Hacking Geany



About this file

This file contains information for anyone wanting to work on the Geany codebase. You should be aware of the open source licenses used - see the README file or the documentation. It is reStructuredText; the source file is HACKING.

You can generate this file by:

  • Passing the --enable-html-docs option to configure.
  • Running make from the doc/ subdirectory.

Writing plugins

  • src/plugindata.h contains the plugin API data types.
  • See plugins/demoplugin.c for a very basic example plugin.
  • src/plugins.c loads and unloads plugins (you shouldn't need to read this really).
  • The API documentation contains a few basic guidelines and hints to write plugins.

You should generate and read the plugin API documentation, see below.

Plugin API documentation

You can generate documentation for the plugin API using the doxygen tool:

  • Pass the --enable-api-docs option to configure.
  • Run make from the doc/ subdirectory.

The documentation will be output to doc/reference/index.html. Alternatively you can view the API documentation online at http://www.geany.org/manual/reference/.

Pull requests

Making pull requests on Github is the preferred way of contributing for geany.


For helping you to get started: https://help.github.com/articles/fork-a-repo

See Rules to contribute for more information.


We are happy to receive patches, but the preferred way is to make a pull request on our Github repository. If you don't want to make a pull request, you can send your patches on the devel mailing list, but the rules are the same: see Rules to contribute for more information.

In general it's best to provide git-formatted patches made from the current Git (see Committing):

$ git commit -a
$ git format-patch HEAD^

We also accept patches against other releases, but it's more work for us.

If you're not using Git, although you're strongly suggested to use it, you can use the diff command:

$ diff -u originalpath modifiedpath > new-feature.patch

However, such a patch won't contain the authoring information nor the patch's description.


Please make sure patches follow the style of existing code - In particular, use tabs for indentation. See Coding.

Rules to contribute

Keep in mind this is best to check with us by email on mailing list whether a new feature is appropriate and whether someone is already working on similar code.

Please, make sure contributions you make follow these rules:

  • changes should be made in a dedicated branch for pull requests.
  • only one feature should be in each pull request (or patch).
  • pull requests (or patches) should not contain changes unrelated to the feature, and commits should be sensible units of change.
  • the submitter should squash together corrections that are part of the development process, especially correcting your own mistakes.
  • Please make sure your modifications follow the style of existing code: see Coding for more information.

See Committing for more information.

Windows tools

See also the 'Building on Windows' document on the website.

File organization

callbacks.c is just for Glade callbacks. Avoid adding code to geany.h if it will fit better elsewhere. See the top of each src/*.c file for a brief description of what it's for.

Plugin API code

Please be aware that anything with a doc-comment (a comment with an extra asterix: /**) is something in the plugin API. Things like enums and structs can usually still be appended to, ensuring that all the existing elements stay in place - this will keep the ABI stable.


Some structs like GeanyCallback cannot be appended to without breaking the ABI because they are used to declare structs by plugins, not just for accessing struct members through a pointer. Normally structs should never be allocated by plugins.

Keeping the plugin ABI stable

Before the 1.0 release series, the ABI can change when necessary, and even the API can change. An ABI change just means that all plugins will not load and they must be rebuilt. An API change means that some plugins might not build correctly.

If you're reordering or changing existing elements of structs that are used as part of the plugin API, you must increment GEANY_ABI_VERSION in plugindata.h. This is usually not needed if you're just appending fields to structs. The GEANY_API_VERSION value should be incremented for any changes to the plugin API, including appending elements.

If you're in any doubt when making changes to plugin API code, just ask us.

Plugin API/ABI design

You should not make plugins rely on the size of a struct. This means:

  • Don't let plugins allocate any structs (stack or heap).
  • Don't let plugins index any arrays of structs.
  • Don't add any array fields to structs in case we want to change the array size later.


  • The @file tag can go in the source .c file, but use the .h header name so it appears normally in the generated documentation. See ui_utils.c for an example.
  • Function doc-comments should always go in the source file, not the header, so they can be updated if/when the implementation changes.


Add user-interface widgets to the Glade 3 file data/geany.glade. Callbacks for the user-interface should go in src/callbacks.c.

