C# winform, How to register to events when other applications enter/exit full screen mode on my application screen (if multiscreens)

Posted on 2010-09-10
Last Modified: 2012-05-10
I have C# winforms application. It has to register to events when any other application enters or exits full-screen-mode, on same screen (if independent multi-screen, I dont care what occurs on the other screens).

presents an idea, but I am not expert to code it, and besides, it needs looping to sense, while I prefer to register to events.

I'd appreciate to get C# code for this.

With appreciation

Question by:michael-lev
  • 2

Author Comment

ID: 33647410
If ther are no adequate events, then I'd like to get method code for my application to sense whether some other application is running full screen on same screen, and I'll call it from time to time.

Author Comment

ID: 33647497
-- I mean detecting if the other application is in TRUE fullscreen (not only maximized).
-- some links are in URL:
LVL 10

Accepted Solution

james-ct16 earned 500 total points
ID: 33661414
Good evening

There is no simple solution to this problem however this might get you headed in the correct direction.

The following code provides to examples the first should be sufficient to detect presentation mode.

To test this simply add a timer to an existing form with a message box and stick power point into presentation mode and message boxes will start appearing.

The next approach you can take to aid this is use the native GetWindowPlacement in user32 this provides the WindowPlacement structure which lets us detect window state (gets your maximized state) however more interestingly it also gets where the control is drawn so if the controls width and height is the size of the screen resolution you have a full screen app, try this with ie or chrome.  Second set of methods provide an example of this.

I suspect you are going to find cases where this doesnt always play fair and will have to deal with those on a case by case basis.

Hope that helps

[DllImport("kernel32.dll", SetLastError = true)]

static extern IntPtr OpenFileMapping(uint dwDesiredAccess, bool bInheritHandle, string lpName);


public enum FileMapAccess : uint


    FileMapCopy = 0x0001,

    FileMapWrite = 0x0002,

    FileMapRead = 0x0004,

    FileMapAllAccess = 0x001f,

    fileMapExecute = 0x0020,


[DllImport("kernel32.dll", SetLastError = true)]

[return: MarshalAs(UnmanagedType.Bool)]

static extern bool CloseHandle(IntPtr hObject);

/// <summary>

/// Determines whether [is in presentation mode].

/// </summary>

/// <returns>

/// 	<c>true</c> if [is in presentation mode]; otherwise, <c>false</c>.

/// </returns>

public bool IsInPresentationMode()


    IntPtr hHandle;

    hHandle = OpenFileMapping((uint)FileMapAccess.FileMapRead, false, "Local\\FullScreenPresentationModeInfo");

    if (IntPtr.Zero == hHandle) 


        return false; 



    return true;


// Second Example


        [return: MarshalAs(UnmanagedType.Bool)]

        static extern bool GetWindowPlacement(IntPtr hWnd, ref WINDOWPLACEMENT lpwndpl);

        private struct WINDOWPLACEMENT


            public int length;

            public int flags;

            public int showCmd;

            public System.Drawing.Point ptMinPosition;

            public System.Drawing.Point ptMaxPosition;

            public System.Drawing.Rectangle rcNormalPosition;


        const UInt32 SW_HIDE = 0;

        const UInt32 SW_SHOWNORMAL = 1;

        const UInt32 SW_NORMAL = 1;

        const UInt32 SW_SHOWMINIMIZED = 2;

        const UInt32 SW_SHOWMAXIMIZED = 3;

        const UInt32 SW_MAXIMIZE = 3;

        const UInt32 SW_SHOWNOACTIVATE = 4;

        const UInt32 SW_SHOW = 5;

        const UInt32 SW_MINIMIZE = 6;

        const UInt32 SW_SHOWMINNOACTIVE = 7;

        const UInt32 SW_SHOWNA = 8;

        const UInt32 SW_RESTORE = 9;

        /// <summary>

        /// Determines whether [is window full screen] [the specified win handle].

        /// </summary>

        /// <param name="winHandle">The win handle.</param>

        /// <returns>

        /// 	<c>true</c> if [is window full screen] [the specified win handle]; otherwise, <c>false</c>.

        /// </returns>

        private bool IsWindowFullScreen(IntPtr winHandle)


            WINDOWPLACEMENT placement = new WINDOWPLACEMENT();

            placement.length = Marshal.SizeOf(placement);

            GetWindowPlacement(winHandle, ref placement);

            // perform screen size calculation

            // screen calculation does not account for multi monitors when full screen left of primary display

            if (placement.rcNormalPosition.Width == Screen.FromHandle(winHandle).Bounds.Width

                && placement.rcNormalPosition.Height == Screen.FromHandle(winHandle).Bounds.Height)


                return true;


            return false;


private void FindFullScreenWindows()

{foreach (Process p in Process.GetProcesses("."))




                    if (p.MainWindowTitle.Length > 0 && IsWindowFullScreen(p.MainWindowHandle))


                        Debug.WriteLine("Full Screen Window Title:" + p.MainWindowTitle.ToString());



                catch { }



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LVL 74

Expert Comment

by:Glen Knight
ID: 34850236
This question has been classified as abandoned and is being closed as part of the Cleanup Program. See my comment at the end of the question for more details.

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