Release v2.2.0

[v2.2.0] – 2026-05-25

Universal Preview Handler support is tha main enhancement of this
release — PDF, HTML, ... Anything that Explorer's Alt+P pane can show
is now supported by TCOfficeView Total Commander plugin.

Upgrading from an earlier version? Total Commander keeps an
already-configured detect string when a plugin is replaced, so
users coming from v2.1 or earlier won't automatically pick up
the new universal file-type support — see
Upgrading from an Earlier Version in README.md.

Added

• Universal Preview Handler support (PDF, HTML, anything Explorer's
  Alt+P pane can show). The plugin advertises support for all file
  type (EXT="*") so fresh installs work out of the box for the common
  formats; users who want truly universal support can switch the detect
  string in TC to EXT="*" (documented in README) and the plugin will
  be asked about every file. A new registry probe in the plugin DLL
  (HasPreviewHandlerForExt, mirroring the host's
  FindPreviewHandlerClsid lookup chain — direct shellex → default
  ProgID → OpenWithProgids → SystemFileAssociations\<ext> →
  SystemFileAssociations\<PerceivedType>) decides at LOAD time
  whether a Windows Preview Handler is actually registered for the
  file's extension; if not, the plugin returns the "decline" value
  so TC moves on to the next configured Lister plugin or its
  built-in viewer. Cost: one zero-allocation registry walk per
  F3 / Ctrl+Q; no host process spawn for files we can't render.

  In practice this gives the user automatic support for PDF (via
  Edge's built-in handler on Windows 10+, or Adobe Acrobat Reader if
  installed), MSG (via Windows' built-in MAPI Mail Previewer),
  and — with EXT="*" — Photoshop PSD, AutoCAD DWG/DXF,
  Sketchup SKP, and anything else that ships a Preview Handler.

• [PreviewHandlers] INI section for per-extension CLSID overrides.
  When several preview handlers are installed for the same file type
  (e.g. both Microsoft Edge and Adobe Reader register one for .pdf,
  whichever was installed last wins system-wide), the user can now
  pin a specific handler for this plugin only by writing
  <.ext>=<CLSID> in the INI:

  [PreviewHandlers]
  .pdf={3A84F9C2-6164-485C-A7D9-4B27F8AC009E}

  Override entries are consulted before the standard registry lookup
  chain; the system-wide registration is the fallback when no override
  matches. Bad CLSIDs are silently ignored at load time. Explorer's
  preview pane and other applications keep using whatever Windows
  picked as the system default — the override is scoped to
  TCOfficeView only. The shipped sample INI documents the format and
  points at the
  HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\PreviewHandlers
  registry key where every installed handler is enumerated with its
  CLSID and friendly name.

• Optional discovery report — set [PreviewHandlers] ReportPath=<path>
  in the INI to enable. When the option is set, the host writes
  (on a low-priority background thread, every time it starts) a
  human-readable text file at the chosen location containing:

  • Section 1 — every installed preview handler on the machine,
    sorted by friendly name, with its CLSID alongside (the master
    pick-list). Source: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\PreviewHandlers.
  • Section 2 — the current per-extension assignment for every
    file type that has a registered handler (walked from HKCR\.*),
    preformatted as commented-out INI lines
    (;.pdf={CLSID} ; Friendly name) sorted by extension and ready
    to copy into the [PreviewHandlers] section of
    TCOfficeView.ini — uncomment a row, swap the CLSID for one of
    the alternatives from section 1 above.

  Written atomically via a .tmp file + MoveFileExW, so the
  report is never observed half-written. Off by default — the
  registry walk is cheap but it's still wasted work on every Lister
  session when the user isn't actively configuring overrides. Turn
  it on while setting up overrides, then comment the line out again.
  Failure (path unwritable, destination locked by an editor, …) is
  logged and silently skipped — the report is a convenience, not a
  requirement for the plugin to function.

• Per-extension deny in [PreviewHandlers] — write .ext= (empty
  value) to skip an extension entirely. TCOfficeView then behaves
  as if no preview handler existed for that file type: the plugin
  DLL returns nullptr from ListLoadW / LISTPLUGIN_ERROR from
  ListLoadNextW, Total Commander routes the file to the next
  configured Lister plugin or its built-in viewer, and the host
  process is never even spawned. Useful when another Lister plugin
  does a better job for a specific file type (e.g. a dedicated PDF
  previewer) and the user wants to keep TCOfficeView for everything
  else.