Use Glade 3.8.5. The 3.8 series still supports GTK+ 2, and earlier point releases did not preserve the order of XML elements, leading to unmanageable diffs.

GTK versions & API documentation

Geany requires GTK >= 2.24 and GLib >= 2.32. API symbols from newer GTK/GLib versions should be avoided or made optional to keep the source code building on older systems.

It is recommended to use the 2.24 API documentation of the GTK libs (including GLib, GDK and Pango) has the advantages that you don't get confused by any newer API additions and you don't have to take care about whether you can use them or not.

You might want to pass the -DGLIB_VERSION_MAX_ALLOWED=GLIB_VERSION_2_32 C preprocessor flag to get warnings about newer symbols from the GLib.

On the contrary, you might also want to get deprecation warnings for symbols deprecated in newer versions, typically when preparing a dependency bump or trying to improve forward compatibility. To do so, use the -UGLIB_VERSION_MIN_REQUIRED flag for GLib deprecations, and -UGDK_DISABLE_DEPRECATION_WARNINGS for GTK and GDK ones. To change the lower deprecation bound for GLib (and then get warnings about symbols deprecated more recently) instead of simply removing it entirely, use -UGLIB_VERSION_MIN_REQUIRED -DGLIB_VERSION_MIN_REQUIRED=GLIB_VERSION_X_YY.

See Compiler options & warnings for how to set such flags.


  • Don't write long functions with a lot of variables and/or scopes - break them down into smaller static functions where possible. This makes code much easier to read and maintain.
  • Use GLib types and functions - gint not int, g_free() not free().
  • Your code should build against GLib 2.32 and GTK 2.24. At least for the moment, we want to keep the minimum requirement for GTK at 2.24 (of course, you can use the GTK_CHECK_VERSION macro to protect code using later versions).
  • Variables should be declared (and initialized) as close as practical to their first use. This reduces the chances of intervening code being inserted between declaration and use, where the variable may be uninitialized.
  • Variables should be defined within the smallest scope that is practical, for example inside a conditional branch which uses them or in the initialization part of a for loop.
  • Local variables that will not be modified should be marked as const to indicate intention. This allows the compiler to give a warning if part of the code accidentally tries to change the value.
  • Pointer parameters should be marked const if the value they point to will not be mutated within the function.
  • Don't let variable names shadow outer variables - use gcc's -Wshadow option.
  • Use the strictest possible data type where practical. For example for an enumeration, use the actual enum type rather than just a gint, use a gchar for individual (ASCII/UTF-8) string characters rather than gint, and use a guint for integers which cannot be negative rather than gint.
  • Do not use G_LIKELY or G_UNLIKELY (except in critical loops). These add noise to the code with little real benefit.

Compiler options & warnings

Use CFLAGS='-Wfoo' ./configure or CFLAGS='-Wfoo' ./autogen.sh to set warning options (as well as anything else e.g. -g -O2).

  • Enable warnings - for gcc use '-Wall -Wextra' (and optionally -Wno-unused-parameter to avoid unused parameter warnings in Glade callbacks).
  • You should try to write ISO C99 code for portability, so always use C /* */ comments and function_name(void) instead of function_name(). This is for compatibility with various Unix-like compilers. You should use -std=c99 to help check this.


Remember for gcc you need to enable optimization to get certain warnings like uninitialized variables, but for debugging it's better to have no optimization on.


  • We use a tab width of 4 and indent completely with tabs not spaces. Note the documentation files use (4) spaces instead, so you may want to use the 'Detect from file' indent pref.
  • Do not add whitespace at the end of lines, this adds to commit noise. When editing with Geany set preference files->Strip trailing spaces and tabs.
  • Use the multiline comment /* */ to comment small blocks of code, functions descriptions or longer explanations of code, etc. The more comments are in your code the better. (See also scripts/fix-cxx-comments.pl in Git).
  • Lines should not be longer than about 100 characters and after 100 characters the lines should be wrapped and indented once more to show that the line is continued.
  • We don't put spaces between function names and the opening brace for argument lists.
  • Variable declarations come first after an opening brace, then one newline to separate declarations and code.
  • 2-operand operators should have a space each side.
  • Function bodies should have 2 blank newlines after them.
  • Align braces together on separate lines.
  • Don't put assignments in 'if/while/etc' expressions except for loops, for example for (int i = 0; i < some_limit; i++).
  • if statements without brace bodies should have the code on a separate line, then a blank line afterwards.
  • Use braces after if/while statements if the body uses another if/while statement.
  • Try to fit in with the existing code style.


