Change Resolution with WinAPI functions

[SpriggsySpriggs]

The below code can be used to change resolution for a given monitor in Windows. This was tested on Windows 10 20H2 64 bit using the 64 bit IDE. It does not work in 32 bit as of yet. It requires v1.5 or higher to compile as-is. The code asks for input for which monitor to change (starting with zero as the first), then the width and height to change to.

Code: QB64: [Select]

1. Option _Explicit
2. $If VERSION < 1.5 Then
3.     $ERROR Stable build v1.5 or higher is required
4. $End If
5. $If 32BIT Then
6.     $ERROR This code can only be ran in the 64 bit IDE at the moment
7. $End If
8.  
9. $Asserts
10. $Console:Only
11.  
12. Const CHANGE_MODE = 1
13.  
14. Const DISP_CHANGE_SUCCESSFUL = 0
15.  
16. Const CDS_FULLSCREEN = &H00000004
17.  
18. Type POINTL
19.     As Long x, y
20. End Type
21.  
22. Type DEVMODE
23.     As String * 32 dmDeviceName
24.     As Integer dmSpecVersion, dmDriverVersion, dmSize, dmDriverExtra
25.     As Long dmFields
26.     As POINTL dmPosition
27.     As Long dmDisplayOrientation, dmDisplayFixedOutput
28.     As Integer dmColor, dmDuplex, dmYResolution, dmTTOption, dmCollate
29.     As String * 32 dmFormName
30.     As Integer dmLogPixels
31.     As Long dmBitsPerPel, dmPelsWidth, dmPelsHeight, dmDisplayFlags, dmDisplayFrequency, dmICMMethod, dmICMIntent, dmMediaType, dmDitherType, dmReserved1, dmReserved2, dmPanningWidth, dmPanningHeight
32. End Type
33.  
34. Type DISPLAY_DEVICE
35.     As Long cb
36.     As String * 32 DeviceName
37.     As String * 128 DeviceString
38.     As Long StateFlags
39.     As String * 128 DeviceID, DeviceKey
40. End Type
41.  
42. Declare CustomType Library
43.     Function EnumDisplayDevices%% Alias "EnumDisplayDevicesA" (ByVal lpDevice As _Offset, Byval iDevNum As Long, Byval lpDisplayDevice As _Offset, Byval dwFlags As Long)
44.     Function EnumDisplaySettings%% Alias "EnumDisplaySettingsA" (ByVal lpszDeviceName As _Offset, Byval iModeNum As Long, Byval lpDevMode As _Offset)
45.     Function ChangeDisplaySettings& Alias "ChangeDisplaySettingsExA" (ByVal lpszDeviceName As _Offset, Byval lpDevMode As _Offset, Byval hwnd As _Offset, Byval dwflags As Long, Byval lParam As _Offset)
46.     Function GetLastError& ()
47. End Declare
48.  
49. Dim As DISPLAY_DEVICE adapter: adapter.cb = Len(adapter)
50. Dim As Long adapterIndex: adapterIndex = 0
51. Dim As _Byte targetModeFound: targetModeFound = 0
52. Dim As String * 32 targetDeviceName
53. Dim As DEVMODE targetMode
54.  
55. Dim As Long index, dispwidth, dispheight
56.  
57. Input "Enter monitor index (zero based): ", index
58. Input "Enter display width and height, separated by comma: ", dispwidth, dispheight
59.  
60. While EnumDisplayDevices(0, adapterIndex, _Offset(adapter), 0)
61.     Dim As DEVMODE mode: mode.dmSize = Len(mode)
62.     Dim As Long modeIndex: modeIndex = 0
63.     While EnumDisplaySettings(_Offset(adapter.DeviceName), modeIndex, _Offset(mode))
64.         If Not targetModeFound And adapterIndex = index Then
65.             If CHANGE_MODE And mode.dmPelsWidth = dispwidth And mode.dmPelsHeight = dispheight And mode.dmDisplayFrequency >= 59 And mode.dmDisplayFrequency <= 60 Then
66.                 targetModeFound = Not targetModeFound
67.                 targetDeviceName = adapter.DeviceName
68.                 targetMode = mode
69.             End If
70.         End If
71.         modeIndex = modeIndex + 1
72.     Wend
73.     adapterIndex = adapterIndex + 1
74. Wend
75. If targetModeFound Then
76.     Dim As Long r
77.     r = ChangeDisplaySettings(_Offset(targetDeviceName), _Offset(targetMode), 0, CDS_FULLSCREEN, 0)
78.     _Assert r = DISP_CHANGE_SUCCESSFUL, Str$(r)
79.  
80.     Sleep
81.  
82.     r = ChangeDisplaySettings(_Offset(targetDeviceName), 0, 0, 0, 0)
83.     _Assert r = DISP_CHANGE_SUCCESSFUL, Str$(r)
84. End If

[OldsCool]

Thought I'd give it a try. loaded it in QB v1.4. have an IDE error on line 32 - 'Expected variablename AS type or END TYPE...I'll upgrade to latest QB64 version. that may be it?

 update...I'm guessing it's the Win7 / 32bit machine I'm using right now...good luck didn't want to waste your time.

[SpriggsySpriggs]

Thought I'd give it a try. loaded it in QB v1.4. have an IDE error on line 32 - 'Expected variablename AS type or END TYPE...I'll upgrade to latest QB64 version. that may be it?

@OldsCool Oh, this code would require at least stable build v1.5 to compile due to the newer way of declaring variables. You can get the latest stable or the dev build for your Windows 7 machine still.

[OldsCool]

Awesome, thanks. I can see many uses for this. I'll upgrade (thought so...) and try it.

[OldsCool]

I just read the second line of your previous post, missed it somehow...Older QB64 versions have been running flawlessly on my Win7/32 machine. I was mostly wondering about the compatibility of your routine with Win7 itself, i Figured the error I was getting was a version issue. if you're still interested I'll let you know how it goes once I upgrade, thanks again .

[SpriggsySpriggs]

@OldsCool I actually updated the post after you mentioned it. You didn't miss anything. Glad you are showing some interest in the thread, though

[SpriggsySpriggs]

@OldsCool You can forget trying to run it as a 32 bit executable. The code doesn't currently work in 32 bit. I tried it myself on another computer. Oh well. 64 bit is the more common build of Windows anyways