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Fix providing EnhancedMetafile to other applications through the clip… - #11988
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…board The shared OLE code in System.Private.Windows.Core only accepts TYMED_HGLOBAL, TYMED_ISTREAM and TYMED_GDI, so every request for CF_ENHMETAFILE (always TYMED_ENHMF) fails before WPF's handler runs. - Add WpfOleServices.AllowedTymeds, which also allows TYMED_ENHMF. It implements IOleServices.AllowedTymeds once the companion dotnet/winforms change flows in, and must be in place before then. - Fix the TYMED_ENHMF branch of WpfOleServices.GetDataHere, which never assigned the handle created from a MemoryStream and returned S_OK with a null handle. It now sets tymed and hEnhMetaFile, and returns E_FAIL when there is no handle, as .NET 9 did. - Add a clipboard test that reads the EMF back the way another application would. It is skipped until the winforms change flows in. Fixes dotnet#11986 Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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Copilot review overview
🟡 Changes recommended
Non-publicly-visible MemoryStream buffers still throw during enhanced-metafile retrieval.
Review effort: Balanced
Findings: 1
Open (1)
What changed in this PR
Restores WPF enhanced-metafile clipboard interoperability on newer .NET versions.
Changes:
- Allows
TYMED_ENHMFin WPF OLE services. - Correctly populates enhanced-metafile storage media.
- Adds native clipboard interoperability coverage.
| File | Description |
|---|---|
WpfOleServices.cs |
Enables and returns enhanced-metafile handles. |
ClipboardTests.cs |
Tests native retrieval of clipboard EMF data. |
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Author
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May be implemented by #12036 instead, although this seems like a simpler, more targeted solution in my opinion |
Shyam-Gupta
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Oct 28, 2026
…nhanced metafiles (#15218) Fixes dotnet/wpf#11986 Companion WPF PR: dotnet/wpf#11988 ## Proposed changes - Add `IOleServices.AllowedTymeds`, following the existing `#if NET static abstract` pattern. - `Composition` reads the allowed media types from the platform instead of the hard-coded `TYMED_HGLOBAL | TYMED_ISTREAM | TYMED_GDI`, in both the managed-to-native and native-to-managed adapters. - `WinFormsOleServices` returns the old value, so WinForms behavior is unchanged. WPF adds `TYMED_ENHMF` in the companion PR. ## Customer Impact - On .NET 10, WPF apps can't provide `CF_ENHMETAFILE` to other applications: every `TYMED_ENHMF` request fails with `DV_E_TYMED` before WPF's handler runs. Pasting EMF into apps like Word fails silently, with no workaround. ## Regression? - Yes. .NET 9 WPF allowed `TYMED_ENHMF`, and the shared mask dropped it. ## Risk - Low. WinForms gets the same value as before, and `IOleServices` is internal. - The value is per platform rather than added to the shared constant, because WinForms can't supply or read EMF. A shared value would make WinForms report EMF as available when it isn't. ## Test methodology - Added `ManagedToNativeAdapterTests`, which fails with `DV_E_TYMED` without this change. - `System.Private.Windows.Core.Tests` passes on net11.0 and net481. - Validated end-to-end with a WPF app on .NET 11 RC 1, using WPF built with the companion change: EMF paste now works for delayed and flushed data. ## Test environment(s) - .NET SDK 11.0.100-rc.1.26420.103, Windows 11 (10.0.26200) ###### Microsoft Reviewers: [Open in CodeFlow](https://microsoft.github.io/open-pr/?codeflow=https://github.com/dotnet/winforms/pull/15218)
Shyam-Gupta
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Oct 28, 2026
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@dipeshmsft, @pranav-gupta-msft, @subhajitm - We validated this change and didn't find any regressions. Could you please review this PR? Also we plan to take it for servicing in 10.0 and 11.0 release. Thanks. |
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Fixes #11986
Depends on dotnet/winforms#15218.
This PR has to merge before that change flows into WPF, or WPF won't build.
Description
On .NET 10, the shared OLE code in System.Private.Windows.Core rejects every
TYMED_ENHMFrequest withDV_E_TYMED, so WPF can't provideCF_ENHMETAFILEto other applications even though the format is still advertised.WpfOleServices.AllowedTymeds, which also allowsTYMED_ENHMF. It implements the newIOleServices.AllowedTymedsfrom dotnet/winforms#TBD.TYMED_ENHMFbranch ofWpfOleServices.GetDataHere, which was unreachable until now. For aMemoryStreamit never assigned the handle to the medium, so it returnedS_OKwith a null handle. It now setstymedandhEnhMetaFile, and returnsE_FAILwhen there is no handle, as .NET 9 did.GetClipboardData, the way another application would. It's skipped until the winforms change flows in.I'd like to request a backport to
release/10.0after this merges.Customer Impact
EMF that WPF apps put on the clipboard can't be pasted into other applications, for example Word's Paste Special → Picture (Enhanced Metafile). It fails silently, and there's no workaround.
Regression
Yes. It works on .NET 9 and is broken on .NET 10.
Testing
build.cmd -packsucceeds, both against the currentMicrosoft.Private.Winformspackage and against a local build of Let each platform declare the TYMEDs it supports so WPF can provide enhanced metafiles winforms#15218.copy: trueandcopy: false.GetClipboardData(CF_ENHMETAFILE)and OLEGetData, for delayed and flushed data. The unpatched runtime fails all three checks.Risk
Low. It only affects
TYMED_ENHMFrequests forEnhancedMetafiledata, which always fail today, and restores the .NET 9 behavior.