SubtitleEdit/subtitleedit · error · InvalidOperationException

Failed to open clipboard

Error message

Failed to open clipboard

What it means

Thrown in CopyImageToClipboardWindows when OpenClipboard(IntPtr.Zero) returns false — the Windows clipboard could not be opened, typically because another application currently has it open. OpenClipboard is exclusive: only one window may have it open at a time. The allocated hGlobal is freed before throwing. This is one of the most common clipboard failures on Windows.

Source

Thrown at src/ui/Logic/ClipboardHelper.cs:261

                    // Write pixel data (flip vertically for bottom-up DIB)
                    IntPtr pixelPtr = IntPtr.Add(ptr, headerSize);
                    for (int y = 0; y < height; y++)
                    {
                        int sourceOffset = (height - 1 - y) * stride;
                        IntPtr destPtr = IntPtr.Add(pixelPtr, y * stride);
                        Marshal.Copy(pixels, sourceOffset, destPtr, stride);
                    }
                }
                finally
                {
                    GlobalUnlock(hGlobal);
                }

                // 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;

View on GitHub (pinned to 17a9f07487)

Solutions

1. Retry OpenClipboard with small delays (e.g. up to N attempts, 50-100ms apart) before giving up, mirroring the SetTextAsync retry pattern.
2. Close other clipboard-viewer/manager applications and retry.
3. If running under RDP/VM, reconnect or disable clipboard redirection temporarily.
4. Check Marshal.GetLastWin32Error() (ERROR_ACCESS_DENIED = 5 confirms contention).

Example fix

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

// after - bounded retry, same strategy as SetTextAsync
bool opened = false;
for (int i = 0; i < 10 && !opened; i++) { opened = OpenClipboard(IntPtr.Zero); if (!opened) Thread.Sleep(50); }
if (!opened) { GlobalFree(hGlobal); throw new InvalidOperationException($"Failed to open clipboard (Win32 error {Marshal.GetLastWin32Error()})."); }

// Mirror the SetTextAsync retry: OpenClipboard is exclusive and commonly contended.
bool opened = false;
for (int i = 0; i < 10 && !opened; i++) { opened = OpenClipboard(IntPtr.Zero); if (!opened) Thread.Sleep(50); }
if (!opened) { GlobalFree(hGlobal); throw new InvalidOperationException($"Failed to open clipboard (Win32 {Marshal.GetLastWin32Error()})."); }

When it happens

Trigger: Another process/window holds the clipboard open (clipboard viewers, remote-desktop/VM tools, screen-grabbers, office clipboard managers); retrying too quickly after a previous open; a process that opened the clipboard and stalled without closing it.

Common situations: Remote Desktop or a VM integration service holding the clipboard; a clipboard manager (ClipX, Ditto, Office); antivirus inspecting clipboard content; rapid successive copy operations.

Related errors

• Failed to allocate global memory
• Failed to lock global memory
• Failed to empty clipboard
• Failed to set clipboard data
• Failed to decode bitmap

AI-assisted analysis of SubtitleEdit/subtitleedit@17a9f07487 (2026-08-13). Data as JSON: /api/errors/ade1bfc1f28d42df. Report an issue: GitHub.