A few of the above can be done with the Git scripts/fix-alignment.pl, but it is quite dumb and it's much better to write it correctly in the first place. scripts/rstrip-whitespace.py just removes trailing whitespace.


struct Bar;

typedef struct Foo  /* struct names normally are the same as typedef names */
    gint    foo;    /* names are somewhat aligned visually */
    gint    bar;    /* fields don't share the same line */
    SomeLongTypeName baz; /* alignment is not strict */
    gchar   *ptr;   /* pointer symbol must go next to variable name, not type */
    Bar     public; /**< only plugin API fields have a doc-comment */

gint some_func(void);

gint some_other_func(void);

/* optional function comment explains something important */
gint function_long_name(gchar arg1, <too many args to fit on this line>,
        gchar argN)
    /* variable declarations always go before code in each scope */
    /* variable names should NOT be aligned at all */
    gint foo, bar;  /* variables can go on the same line */
    gint baz;       /* but often don't */
    gchar *ptr;     /* pointer symbol must go next to variable name, not type */
    gchar *another; /* pointers should normally go on separate lines */

    /* Some long comment block
     * taking several different
     * lines to explain */
    if (foo)
        /* variables only used in one scope should normally be declared there */
        gint dir = -1;

        bar = foo;
        if ((bar & (guint)dir) != 7)
            some_code(arg1, <too many args to fit on this line>,
                argN - 1, argN);


/** Explains using doc-comments for plugin API functions.
 * First line should be short and use the third person tense - 'explains',
 * not 'explain'.
 * @return Some number.
 * @since 1.22. */
gint another_function(void)

Header Includes

In order to make including various headers in Geany more convenient, each file should include what it uses. If there is a file named foo.c, and a file named foo.h, it should be possible to include foo.h on its own without depending on stuff in foo.c that is included for the first time before foo.h.

Private Headers

If there is some data that needs to be shared between various parts of the core code, put them in a "private header", that is, if the public header is called foo.h, then make a fooprivate.h header that contains the non-public functions, types, globals, etc that are needed. Other core source files can then just include the foo.h and/or fooprivate.h depending what they need, without exposing that stuff to plugins.

Order of Includes

Inside a source file the includes section should be ordered like this:

  1. Always include the config.h file at the start of every source file, for example:

    #ifdef HAVE_CONFIG_H
    # include "config.h"

    This allows the Autotools and other build systems use the ./configure time settings. If you don't do this, there's likely to be a number of macros that you'll have to define in the build system or custom headers.

    Warning: Never include config.h in headers, and especially in "public" headers that plugins might include.

  2. Then include the header that has the same name as the source file (if applicable). For example, for a source file named foo.c, include the foo.h below the config.h include. If there is a fooprivate.h, foo.c will most likely want to include that too, put it in with includes in #3.

  3. At this point, it should be safe to include all the headers that declare whatever is needed. If everything generally "includes what it uses" and all files included contain the appropriate multiple-declaration guards then the order of includes is fairly arbitrary. Prefer to use English alphabetic order if possible.

  4. By now it doesn't really matter about the order, nothing below here is "our problem". Semi-arbitrarily, you should use an include order like this:

    1. Standard C headers
    2. Non-standard system headers (eg. windows.h or unistd.h)
    3. GLib/GTK+ or related headers
  5. Everything else that should not influence 1-4.

Including in Header Files

Headers should also include what they use. All of the types should defined in order to allow the header to be included stand-alone. For example, if a header uses a GtkWidget*, it should #include <gtk/gtk.h>. Or, if a headers uses a GPtrArray*, it should #include <glib.h> to ensure that all of the types are declared, whether by pointers/opaquely or fully, as required. Since all headers will use a G_BEGIN_DECLS and G_END_DECLS guard for C++, the bare minimum for a header is to include glib.h or <gtk/gtk.h> or gtkcompat.h or some other header that makes those macros available.


