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利用VB动态改变Windows显示模式的两种方法

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利用VB动态改变Windows显示模式的两种方法



   在Windows系统中,系统提供了用于动态改变屏幕分辨率和显示颜色数的API函数。在这篇文章中,我将介绍使用两种方法改变Windows的显示模式。
  要改变显示模式,首先要获得显示系统支持的显示模式。显示系统支持的所有的显示模式是利用API函数EnumDisplaySettings获得的。然后有两种方法切换显示模式,一种是利用Windows API函数ChangeDisplaySettings另外一种方法是利用Windows附带的一个QuickRES库,通过调用QuickRES库实现显示模式的切换。
  首先在VB中建立一个工程文件,然后在Form1中加入一个ListBox控件和两个CommandButton控件,然后在Form1的代码窗口中加入以下代码:
  Option Explicit
  Private Type RECT
   Left As Long
   Top As Long
   Right As Long
   Bottom As Long
  End Type
  Private Declare Function ChangeDisplaySettings Lib “user32" Alias “ChangeDisplaySettingsA" _
  (lpDevMode As Any, ByVal dwflags As Long) As Long
  Private Declare Function EnumDisplaySettings Lib“user32" Alias“EnumDisplaySettingsA" _
  (ByVal lpszDeviceName As String, ByVal iModeNum As Long, lpDevMode As Any) As Long
  Private Declare Function SendMessageByLong& Lib“user32" Alias“SendMessageA" _
  (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, ByVal lParam As Long)
  Private Declare Function InvalidateRect Lib “user32" (ByVal hwnd As Long, lprect As Any, _
   ByVal bErase As Long) As Long
  Private Declare Function PostMessage Lib “user32" Alias “PostMessageA" (ByVal hwnd As Long, _
  ByVal wMsg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
  Private Type DEVMODE
  dmDeviceName As String * 32
  dmSpecVersion As Integer
  dmDriverVersion As Integer
  dmSize As Integer
  dmDriverExtra As Integer
  dmFields As Long
  dmOrientation As Integer
  dmPaperSize As Integer
  dmPaperLength As Integer
  dmPaperWidth As Integer
  dmScale As Integer
  dmCopies As Integer
  dmDefaultSource As Integer
  dmPrintQuality As Integer
  dmColor As Integer
  dmDuplex As Integer
  dmYResolution As Integer
  dmTTOption As Integer
  dmCollate As Integer
  dmFormName(1 To 32) As Byte
  dmLogPixels As Integer
  dmBitsPerPel As Long
  dmPelsWidth As Long
  dmPelsHeight As Long
  dmDisplayFlags As Long
  dmDisplayFrequency As Long
  dmICMMethod As Long
  'Windows 95 only
  dmICMIntent As Long
  ’ Windows 95 only
  dmMediaType As Long
  ' Windows 95 only
  dmDitherType As Long
  ' Windows 95 only
  dmReserved1 As Long
  ' Windows 95 only
  dmReserved2 As Long
  ' Windows 95 only
  End Type
  Const DM_BITSPERPEL = &H40000
  Const DM_PELSWIDTH = &H80000
  Const DM_PELSHEIGHT = &H100000
  Const DM_DISPLAYFLAGS = &H200000
  Const DM_DISPLAYFREQUENCY = &H400000
  Const DISP_CHANGE_SUCCESSFUL = 0
  Const DISP_CHANGE_RESTART = 1
  Const DISP_CHANGE_FAILED = -1
  Const DISP_CHANGE_BADMODE = -2
  Const DISP_CHANGE_NOTUPDATED = -3
  Const DISP_CHANGE_BADFLAGS = -4
  Const DISP_CHANGE_BADPARAM = -5
  Const CDS_UPDATEREGISTRY = 1
  Const CDS_FORCE As Long = &H80000000
  Const CDS_RESET = &H40000000
  Const HWND_BROADCAST = &HFFFF&
  Const WM_SYSCOLORCHANGE = &H15
  Const WM_PALETTECHANGED = &H311
  Const WM_DISPLAYCHANGE = &H7E
  Const WM_SETTINGCHANGE = &H1A
  Dim ModeCube(63) As DEVMODE
  Dim lproc As Long
  Sub EndApp()
  Icon_Del (Form1.Command1.hwnd)
  End
  End Sub
  Sub ShowIcon()
  Dim l As Long
  If (Icon_Add(Form1.Command1.hwnd, Form1.Picture)) Then
  lproc = SetWindowLong(Form1.Command1.hwnd, GWL_WNDPROC, AddressOf DialogProc)
  Else
  MsgBox (“无法建立程序图标!")
