NickeManarin/ScreenToGif · warning · Exception

It was not possible to get a list of known screens.

Error message

It was not possible to get a list of known screens.

What it means

Identical root cause to error 41 but thrown inside DownloadDialog.CenterOnScreen(). MonitorHelper.AllMonitorsGranular() returns an empty list, so the FirstOrDefault chain (point-containing, primary, any) resolves to null and the generic Exception fires. This dialog centers itself on the closest monitor before showing, and cannot do so without an enumerated screen.

Source

Thrown at ScreenToGif/Windows/Other/DownloadDialog.xaml.cs:267

    }

    private void Window_Closing(object sender, System.ComponentModel.CancelEventArgs e)
    {
        Global.UpdateAvailable.TaskCompletionSource = null;
    }


    private void CenterOnScreen()
    {
        //Since the list of monitors could have been changed, it needs to be queried again.
        var monitors = MonitorHelper.AllMonitorsGranular();

        //Detect closest screen to the point (previously selected top/left point or current mouse coordinate).
        var point = new Point((int)Left, (int)Top);
        var closest = monitors.FirstOrDefault(x => x.Bounds.Contains(point)) ?? monitors.FirstOrDefault(x => x.IsPrimary) ?? monitors.FirstOrDefault();

        if (closest == null)
            throw new Exception("It was not possible to get a list of known screens.");

        //Move the window to the correct location.
        Left = closest.WorkingArea.Left + closest.WorkingArea.Width / 2d - ActualWidth / 2d;
        Top = closest.WorkingArea.Top + closest.WorkingArea.Height / 2d - ActualHeight / 2d;
    }
}

View on GitHub (pinned to a4d0a67c21)

Solutions

1. Ensure a display is connected and active before triggering the download dialog.
2. Reconnect displays and reopen the dialog so CenterOnScreen re-enumerates.
3. Catch the exception in CenterOnScreen and skip centering (let WPF place the window) instead of crashing the download flow.
4. Guard: if the monitor list is empty, fall back to SystemParameters.WorkArea for centering.

Example fix

// before
var monitors = MonitorHelper.AllMonitorsGranular();
var point = new Point((int)Left, (int)Top);
var closest = monitors.FirstOrDefault(x => x.Bounds.Contains(point)) ?? monitors.FirstOrDefault(x => x.IsPrimary) ?? monitors.FirstOrDefault();
if (closest == null)
    throw new Exception("It was not possible to get a list of known screens.");
Left = closest.WorkingArea.Left + closest.WorkingArea.Width / 2d - ActualWidth / 2d;
Top = closest.WorkingArea.Top + closest.WorkingArea.Height / 2d - ActualHeight / 2d;

// after: fall back to primary working area, never throw on layout
var monitors = MonitorHelper.AllMonitorsGranular();
var closest = monitors.FirstOrDefault(x => x.Bounds.Contains(new Point((int)Left, (int)Top))
           ?? monitors.FirstOrDefault(x => x.IsPrimary)
           ?? monitors.FirstOrDefault();

var area = closest?.WorkingArea ?? SystemParameters.WorkArea;
Left = area.Left + area.Width / 2d - ActualWidth / 2d;
Top = area.Top + area.Height / 2d - ActualHeight / 2d;

// Validate enumeration before centering the dialog.
var monitors = MonitorHelper.AllMonitorsGranular();
if (monitors.Count == 0)
{
    // Fall back to the WPF primary working area; do not throw.
    var wa = SystemParameters.WorkArea;
    Left = wa.Left + wa.Width / 2d - ActualWidth / 2d;
    Top = wa.Top + wa.Height / 2d - ActualHeight / 2d;
    return;
}

static Rect ResolveCenterArea(List<Monitor> monitors, Point point)
{
    var closest = monitors.FirstOrDefault(x => x.Bounds.Contains(point))
               ?? monitors.FirstOrDefault(x => x.IsPrimary)
               ?? monitors.FirstOrDefault();
    return closest?.WorkingArea ?? SystemParameters.WorkArea;
}

try
{
    CenterOnScreen();
}
catch (Exception e) when (e.Message.Contains("list of known screens"))
{
    // Center on the WPF primary work area; the download must still proceed.
    LogWriter.Log(e, "Monitor enumeration failed in CenterOnScreen; using SystemParameters.WorkArea.");
    var wa = SystemParameters.WorkArea;
    Left = wa.Left + wa.Width / 2d - ActualWidth / 2d;
    Top = wa.Top + wa.Height / 2d - ActualHeight / 2d;
}

When it happens

Trigger: CenterOnScreen() is called when the DownloadDialog is being positioned/shown. AllMonitorsGranular() returns empty because User32.EnumDisplayMonitors enumerated no displays — the same native-empty condition as error 41 but triggered from a different window's layout path.

Common situations: Monitors disconnected/locked while a download was triggered; the dialog opens during a display-settings-change transition; running from a non-interactive or RDP-disconnected session; display driver crashed leaving no GDI desktop during the dialog open.

Related errors

• It was not possible to get a list of known screens.
• It was not possible to get a list of known screens.
• Could not find a proper output device for the area of L: {Le
• It was not possible to move the current selected region to t

AI-assisted analysis of NickeManarin/ScreenToGif@a4d0a67c21 (2026-08-13). Data as JSON: /api/errors/cdbe8912be6f24cb. Report an issue: GitHub.