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 data formats currently available on the clipboard
Obtaining current Internet Explorer browser version and UserAgent
Enumerating raw input devices attached to the system (keyboard, mouse, human interface device)
How to print FoxPro form
GDI+: copying to the Clipboard (a) image of active FoxPro window/form, (b) image file
Creating a clipping region from the path selected into the device context of a form
Storing content of the Clipboard to a bitmap file
FindText -- the hopeless and useless Common Dialog
How to create transparent areas inside a form -- punching holes in the form
Enumerating Processes -- WinNT
Using EnumPrinters function to enumerate locally installed printers
Placing a button on the VFP form as a new child window
Retrieving the name of the primary domain controller (PDC) and join status information
A procedure for setting file times
Storing screen shot of a form to bitmap file
Using the DeleteFile
Disabling mouse and keyboard input for the main VFP window (with the app still running)
Using the Semaphore object to allow only one instance of VFP application running
How to print a bitmap file
Attaching menu to a top-level form
How to change display settings: screen resolution, screen refresh rate

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Before you begin:
This code sample shows how to switch the monitor resolution to 800x600 pixels and back, keeping the existing refresh rate.

Before changing the resolution the code verifies if the hardware supports the requested graphics mode.



See also:
  • How to adjust monitor brightness (Vista, monitor with DDC support)
  • How to detect if additional monitor is connected and active
  • #include "stdafx.h"
    #include < windows.h >
    #include "conio.h"
    
    void ListDisplayDevices()
    {
        int index=0;
        DISPLAY_DEVICE dd;
        dd.cb = sizeof(DISPLAY_DEVICE);
    
        while (EnumDisplayDevices(NULL, index++, &dd, 0))
        {
            if (dd.StateFlags & DISPLAY_DEVICE_PRIMARY_DEVICE) printf("* ");
            printf("%s, %s\n", dd.DeviceName, dd.DeviceString);
        }
    }
    
    DISPLAY_DEVICE GetPrimaryDevice()
    {
        int index=0;
        DISPLAY_DEVICE dd;
        dd.cb = sizeof(DISPLAY_DEVICE);
    
        while (EnumDisplayDevices(NULL, index++, &dd, 0))
        {
            if (dd.StateFlags & DISPLAY_DEVICE_PRIMARY_DEVICE) return dd;
        }
        return dd;
    }
    
    void ListDisplaySettings(int index)
    {
        DISPLAY_DEVICE dd;
        dd.cb = sizeof(DISPLAY_DEVICE);
        if (!EnumDisplayDevices(NULL, index, &dd, 0))
        {
            printf("EnumDisplayDevices failed:%d\n", GetLastError());
            return;
        }
    
        DISPLAY_DEVICE monitor;
        monitor.cb = sizeof(DISPLAY_DEVICE);
        if (!EnumDisplayDevices(dd.DeviceName, index, &monitor, 0))
        {
            printf("EnumDisplayDevices failed:%d\n", GetLastError());
            return;
        }
    
        DEVMODE dm;
        dm.dmSize = sizeof(DEVMODE);
    
        if (!EnumDisplaySettings(dd.DeviceName, ENUM_CURRENT_SETTINGS, &dm))
        {
            printf("EnumDisplaySettings failed:%d\n", GetLastError());
            return;
        }
    
        printf("Device name: %s\n", dd.DeviceName);
        printf("Monitor name: %s\n", monitor.DeviceID);
        printf("Refresh rate, in hertz: %d\n", dm.dmDisplayFrequency);
        printf("Color depth: %d\n", dm.dmBitsPerPel);
        printf("Screen resolution, in pixels: %d x %d\n", 
            dm.dmPelsWidth, dm.dmPelsHeight);
    }
    
    void SetDisplayDefaults()
    {
        //changes the settings of the default display device
        //to the default mode
        ChangeDisplaySettings(NULL, 0);
    }
    
    BOOL SetDisplayResolution(long PelsWidth, long PelsHeight)
    {
        DISPLAY_DEVICE dd = GetPrimaryDevice();
        DEVMODE dm;
        dm.dmSize = sizeof(DEVMODE);
        if (!EnumDisplaySettings(dd.DeviceName, ENUM_CURRENT_SETTINGS, &dm))
        {
            printf("EnumDisplaySettings failed:%d\n", GetLastError());
            return FALSE;
        }
    
        dm.dmPelsWidth = PelsWidth;
        dm.dmPelsHeight = PelsHeight;
        dm.dmFields = (DM_PELSWIDTH | DM_PELSHEIGHT);
        if (ChangeDisplaySettings(&dm, CDS_TEST) !=DISP_CHANGE_SUCCESSFUL)
        {
            printf("\nIllegal graphics mode: %d\n", GetLastError());
            return FALSE;
        }
    
        return (ChangeDisplaySettings(&dm, 0)==DISP_CHANGE_SUCCESSFUL);
    }
    
    void _tmain()
    {
        ListDisplayDevices();
        ListDisplaySettings(0);
    
        if (SetDisplayResolution(800, 600))
        {
            printf("\nPress Enter to return to default mode.\n");
            getch();
            SetDisplayDefaults();
        }
        else
        {
            printf("\nPress Enter to close this window.\n");
            getch();
        }
        return;
    }
    
    
    

    User rating: 10/10 (2 votes)
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    2648 bytes  
    Created: 2003-01-21 10:56:03  
    Modified: 2013-09-20 13:29:51  
    Visits in 7 days: 575  
    Listed functions:
    ChangeDisplaySettings
    EnumDisplayDevices
    EnumDisplaySettings
    GetDesktopWindow
    GetMonitorInfo
    MonitorFromWindow
    Printer friendly API declarations
    My comment:
    A screenshot of C# version of this code sample.


    * * *
    Five ways of obtaining current monitor resolution:

  • The SYSMETRIC(1 | 2) is the simplest one. Very likely it is a wrapper around either GetSystemMetrics (SM_CXFULLSCREEN | SM_CYFULLSCREEN) call or SystemParametersInfo call. Each of three reports data for the primary monitor only.

  • Presented in the code sample above, the EnumDisplaySettings populates the DEVMODE structure. Members dmPelsWidth and dmPelsHeight of this structure contain the width and the height for enumerated monitor.

  • The GetMonitorInfo populates the MONITORINFO structure. The rcMonitor member in this structure is the RECT structure itself. It contains the display monitor rectangle expressed in virtual-screen coordinates.

  • The GetWindowPlacement populates a rectangle -- RECT rcNormalPosition. Call this function with the handle to the desktop window. For multiple monitor configuration, such desktop rectanlge is a combination of all active monitor rectangles.

  • Normally the mouse cursor is confined inside the desktop window. The GetClipCursor copies the desktop window dimensions into the RECT structure.
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    User Contributed Notes:
    Rosemar | 2006-12-08 11:49:22
    I have 2 computers.

    One of then, with Windows XP and another one, with Windows 98.

    In the machine with Windows XP this code works right, but, in another computer with Windows 98, when I run the code, the desktop area lost the original icons positions and the Windows Task Bar became HIDED outside the desktop area.

    This problem have solution ?

    Thank's.
    A.M. | 2006-12-11 20:09:50
    You may try to refresh the Desktop window by calling an API function like ShowWindow, MoveWindow, SetWindowPos, SetForegroundWindow, SwitchToThisWindow.

    Win98 -- this is an old system. Some API calls are not supported or behave in a different way.

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