  End
  End If
  End Sub
  Sub LoadDisplayMode()
  Dim i As Long
  Dim l1 As Long
  Dim astr As String
  i = 0
  '遍历所有的显示模式并在List1中显示出来
  Do
  ModeCube(i).dmFields = DM_BITSPERPEL Or DM_PELSWIDTH Or DM_PELSHEIGHT Or _
  DM_DISPLAYFLAGS Or DM_DISPLAYFREQUENCY
  ModeCube(i).dmSize = Len(ModeCube(i))
  '获得显示模式并保存到数组中
  l1 = EnumDisplaySettings(vbNullString, i, ModeCube(i))
  If l1 Then
  astr = Str$(ModeCube(i).dmPelsWidth) + “*" + Trim$(Str$(ModeCube(i).dmPelsHeight)) +“ "
  Select Case ModeCube(i).dmBitsPerPel
  Case 4
  astr = astr + “16色"
  Case 8
  astr = astr + “256色"
  Case 16
  astr = astr +“16位高彩"
  Case 24
  astr = astr + “24位真彩"
  Case Else
  astr = astr + Str$(ModeCube(i).dmBitsPerPel)
  End Select
  i = i + 1
  End If
  List1.AddItem astr
  Loop Until (l1 = False) '获得最后一个显示模式之后EnumDisplaySettings会返回False
  End Sub
  Private Sub Command1_Click()
  Dim aDev As DEVMODE
  Dim b, xxa, xxb, xxc, xxd As Long
  If List1.ListIndex < 0 Then Exit Sub
  aDev = ModeCube(List1.ListIndex)
  'CDS_FORCE在Microsoft的开发文档中没有说明
  b = ChangeDisplaySettings(aDev, CDS_FORCE)
  '改变完显示模式设置之后向所有的窗口发送显示模式改变消息
  xxc= Send Message ByLong(HWND_BROADCAST, WM_SYSCOLORCHANGE, 0&, 0&)
  xxa = SendMessageByLong(HWND_BROADCAST, WM_PALETTECHANGED, Me.hwnd, 0&)
  xxb = PostMessage(HWND_BROADCAST, WM_SYSCOLORCHANGE, 0&, 0&)
  xxd = InvalidateRect(0&, ByVal 0, 1&)
  End Sub
  Private Sub Command2_Click()
  Dim aDev As DEVMODE
  Dim tempVar As String
  Dim RetVal
  Dim shellString As String
  If List1.ListIndex < 0 Then Exit Sub
  aDev = ModeCube(List1.ListIndex)
  tempVar = LTrim$(Str(aDev.dmPelsWidth)) + “x" + LTrim$(Str(aDev.dmPelsHeight)) +
  “x" + LTrim$(Str(aDev.dmBitsPerPel))
  Debug.Print tempVar
  shellString =“Rundll.exe DeskCp16.dll,QUICKRES_RUNDLLENTRY "
  shellString = shellString + tempVar
  '调用Windows中的QuickRes库来改变显示模式,如果你的系统中没有安装QuickRes系统将会产生一个错误
  RetVal = Shell(shellString, 1)
  End Sub
  Private Sub Form_Load()
  Command1.Caption = “使用API函数改变分辨率"
  Command2.Caption =“使用QuickRes库"
  LoadDisplayMode
  End Sub
  运行程序,点击选择ListBox中的显示模式,然后按下“使用API函数改变分辨率”键或者“使用QuickRes库”键,就可以切换显示模式到所需要的模式了。
  需要说明的一点是,在程序中的改变显示模式的语句 b = ChangeDisplaySettings(aDev, CDS_FORCE) 中的常量CDS_FORCE是一个未公开(UnDocument)的定义,在微软的帮助文档是没有有关的说明的。
  以上的程序在Win98、VB6下运行通过。(长沙 陈锐)
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