Files
PowerToys/installer/PowerToysSetupCustomActionsVNext/CustomAction.def
Boliang Zhang e932fe6e61 Remove unused dependencies and shrink installer size (#47233)
## Summary of the Pull Request

Two related installer changes to (1) eliminate genuinely-unused
dependencies and (2) deduplicate shared WinAppSDK files between
`<install>\` and `<install>\WinUI3Apps\` to shrink the installer
download.

### 1. Remove unused dependencies (~11 MB savings per output location)

- **System.Data.SqlClient**: Removed from MouseWithoutBorders projects
and the central `Directory.Packages.props` pin. It was a transitive
dependency of `Microsoft.Windows.Compatibility` but PowerToys has zero
SQL database usage.
- **Unused `using` import**: Removed `using
System.ServiceModel.Channels` from MouseWithoutBorders `Program.cs` (no
WCF usage).
- **MFC / C++ AMP / OpenMP DLLs**: Added `RemoveUnusedVCRuntimeDlls`
target in `Directory.Build.targets` to clean up `mfc140*`, `mfcm140*`,
`vcamp140*`, and `vcomp140*` DLLs that leak from the VC++
Redistributable tree but are not imported by any PowerToys binary
(verified with `dumpbin /dependents` across all installed binaries).
Also excluded MFC DLLs from installer file collection.

### 2. WinAppSDK file deduplication (build-time only; install-time uses
copy)

**Background**: The `WinUI3Apps` subfolder must remain a real directory
because MSIX sparse package registration applies DACL changes to the
`ExternalLocation` folder (PR #47177). Flattening is not viable.

**Build-time** (`generateAllFileComponents.ps1`): computes the SHA256
intersection of root and `WinUI3Apps` files, and for each file that is
also present in the BaseApplications WXS file list, removes the
duplicate from the WinUI3Apps WXS component list and writes its name to
a `hardlinks.txt` manifest. The BaseApplications cross-check ensures we
never deduplicate a file the MSI does not actually deploy at the install
root, which would otherwise leave both copies missing post-install. The
manifest is written as UTF-8 without BOM (via
`[System.IO.File]::WriteAllLines` with `UTF8Encoding($false)`) so its
encoding is identical regardless of the build host's PowerShell version.
This step produces the **MSI download-size win** (~97 MB smaller cab;
LZX:21 was already deduplicating most byte-identical content
automatically inside the cab).

**Install-time** (`CreateWinAppSDKHardlinksCA` custom action):
- Reads `hardlinks.txt` after `InstallFiles` as a raw byte stream and
converts each line to a `std::wstring` via `MultiByteToWideChar(CP_UTF8,
MB_ERR_INVALID_CHARS, ...)`. Avoids `std::wifstream`'s ANSI-codepage
codecvt so non-ASCII paths can never be silently mangled.
- For each entry, computes `(installDir / fileName).lexically_normal()`
and `(winui3Dir / fileName).lexically_normal()`, then verifies via
`std::mismatch` that each resolved path is still rooted at its
respective folder. Manifest entries containing `..`, absolute paths, or
alternate-stream syntax are logged and skipped.
- Materialises each validated entry from `<install>\<name>` into
`<install>\WinUI3Apps\<name>` via `fs::copy_file` (overwrite_existing).
- Reports the per-file copy / failure counts to the install log. If
every entry failed (`created == 0 && failed > 0`), the CA escalates to
`E_FAIL` so the install does not silently succeed with an unusable
WinUI3Apps tree.

`DeleteWinAppSDKHardlinksCA` removes the materialised copies before
`RemoveFiles` on uninstall, using the same UTF-8 reader and per-entry
containment check.

**WiX sequencing**: `CreateWinAppSDKHardlinks` runs
`After="InstallFiles"` with `Condition="NOT Installed OR
WIX_UPGRADE_DETECTED OR REINSTALL"` so a `msiexec /fa` repair refreshes
the deduplicated copies (otherwise `RemoveFiles` would orphan them).

#### Why copy and not hard-link

A hard-linked variant of this CA was originally proposed but caused a
Monaco preview-handler regression. Hard-links share an NTFS inode (and
therefore one DACL) between `<install>\<file>` and
`<install>\WinUI3Apps\<file>`. The MSIX sparse-package registrations for
PowerRename / ImageResizer / FileLocksmith / NewPlus run after the dedup
CA and propagate the `WinUI3Apps` parent's rich DACL (Capability SID, 5×
Package SIDs, 5× conditional SYSAPPID ACE, RC SID) onto the shared
inode. The root path then also exposes the rich DACL, which trips a
kernel "stricter access evaluation" path that blocks the LOW-IL
`prevhost.exe` from `LoadLibrary`-ing `hostfxr.dll` (and the rest of the
.NET runtime), turning the Monaco preview pane blank for `.json` / `.md`
/ `.cs` / `.xaml` / `.svg` / `.xml` files.

`fs::copy_file` creates a **fresh inode** for the WinUI3Apps copy. The
root inode keeps its simple DACL (`SY:F + BA:F + owner:F` + inherited
`BU:RX`) so LOW-IL `prevhost.exe` can still load it — Monaco preview
works. The WinUI3Apps copy inherits the WinUI3Apps parent's rich DACL
via normal NTFS inheritance (matches 0.99.1 behaviour exactly) — MSIX
context-menu shells continue to work.

#### Trade-off

| Metric | Hard-link variant (rejected) | This PR (file copy) | 0.99.1
(no dedup) |
|---|---|---|---|
| MSI size | ~296 MB | ~296 MB | ~393 MB |
| On-disk after install | ~2,475 MB | ~2,772 MB | ~2,772 MB |
| DACL contamination risk | YES (broke Monaco) | NO | NO |

The on-disk savings (~297 MB) are given up in exchange for eliminating
the DACL contamination risk; the **installer download savings (~97 MB)**
are preserved by the build-time WiX/cab dedup.

