by Fallout[] (2 Submissions)
Category: Windows System Services
Compatability: Visual Basic 5.0
Difficulty: Unknown Difficulty
Originally Published: Sat 18th September 1999
Date Added: Mon 8th February 2021
Rating: 
(1 Votes)
This routine, like the ListView method in Enumerating the Available Display Resolutions, uses Windows' EnumDisplaySettings API to retrieve all
API Declarations
Alias "EnumDisplaySettingsA" _
(ByVal lpszDeviceName As Long, _
ByVal iModeNum As Long, _
lpDevMode As Any) As Boolean
Public Declare Function GetDeviceCaps Lib "gdi32" _
(ByVal hdc As Long, _
ByVal nIndex As Long) As Long
Public Declare Function ChangeDisplaySettings Lib "user32" _
Alias "ChangeDisplaySettingsA" _
(lpDevMode As Any, _
ByVal dwflags As Long) As Long
Public Declare Function SetMenuDefaultItem Lib "user32" _
(ByVal hMenu As Long, _
ByVal uItem As Long, _
ByVal fByPos As Long) As Long
Public Declare Function GetMenu Lib "user32" _
(ByVal hWnd As Long) As Long
Public Declare Function GetSubMenu Lib "user32" _
(ByVal hMenu As Long, _
ByVal nPos As Long) As Long
Public Const LOGPIXELSX As Long = 88
Public Const LOGPIXELSY As Long = 90
Public Const BITSPIXEL As Long = 12
Public Const HORZRES As Long = 8
Public Const VERTRES As Long = 10
Public Const CCDEVICENAME As Long = 32
Public Const CCFORMNAME As Long = 32
Public Const DM_GRAYSCALE As Long = &H1
Public Const DM_INTERLACED As Long = &H2
Public Const DM_BITSPERPEL As Long = &H40000
Public Const DM_PELSWIDTH As Long = &H80000
Public Const DM_PELSHEIGHT As Long = &H100000
Public Const DM_DISPLAYFLAGS As Long = &H200000
Public Const CDS_UPDATEREGISTRY As Long = &H1
Public Const CDS_TEST As Long = &H2
Public Const CDS_FULLSCREEN As Long = &H4
Public Const CDS_GLOBAL As Long = &H8
Public Const CDS_SET_PRIMARY As Long = &H10
Public Const CDS_NORESET As Long = &H10000000
Public Const CDS_SETRECT As Long = &H20000000
Public Const CDS_RESET As Long = &H40000000
Public Const CDS_FORCE As Long = &H80000000
'Return values for ChangeDisplaySettings
'Public Const DISP_CHANGE_SUCCESSFUL = 0
'Public Const DISP_CHANGE_RESTART = 1
'Public Const DISP_CHANGE_FAILED = -1
'Public Const DISP_CHANGE_BADMODE = -2
'Public Const DISP_CHANGE_NOTUPDATED = -3
'Public Const DISP_CHANGE_BADFLAGS = -4
'Public Const DISP_CHANGE_BADPARAM = -5
Public 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
VBcoders
Dim currHRes As Long
Dim currVRes As Long
Dim currBPP As Long
'var set in mnuModes
Dim currMenuItem As Long
'array of valid resolutions & colour depths
Dim resArray() As Long
'const for the members of the array
'i.e. resArray(resWidth, Index) = 1024
'i.e. resArray(resHeight, Index) = 768
'i.e. resArray(resDepth, Index)= 16 'Bits per pixel
Const resWidth = 1
Const resHeight = 2
Const resDepth = 3
Private Sub Form_Load()
'retrieves the current screen resolution for
'later comparison against DEVMODE values in
'CompareSettings.
currHRes = GetDeviceCaps(hdc, HORZRES)
currVRes = GetDeviceCaps(hdc, VERTRES)
currBPP = GetDeviceCaps(hdc, BITSPIXEL)
Dim maxItems As Long
InitializeDisplayMenu maxItems
FinalizeDisplayMenu maxItems
End Sub
Private Sub FinalizeDisplayMenu(maxItems As Long)
'This adds a separator and a final menu item,
'providing the ability to open the control panel
'display settings page from the app.
If maxItems > 0 Then
Dim hMenu As Long
Dim r As Long
'add the separator
maxItems = maxItems + 1
Load mnuModes(maxItems)
mnuModes(maxItems).Caption = "-"
'add the final item
maxItems = maxItems + 1
Load mnuModes(maxItems)
mnuModes(maxItems).Caption = "Show Display Settings"
'finally, bold the newly-added menuitem
hMenu = GetSubMenu(GetMenu(Me.hWnd), 0)
Call SetMenuDefaultItem(hMenu, maxItems - 1, True)
End If
End Sub
Private Sub InitializeDisplayMenu(maxItems As Long)
Dim DM As DEVMODE
Dim dMode As Long
'36 should be enough to hold your settings.
