbrBackground := COLOR_BACKGROUND; //窗口背景颜色黑色
  //LoadCursor()
  swndClass.hCursor := LoadCursor(0, IDC_ARROW); //窗口采用箭头光标
  swndClass.hIcon := LoadIcon(0, IDI_APPLICATION); //窗口最小化图标：采用缺省图标
  swndClass.hInstance := hInstance; //窗口实例句柄
  swndClass.lpfnWndProc := @WindowProc; //窗口处理函数
  swndClass.lpszClassName := 'myWnd'; //窗口类名
  swndClass.lpszMenuName := nil; //窗口菜单
  swndClass.style := CS_DBLCLKS; //窗口样式
  if RegisterClass(swndClass) = 0 then
  begin
    Writeln('windows class register error!');
    Exit;
  end;

  mHwnd := CreateWindowEx(0, 'myWnd', 'Delphi Windows', WS_OVERLAPPEDWINDOW, CW_USEDEFAULT, CW_USEDEFAULT, 544, 375, HWND_DESKTOP, 0, hInstance, 0);

  ShowWindow(mHwnd, SW_SHOW);
  UpdateWindow(mHwnd);
  while GetMessage(message, 0, 0, 0) do
  begin
    TranslateMessage(message);
    DispatchMessage(message);
  end;

  Readln;
end.