  • Commit one thing at a time, do small commits. Commits should be meaningful and not too big when possible; multiple small commits are good if there is no good reason to group them.
  • Use meaningful name and email in the Author and Committer fields. This helps knowing who did what and allows to contact the author if there is a good reason to do so (unlikely, but can happen).
  • When working on a new feature, create a new branch for it. When merging it, use the --no-ff option to make sure a merge commit will be created to better track what happened. However, if the feature only took one commit you might merge it fast-forward since there is not history to keep together.

Commit messages

Follow the standard Git formatting:

  • No line should use more than about 80 characters (around 72 is best).

  • The first line is the commit's summary and is followed by an empty line. This summary should be one line and one line only, thus less than 80 characters. This summary should not include any punctuation unless really needed. See it as the subject of an email: keep it concise and as precise as you can, but not tool long.

  • Following lines are optional detailed commit information, with paragraphs separated by blank lines. This part should be as long as needed to describe the commit in depth, should use proper punctuation and should include any useful information, like the motivation for the patch and/or any valuable details the diff itself don't provide or don't make clear. Make it as complete as you think it makes sense, but don't include an information that is better explained by the commit's diff.

    It is OK to use ASCII formatting like bullet list using "*" or "-", etc. if useful, but emphasis (bold, italic, underline) should be avoided.


Ask the user if spawn fails in utils_open_browser()

Ask the user to configure a valid browser command if spawning it
fails rather than falling back to some arbitrary hardcoded defaults.

This avoid spawning an unexpected browser when the configured one is
wrong, and gives the user a chance to correctly fix the preference.


  • Run with -v to print any debug messages.
  • You can use a second instance (geany -i).
  • To check first-run behaviour, use an alternate config directory by passing -c some_dir (but make sure the directory is clean first).
  • For debugging tips, see GDB.

Bugs to watch out for

  • Forgetting to check doc->is_valid when looping through documents_array - instead use foreach_document().
  • Inserting fields into structs in the plugin API instead of appending.
  • Not breaking the plugin ABI when necessary.
  • Using an idle callback that doesn't check main_status.quitting.
  • Forgetting CRLF line endings on Windows.
  • Not handling Tabs & Spaces indent mode.


We try to use an unmodified version of Scintilla - any new lexers or other changes should be passed on to the maintainers at http://scintilla.org. We normally update to a new Scintilla release shortly after one is made. See also scintilla/README.

Tagmanager was originally taken from Anjuta 1.2.2, and parts of it (notably c.c) have been merged from later versions of Anjuta and CTags. The independent Tagmanager library itself ceased development before Geany was started. It's source code parsing is mostly taken from Exuberant CTags (see http://ctags.sf.net). If appropriate it's good to pass language parser changes back to the CTags project.


Some of these notes below are brief (or maybe incomplete) - please contact the geany-devel mailing list for more information.

Using pre-defined autotools values

When you are use macros supplied by the autotools like GEANY_PREFIX, GEANY_LIBDIR, GEANY_DATADIR and GEANY_LOCALEDIR be aware that these might not be static strings when Geany is configured with --enable-binreloc. Then these macros will be replaced by function calls (in src/prefix.h). So, don't use anything like printf("Prefix: " GEANY_PREFIX); but instead use printf("Prefix: %s", GEANY_PREFIX);

Adding a source file foo.[hc] in src/ or plugins/

  • Add foo.c, foo.h to SRCS in path/Makefile.am.
  • Add path/foo.c to po/POTFILES.in (for string translation).

Adding a filetype

You can add a filetype without syntax highlighting or tag parsing, but check to see if those features have been written in upstream projects first (scintilla or ctags).


If you want to reuse an existing lexer and/or tag parser, making a custom filetype is probably easier - it doesn't require any changes to the source code. Follow instructions in the manual: http://geany.org/manual/index.html#custom-filetypes. Don't forget to update the [Groups] section in filetype_extensions.conf.


