Implement generic object subclass creation in a more... generic... way

That actually works for subclasses of subclasses too without too much
boilerplate, and also keeps the GObject boilerplate in a single file
instead of having it for every single subclass.

gst-plugin/src/base_src.rs

@@ -0,0 +1,89 @@
+// Copyright (C) 2017 Sebastian Dröge <sebastian@centricular.com>
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use std::ptr;
+use std::mem;
+use mopa;
+
+use glib_ffi;
+use gobject_ffi;
+use gst_ffi;
+use gst_base_ffi;
+
+use glib;
+use glib::translate::*;
+use gst;
+use gst::prelude::*;
+use gst_base;
+use gst_base::prelude::*;
+
+use object::*;
+use element::*;
+
+pub trait BaseSrcImpl: mopa::Any + ElementImpl + Send + Sync + 'static {}
+
+mopafy!(BaseSrcImpl);
+
+pub unsafe trait BaseSrc: IsA<gst_base::BaseSrc> {}
+
+pub unsafe trait BaseSrcClass<T: ObjectType>
+where
+    T::RsType: IsA<gst_base::BaseSrc>,
+    T::ImplType: BaseSrcImpl,
+{
+}
+
+glib_wrapper! {
+    pub struct RsBaseSrc(Object<InstanceStruct<RsBaseSrc>>): [gst_base::BaseSrc => gst_base_ffi::GstBaseSrc,
+                                                              gst::Element => gst_ffi::GstElement,
+                                                              gst::Object => gst_ffi::GstObject];
+
+    match fn {
+        get_type => || get_type::<RsBaseSrc>(),
+    }
+}
+
+unsafe impl<T: IsA<gst_base::BaseSrc>> BaseSrc for T {}
+pub type RsBaseSrcClass = ClassStruct<RsBaseSrc>;
+
+// FIXME: Boilerplate
+unsafe impl BaseSrcClass<RsBaseSrc> for gst_base_ffi::GstBaseSrcClass {}
+unsafe impl BaseSrcClass<RsBaseSrc> for RsBaseSrcClass {}
+unsafe impl ElementClass<RsBaseSrc> for gst_base_ffi::GstBaseSrcClass {}
+unsafe impl ElementClass<RsBaseSrc> for RsBaseSrcClass {}
+
+// FIXME: Boilerplate
+impl BaseSrcImpl for Box<BaseSrcImpl> {}
+
+// FIXME: Boilerplate
+impl ElementImpl for Box<BaseSrcImpl> {
+    fn change_state(
+        &self,
+        element: &gst::Element,
+        transition: gst::StateChange,
+    ) -> gst::StateChangeReturn {
+        let imp: &BaseSrcImpl = self.as_ref();
+        imp.change_state(element, transition)
+    }
+}
+
+impl ObjectType for RsBaseSrc {
+    const NAME: &'static str = "RsBaseSrc";
+    type GlibType = gst_base_ffi::GstBaseSrc;
+    type GlibClassType = gst_base_ffi::GstBaseSrcClass;
+    type RsType = RsBaseSrc;
+    type ImplType = Box<BaseSrcImpl>;
+
+    fn glib_type() -> glib::Type {
+        unsafe { from_glib(gst_base_ffi::gst_base_src_get_type()) }
+    }
+
+    fn class_init(klass: &mut Self::GlibClassType) {
+        ElementClass::override_vfuncs(klass);
+    }
+}

gst-plugin/src/demuxer.rs

@@ -13,6 +13,7 @@ use std::u64;
 use std::collections::BTreeMap;
 
 use error::*;
+use object::{register_type, ImplTypeStatic};
 use element::*;
 
 use glib;
@@ -92,6 +93,7 @@ impl Stream {
     }
 }
 
+// TODO: Get rid of this wrapper
 pub struct DemuxerWrapper {
     cat: gst::DebugCategory,
     demuxer: Mutex<Box<DemuxerImpl>>,
@@ -384,22 +386,19 @@ impl Demuxer {
         }
     }
 