#### Edge cases handled

- Empty duplicate list: `hardlinks.txt` always written, CA handles
empty.
- All files duplicated: `Generate-FileComponents` returns early for
empty list.
- File stripped from BaseApplications by an earlier build step:
BaseApplications cross-check skips it during dedup so neither copy goes
missing.
- Manifest entry escapes install root (`..`, absolute path): rejected
per-entry, install continues.
- Manifest line is non-UTF-8: rejected per-entry, install continues.
- Source missing at install time: per-entry skip, install continues.
- All copies fail: install aborts loudly via `E_FAIL` (catastrophic-case
escalation).
- Upgrade or `msiexec /fa` repair: CA fires (`NOT Installed OR
WIX_UPGRADE_DETECTED OR REINSTALL`).

**MSI repair risk**: Burn bundle uses `SuppressRepair=yes` and
`MajorUpgrade` (full uninstall + reinstall) for all version upgrades, so
the standard upgrade path is unaffected. The `OR REINSTALL` clause
covers power users running `msiexec /fa` directly.

## PR Checklist

- [x] **Communication:** Discussed approach via PRs #46866, #47177,
#46745
- [ ] **Tests:** Installer infrastructure only — no runtime behaviour
changes
- [ ] **Localization:** N/A
- [ ] **Dev docs:** N/A
- [ ] **New binaries:** N/A

## Detailed Description of the Pull Request / Additional comments

Based on the approach from PR #46745 by @yeelam-gordon, rebased onto
latest main and switched from hard-links to file copies after the DACL
contamination root cause was identified. Hardening (UTF-8 read, path
containment, catastrophic-case escalation, REINSTALL repair,
BaseApplications-filtered dedup) added in response to review feedback.

These changes are purely build/installer infrastructure — no runtime
behaviour changes to any PowerToys module.

## Validation Steps Performed

Validated on a 0.99.4 / 0.99.5 local install (per-user
`%LocalAppData%\PowerToys`):

-  `dumpbin /dependents` across the installed PowerToys tree confirmed
zero binaries import `mfc140*`, `mfcm140*`, `vcamp140*`, or `vcomp140*`
— the cleanup target removes ~11 MB of genuinely unused VC runtime DLLs.
-  `System.Data.SqlClient` has zero call-sites in PowerToys source.
-  Local installer build produces a 296 MB MSI (down from 393 MB
pre-dedup, ~97 MB cab savings purely from the build-time WiX dedup).
-  MSI table inspection (`wix msi decompile`) confirms the deferred CAs
are present (`CreateWinAppSDKHardlinks`, `DeleteWinAppSDKHardlinks`) and
the `hardlinks.txt` File row is registered.
-  MSI table inspection confirms .NET runtime DLLs (`hostfxr.dll`,
`coreclr.dll`, `hostpolicy.dll`, `clretwrc.dll`, `Accessibility.dll`,
`backup_restore_settings.json`) appear ONLY in
`BaseApplicationsFiles_File_*`, NOT in `WinUI3ApplicationsFiles_File_*`
— proving the build-time dedup worked.
-  Post-install verification: deduplicated files materialised at both
root and WinUI3Apps with byte-identical SHA256 hashes, and `fsutil
hardlink list` returns link-count == 1 for each — proving the
install-time copy approach worked, not hard-link.
-  DACL on root .NET runtime DLLs is clean: no Package SID, no
Capability SID, no SYSAPPID conditional ACE, no `ALL APPLICATION
PACKAGES` ACE — Monaco preview load path is safe.
-  DACL on WinUI3Apps copies has the rich MSIX inheritance —
context-menu shells continue to work (matches 0.99.1).
-  All four MSIX sparse packages (PowerRename, ImageResizer,
FileLocksmith, NewPlus) registered after install.

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
2026-05-15 17:15:11 +08:00

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Modula-2

LIBRARY "PowerToysSetupCustomActionsVNext"
EXPORTS
LaunchPowerToysCA
CheckGPOCA
CleanVideoConferenceRegistryCA
ApplyModulesRegistryChangeSetsCA
DetectPrevInstallPathCA
RemoveScheduledTasksCA
RestoreBuiltInNewContextMenuCA
TelemetryLogInstallSuccessCA
TelemetryLogInstallCancelCA
TelemetryLogInstallFailCA
TelemetryLogUninstallSuccessCA
TelemetryLogUninstallCancelCA
TelemetryLogUninstallFailCA
TelemetryLogRepairCancelCA
TelemetryLogRepairFailCA
TerminateProcessesCA
InstallEmbeddedMSIXCA
InstallDSCModuleCA
InstallCmdPalPackageCA
UnApplyModulesRegistryChangeSetsCA
UnRegisterCmdPalPackageCA
UnRegisterContextMenuPackagesCA
UninstallEmbeddedMSIXCA
UninstallDSCModuleCA
UninstallServicesCA
UninstallCommandNotFoundModuleCA
UpgradeCommandNotFoundModuleCA
UnsetAdvancedPasteAPIKeyCA
CleanImageResizerRuntimeRegistryCA
CleanFileLocksmithRuntimeRegistryCA
CleanPowerRenameRuntimeRegistryCA
CleanNewPlusRuntimeRegistryCA
SetBundleInstallLocationCA
InstallPackageIdentityMSIXCA
UninstallPackageIdentityMSIXCA
CreateWinAppSDKHardlinksCA
DeleteWinAppSDKHardlinksCA