README

LazAssPicker

Open Lazarus projects and files with the build you choose.

A file-association companion for multiple Lazarus builds.

LazAssPicker is primarily a companion for my Lazarus installations managed by fpcupdeluxe. I keep its executable beside fpcupdeluxe and use it to connect my Lazarus builds to the system's file manager.

It is built on FileAss, our component for registering file types with the desktop, and needs nothing beyond it and the standard Lazarus libraries.

It also supports multiple Lazarus builds you install or compile yourself. fpcupdeluxe is optional: add your builds manually or import their desktop launchers or Windows shortcuts, then choose how your projects and source files open.

Double-click a Lazarus project or source file anywhere on your system to open it in your chosen default build. Right-click → Open With to choose another Lazarus build. Each build keeps its own IDE configuration and launch arguments.

Keep a stable Lazarus for everyday work, trunk for testing, and another build for an older project or a different compiler. The GUI gives you one place to configure those file associations. You can then open your projects and files from the folders where you already keep them.

The screenshot uses example installations.

Start beside fpcupdeluxe

For fpcupdeluxe-managed installations, place the lazasspicker executable (lazasspicker.exe on Windows) in the same folder as fpcupdeluxe and run it. It is a single executable; no image files need to be copied beside it.

fpcupdeluxe/
├── fpcupdeluxe-x86_64-linux
├── fpcupdeluxe.ini
└── lazasspicker

On first launch, LazAssPicker reads the nearby fpcupdeluxe.ini, follows its InstallDirectory, checks nearby installation folders, and imports Lazarus desktop launchers (on Windows, the shortcuts on the desktop and in the Start menu). An older build can still be found through its launcher or lazarus.cfg even when the current fpcupdeluxe INI points somewhere else.

Keep the executable elsewhere if you prefer. Scan fpcupdeluxe folder accepts the fpcupdeluxe program folder, a single installation, or a parent containing several installations. Selected scan folders are remembered.

For builds you manage yourself, use Add build to select each Lazarus executable and set its launch arguments and working directory, or use Import launcher for an existing .desktop file or Windows shortcut. No fpcupdeluxe INI is required.

Choose a build

1. Check the builds you want available in Open With.
2. Choose your Double-click default.
3. Select the file types, then click Apply associations.

Double-clicking a supported file opens it in your chosen default. To use a different compiler or IDE version, right-click the file and choose a build from Open With. The exact menu arrangement depends on your file manager.

You can also select a build and click Open project or file. This opens the selected files immediately, without changing your associations.

After installing or updating a build with fpcupdeluxe, click Rescan, review the launch settings, and apply any changes. Import launcher handles an individual .desktop file or shortcut; Add build handles a manually installed Lazarus.

Each build's settings

Under each build, LazAssPicker shows the IDE configuration folder it starts with, found the way Lazarus finds it: --pcp= (or --primary-config-path=) in the launch arguments, otherwise the same option in the lazarus.cfg beside the Lazarus executable, otherwise the default - ~/.lazarus, or %LOCALAPPDATA%\lazarus on Windows. A relative folder and ~/ are read as Lazarus reads them. The same build found through a shortcut and through a folder scan is listed once.

Lazarus versions cannot share one configuration folder, so when two checked builds would start with the same one, LazAssPicker says so beside the build and again when you apply. Launch arguments that write --pcp <folder> with a space are refused: Lazarus reads only --pcp=<folder> and would open the folder as a file. Quotes around the folder in lazarus.cfg are pointed out: Lazarus 5 takes them off, but 4 and older read them as part of the folder's name.

What it changes

Discovery only reads installation files and existing launchers. LazAssPicker does not edit fpcupdeluxe, its INI files, Lazarus installations, lazarus.cfg, or the original desktop shortcuts. Scanning does not start Lazarus or run fpcupdeluxe.

Applying associations writes LazAssPicker-owned desktop entries and MIME registrations to your user data folder, and updates the selected defaults in your user configuration. On Windows they go under HKEY_CURRENT_USER\Software\Classes, and the settings under %LOCALAPPDATA%\lazasspicker. No administrator access is needed.

Remove associations removes those registrations and restores previous default entries where LazAssPicker is still selected. If you chose another application afterward, that newer choice is preserved. Your saved build list is kept. Removing a build from the list never deletes its installation.

Lazarus itself may save its normal IDE settings when you launch it.

The double-click default on Windows

Windows lets no program set the default by itself. LazAssPicker registers every build in Open with and sets its default for the file types, and Windows uses that until you pick an app with Always use this app. Such a choice wins over LazAssPicker's, and LazAssPicker says so after applying. To change it, right-click a file of that type, choose Open with, choose another app, pick the build and tick Always use this app.

Supported files

On Linux, Pascal source extensions share the system's text/x-pascal MIME type. Choosing a default for one affects other files the desktop identifies as Pascal too. Projects, packages, forms, and includes receive specific MIME registrations; LazAssPicker does not make Lazarus the default for all XML or plain-text files.

Build from source

Requires Free Pascal, Lazarus (GTK3 on Linux, win32 on Windows), and the FileAss runtime package. Register fileass_runtime.lpk with Lazarus, then open lazasspicker.lpi in the IDE or build from a terminal:

lazbuild --add-package-link ../FileAss/component/fileass_runtime.lpk
./build.sh
./bin/lazasspicker

For Windows, build with lazbuild --ws=win32 lazasspicker.lpi, or cross-build from Linux with ./build.sh --os=win64 --cpu=x86_64 --ws=win32.

Set LAZBUILD if lazbuild is not on your PATH. The application uses the RTL, FCL, LCL and FileAss. On Linux it also uses the normal desktop utilities update-mime-database, update-desktop-database and gio. The artwork and icon are embedded.

When moving the executable after applying associations, run it from its new location and apply again so the desktop entries point to the new path.

Release packages

Run ./release.sh on Linux to build both packages in dist/: a Linux x86-64 archive and a Windows x86-64 zip, each with a SHA-256 checksum. Each holds the standalone executable, this README, the license, and the documentation images. Only the executable needs to be placed beside fpcupdeluxe. Build options such as --pcp=/path/to/config can be passed through release.sh to Lazarus. The version is recorded in VERSION.

The window shows its version, and Check for new releases opens the releases page.

Current scope

Linux with GTK3: discovery, quoted paths, multiple files, MIME recognition, registration, switching defaults, restoring and removing were checked in an isolated home with example builds, and the window in light and dark themes on a nested X display. Native Wayland and other desktops have not been verified.

Windows 10: discovery from fpcupdeluxe and shortcuts, registration, a double-click through the shell with Unicode and spaces in the path, Open with another build, the window, and removal were checked with example builds. Windows 11 has not been tried.

macOS is not built. Every Lazarus.app usually carries the same bundle identifier, and macOS passes no launch arguments when it opens a file, so the builds cannot each sit in Open With with their own configuration. One direction would make LazAssPicker.app the only handler and have it ask which build to open. We won't build that unless someone asks for it. This program chooses a launch target; it does not change project compiler settings or convert a project for another Lazarus version.

License

0BSD. Copyright (c) 2026 Tony Stone.