API Options

This mode requires you to write another TOML file. gtk/Gir.toml is a good example.

[options]
girs_directories = ["gir-files"]
library = "Gtk"
version = "3.0"
min_cfg_version = "3.4"
target_path = "."
# Path where objects generated (defaults to <target_path>/src/auto)
# auto_path = "src/auto"
work_mode = "normal"
# Whether the library uses https://gitlab.gnome.org/GNOME/gi-docgen for its documentation
use_gi_docgen = false
generate_safety_asserts = true
deprecate_by_min_version = true
# With this option enabled, versions for gir and gir-files saved only to one file to minimize noise,
# can also take path to the directory for saving "versions.txt" or filename with extension.
# Relative to target_path
single_version_file = true
# Trust the nullability information about return values. If this is disabled
# then any pointer return type is assumed to be nullable unless there is an
# explicit override for it.
# This has to be used carefully as many libraries are missing nullable
# annotations for return values, which then will cause a panic once an
# unexpected NULL is returned.
trust_return_value_nullability = false
# Disable running `cargo fmt` on generated files
# (defaults to false)
disable_format = true
# Always generate a Builder if possible. This is mostly a convenient setter as most of the
# time you might want the Builder to be generated. Ignoring none-desired ones can still be done with per object `generate_builder` configuration.
# (defaults to false)
generate_builder = true

This mode generates only the specified objects. You can either add the object's fullname to the generate array or add it to the manual array (but in this case, it won't be generated, just used in other functions/methods instead of generating an "ignored" argument). Example:

generate = ["Gtk.Widget", "Gtk.Window"]
manual = ["Gtk.Button"]

So in here, both GtkWidget and GtkWindow will be fully generated and functions/methods using GtkButton will be uncommented. To generate code for all global functions, add Gtk.* to the generate array.

To also generate a Builder struct for a widget, it needs to be set with the generate_builder flag in object configuration:

[[object]]
name = "Gtk.TreeView"
status = "generate"
generate_builder = true

If the object doesn't already have a Default implementation through a constructor method without arguments, generating a Builder struct will add a Default implementation for the object.

If you want to remove warning messages about the not bound Builders during the generation you don't want to be generated, you can ignore them with the generate_builder flag in object configuration:

[[object]]
name = "Gtk.TreeView"
status = "generate"
generate_builder = false

If there is some work which has to be done post-construction before the builder's build method returns, you can set the builder_postprocess value in the object configuration:

[[object]]
name = "Gtk.Application"
status = "generate"
generate_builder = true
builder_postprocess = "Application::register_startup_hook(&ret);"

For the duration of the code in builder_postprocess the binding ret will be the value to be returned from the build method.

Sometimes Gir understands the object definition incorrectly or the .gir file contains an incomplete or wrong definition, to fix it, you can use the full object configuration:

[[object]]
# object's fullname
name = "Gtk.SomeClass"
# can be also "manual" and "ignore" but it's simpler to just put the object in the same array
status = "generate"
# replace the parameter name for the child in child properties (instead "child")
child_name = "item"
# mark object as final type, i.e. one without any further subclasses. this
# will not generate trait SomeClassExt for this object, but implement all
# functions in impl SomeClass
final_type = true
# mark the object as a fundamental type in case the GIR file lacks the annotation
# note that fundamental types don't make use of IsA/Cast traits and you should
# implement something similar manually
# gir is only capable for generating the type definitions along with their functions
fundamental_type = false
# mark the enum as exhaustive. This must only be done if it is impossible for
# the C library to add new variants to the enum at a later time but allows
# for more optimal code to be generated.
exhaustive = false
# allow rename result file
module_name = "soome_class"
# override starting version
version = "3.12"
# prefixed object in mod.rs with #[cfg(mycond)]
cfg_condition = "mycond"
# if you want to generate builder with name SomeClassBuilder
generate_builder = true
# trust return value nullability annotations for this specific type.
# See above for details and use with care
trust_return_value_nullability = false
# Tweak the visibility of the type
visibility = "pub" # or 'crate' / 'private' / 'super'
# The default value to used for the `Default` implementation. It only
# works for flags and enums. You have to pass the "GIR" member name.
default_value = "fill"
# Change the name of the generated trait to e.g avoid naming conflicts
trait_name = "TraitnameExt" 
# In case you don't want to generate the documentation for this type.
generate_doc = false
    # define overrides for function
    [[object.function]]
    # filter functions from object
    name = "set_website_label"
    # alternative way to apply override for many functions. Will be used with '^' and '$' on both sides
    # can be used instead of `name` almost anywhere
    # pattern = "[gs]et_value"
    # don't generate function
    ignore = true
    # override starting version
    version = "3.12"
    # prefixed function with #[cfg(mycond)]
    cfg_condition = "mycond"
    # prefixed function with #[doc(hidden)]
    doc_hidden = true
    # define a list of function parameters to be ignored when the documentation is generated
    doc_ignore_parameters = ["some_user_data_param"]
    # disable length_of autodetection
    disable_length_detect = true
    # write function docs to trait other than default "xxxExt",
    # also works in [object.signal] and [object.property]
    doc_trait_name = "SocketListenerExtManual"
    # disable generation of future for async function
    no_future = true
    # to rename the generated function
    rename = "something_else"
    # to override the default safety assertions: "none", "skip",
    # "not-initialized", "in-main-thread"
    assertion = "in-main-thread"
    # Tweak the visibility of the function
    visibility = "pub" # or 'crate' / 'private' / 'super'
    # In case you don't want to generate the documentation for this method.
    generate_doc = false
        # override for parameter
        [[object.function.parameter]]
        # filter by name
        name = "website_label"
        # allow to remove/add Option<>
        nullable = true
        # Take the parameter by value instead of by ref
        move = true
        # allow to make parameter immutable
        const = true
        # parameter is calculated as length of string or array and removed from function declaration
        # (for length of return value use "return")
        length_of = "str"
        # change string type. Variants: "utf8", "filename", "os_string"
        string_type = "os_string"
        # make function unsafe to call (emits `fn unsafe`)
        unsafe = true

