C#•2mo ago

First use of Winforms' Clipboard methods results in an ExternalException

Was debugging a Winforms app bug where the following code would fail but only if it is the first time of using any Clipboard method.

private static readonly object ClipboardLock = new object();
private static bool CopyData(IDataObject data, bool copy = true)
{
    if (data == null)
        return false;

    lock (ClipboardLock)
        Clipboard.SetDataObject(data, copy, 20, 100);

    return true;
}

private static readonly object ClipboardLock = new object();
private static bool CopyData(IDataObject data, bool copy = true)
{
    if (data == null)
        return false;

    lock (ClipboardLock)
        Clipboard.SetDataObject(data, copy, 20, 100);

    return true;
}

When used for the first time since the app launch, it throws the following exception: System.Runtime.InteropServices.ExternalException (0x800401D0): Requested Clipboard operation did not succeed Interestingly enough, if you just add a random Clipboard method BEFORE the SetDataObject call, everything works fine without any errors Could someone help me to figure out what might be causing it? Thanks in advance!

61 Replies

Trinitek•2mo ago

hresult 800401D0 is CLIPBRD_E_CANT_OPEN. do you have a full stacktrace for this?

faintOP•2mo ago

Best I can find in the console is this:

System.Runtime.InteropServices.ExternalException (0x800401D0): Requested Clipboard operation did not succeed.
at System.Windows.Forms.Clipboard.SetDataObject(Object data, Boolean copy, Int32 retryTimes, Int32 retryDelay)
at ShareX.HelpersLib.ClipboardHelpers.CopyData(IDataObject data, Boolean copy) in C:\Users\faint\RiderProjects\ShareX\ShareX.HelpersLib\Helpers\ClipboardHelpers.cs:line 56
at ShareX.HelpersLib.ClipboardHelpers.CopyImageDefaultFillBackground(Image img, Color background) in C:\Users\faint\RiderProjects\ShareX\ShareX.HelpersLib\Helpers\ClipboardHelpers.cs:line 156
at ShareX.HelpersLib.ClipboardHelpers.CopyImage(Image img, String fileName) in C:\Users\faint\RiderProjects\ShareX\ShareX.HelpersLib\Helpers\ClipboardHelpers.cs:line 123

System.Runtime.InteropServices.ExternalException (0x800401D0): Requested Clipboard operation did not succeed.
at System.Windows.Forms.Clipboard.SetDataObject(Object data, Boolean copy, Int32 retryTimes, Int32 retryDelay)
at ShareX.HelpersLib.ClipboardHelpers.CopyData(IDataObject data, Boolean copy) in C:\Users\faint\RiderProjects\ShareX\ShareX.HelpersLib\Helpers\ClipboardHelpers.cs:line 56
at ShareX.HelpersLib.ClipboardHelpers.CopyImageDefaultFillBackground(Image img, Color background) in C:\Users\faint\RiderProjects\ShareX\ShareX.HelpersLib\Helpers\ClipboardHelpers.cs:line 156
at ShareX.HelpersLib.ClipboardHelpers.CopyImage(Image img, String fileName) in C:\Users\faint\RiderProjects\ShareX\ShareX.HelpersLib\Helpers\ClipboardHelpers.cs:line 123

ClipboardHelpers.cs:line 56 is the Clipboard.SetDataObject call

Trinitek•2mo ago

curious, does this also happen after you reboot the computer?

faintOP•2mo ago

Well, I as a user of this app have been having this bug for like a week or even more, and I definitely have rebooted. Or do you mean try it on like a fresh boot, so there're no apps open and stuff?

Trinitek•2mo ago

yes, fresh reboot the Windows clipboard has a concept of ownership where another app can lock it, and if there's a bug, it can stay locked

faintOP•2mo ago

Also fwiw it definitely wasn't a thing until some point. I tried to remember what could have been updated in the last few months, and the one that seems very interesting is updating all the projects to .NET 9.0 from .NET 4.8

Trinitek•2mo ago

in the past I have used a tool like https://www.nirsoft.net/utils/inside_clipboard.html to reveal the current owner

faintOP•2mo ago

Oh yeah I tried using that as well but honestly couldn't really figure out how to use it

Trinitek•2mo ago

yes there could be a behavior change here

faintOP•2mo ago

Alright, I'll try to restart real quick, be right back

Trinitek•2mo ago

the owner would be in the bottom, like "firefox", with the PID next to it

faintOP•2mo ago

That’s interesting, it works now that I’ve closed as many apps as I could Nevermind, not anymore :/

faintOP•2mo ago

That's what I see there

faintOP•2mo ago

Selecting it doesn't show anything

Trinitek•2mo ago

no owner info, hmm

faintOP•2mo ago

Though the format is afaict set correctly

Trinitek•2mo ago

well, CF_BITMAPs are supposed to have image data and not be size zero, so something has gone wrong somewhere this is ShareX? it may or may not be ShareX's fault

faintOP•2mo ago

Yeah, just interesting that it managed to get the data format right, but the data itself is lost :smilethink: Yeah, it is, I'm trying to debug why it doesn't work

