动态改变屏幕设置 Private Declare Function lstrcpy Lib "kernel32" Alias "lstrcpyA" (lpString1 As Any, lpString2 As Any) As Long Const CCHDEVICENAME = 32 Const CCHFORMNAME = 32 Private Type DEVMODE dmDeviceName As String * CCHDEVICENAME 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 As String * CCHFORMNAME dmUnusedPadding As Integer dmBitsPerPel As Integer dmPelsWidth As Long dmPelsHeight As Long dmDisplayFlags As Long dmDisplayFrequency As Long End Type Private Declare Function _ ChangeDisplaySettings Lib _ "User32" Alias "ChangeDisplaySettingsA" (_ ByVal lpDevMode As Long, _ ByVal dwflags As Long) As Long '函数 Public Function SetDisplayMode(Width As _ Integer,Height As Integer, Color As _ Integer) As Long Const DM_PELSWIDTH = &H80000 Const DM_PELSHEIGHT = &H100000 Const DM_BITSPERPEL = &H40000 Dim NewDevMode As DEVMODE Dim pDevmode As Long With NewDevMode .dmSize = 122 If Color = -1 Then .dmFields = DM_PELSWIDTH Or DM_PELSHEIGHT Else .dmFields = DM_PELSWIDTH Or _ DM_PELSHEIGHT Or DM_BITSPERPEL End If .dmPelsWidth = Width .dmPelsHeight = HeightIf Color <> -1 Then .dmBitsPerPel = Color End If End With pDevmode = lstrcpy(NewDevMode, NewDevMode) SetDisplayMode = ChangeDisplaySettings(pDevmode, 0) End Function 例子调用:改变为 640x480x24位: i = SetDisplayMode(640, 480, 24) 如果成功返回 0 。
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。
Option Explicit Const WM_DISPLAYCHANGE = &H7E Const HWND_BROADCAST = &HFFFF& Const EWX_LOGOFF = 0 Const EWX_SHUTDOWN = 1 Const EWX_REBOOT = 2 Const EWX_FORCE = 4 Const CCDEVICENAME = 32 Const CCFORMNAME = 32 Const DM_BITSPERPEL = &H40000 Const DM_PELSWIDTH = &H80000 Const DM_PELSHEIGHT = &H100000 Const CDS_UPDATEREGISTRY = &H1 Const CDS_TEST = &H4 Const DISP_CHANGE_SUCCESSFUL = 0 Const DISP_CHANGE_RESTART = 1 Const BITSPIXEL = 12 Private Type DEVMODE dmDeviceName As String * CCDEVICENAME 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 As String * CCFORMNAME dmUnusedPadding As Integer dmBitsPerPel As Integer dmPelsWidth As Long dmPelsHeight As Long dmDisplayFlags As Long dmDisplayFrequency As Long End Type Private Declare Function EnumDisplaySettings Lib "user32" Alias "EnumDisplaySettingsA" (ByVal lpszDeviceName As Long, ByVal iModeNum As Long, lpDevMode As Any) As Boolean Private Declare Function ChangeDisplaySettings Lib "user32" Alias "ChangeDisplaySettingsA" (lpDevMode As Any, ByVal dwFlags As Long) As Long Private Declare Function ExitWindowsEx Lib "user32" (ByVal uFlags As Long, ByVal dwReserved As Long) As Long Private Declare Function GetDeviceCaps Lib "gdi32" (ByVal hdc As Long, ByVal nIndex As Long) As Long Private Declare Function CreateDC Lib "gdi32" Alias "CreateDCA" (ByVal lpDriverName As String, ByVal lpDeviceName As String, ByVal lpOutput As String, ByVal lpInitData As Any) As Long Private Declare Function DeleteDC Lib "gdi32" (ByVal hdc As Long) As Long Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long Dim OldX As Long, OldY As Long, nDC As Long Sub ChangeRes(X As Long, Y As Long, Bits As Long) Dim DevM As DEVMODE, ScInfo As Long, erg As