        # override for return value
        [object.function.return]
        # allow to remove/add Option<> to return value
        nullable = true
        # convert bool return types to Result<(), glib::BoolError> with
        # the given error message on failure
        bool_return_is_error = "Function failed doing what it is supposed to do"
        # convert Option return types to Result<T, glib::BoolError> with
        # the given error message on failure
        nullable_return_is_error = "Function failed doing what it is supposed to do"
        # always include the return value of throwing functions in the returned Result<...>,
        # without this option bool and guint return values are assumed to indicate success or error,
        # and are not included in the returned Result<...>
        use_return_for_result = true
        # change string type. Variants: "utf8", "filename", "os_string"
        string_type = "os_string"
        # overwrite type
        type = "Gtk.Widget"

            # Override callback's parameter
            [[object.function.parameter.callback_parameter]]
            name = "name_of_the_callback_parameter"
            nullable = true
    # virtual methods support the same configuration for parameters and return types as functions
    # note that they are not used for code generation yet.
    [[object.virtual_method]]
    # filter virtual method from object
    name = "set_website_label"
    # alternative way to apply override for many functions. Will be used with '^' and '$' on both sides
    # can be used instead of `name` almost anywhere
    # pattern = "[gs]et_value"
    # don't generate function
    ignore = true
    # override starting version
    version = "3.12"
    # prefixed function with #[cfg(mycond)]
    cfg_condition = "mycond"
    # prefixed function with #[doc(hidden)]
    doc_hidden = true
    # define a list of function parameters to be ignored when the documentation is generated
    doc_ignore_parameters = ["some_user_data_param"]
    # write function docs to trait other than default "xxxExt",
    # also works in [object.signal] and [object.property]
    doc_trait_name = "SocketListenerExtManual"
    # to rename the generated function
    rename = "something_else"
    # In case you don't want to generate the documentation for this method.
    generate_doc = false
    [[object.signal]]
    name = "activate-link"
    # replace trampoline bool return type with `Inhibit`
    inhibit = true
    ignore = true
    version = "3.10"
    doc_hidden = true
    # In case you don't want to generate the documentation for this signal.
    generate_doc = false
        [[object.signal.parameter]]
        name = "path_string"
        # allow to use different names in closure
        new_name = "path"
        # can be also "borrow" and "none": Add some transformation between ffi trampoline parameters and rust closure
        transformation = "treepath"
        nullable = true
        [object.signal.return]
        nullable = true
    # override for properties
    [[object.property]]
    name = "baseline-position"
    version = "3.10"
    ignore = true
    # In case you don't want to generate the documentation for this property.
    generate_doc = false
    [[object.property]]
    name = "events"
    # generate only `connect_property_events_notify`, without `get_property_events` and `set_property_events`
    # supported values: "get", "set", "notify"
    generate = ["notify"]

Since there are no child properties in .gir files, it needs to be added for classes manually:

[[object]]
name = "Gtk.SomeClassWithChildProperties"
status = "generate"
# replace parameter name for child in child properties (instead of "child")
child_name = "item"
# define concrete child type (instead of "Widget")
child_type = "Gtk.MenuItem"
    [[object.child_prop]]
    name = "position"
    type = "gint"
    doc_hidden = true

For enumerations and bitflags, you can configure the members and mark the type as #[must_use]:

[[object]]
name = "Gdk.EventType"
status = "generate"
# generates #[must_use] attribute for the type
must_use = true
# override starting version
version = "3.12"
    [[object.member]]
    name = "2button_press"
    # allows to skip elements with bad names, other members with same value used instead
    ignore = true
    # Allow to add a cfg condition
    cfg_condition = "target_os = \"linux\""
    # In case you don't want to generate the documentation for this member.
    generate_doc = false
    [[object.member]]
    name = "touchpad_pinch"
    # define starting version when member added
    version = "3.18"

For enumerations and bitflags, you can also configure additional #[derive()] clauses optionally conditioned to a cfg.

