API to change resolution

stickmangumby · #1 09-26-2004, 05:27 AM

I've had minimal contact with API in VB6, and from what I have discerned API seems quite different in VB.net

I'm looking for some API to change the colour depth of the monitor so that i can use a transparency key to make rounded forms, which doesn't seem to work in 32 bit colour.

ThankS

stickmangumby · #2 10-03-2004, 05:06 AM

^^bump^^

ive tried using the VB6 API for changing resolution and colour depth, but when .net converted it it went a lot spastic, and i couldnt sort it out nomatter what i did.

im getting desperate!

Dennis DVR · #3 10-03-2004, 06:15 AM

here's the test code that I made, the original source code was in C# I just converted it to VB.NET

it is very similar to the legacy VB6 code.

Code:

Imports System.Runtime.InteropServices 'add this to your VB code

    Const CCDEVICENAME As Short = 32
    Const CCFORMNAME As Short = 32
    Const DM_BITSPERPEL = &H40000
    Const DM_PELSWIDTH = &H80000
    Const DM_PELSHEIGHT = &H100000
    Const CDS_UPDATEREGISTRY = &H1
    Const CDS_TEST = &H2
    Const CDS_FULLSCREEN = &H4
    Const DISP_CHANGE_SUCCESSFUL = 0
    Const DISP_CHANGE_RESTART = 1

    Const HWND_BROADCAST = &HFFFF&
    Const WM_DISPLAYCHANGE = &H7E&
    Const SPI_SETNONCLIENTMETRICS = 42

    Private Structure SetResolution
        <MarshalAs(UnmanagedType.ByValTStr, SizeConst:=CCDEVICENAME)> _
        Public dmDeviceName As String 'You can also use the Dim i guess
        Public dmSpecVersion As Short
        Public dmDriverVersion As Short
        Public dmSize As Short
        Public dmDriverExtra As Short
        Public dmFields As Integer
        Public dmOrientation As Short
        Public dmPaperSize As Short
        Public dmPaperLength As Short
        Public dmPaperWidth As Short
        Public dmScale As Short
        Public dmCopies As Short
        Public dmDefaultSource As Short
        Public dmPrintQuality As Short
        Public dmColor As Short
        Public dmDuplex As Short
        Public dmYResolution As Short
        Public dmTTOption As Short
        Public dmCollate As Short
        'equivalent of dmFormName * CCFORMNAME
        <MarshalAs(UnmanagedType.ByValTStr, SizeConst:=CCFORMNAME)> _
        Public dmFormName As String
        Public dmLogPixels As Short
        Public dmBitsPerPel As Short
        Public dmPelsWidth As Integer
        Public dmPelsHeight As Integer

        Public dmDisplayFlags As Integer
        Public dmDisplayFrequency As Integer

        Public dmICMMethod As Integer
        Public dmICMIntent As Integer
        Public dmMediaType As Integer
        Public dmDitherType As Integer
        Public dmReserved1 As Integer
        Public dmReserved2 As Integer

        Public dmPanningWidth As Integer
        Public dmPanningHeight As Integer

    End Structure
    Private Declare Function EnumDisplaySettings Lib "user32" Alias "EnumDisplaySettingsA" (ByVal lpszDeviceName As String, ByVal iModeNum As Integer, ByRef lpDevMode As SetResolution) As Integer
    Private Declare Function ChangeDisplaySettings Lib "user32" Alias "ChangeDisplaySettingsA" (ByRef lpDevMode As SetResolution, ByVal dwFlags As Long) As Integer

    'you need a command button 
    Private Sub ChangeRes_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ChangeRes.Click
        Dim scrResolution As SetResolution
        Dim lResult As Integer
        Dim iAns As Integer

        '
        ' Retrieve info about the current graphics mode
        ' on the current display device.
        '
        scrResolution.dmDeviceName = ""
        scrResolution.dmFormName = ""
        scrResolution.dmSize = Marshal.SizeOf(scrResolution)
        lResult = EnumDisplaySettings("", -1, scrResolution)
        '
        ' Set the new resolution. Don't change the color
        ' depth so a restart is not necessary.
        '
        With scrResolution
            'this is not necessary in C# I think
            .dmFields = DM_PELSWIDTH Or DM_PELSHEIGHT 'Or DM_BITSPERPEL
            