  The plugin DLL re-reads the [PreviewHandlers] section from the
  INI on every ListLoadW / ListLoadNextW call, so deny-list edits
  take effect immediately without restarting Total Commander. The
  host re-reads the section on every spawn and honours the deny list
  inside FindPreviewHandlerClsid as a defence-in-depth backstop in
  case the DLL ever forwards a file for a denied extension.

Changed

• README's “Supported Formats” section is now an indicative list of
  common handlers rather than the authoritative whitelist (which is
  whatever the user's machine has registered). The “When MS Office
  Is Not Installed” section was renamed and rewritten to reflect the
  new behaviour: silent decline + TC fall-through for files with no
  handler, and the fallback panel reserved for cases where a handler
  IS registered but fails at run time.

Fixed

• [PreviewHandlers] parser rejected entries that ended with an
  inline ;comment. The sample INI documented the format
  .pdf={CLSID} ; Friendly name, exactly the same shape the
  discovery report produces for copy-paste — but the parser passed
  the value, comment and all, straight to CLSIDFromString, which
  is strict about trailing characters and silently dropped the
  entry. The override therefore had no effect even though the user
  had written it correctly per the docs. Values are now stripped
  of any inline ;… tail and surrounding whitespace before being
  parsed. Each successfully-loaded override is also logged
  (PreviewHandlers override: .pdf -> {…}), and each rejected
  entry is logged as REJECTED (bad CLSID) so typos are easier
  to spot.

• ListGetDetectString now returns EXT="*" instead of a
  hard-coded list of Office extensions. Total Commander calls this
  exported function the first time it needs to query the plugin's
  detect string and stores the returned value in wincmd.ini,
  overriding whatever defaultextension= in pluginst.inf set
  initially. The stale hard-coded list was the real reason new
  file types (PDF, HTML, …) were not picked up automatically on
  fresh installs — they simply weren't in the string TC saw. With
  the new value, fresh installs route every file through the plugin
  DLL's HasPreviewHandlerForExt registry probe, exactly the way
  the new universal-handler architecture was meant to work.

  Existing users coming from v2.1 or earlier need a one-off
  configuration refresh to pick this up — see Notes below.

• ListLoadNextW no longer leaves a stale preview on screen when
  navigating (n / p keys in the Lister) to a file the plugin
  can't handle. The previous code returned the wrong constant on
  the failure path — 0 instead of 1 — so Total Commander
  interpreted "no handler for this file" as success, kept the
  Lister window open, and left the prior file's rendering visible
  in it. The plugin now uses the documented LISTPLUGIN_OK (0) /
  LISTPLUGIN_ERROR (1) constants (added to listplug.h for
  clarity) and returns LISTPLUGIN_ERROR whenever it can't load
  the requested file — at which point TC closes the Lister and
  routes the file to the next configured plugin or its built-in
  viewer. The success path was also corrected from 1 to 0;
  this had been silently wrong since the plugin's first release but
  TC's tolerance for either value masked it.

• pluginst.inf no longer ships either detect= or
  defaultextension=. The former is recognised by Total Commander
  only for archive (WCX) plugins; the latter would, if TC reads it at
  install time, write a finite EXT="…" list to wincmd.ini that
  would then conflict with the EXT="*" value the plugin's
  ListGetDetectString returns on first use. ListGetDetectString
  is now the single source of truth — the plugin DLL itself decides
  which files TC should ask it about, and the answer is "all of
  them; my registry probe will decline the ones I can't render".

Notes

• Upgrading from v2.1.0 or earlier requires a one-off configuration
  refresh to enable the new universal file-type support. Total
  Commander does not overwrite an already-stored detect string when
  a plugin's DLL is replaced — even if ListGetDetectString would
  return something different — so existing installs keep the old
  Office-only detect string and never get asked about PDF, HTML, or
  the other newly-supported file types.

  Two ways to refresh it:

  1. Remove and re-add the plugin in Total Commander →
     Configuration → Options → Plugins → Lister plugins →
     Configure. On the next file preview, TC will ask the new
     plugin DLL for its detect string and store EXT="*".
  2. Edit wincmd.ini directly — Total Commander's GUI does
     not expose a way to change a Lister plugin's detect string at
     all, so this is the only way without going through Remove /
     Add. Close TC, edit the <N>_detect= line under
     [ListerPlugins] (where <N> is the slot whose
     <N>= line is the TCOfficeView DLL path) to EXT="*", save,
     and reopen TC.

  Both procedures are spelled out step-by-step in README.md →
  Upgrading from an Earlier Version.