[[object]]
name = "Gst.Format"
status = "generate"
    [[object.derive]]
    name = "Serialize, Deserialize"
    cfg_condition = "feature = \"serde\""

For global functions, the members can be configured by configuring the Gtk.* object:

[[object]]
name = "Gtk.*"
status = "generate"
    [[object.function]]
    name = "stock_list_ids"
    # allows to ignore global functions
    ignore = true
    # allows to define if the function was moved to a trait 
    doc_trait_name = "StockExt"
    # allows to define if the function was moved to a struct
    doc_struct_name = "Stock"
    # In case you don't want to generate the documentation for this function.
    generate_doc = false

Which will prevent gir from generating stock_list_ids. If you want to specify that a function will be manually implemented, you can use:

[[object]]
name = "Gtk.Entry"
status = "generate"
    [[object.function]]
    name = "get_invisible_char"
    manual = true

This will prevent gir from generating get_invisible_char and it won't generate get_property_invisible_char which would have been generated if we had used "ignore = true".

Note that you must not place Gtk.* into the generate array and additionally configure its members.

You can control the generation of constants in a similar fashion:

[[object]]
name = "Gtk.*"
status = "generate"
    [[object.constant]]
    pattern = "*"
    # No constants will be generated
    ignore = true
    # In case you don't want to generate the documentation for this constant.
    generate_doc = false

Constants also support version and cfg_condition fields.

In various cases, GObjects or boxed types can be used from multiple threads and have certain concurrency guarantees. This can be configured with the concurrency setting at the top-level options or per object. It will automatically implement the Send and Sync traits for the resulting object and set appropriate trait bounds for signal callbacks. The default is none, and apart from that send and send+sync are supported.

[[object]]
# object's fullname
name = "Gtk.SomeClass"
# can be also "manual" and "ignore" but it's simpler to just put the object in the same array
status = "generate"
# concurrency of the object, default is set in the top-level options or
# otherwise "none". Valid values are "none", "send" and "send+sync"
concurrency = "send+sync"

Note that send is only valid for types that are either not reference counted (i.e. clone() copies the object) or that are read-only (i.e. no API for mutating the object exists). send+sync is valid if the type can be sent to different threads and all API allows simultaneous calls from different threads due to internal locking via e.g. a mutex.

[[object]]
name = "Gtk.Something"
status = "manual"
# Can also be "ref-mut", "ref-immut"
ref_mode = "ref"

When manually generating bindings, it can happen that the reference mode detected by GIR is different than what was implemented and conversion to the C types are wrong in autogenerated functions that have such objects as argument. This can be overridden with the ref_mode configuration.

Getters are automatically renamed to comply with Rust codying style guidelines. However, this can cause name clashes with existing functions. If you want to bypass the automatic renaming mechanism, use bypass_auto_rename = true:

[[object]]
name = "Gtk.TextBuffer"
[...]
    [[object.function]]
    name = "get_insert"
    # Avoid clash with the `insert` operation.
    bypass_auto_rename = true

Some constructors are not annotated as constructor in the gir files. In order for the naming convention to be applied, you can force a function to be considered as a constructor:

[[object.function]]
name = "new_for_path"
# Not annotated as constructor in Gir => force it to apply naming convention
constructor = true

conversion_type "Option"

The conversion_type variant Option is available for types T implementing glib::TryFromGlib<Error=GlibNoneError>. As a reminder, this allows implementing FromGlib for Option<T> and usually goes alongside with ToGlib for both T and Option<T>. In this case, Option<T> will be used for return values (including ffi output arguments). For in-arguments, except if the parameter is declared mandatory, impl Into<Option<T>> so that either an Option<T> or T can be used.

Ex. from gstreamer-rs:

#![allow(unused)]
fn main() {
[[object]]
name = "Gst.ClockTime"
status = "manual"
conversion_type = "Option"
}

The type ClockTime implements glib::TryFromGlib<Error=GlibNoneError> (and OptionToGlib), which means that its Rust representation can take advantage of Option<ClockTime>.