Trinitek•2mo ago

oh I see, this is after SetData and it throws what was the owner before you tried to copy?

faintOP•2mo ago

Reopened the app and I see this:

faintOP•2mo ago

After screenshotting and making that method call SetDataObject, it's now just CF_BITMAP Weird, after a rebuild I can't repro this at all :/

Trinitek•2mo ago

I still suspect another unrelated app is opening the clipboard and failing to close it

faintOP•2mo ago

I think I broke InsideClipboard lol. It won't load at all now

Trinitek•2mo ago

it has a tendency to freeze if one of the listed formats has a massive amount of data in it it tries to materialize the whole thing at once

faintOP•2mo ago

Is there any way I can see what app is opening it? If it's the owner field in InsideClipboard, then it happens with any app

Trinitek•2mo ago

yeah that's the owner field there's nothing obviously wrong with the WinForms Clipboard class on net9, that's PInvoking the OLE Clipboard class provided by Win32, which is exactly what Framework did the stacktrace eventually ends up at https://github.com/dotnet/winforms/blob/main/src/System.Windows.Forms/System/Windows/Forms/OLE/WinFormsOleServices.cs#L154

faintOP•2mo ago

@T'tk Hey, in case you want to know, I found a very interesting thing. I decided to make a sample WinForms app to see if I can repro this bug and I could do so. Then I got curious if downgrading to an older .NET version (specifically net48) would fix it (because that's the only big update I can update that ShareX has had recently), and it did fix this bug. So, did I just discover some .NET / WinForms bug? :wires: nevermind, .net 4.8's winforms just didnt throw any exceptions for me :/ the issue is still there

Trinitek•2mo ago

. I'm still of the opinion it's another app on your system

faintOP•2mo ago

I tried using GetOpenClipboardWindow to see what app is using clipboard and it didn't show any :/

GetOpenClipboardWindow function (winuser.h) - Win32 apps

Retrieves the handle to the window that currently has the clipboard open.

Trinitek•2mo ago

does https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-getclipboardowner say anything? also, how big is the image that you're trying to copy?

faintOP•2mo ago

It happens with any data type. For instance, a text I was trying to copy in my sample app is only 9 characters It returned some HWND, though I'm not sure how I can check what window it is from this HWND

Trinitek•2mo ago

there's an app called Spy++ that comes with the Visual Studio C++ tools or, I can get you a code snippet to locate the process one moment

faintOP•2mo ago

appreciate it!

Trinitek•2mo ago

public sealed record ClipboardInfo
{
    public required IDataObject DataObject { get; init; }
    public required string[] Formats { get; init; }
    public required string? OwnerProcessName { get; init; }
    public required int? OwnerProcessId { get; init; }
    public required int? OwnerHwnd { get; init; }
    public required string? OwnerHwndText { get; init; }

    public unsafe static ClipboardInfo Create()
    {
        IDataObject dataObject = System.Windows.Clipboard.GetDataObject();
        string[] formats = dataObject.GetFormats(autoConvert: false);
        string? ownerProcessName;
        int? ownerProcessId;
        int? ownerHwnd;
        string? ownerHwndText;

        var hwnd = Windows.Win32.PInvoke.GetClipboardOwner();

        if (hwnd.IsNull)
        {
            ownerProcessName = null;
            ownerProcessId = null;
            ownerHwnd = null;
            ownerHwndText = null;

            goto end;
        }

        ownerHwnd = (int)hwnd.Value;

        Span<char> hwndText = new char[32];
        int textLength = Windows.Win32.PInvoke.GetWindowText(hwnd, hwndText);

        ownerHwndText = textLength == 0
            ? null
            : new string(hwndText[..textLength]);

        uint pid = 0;

        uint threadId = Windows.Win32.PInvoke.GetWindowThreadProcessId(hwnd, &pid);

        if (threadId == 0)
        {
            ownerProcessId = null;
            ownerProcessName = null;

            goto end;
        }

        ownerProcessId = (int)pid;

        using (var process = Process.GetProcessById((int)pid))
        {
            ownerProcessName = process.ProcessName;
        }

    end:
        return new()
        {
            DataObject = dataObject,
            Formats = formats,
            OwnerProcessName = ownerProcessName,
            OwnerProcessId = ownerProcessId,
            OwnerHwnd = ownerHwnd,
            OwnerHwndText = ownerHwndText
        };
    }
}

public sealed record ClipboardInfo
{
    public required IDataObject DataObject { get; init; }
    public required string[] Formats { get; init; }
    public required string? OwnerProcessName { get; init; }
    public required int? OwnerProcessId { get; init; }
    public required int? OwnerHwnd { get; init; }
    public required string? OwnerHwndText { get; init; }

    public unsafe static ClipboardInfo Create()
    {
        IDataObject dataObject = System.Windows.Clipboard.GetDataObject();
        string[] formats = dataObject.GetFormats(autoConvert: false);
        string? ownerProcessName;
        int? ownerProcessId;
        int? ownerHwnd;
        string? ownerHwndText;

        var hwnd = Windows.Win32.PInvoke.GetClipboardOwner();

        if (hwnd.IsNull)
        {
            ownerProcessName = null;
            ownerProcessId = null;
            ownerHwnd = null;
            ownerHwndText = null;

            goto end;
        }

        ownerHwnd = (int)hwnd.Value;

        Span<char> hwndText = new char[32];
        int textLength = Windows.Win32.PInvoke.GetWindowText(hwnd, hwndText);

        ownerHwndText = textLength == 0
            ? null
            : new string(hwndText[..textLength]);

        uint pid = 0;

        uint threadId = Windows.Win32.PInvoke.GetWindowThreadProcessId(hwnd, &pid);

        if (threadId == 0)
        {
            ownerProcessId = null;
            ownerProcessName = null;

            goto end;
        }

        ownerProcessId = (int)pid;

        using (var process = Process.GetProcessById((int)pid))
        {
            ownerProcessName = process.ProcessName;
        }

    end:
        return new()
        {
            DataObject = dataObject,
            Formats = formats,
            OwnerProcessName = ownerProcessName,
            OwnerProcessId = ownerProcessId,
            OwnerHwnd = ownerHwnd,
            OwnerHwndText = ownerHwndText
        };
    }
}

the PInvokes are code-generated by CsWin32, so I can't include those

faintOP•2mo ago

uhhhh

Trinitek•2mo ago

you need to add a reference to CsWin32 and then add the function names in a file called NativeMethods.txt that file should contain

GetClipboardOwner
GetWindowText
GetWindowThreadProcessId

GetClipboardOwner
GetWindowText
GetWindowThreadProcessId

exactly as written oh yes, also System.Windows.Clipboard is a WPF type, so you may need to add a <UseWPF>true</UseWPF> to your csproj

faintOP•2mo ago

Can I just use the Winforms' alternative?

Trinitek•2mo ago

I'm just using that to get a string[] of the available format names, so I think so yes

faintOP•2mo ago

Sorry for long response, my VPN died (without it I cant access Discord). I modified your code a bit to remove the GetDataObject call (because as you remember any clipboard call before SetDataObject fixes the issue). The process name shows the one I copied from the last. But regardless of the app, it still never works

Trinitek•2mo ago

alright you had a workaround earlier, where you could invoke another clipboard function, and then the copy would work

faintOP•2mo ago

yeah

Trinitek•2mo ago

does that consistently work?

faintOP•2mo ago

hm let me try it a few times Yes, seem to be working all the time

Trinitek•2mo ago

I think I'm out of things to suggest to "fix" it without the workaround, but I'll point you to this thread which has some relevant discussion https://github.com/dotnet/wpf/issues/9901 nevermind that's on the WPF repo, the issue is actually coming from something lower in the system

faintOP•2mo ago

Yeah, saw this one. I tried doing this but opening it in any editor made my system go crazy :slughollow:

GitHub

Clipboard.SetText fails with CLIPBRD_E_CANT_OPEN · Issue #9901 · ...

Description Most of the time, the call to Clipboard.SetText takes several hundred milliseconds and then fails with CLIPBRD_E_CANT_OPEN in the flush operation. The WinForms implementation works fine...

Trinitek•2mo ago

uh. is that 19 GB

faintOP•2mo ago

yeah that's the thing - it's only 900mb

Trinitek•2mo ago

900 mb, okay that's still really big no wonder InsideClipboard froze earlier

faintOP•2mo ago

I also tried doing something like cat output.txt | clip but it didn't work either well, that time it wasn't that big

Trinitek•2mo ago

and that's after copying from ShareX?

faintOP•2mo ago

iirc yes

Trinitek•2mo ago

could you try doing CopyData with copy = false

faintOP•2mo ago

yeah well that will work because the stacktrace points at the use of OleFlushClipboard and if we set copy to false, it will skip that part

faintOP•2mo ago

the error occurs here:

Trinitek•2mo ago

shrug. I guess the data is too large to flush reliably.

faintOP•2mo ago

well I don't really think this is that big :wires:

Trinitek•2mo ago

lol

faintOP•2mo ago

Just curious, can you reproduce this issue on your machine?

Trinitek•2mo ago

I've never gotten this error unless another app had the clipboard open, and that's something that's usually handled with a retry idk. your clipboard is fucked. that's all I've got.

faintOP•2mo ago

windows my beloved. I guess I’ll have to reinstall it because I’ve noticed some other weird bugs like how opening the settings app freezes my ENTIRE OS for like five seconds Anyways uh I appreciate your help, thank you so much for your time and enthusiasm! Have a good one I guess I can leave this thread open as technically it hasn’t been solved?

Trinitek•2mo ago

you can leave it

Gaming

Programming

First use of Winforms' Clipboard methods results in an ExternalException

Did you find this page helpful?