Using Win32 functions in Visual FoxPro Image Gallery
Code examples:
How to change display settings: screen resolution, screen refresh rate
Capturing keyboard activity of another application with the Raw Input API (VFP9)
Converting Unicode data from the Clipboard to a character string using a given code page
Copying picture of the active form to the Clipboard using Enhanced Metafile API functions
Enumerating raw input devices attached to the system (keyboard, mouse, human interface device)
Enumerating data formats currently available on the clipboard
GDI+: copying to the Clipboard (a) image of active FoxPro window/form, (b) image file
Disabling mouse and keyboard input for the main VFP window (with the app still running)
Current keyboard type
Storing content of the Clipboard to a bitmap file
Displaying icons in the system tray (VFP9)
Custom HttpRequest class (WinINet)
Attaching menu to a top-level form
Using Beep and Sleep functions to make the old tin buzz sing (WinNT only?)
How to activate Windows Calculator
Using InternetSetFilePointer when resuming interrupted download from the Internet
Minimizing all running applications
Storing screen shot of a form to bitmap file
Sending email messages with Simple MAPI
How to print a bitmap file
Drawing Windows predefined bitmaps using the LoadBitmap functions
Using Path functions from Shell Lightweight Utility APIs (shlapi.dll)
Obtaining current Internet Explorer browser version and UserAgent
Using EnumPrinters function to enumerate locally installed printers
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: 178  
    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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