You should use the newer [build-menu] section for default build commands - the older [build_settings] may not work correctly for custom filetypes.


  • Add GEANY_FILETYPES_FOO to filetypes.h.
  • Initialize GEANY_FILETYPES_FOO in init_builtin_filetypes() of filetypes.c.
  • Update data/filetype_extensions.conf.

The remaining notes relate mostly to built-in filetypes.

filetypes.* configuration file

All languages need a data/filetypes.foo configuration file. See the "Filetype definition files" section in the manual and/or data/filetypes.c for an example.

Programming languages should have:

  • [keywords] if the lexer supports it.
  • [settings] mostly for comment settings.
  • [build-menu] (or [build_settings]) for commands to run.

For languages with a Scintilla lexer, there should be a [styling] section, to correspond to the styles used in highlighting_styles_FOO[] in highlightingmappings.h - see below.

Don't forget to add the newly created filetype file to data/Makefile.am.

Syntax highlighting

It may be possible to use an existing Scintilla lexer in the scintilla/ subdirectory - if not, you will need to find (or write) one, LexFoo.cxx. Try the official Scintilla project first.


We won't accept adding a lexer that conflicts with one in Scintilla. All new lexers should be submitted back to the Scintilla project to save duplication of work.

When adding a lexer, update:

  • scintilla/Makefile.am
  • scintilla/src/Catalogue.cxx - add a LINK_LEXER command manually

For syntax highlighting, you will need to edit highlighting.c and highlightingmappings.h and add the following things:

  1. In highlightingmappings.h:

    1. define highlighting_lexer_FOO to the Scintilla lexer ID for this filtype, e.g. SCLEX_CPP.
    2. define the highlighting_styles_FOO array that maps Scintilla style states to style names in the configuration file.
    3. define highlighting_keywords_FOO to EMPTY_KEYWORDS if the filtype has no keywords, or as an HLKeyword array mapping the Scintilla keyword IDs to names in the configuration file.
    4. define highlighting_properties_FOO to EMPTY_PROPERTIES, or as an array of HLProperty if the filetype requires some lexer properties to be set. However, note that properties should normally be set in the [lexer_properties] section of the configuration file instead.

    You may look at other filtype's definitions for some examples (Ada, CSS or Diff being good examples).

  2. In highlighting.c:

    1. Add init_styleset_case(FOO); in highlighting_init_styles().
    2. Add styleset_case(FOO); in highlighting_set_styles().
  3. Write data/filetypes.foo configuration file [styling] section. See the manual and see data/filetypes.d for a named style example.


Please try to make your styles fit in with the other filetypes' default colors, and to use named styles where possible (e.g. "commentline=comment"). Filetypes that share a lexer should have the same colors. If not using named styles, leave the background color empty to match the default color.

Error message parsing

New-style error message parsing is done with an extended GNU-style regex stored in the filetypes.foo file - see the [build_settings] information in the manual for details.

Old-style error message parsing is done in msgwin_parse_compiler_error_line() of msgwindow.c - see the ParseData typedef for more information.

Other features

If the lexer has comment styles, you should add them in highlighting_is_comment_style(). You should also update highlighting_is_string_style() for string/character styles. For now, this prevents calltips and autocompletion when typing in a comment (but it can still be forced by the user).

For brace indentation, update lexer_has_braces() in editor.c; indentation after ':' is done from on_new_line_added().

If the Scintilla lexer supports user type keyword highlighting (e.g. SCLEX_CPP), update document_update_tags() in document.c.

Adding a TagManager parser

This assumes the filetype for Geany already exists.

First write or find a CTags compatible parser, foo.c. Check this fork: https://github.com/universal-ctags/ctags

There may be some unmerged language patches for CTags at: http://sf.net/projects/ctags - see the tracker.

(You can also try the Anjuta project's anjuta-tags codebase.)


From Geany 1.22 GLib's GRegex engine is used instead of POSIX regex, unlike CTags. It should be close enough to POSIX to work OK. We no longer support regex parsers with the "b" regex flag option set and Geany will print debug warnings if it's used. CTags supports it but doesn't currently (2011) include any parsers that use it. It should be easy to convert to extended regex syntax anyway.


