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HACKING.md

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Hacking

Contents

This part serves as a general overview over which parts of the code do what. Which should help if more substantial changes or bug fixes are necessary. For detailed information on structures and functions, refer to the documentation in the code itself, which can also be accessed through go doc:

Run

    go doc --all -u github.com/grandchild/linux_installer

and

    go doc --all -u github.com/grandchild/linux_installer/gui

to see text documentation for all symbols.

To read documentation for a specific item, e.g. the installFile() and the updateProgressbar() functions, run:

    go doc --all -u github.com/grandchild/linux_installer installFile
    go doc --all -u github.com/grandchild/linux_installer/gui updateProgressbar

Code Structure

The code's entry point is the main() function in main/main.go, which simply calls the actual main function which is run.go's Run() function(1).

All GUI code is placed in its own "main" package, inside the gui/ folder, because it is compiled separately as a Go plugin (a Go-specific kind of .so dynamic library). This allows compiling the installer without linking to GTK3 explicitly, which in turn allows running the installer on older Linux distributions, and falling back gracefully to an error message and allowing CLI installation mode. If the code would not be separated out into the plugin, the installer would always fail on systems without GTK3, reporting only a linker error and without recourse.

Main Go Files

run.go is the entry point and parses commandline flags and decides whether to run in GUI or CLI mode.

install.go provides the Installer type that performs the actual installation. It is used by all installation modes. The installer scans all zips present in the data_compressed folder, and prepares a list of files to be installed. Once the actual installation starts, it copies them to the target location on the system. It then creates an uninstaller script as well as an application menu shortcut, and runs any hook scripts that have been defined (for either before or after installation).

install_linux.go contains the Linux-specific system calls and application-menu, uninstaller and pre-/post-hooks (which are all OS-specific). It is only compiled when compiling for Linux (which is what the very first line in the file does).

gui/gui.go describes the GUI's behavior. It contains the event handlers at the top, followed by the constructor. The second half of the code are various functions the GUI code uses, such as switching from one screen to the next, or checking on the installer's progress.

config.go defines the structure for the config.yml file. It is used throughout the code, for accessing variables and options.

Helper Go Files

resources.go is the interface around go-rice, the library used for appending data to the compiled executable—creating the packaged installer. Refer to the go-rice documentation for more details.

translate.go implements internationalization functions, and uses language files inside resources/languages/ to render any user-facing string in the chosen language of the installer. It also detects the system locale to allow meaningful user communication before a language can be chosen.

variables.go provides a simple templating engine to expand variables inside strings. This can even be done recursively (i.e. a variable value may contain a variable reference as well).

gui/gui_utils.go contains wrappers for retrieving various GTK3 widget types from the gui definition file. Go famously has no generics, making this list of similar functions necessary. They all do the same thing, which is casting a widget loaded from the builder into the desired type.

Metadata

doc.go Contains a general description of the installer package, accessible through go doc (See above).

go.mod & go.sum Contain a list of dependencies, their versions and checksums. Used with go mod.

Note: go mod only works if your Go version is 1.11 or higher. Use go version to check.

Unused Go Files

install_windows.go Roughly implements the functions from install_linux but is largely untested since this installer is not used on Windows, since it would need to be shipped with GTK3 libraries. Which would defeat the purpose of having a packaged installer.

tui.go A tentative implementation of an ncurses-based terminal-graphical UI for the installer. Incomplete. The CLI mode serves well enough.

(1)

The reason for the existence of main/main.go is that a Go program's main function has to be placed inside a package called "main". But the installer package with most of the code should be called "installer", not "main" in order to behave more like an importable library. Thus the slightly awkward cage for main.