Using Win32 functions in Visual FoxPro Image Gallery
Code examples:
Custom GDI+ class
How to change display settings: screen resolution, screen refresh rate
Displaying dimmed window behind VFP top-level form
Enumerating devices installed on the local machine
Using Video Capture: displaying on FoxPro form frames and previewing video obtained from a digital camera
Round FoxPro form
Winsock: sending email messages (SMTP, port 25)
Configuring DEVMODE structure for a printer
Storing content of the Clipboard to a bitmap file
Winsock: connecting to a news server (NNTP, port 119)
How to view icons stored in executable files (Icon Viewer) - II
Custom FTP Class for Visual FoxPro application
Creating irregularly shaped FoxPro form using transparency color key
How to convert a bitmap file to monochrome format (1 bpp)
Creating a directory on the FTP
How to activate Windows Calculator
How to put a horizontal text scrolling on the form (a news line, marquee)
Using FoxTray ActiveX control: System Tray Icon and menu attached to VFP form
Customizing the frame of top-level form: removing the standard frame (VFP9, Vista)
GDI+: Implementing image scrolling with inertia
Encapsulating access to the Windows Services in a class
How to prevent users from accessing the Windows Desktop and from switching to other applications
How to put a vertical text scrolling on the form (a movie cast)
Reading and setting the priority class values for the current process and thread
How to detect if additional monitor is connected and active

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Before you begin:
Nowadays having two monitors connected to a PC becomes more a common place rather than exception. This code sample explains how to detect all available monitors through enumerating display devices and their properties.


See also:
  • How to change display settings: screen resolution, screen refresh rate
  • How to adjust monitor brightness (Vista, monitor with DDC support)
  • using System;
    using System.Runtime.InteropServices;
    using System.Windows.Forms;
    
    namespace ConsoleApplication1
    {
        partial class Program
        {
            public const int ENUM_CURRENT_SETTINGS = -1;
    
            [StructLayout(LayoutKind.Sequential)]
            public struct DISPLAY_DEVICE
            {
                public int cb;
                [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]
                public string DeviceName;
                [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 128)]
                public string DeviceString;
                public int StateFlags;
                [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 128)]
                public string DeviceID;
                [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 128)]
                public string DeviceKey;
    
                public DISPLAY_DEVICE(int flags)
                {
                    cb = 0;
                    StateFlags = flags;
                    DeviceName = new string((char)32, 32);
                    DeviceString = new string((char)32, 128);
                    DeviceID = new string((char)32, 128);
                    DeviceKey = new string((char)32, 128);
                    cb = Marshal.SizeOf(this);
                }
            }
    
            [StructLayout(LayoutKind.Sequential)]
            public struct DEVMODE
            {
                [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]
                public string dmDeviceName;
                public short dmSpecVersion;
                public short dmDriverVersion;
                public short dmSize;
                public short dmDriverExtra;
                public int dmFields;
                public short dmOrientation;
                public short dmPaperSize;
                public short dmPaperLength;
                public short dmPaperWidth;
                public short dmScale;
                public short dmCopies;
                public short dmDefaultSource;
                public short dmPrintQuality;
                public short dmColor;
                public short dmDuplex;
                public short dmYResolution;
                public short dmTTOption;
                public short dmCollate;
                [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]
                public string dmFormName;
                public short dmUnusedPadding;
                public short dmBitsPerPel;
                public int dmPelsWidth;
                public int dmPelsHeight;
                public int dmDisplayFlags;
                public int dmDisplayFrequency;
            }
    
            static void EnumMonitors()
            {
                foreach (Screen screen in Screen.AllScreens)
                {
                    Console.WriteLine("*** Managed output");
    
                    Console.WriteLine("Display Device: {0}\t\n" +
                        "\tBPP={1}\n\tWidth={2}\n\tHeight={3}\n\n",
                        screen.DeviceName, screen.BitsPerPixel,
                        screen.Bounds.Width, screen.Bounds.Height);
    
                    DISPLAY_DEVICE monitor =
                        new DISPLAY_DEVICE(0);
    
                    EnumDisplayDevices(screen.DeviceName, 0,
                        ref monitor, 0);
    
                    DEVMODE dm = new DEVMODE();
    
                    EnumDisplaySettings(screen.DeviceName,
                        ENUM_CURRENT_SETTINGS, ref dm);
    
                    Console.WriteLine("*** Unmanaged output");
    
                    Console.WriteLine("\tMonitor: {0}\n\t\t{1}\n\t\t{2}",
                        monitor.DeviceName, 
                        monitor.DeviceString, monitor.DeviceID);
    
                    Console.WriteLine(
                        "\t\t\tFreq.={0}\n" +
                        "\t\t\tBPP={1}\n" +
                        "\t\t\tWidth={2}\n" +
                        "\t\t\tHeight={3}\n",
                        dm.dmDisplayFrequency, dm.dmBitsPerPel,
                        dm.dmPelsWidth, dm.dmPelsHeight);
    
                }
                Console.WriteLine("Number of monitors: {0}", 
                    Screen.AllScreens.Length);
            }
    
            [DllImport("User32.dll")]
            private static extern bool EnumDisplayDevices(
                string lpDevice, int iDevNum,
                ref DISPLAY_DEVICE lpDisplayDevice, int dwFlags);
    
            [DllImport("User32.dll")]
            private static extern bool EnumDisplaySettings(
                string devName, int modeNum, ref DEVMODE devMode);
    
        }
    }
    

    User rating: 9/10 (1 votes)
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    4306 bytes  
    Created: 2008-12-09 14:50:37  
    Modified: 2014-01-30 13:58:32  
    Visits in 7 days: 42  
    Listed functions:
    EnumDisplayDevices
    EnumDisplaySettings
    GetMonitorInfo
    MonitorFromWindow
    Printer friendly API declarations
    My comment:
    In the cursor created by this code sample, each connected monitor is indicated by non-empty MonitorName value.

    For an active monitor (the desktop extends to such monitor), several other values are populated:

  • Screenwidth
  • Screenheight
  • Bitsperpixel
  • DsppositionX
  • DsppositionY

    From the screen dimensions and the display position it is possible to determine whether a given window is visible on a particular display.

    * * *
    Read Two monitors are better than one by Tony Northrup published on Microsoft website. Bet he might be busy writing a sequel "N+1 monitors better than N".

    * * *
    Some graphics cards and external units (Matrox) support connections to multiple monitors, three and more.
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