Additionally, the user can instruct gir to expect Some or Ok results for specific arguments or return values. E.g.:

#![allow(unused)]
fn main() {
[[object]]
name = "Gst.Clock"
status = "generate"
manual_traits = ["ClockExtManual"]
    [[object.function]]
    name = "get_calibration"
        [[object.function.parameter]]
        name = "internal"
        mandatory = true
}

In the above example, the user instructs gir to consider the internal argument (which also happens to be an out argument) with type gir Gst.ClockTime can be represented as a ClockTime without the Option. This argument is actually part of a set of output arguments. With the above gir declaration, the generated signature is the following (the implementation takes care of expecting the value to be defined):

#![allow(unused)]
fn main() {
    fn get_calibration(
        &self,
    ) -> (
        ClockTime,
        Option<ClockTime>,
        Option<ClockTime>,
        Option<ClockTime>,
    );
}

For a return value, the mandatory declaration reads:

#![allow(unused)]
fn main() {
    [[object.function]]
    name = "util_get_timestamp"
    /.../
        [object.function.return]
        always returns a value
        mandatory = true
}

conversion_type "Result"

The conversion_type variant Result is available for types T implementing glib::TryFromGlib<Error=Err> where Err is neither GlibNoneError nor GlibNoneOrInvalidError. In this case, Result<T, ErrorType> will be used for return values (including ffi output arguments) and the type itself in argument position.

In gstreamer-rs, the C type GstStateChangeReturn can represent both a successful or an error return value. In Rust, the Result enum is the idiomatic way of returning an error. In gstreamer-rs, bindings to functions returning GstStateChangeReturn had to be manually implemented so as to return Result<StateChangeSuccess, StateChangeError>. Note that in this case, the type implementing TryFromGlib is StateChangeSuccess and not GstStateChangeReturn. These functions can be auto-generated using:

#![allow(unused)]
fn main() {
[[object]]
name = "Gst.StateChangeReturn"
status = "generate"
must_use = true
    [object.conversion_type]
    variant = "Result"
    ok_type = "gst::StateChangeSuccess"
    err_type = "gst::StateChangeError"
}

Boxed types vs. BoxedInline types

For boxed types / records, gir auto-detects copy/free or ref/unref function pairs for memory management on records. It falls back to generic g_boxed_copy/g_boxed_free if these are not found, based on an existing implementation of get_type. Otherwise no record implementation can be generated.

This works for the majority of boxed types, which are literally boxed: their memory is always allocated on the heap and memory management is left to the C library. Some boxed types, however, are special and in C code they are usually allocated on the stack or inline inside another struct. As such, their struct definition is public and part of the API/ABI. Usually these types are relatively small and allocated regularly, which would make heap allocations costly.

These special boxed types are usually allocated by the caller of the C functions, and the functions are then only filling in the memory and taking values of this type as (out caller-allocates) parameters.

In most other bindings, heap allocations are used for these boxed types too but in Rust we can do better and actually allocate them on the stack or inline inside another struct.

Gir calls these special boxed types "boxed inline".

[[object]]
name = "GLib.TreeIter"
status = "generate"
boxed_inline = true

For inline-allocated boxed types it is possible to provide Rust expressions in the configuration for initializing newly allocated memory for them, to copy from one value into another one, and to free any resources that might be stored in values of that boxed types.

By default the memory is zero-initialized and copying is done via std::ptr::copy(). If the boxed type contains memory that needs to be freed then these functions must be provided.

The following configuration is equivalent with the one above.

[[object]]
name = "GLib.TreeIter"
status = "generate"
boxed_inline = true
init_function_expression = "|_ptr| ()"
copy_into_function_expression = "|dest, src| { std::ptr::copy_nonoverlapping(src, dest, 1); }"
clear_function_expression = "|_ptr| ()"

Generation in API mode

To generate the Rust-user API level, The command is very similar to the previous one. It's better to not put this output in the same directory as where the FFI files are. Just run:

cargo run --release -- -c YourGirFile.toml -d ../gir-files -o the-output-directory

Now it should be done. Just go to the output directory (so the-output-directory/auto in our case) and try to build using cargo build. Don't forget to update your dependencies in both projects: nothing much to do in the FFI/sys one but the Rust-user API level will need to have a dependency over the FFI/sys one.

Now, at your crate entry point (generally lib.rs), add the following to include all generated files:

#![allow(unused)]
fn main() {
pub use auto::*;
}

Add manual bindings alongside generated code

Unfortunately, gir isn't perfect (yet) and will certainly not be able to generate all the code on its own. So here's what a gir generated folder looks like:

- your_folder
|
|- Cargo.toml
|- src
 |
 |- lib.rs
 |- auto
  |
  |- (all files generated by gir)

You can add your manual bindings directly inside the src folder (at the same level as lib.rs). Then don't forget to reexport them. Let's say you added a Color type in a color.rs file. You need to add in lib.rs: