Splunk

Playing with shell extensions to provide some custom context menus.

Consists of two parts:

• A simple command line client that is called from registry commands. It executes the requested operation.
• A UI companion that can configure registry commands, and some other stuff.

A few limitations that could be reconsidered:

• Operations on files are enabled generically, eventually specific extensions could be supported.
• If the commands produce output (stdout/stderr) it is placed in the clipboard for the user.

Built with VS2022 and .NET8.

Commands

Commands vary depending on which part of the explorer they originate in.

Context	Description
Dir	Right click in explorer right pane or windows desktop with a directory selected.
DirBg	Right click in explorer right pane with nothing selected (background).
DeskBg	Right click in windows desktop with nothing selected (background).
Folder	Right click in explorer left pane (navigation) with a folder selected.
File	Right click in explorer right pane or windows desktop with a file selected.

These are the builtin commands. It's stuff I've wanted to add to an explorer context menu.

Menu Item	Context	Action
Commander	Dir	Open a new explorer next to the current. Simulates old school Commander.
Tree	Dir	Copy a tree of selected directory to clipboard.
Open in Sublime	Dir/DirBg	Open selected directory/here in Sublime Text.
Find in Everything	Dir/DirBg	Open selected directory/here in Everything.
Execute	File	Execute if executable otherwise open. Suppresses console window creation.

Implementation

Registry Conventions

Registry sections of interest:

• HKEY_LOCAL_MACHINE (HKLM): defaults for all users using a machine (administrator)
• HKEY_CURRENT_USER (HKCU): user specific settings (not administrator)
• HKEY_CLASSES_ROOT (HKCR): virtual hive of HKEY_LOCAL_MACHINE with HKEY_CURRENT_USER overrides (administrator)

HKEY_CLASSES_ROOT should be used only for reading currently effective settings. A write to HKEY_CLASSES_ROOT is always redirected to HKEY_LOCAL_MACHINE\Software\Classes. In general, write directly to HKEY_LOCAL_MACHINE\Software\Classes or HKEY_CURRENT_USER\Software\Classes and read from HKEY_CLASSES_ROOT.

Splunk bases all registry accesses (R/W) at HKEY_CURRENT_USER\Software\Classes aka REG_ROOT.

Splunk Commands

Splunk command specifications contain these properties:

Property	Description
Id	Short name for internal id and registry key.
RegPath	Where to install in REG_ROOT.
Text	As it appears in the context menu.
CommandLine	Full command string to execute.

Supported RegPaths are:

Context	RegPath
Dir	HKCU\Directory
DirBg	HKCU\Directory\Background
DeskBg	HKCU\DesktopBackground
Folder	HKCU\Folder
File	HKCU*

This generates registry entries that look like:

[REG_ROOT\spec.RegPath\shell\spec.Id]
@=""
"MUIVerb"=spec.Text
[REG_ROOT\spec.RegPath\shell\Id\command]
@=spec.CommandLine

CommandLine is a free-form string that is executed as if entered at the command line. There are some macros available.

Built in macros:

Macro	Description	Notes
%L	Selected file or directory name.	Only Dir, File.
%D	Selected file or directory with expanded named folders.	Only Dir, File, Folder
%V	The directory of the selection, maybe unreliable?	All except Folder.
%W	The working directory.	All except Folder.
%<0-9>	Positional arg.
%*	Replace with all parameters.
%~	Replace with all parameters starting with the second parameter.

Splunk-specific macros:

Macro	Description
%ID	The Id property value.
%SPLUNK	Path to the Splunk executable.

!! Note that all paths and macros that expand to paths must be wrapped in double quotes.

The usual env vars like %ProgramFiles% are also supported.

Submenus

Not used currently in Splunk but could be useful later.

Note!! Must use MUIVerb, not default value @="text". A hard learn.

[HKCU\Directory]

[HKCU\Directory\shell]

[HKCU\Directory\shell\top_menu]
@=""
"MUIVerb"="Top Menu"
"subcommands"=""

[HKCU\Directory\shell\top_menu\shell]

[HKCU\Directory\shell\top_menu\shell\sub_menu_1]
@=""
"MUIVerb"="Sub Menu 1"

[HKCU\Directory\shell\top_menu\shell\sub_menu_1\command]
@="my_command.exe"

[HKCU\Directory\shell\top_menu\shell\sub_menu_2]
@=""
"MUIVerb"="Sub Menu 2"

[HKCU\Directory\shell\top_menu\shell\sub_menu_2\command]
@="my_command.exe"

Refs

• General how to: https://learn.microsoft.com/en-us/windows/win32/shell/context-menu-handlers
• Detailed registry editing: https://mrlixm.github.io/blog/windows-explorer-context-menu/
• Shell command vars: https://superuser.com/questions/136838/which-special-variables-are-available-when-writing-a-shell-command-for-a-context