SubtitleEdit/subtitleedit · error · InvalidOperationException

Failed to set clipboard data

Error message

Failed to set clipboard data

What it means

Thrown in CopyImageToClipboardWindows when SetClipboardData(CF_DIB, hGlobal) returns IntPtr.Zero after EmptyClipboard succeeded. The data was not accepted, most often because the clipboard was re-locked by another app between EmptyClipboard and SetClipboardData, or the CF_DIB payload (header/pixels) was malformed. On success ownership transfers to the clipboard; on failure the code frees hGlobal.

Source

Thrown at src/ui/Logic/ClipboardHelper.cs:275

                // Open clipboard and set data
                if (!OpenClipboard(IntPtr.Zero))
                {
                    GlobalFree(hGlobal);
                    throw new InvalidOperationException("Failed to open clipboard");
                }

                try
                {
                    if (!EmptyClipboard())
                    {
                        GlobalFree(hGlobal);
                        throw new InvalidOperationException("Failed to empty clipboard");
                    }

                    if (SetClipboardData(CF_DIB, hGlobal) == IntPtr.Zero)
                    {
                        GlobalFree(hGlobal);
                        throw new InvalidOperationException("Failed to set clipboard data");
                    }

                    // Clipboard now owns the memory
                    hGlobal = IntPtr.Zero;
                }
                finally
                {
                    CloseClipboard();
                }
            }
            catch (Exception ex)
            {
                Debug.WriteLine($"Failed to copy image to clipboard on Windows: {ex.Message}");
                throw;
            }
            finally
            {
                if (hGlobal != IntPtr.Zero)

View on GitHub (pinned to 17a9f07487)

Solutions

1. Validate the BITMAPINFOHEADER fields (biSize == Marshal.SizeOf<BITMAPINFOHEADER>(), biCompression == BI_RGB, biSizeImage == imageSize, biPlanes == 1, biBitCount == 32).
2. Confirm stride == width*4 and the bottom-up row order is correct before SetClipboardData.
3. Retry the open/empty/set sequence; check Marshal.GetLastWin32Error().
4. Disable clipboard managers/redirectors that may be stealing the clipboard between calls.

Example fix

// before
if (SetClipboardData(CF_DIB, hGlobal) == IntPtr.Zero) { GlobalFree(hGlobal); throw new InvalidOperationException("Failed to set clipboard data"); }

// after - assert header integrity and surface the Win32 error
if (header.biSize != (uint)headerSize || header.biCompression != BI_RGB || header.biSizeImage != (uint)imageSize)
    throw new InvalidOperationException("Malformed DIB header before SetClipboardData.");
if (SetClipboardData(CF_DIB, hGlobal) == IntPtr.Zero)
{
    var winErr = Marshal.GetLastWin32Error();
    GlobalFree(hGlobal);
    throw new InvalidOperationException($"Failed to set clipboard data (Win32 error {winErr}).");
}

if (header.biSize != (uint)headerSize || header.biCompression != BI_RGB || header.biSizeImage != (uint)imageSize)
    throw new InvalidOperationException("Malformed DIB header before SetClipboardData.");
if (stride != width * 4) throw new InvalidOperationException("Stride mismatch.");

if (SetClipboardData(CF_DIB, hGlobal) == IntPtr.Zero)
{
    var e = Marshal.GetLastWin32Error();
    GlobalFree(hGlobal);
    throw new InvalidOperationException($"Failed to set clipboard data (Win32 {e}).");
}

When it happens

Trigger: Another process grabbed the clipboard between EmptyClipboard and SetClipboardData; the BITMAPINFOHEADER/pixel layout is invalid (wrong biSize, mismatched biSizeImage/stride, bad biCompression); the global block is too large or not properly locked-writable.

Common situations: Clipboard contention with RDP/clipboard managers; a malformed DIB header (e.g. wrong header size, non-BI_RGB compression); alpha-channel/stride mismatch; rare memory pressure.

Related errors

• Failed to allocate global memory
• Failed to decode bitmap
• Failed to lock global memory
• Failed to open clipboard
• Failed to empty clipboard

AI-assisted analysis of SubtitleEdit/subtitleedit@17a9f07487 (2026-08-13). Data as JSON: /api/errors/b9f3bea3d54e4fbf. Report an issue: GitHub.