'It's trimmed back at the end of this routine.
ReDim resArray(1 To 3, 0 To 35)
'set the DEVMODE flags and structure size
DM.dmFields = DM_PELSWIDTH Or DM_PELSHEIGHT Or DM_BITSPERPEL
DM.dmSize = LenB(DM)
'The first mode is 0
dMode = 0
'call the API to retrieve the values for the
'specified dMode
Do While EnumDisplaySettings(0&, dMode, DM) > 0
'if the BitsPerPixel is greater than 4
'(16 colours), then add the item to a menu
If DM.dmBitsPerPel >= 4 Then
Call MenuAdd(DM, resArray(), maxItems)
End If
'increment and call again. Continue until
'EnumDisplaySettings returns 0 (no more settings)
dMode = dMode + 1
Loop
'trim back the resArray to fit the number of actual entries.
ReDim Preserve resArray(1 To 3, 0 To maxItems)
End Sub
Private Function CompareSettings(DM As DEVMODE) As Long
'compares the current screen resolution with
'the current DEVMODE values. Returns TRUE if
'the horizontal and vertical resolutions, and
'the bits per pixel colour depth, are the same.
CompareSettings = (DM.dmBitsPerPel = currBPP) And _
DM.dmPelsHeight = currVRes And _
DM.dmPelsWidth = currHRes
End Function
Private Sub MenuAdd(DM As DEVMODE, resArray() As Long, mnuCount As Long)
Dim mType As String
'used to determine when the colour depth has
'changed, so we can add a separator to the menu.
Static lastBitsPerPel As Long
'select the appropriate text string based on
'the colour depth
Select Case DM.dmBitsPerPel
Case 4: mType = "16 Color"
Case 8: mType = "256 Color"
Case 16: mType = "High Color"
Case 24, 32: mType = "True Color"
End Select
'if this is the first item, we can't load the menu
'array item, and it will not require a separator.
If mnuCount > 0 Then
'load a new menu item to the array
Load mnuModes(mnuCount)
'determine if the colour depth has changed. If so,
'make the caption a separator, and load a new item
'to hold the item.
If lastBitsPerPel <> DM.dmBitsPerPel Then
mnuModes(mnuCount).Caption = "-"
mnuCount = mnuCount + 1
Load mnuModes(mnuCount)
End If
End If
'create the menu caption
mnuModes(mnuCount).Caption = DM.dmPelsWidth & "x" & _
DM.dmPelsHeight & " [" & _
DM.dmBitsPerPel & " bit " & _
mType & "]"
'see if this is the current resolution,
'and if so, check the menu item
mnuModes(mnuCount).Checked = CompareSettings(DM)
If mnuModes(mnuCount).Checked Then currMenuItem = mnuCount
resArray(resWidth, mnuCount) = DM.dmPelsWidth
resArray(resHeight, mnuCount) = DM.dmPelsHeight
resArray(resDepth, mnuCount) = DM.dmBitsPerPel
'save the current DEVMODE value for depth
'and increment the menu item count, ready for
'the next call
lastBitsPerPel = DM.dmBitsPerPel
mnuCount = mnuCount + 1
End Sub
Private Sub cmdLoadMenu_Click()
Dim maxItems As Long
InitializeDisplayMenu maxItems
cmdLoadMenu.Enabled = False
FinalizeDisplayMenu maxItems
End Sub
Private Sub mnuModes_Click(Index As Integer)
Dim DM As DEVMODE
Select Case Index
Case mnuModes.Count
'show the display control panel
Call Shell("rundll32.exe shell32.dll,Control_RunDLL desk.cpl,,3", 1)
Case Else
'change the current resolution, no prompting
'BE CAREFUL .. you could set your system to a
'setting which renders the display difficult to read.
With DM
.dmPelsWidth = resArray(resWidth, Index)
.dmPelsHeight = resArray(resHeight, Index)
.dmBitsPerPel = resArray(resDepth, Index)
.dmFields = DM_PELSWIDTH Or DM_PELSHEIGHT Or DM_BITSPERPEL
.dmSize = LenB(DM)
End With
If ChangeDisplaySettings(DM, CDS_FORCE) <> 0 Then
MsgBox "Error! Perhaps your hardware is not up to the task?"
End If
'indicate the current menu selection
mnuModes(currMenuItem).Checked = False
mnuModes(Index).Checked = True
currMenuItem = Index
End Select
End Sub
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