Long, an As VbMsgBoxResult 'Get the info into DevM erg = EnumDisplaySettings(0&, 0&, DevM) 'This is what we're going to change DevM.dmFields = DM_PELSWIDTH Or DM_PELSHEIGHT Or DM_BITSPERPEL DevM.dmPelsWidth = X 'ScreenWidth DevM.dmPelsHeight = Y 'ScreenHeight DevM.dmBitsPerPel = Bits '(can be 8, 16, 24, 32 or even 4) 'Now change the display and check if possible erg = ChangeDisplaySettings(DevM, CDS_TEST) 'Check if succesfull Select Case erg& Case DISP_CHANGE_RESTART an = MsgBox("You've to reboot", vbYesNo + vbSystemModal, "Info") If an = vbYes Then erg& = ExitWindowsEx(EWX_REBOOT, 0&) End If Case DISP_CHANGE_SUCCESSFUL erg = ChangeDisplaySettings(DevM, CDS_UPDATEREGISTRY) ScInfo = Y * 2 ^ 16 + X 'Notify all the windows of the screen resolution change SendMessage HWND_BROADCAST, WM_DISPLAYCHANGE, ByVal Bits, ByVal ScInfo MsgBox "Everything's ok", vbOKOnly + vbSystemModal, "It worked!" Case Else MsgBox "Mode not supported", vbOKOnly + vbSystemModal, "Error" End Select End Sub Private Sub Form_Load() Dim nDC As Long 'retrieve the screen's resolution OldX = Screen.Width / Screen.TwipsPerPixelX OldY = Screen.Height / Screen.TwipsPerPixelY 'Create a device context, compatible with the screen nDC = CreateDC("DISPLAY", vbNullString, vbNullString, ByVal 0&) 'Change the screen's resolution ChangeRes 640, 480, GetDeviceCaps(nDC, BITSPIXEL) End Sub Private Sub Form_Unload(Cancel As Integer) 'restore the screen resolution ChangeRes OldX, OldY, GetDeviceCaps(nDC, BITSPIXEL) 'delete our device context DeleteDC nDC End Sub
Private Declare Function lstrcpy Lib "kernel32" Alias "lstrcpyA" (lpString1 As Any, lpString2 As Any) As Long
Const CCHDEVICENAME = 32
Const CCHFORMNAME = 32
Private Type DEVMODE
dmDeviceName As String * CCHDEVICENAME
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 As String * CCHFORMNAME
dmUnusedPadding As Integer
dmBitsPerPel As Integer
dmPelsWidth As Long
dmPelsHeight As Long
dmDisplayFlags As Long
dmDisplayFrequency As Long
End Type
Private Declare Function _
ChangeDisplaySettings Lib _
"User32" Alias "ChangeDisplaySettingsA" (_
ByVal lpDevMode As Long, _
ByVal dwflags As Long) As Long
'函数
Public Function SetDisplayMode(Width As _
Integer,Height As Integer, Color As _
Integer) As Long
Const DM_PELSWIDTH = &H80000
Const DM_PELSHEIGHT = &H100000
Const DM_BITSPERPEL = &H40000
Dim NewDevMode As DEVMODE
Dim pDevmode As Long
With NewDevMode
.dmSize = 122
If Color = -1 Then
.dmFields = DM_PELSWIDTH Or DM_PELSHEIGHT
Else
.dmFields = DM_PELSWIDTH Or _
DM_PELSHEIGHT Or DM_BITSPERPEL
End If
.dmPelsWidth = Width
.dmPelsHeight = HeightIf Color <> -1 Then
.dmBitsPerPel = Color
End If
End With
pDevmode = lstrcpy(NewDevMode, NewDevMode)
SetDisplayMode = ChangeDisplaySettings(pDevmode, 0)
End Function
例子调用:改变为 640x480x24位:
i = SetDisplayMode(640, 480, 24)
如果成功返回 0 。
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。
Const WM_DISPLAYCHANGE = &H7E
Const HWND_BROADCAST = &HFFFF&
Const EWX_LOGOFF = 0
Const EWX_SHUTDOWN = 1
Const EWX_REBOOT = 2
Const EWX_FORCE = 4
Const CCDEVICENAME = 32