            .dmPelsWidth = 1024 'here the resolution
            .dmPelsHeight = 768
            '.dmBitsPerPel = 32 (could be 8, 16, 32 or even 4)
        End With
        '
        ' Change the display settings to the specified graphics mode.
        '
        lResult = ChangeDisplaySettings(scrResolution, CDS_TEST)
        If lResult = -1 Then
            MsgBox("Mode not supported", vbSystemModal, "Error")
        Else
            lResult = ChangeDisplaySettings(scrResolution, CDS_UPDATEREGISTRY)
            Select Case lResult
                Case DISP_CHANGE_RESTART
                     Msgbox("You need to restart your computer", vbInformation, "Resolution Changed")    
                Case DISP_CHANGE_SUCCESSFUL
                    MsgBox("Screen resolution changed", vbInformation, "Resolution Changed")
                Case Else
                    MsgBox("Mode not supported", vbSystemModal, "Error")
            End Select
        End If
    End Sub

try to experiment on the source code.
I haven't explain the code much just be careful about the declaration type of the variable.

alink · #4 11-13-2004, 12:22 PM

Thanks for your solution Duane. I was wondering if it's possible to change the resolution on a secondary monitor. When having dual monitors on "dual view" the program only changes the resolution on monitor 1 and not 2.

Dennis DVR · #5 11-14-2004, 04:47 AM

Hi, alink

I don't use dual monitor so I'm not sure if it will work for you

but i'm positive that it can be done using EnumDisplayDevices and ChangeDisplaySetiingsEx API function.

This is what i've come-up.

Code:

Imports System.Runtime.InteropServices

Const CCDEVICENAME As Short = 32
Const CCFORMNAME As Short = 32
Const DM_BITSPERPEL = &H40000
Const DM_PELSWIDTH = &H80000
Const DM_PELSHEIGHT = &H100000
Const CDS_UPDATEREGISTRY = &H1
'Const CDS_TEST = &H2
'Const CDS_FULLSCREEN = &H4
'Const DISP_CHANGE_SUCCESSFUL = 0
'Const DISP_CHANGE_RESTART = 1

'Const HWND_BROADCAST = &HFFFF&
'Const WM_DISPLAYCHANGE = &H7E&
'Const SPI_SETNONCLIENTMETRICS = 42
Const DISPLAY_DEVICE_ATTACHED_TO_DESKTOP = &H1 'Device that is part of desktop
Const DISPLAY_PRIMARY_DEVICE = &H4 'Primary device

'Holds the information of display adpter
Private Structure DISPLAY_DEVICE
     Public cb As Integer
     <MarshalAs(UnmanagedType.ByValTStr, SizeConst:=CCDEVICENAME)> _
     Public DeviceName As String
     <MarshalAs(UnmanagedType.ByValTStr, SizeConst:=128)> _
     Public DeviceString As String
     Public StateFlags As Short
     <MarshalAs(UnmanagedType.ByValTStr, SizeConst:=128)> _
     Public DeviceID As String
     <MarshalAs(UnmanagedType.ByValTStr, SizeConst:=128)> _
     Public DeviceKey As String
End Structure

'Holds the setting of display adapter
Private Structure SetResolution
     <MarshalAs(UnmanagedType.ByValTStr, SizeConst:=CCDEVICENAME)> _
     Public dmDeviceName As String
     Public dmSpecVersion As Short
     Public dmDriverVersion As Short
     Public dmSize As Short
     Public dmDriverExtra As Short
     Public dmFields As Integer
     Public dmOrientation As Short
     Public dmPaperSize As Short
     Public dmPaperLength As Short
     Public dmPaperWidth As Short
     Public dmScale As Short
     Public dmCopies As Short
     Public dmDefaultSource As Short
     Public dmPrintQuality As Short
     Public dmColor As Short
     Public dmDuplex As Short
     Public dmYResolution As Short
     Public dmTTOption As Short
     Public dmCollate As Short

     <MarshalAs(UnmanagedType.ByValTStr, SizeConst:=CCFORMNAME)> _
     Public dmFormName As String
     Public dmLogPixels As Short
     Public dmBitsPerPel As Short
     Public dmPelsWidth As Integer
     Public dmPelsHeight As Integer
     Public dmDisplayFlags As Integer
     Public dmDisplayFrequency As Integer
     Public dmICMMethod As Integer
     Public dmICMIntent As Integer
     Public dmMediaType As Integer
     Public dmDitherType As Integer
     Public dmReserved1 As Integer
     Public dmReserved2 As Integer
     Public dmPanningWidth As Integer
     Public dmPanningHeight As Integer
End Structure
'API declaration set or get display adpter information
Private Declare Function EnumDisplayDevices Lib "user32" Alias "EnumDisplayDevicesA" (ByVal Unused As Integer, ByVal iDevNum As Short, ByRef lpDisplayDevice As DISPLAY_DEVICE, ByVal dwFlags As Integer) As Integer
    Private Declare Function EnumDisplaySettings Lib "user32" Alias "EnumDisplaySettingsA" (ByVal lpszDeviceName As String, ByVal iModeNum As Integer, ByRef lpDevMode As SetResolution) As Integer
    Private Declare Function ChangeDisplaySettingsEx Lib "user32" Alias "ChangeDisplaySettingsExA" (ByVal lpszDeviceName As String, ByRef lpDevMode As SetResolution, ByVal hWnd As Integer, ByVal dwFlags As Integer, ByVal lParam As Integer) As Integer