  • Add foo.c to SRCS in Makefile.am.
  • Add Foo to parsers.h
  • Add TM_PARSER_FOO to src/tagmanager/tm_parser.h. The list here must follow exactly the order in parsers.h.

In tagmanager/src/tm_parsers.c: Add a map_FOO TMParserMapEntry mapping each kind's letter from foo.c's FooKinds to the appropriate TMTagType, and add the corresponding MAP_ENTRY(FOO) to parser_map. (You may want to make the symbols.c change before doing this).

In filetypes.c, init_builtin_filetypes(): Set the 2nd argument of the FT_INIT() macro for this filetype to FOO.

In symbols.c: Unless your parser uses C-like tag type kinds, update add_top_level_items() for foo, calling tag_list_add_groups(). See get_tag_type_iter() for which tv_iters fields to use.


The tag parser tests checks if the proper tags are emitted for a given source. Tests for tag parsers consist of two files: the source to parse, and the expected output. Tests are run using make check.

The source to parse should be in the file tests/ctags/mytest.ext, where mytest is the name you choose for your test, and ext is an extension recognized by Geany as the language the test file is for. This file should contain a snippet of the language to test for. It can be either long or short, depending on what it tests.

The expected output should be in the file tests/ctags/mytest.ext.tags (which is the same name as the source, but with .tags appended), and should be in the format generated by geany -g. This file contains the tag information expected to be generated from the corresponding source file.

When you have these two files, you have to list your new test along the other ones in the test_source variable in tests/ctags/Makefile.am. Please keep this list sorted alphabetically.

Upgrading Scintilla

To upgrade the local Scintilla copy, use the scripts/update-scintilla.sh script.

To use it, you need to first obtain a copy of the Scintilla sources you want to update to. This will generally mean checking out a release tag from the Scintilla Mercurial repository, or extracting a tarball.

Then, just run the script from Geany's to source directory passing the path to the Scintilla source directory as first argument, and follow the instructions, if any:

./scripts/update-scintilla.sh /path/to/scintilla/


Stop on warnings

When a GLib or GTK warning is printed, often you want to get a backtrace to find out what code caused them. You can do that with the --g-fatal-warnings argument, which will abort Geany on the first warning it receives.

But for ordinary testing, you don't always want your editor to abort just because of a warning - use:

(gdb) b handler_log if level <= G_LOG_LEVEL_WARNING

Running with batch commands


$ gdb src/geany -x gdb-commands

Where gdb-commands is a file with the following lines:

set pagination off
b handler_log if level <= G_LOG_LEVEL_WARNING
r -v

Loading a plugin

This is useful so you can load plugins without installing them first. Alternatively you can use a symlink in ~/.config/geany/plugins or $prefix/lib/geany (where $prefix is /usr/local by default).

The gdb session below was run from the toplevel Geany source directory. Start normally with e.g. "gdb src/geany". Type 'r' to run. Press Ctrl-C from the gdb window to interrupt program execution.


Program received signal SIGINT, Interrupt.
0x00d16402 in __kernel_vsyscall ()
(gdb) call plugin_new("./plugins/.libs/demoplugin.so")
** INFO: Loaded:   ./plugins/.libs/demoplugin.so (Demo)
$1 = (Plugin *) 0x905a890
(gdb) c

Program received signal SIGINT, Interrupt.
0x00d16402 in __kernel_vsyscall ()
(gdb) call plugin_free(0x905a890)
** INFO: Unloaded: ./plugins/.libs/demoplugin.so
(gdb) c

Building Plugins

The geany-plugins autotools script automatically detects the installed system Geany and builds the plugins against that.

To use plugins with a development version of Geany built with a different prefix, the plugins will need to be compiled against that version if the ABI has changed.

To do this you need to specify both --prefix and --with-geany-libdir to the plugin configure. Normally the plugin prefix is the same as the Geany prefix to keep plugins with the version of Geany that they are compiled against, and with-geany-libdir is the Geany prefix/lib.

Whilst it is possible for the plugin prefix to be different to the prefix of the libdir (which is why there are two settings), it is probably better to keep the version of Geany and its plugins together.