Const CCFORMNAME = 32
Const DM_BITSPERPEL = &H40000
Const DM_PELSWIDTH = &H80000
Const DM_PELSHEIGHT = &H100000
Const CDS_UPDATEREGISTRY = &H1
Const CDS_TEST = &H4
Const DISP_CHANGE_SUCCESSFUL = 0
Const DISP_CHANGE_RESTART = 1
Const BITSPIXEL = 12
Private Type DEVMODE
dmDeviceName As String * CCDEVICENAME
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 As String * CCFORMNAME
dmUnusedPadding As Integer
dmBitsPerPel As Integer
dmPelsWidth As Long
dmPelsHeight As Long
dmDisplayFlags As Long
dmDisplayFrequency As Long
End Type
Private Declare Function EnumDisplaySettings Lib "user32" Alias "EnumDisplaySettingsA" (ByVal lpszDeviceName As Long, ByVal iModeNum As Long, lpDevMode As Any) As Boolean
Private Declare Function ChangeDisplaySettings Lib "user32" Alias "ChangeDisplaySettingsA" (lpDevMode As Any, ByVal dwFlags As Long) As Long
Private Declare Function ExitWindowsEx Lib "user32" (ByVal uFlags As Long, ByVal dwReserved As Long) As Long
Private Declare Function GetDeviceCaps Lib "gdi32" (ByVal hdc As Long, ByVal nIndex As Long) As Long
Private Declare Function CreateDC Lib "gdi32" Alias "CreateDCA" (ByVal lpDriverName As String, ByVal lpDeviceName As String, ByVal lpOutput As String, ByVal lpInitData As Any) As Long
Private Declare Function DeleteDC Lib "gdi32" (ByVal hdc As Long) As Long
Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long
Dim OldX As Long, OldY As Long, nDC As Long
Sub ChangeRes(X As Long, Y As Long, Bits As Long)
Dim DevM As DEVMODE, ScInfo As Long, erg As Long, an As VbMsgBoxResult
'Get the info into DevM
erg = EnumDisplaySettings(0&, 0&, DevM)
'This is what we're going to change
DevM.dmFields = DM_PELSWIDTH Or DM_PELSHEIGHT Or DM_BITSPERPEL
DevM.dmPelsWidth = X 'ScreenWidth
DevM.dmPelsHeight = Y 'ScreenHeight
DevM.dmBitsPerPel = Bits '(can be 8, 16, 24, 32 or even 4)
'Now change the display and check if possible
erg = ChangeDisplaySettings(DevM, CDS_TEST)
'Check if succesfull
Select Case erg&
Case DISP_CHANGE_RESTART
an = MsgBox("You've to reboot", vbYesNo + vbSystemModal, "Info")
If an = vbYes Then
erg& = ExitWindowsEx(EWX_REBOOT, 0&)
End If
Case DISP_CHANGE_SUCCESSFUL
erg = ChangeDisplaySettings(DevM, CDS_UPDATEREGISTRY)
ScInfo = Y * 2 ^ 16 + X
'Notify all the windows of the screen resolution change
SendMessage HWND_BROADCAST, WM_DISPLAYCHANGE, ByVal Bits, ByVal ScInfo
MsgBox "Everything's ok", vbOKOnly + vbSystemModal, "It worked!"
Case Else
MsgBox "Mode not supported", vbOKOnly + vbSystemModal, "Error"
End Select
End Sub
Private Sub Form_Load() Dim nDC As Long
'retrieve the screen's resolution
OldX = Screen.Width / Screen.TwipsPerPixelX
OldY = Screen.Height / Screen.TwipsPerPixelY
'Create a device context, compatible with the screen
nDC = CreateDC("DISPLAY", vbNullString, vbNullString, ByVal 0&)
'Change the screen's resolution
ChangeRes 640, 480, GetDeviceCaps(nDC, BITSPIXEL)
End Sub
Private Sub Form_Unload(Cancel As Integer)
'restore the screen resolution
ChangeRes OldX, OldY, GetDeviceCaps(nDC, BITSPIXEL)
'delete our device context
DeleteDC nDC
End Sub