'Command Button Click event
Private Sub ChangeRes_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ChangeRes.Click
     Dim scrResolution As SetResolution
     Dim DisplayDevice As DISPLAY_DEVICE
     Dim DD() As DISPLAY_DEVICE 'Holds the information of display devices
     Dim RS() As SetResolution ''Holds the settings of display devices
     Dim lResult As Integer = 1
     Dim nMonitor As Short
     Dim nSetting As Short
     '
     ' Retrieve info about the current graphics mode
     ' on the current display device.
     '
     'cmbResolution.Items.Clear()
     'Get all available desktop monitor
     Do While lResult <> 0
         DisplayDevice.cb = Marshal.SizeOf(DisplayDevice)
         scrResolution.dmSize = Marshal.SizeOf(scrResolution)
         lResult = EnumDisplayDevices(0, nMonitor, DisplayDevice, 0)
         If DisplayDevice.StateFlags = DISPLAY_DEVICE_ATTACHED_TO_DESKTOP Or _
            DisplayDevice.StateFlags = DISPLAY_PRIMARY_DEVICE Or _
            DisplayDevice.StateFlags = (DISPLAY_DEVICE_ATTACHED_TO_DESKTOP Or DISPLAY_PRIMARY_DEVICE) Then 'is it part of the desktop device or is it primary adapter or both
             ReDim Preserve DD(nMonitor)
             DD(nMonitor) = DisplayDevice
            'This part can be used if you want to retrieve all the available resolution for the desktop adapter (make sure the resolution supported by monitor)
            ' Do While EnumDisplaySettings(DisplayDevice.DeviceName, nSetting, scrResolution) <> 0
           '      cmbResolution.Items.Add(DisplayDevice.DeviceString & " " & scrResolution.dmPelsWidth & " x " & scrResolution.dmPelsHeight & " " & scrResolution.dmBitsPerPel & " Bits")
           '         nSetting += 1
           '     Loop
           '     cmbResolution.Sorted = True
            End If
            nMonitor += 1
        Loop
        
        'set the resolution to all desktop adapter
        For nMonitor = 0 To UBound(DD)
            ReDim Preserve RS(nMonitor)
            RS(nMonitor).dmSize = Marshal.SizeOf(RS(nMonitor))
            With RS(nMonitor)
                .dmFields = DM_PELSWIDTH Or DM_PELSHEIGHT 'Or DM_BITSPERPEL
                'Here's the resolution
                .dmPelsWidth = 1024
                .dmPelsHeight = 768

                '.dmBitsPerPel = 32 (could be 8, 16, 32 or even 4)
            End With
            'change the resolution of Display Adpter
            lResult = ChangeDisplaySettingsEx(DD(nMonitor).DeviceName, RS(nMonitor), 0, CDS_UPDATEREGISTRY, 0)
            If lResult = -1 Then
                MsgBox("Mode not supported", vbSystemModal, "Error")
            End If
        Next
End Sub

You should experiment on the code, as I have said I never tried the code on a dual monitor, but I'm positive that the above API can do the trick.

You can also set different resolution for each display adapter.

Note: I use ChangeDisplaySettingsEx to change the resolution of other display adapter which is part of the desktop. ChangeDisplySetting change the default adpter only.

Dennis DVR · #6 11-17-2004, 06:22 PM

PM

Quote:

Originally Posted by alink

Hey Duane, first off thanks again for your solution. It worked great in VB.net. I was trying to port it to vb6 and ran into a few problems. I also posted a reply on the appropriate thread but I dont see it today... Any ideas why it was deleted? I copy and pasted what I had done so far and explained I had trouble interpreting the marshalas command since im unsure of how it works.

I really like how in vb.net I could use a class and then just have all my forms call that, but I couldnt do something similar in vb6, so was trying to do it all in one form, but ran into probs as above.

Regards, and I'll be sure to pass on your helpfulness in the future

Quote:

Originally Posted by alink

Hey Duane,

I originally didn't find my post and was wondering if it was deleted. I checked a few hours later and decided to search using all posts by me and found it. I'll try it out and let you know what happens. Thanks again for being so quick to reply and so helpful.

Hi alink

Your last post isn't VB.NET related so I asked the moderator to move it to its proper thread

Just for the record, here's the link
http://www.xtremevbtalk.com/showthread.php?t=198335