-    fn class_init(
+    fn class_init(klass: &mut RsElementClass, demuxer_info: &DemuxerInfo) {
-        klass: &mut RsElementClass,
+        klass.set_metadata(
-        long_name: &str,
+            &demuxer_info.long_name,
-        classification: &str,
+            &demuxer_info.classification,
-        description: &str,
+            &demuxer_info.description,
-        author: &str,
+            &demuxer_info.author,
-        input_caps: &gst::Caps,
+        );
-        output_caps: &gst::Caps,
-    ) {
-        klass.set_metadata(long_name, classification, description, author);
 
         let pad_template = gst::PadTemplate::new(
             "sink",
             gst::PadDirection::Sink,
             gst::PadPresence::Always,
-            input_caps,
+            &demuxer_info.input_caps,
         );
         klass.add_pad_template(pad_template);
 
@@ -407,7 +406,7 @@ impl Demuxer {
             "src_%u",
             gst::PadDirection::Src,
             gst::PadPresence::Sometimes,
-            output_caps,
+            &demuxer_info.output_caps,
         );
         klass.add_pad_template(pad_template);
     }
@@ -688,7 +687,7 @@ impl Demuxer {
 impl ElementImpl for Demuxer {
     fn change_state(
         &self,
-        element: &RsElement,
+        element: &gst::Element,
         transition: gst::StateChange,
     ) -> gst::StateChangeReturn {
         let mut ret = gst::StateChangeReturn::Success;
@@ -725,32 +724,34 @@ impl ElementImpl for Demuxer {
     }
 }
 
+struct DemuxerStatic {
+    name: String,
+    demuxer_info: DemuxerInfo,
+}
+
+impl ImplTypeStatic<RsElement> for DemuxerStatic {
+    fn get_name(&self) -> &str {
+        self.name.as_str()
+    }
+
+    fn new(&self, element: &RsElement) -> Box<ElementImpl> {
+        Demuxer::init(element, &self.demuxer_info)
+    }
+
+    fn class_init(&self, klass: &mut RsElementClass) {
+        Demuxer::class_init(klass, &self.demuxer_info);
+    }
+}
+
 pub fn demuxer_register(plugin: &gst::Plugin, demuxer_info: DemuxerInfo) {
     let name = demuxer_info.name.clone();
     let rank = demuxer_info.rank;
 
-    let long_name = demuxer_info.long_name.clone();
+    let demuxer_static = DemuxerStatic {
-    let classification = demuxer_info.classification.clone();
+        name: format!("Demuxer-{}", name),
-    let description = demuxer_info.description.clone();
+        demuxer_info: demuxer_info,
-    let author = demuxer_info.author.clone();
+    };
-    let input_caps = demuxer_info.input_caps.clone();
-    let output_caps = demuxer_info.output_caps.clone();
 
-    element_register(
+    let type_ = register_type(demuxer_static);
-        plugin,
+    gst::Element::register(plugin, &name, rank, type_);
-        &name,
-        rank,
-        move |klass| {
-            Demuxer::class_init(
-                klass,
-                &long_name,
-                &classification,
-                &description,
-                &author,
-                &input_caps,
-                &output_caps,
-            )
-        },
-        move |element| Demuxer::init(element, &demuxer_info),
-    );
 }

gst-plugin/src/element.rs

@@ -6,10 +6,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use std::ffi::CString;
 use std::ptr;
 use std::mem;
-use std::sync::atomic::AtomicBool;
 use mopa;
 
 use glib_ffi;
@@ -21,10 +19,12 @@ use glib::translate::*;
 use gst;
 use gst::prelude::*;
 
+use object::*;
+
 pub trait ElementImpl: mopa::Any + Send + Sync + 'static {
     fn change_state(
         &self,
-        element: &RsElement,
+        element: &gst::Element,
         transition: gst::StateChange,
     ) -> gst::StateChangeReturn {
         element.parent_change_state(transition)
@@ -53,7 +53,11 @@ pub unsafe trait Element: IsA<gst::Element> {
     }
 }
 
-pub unsafe trait ElementClass {
+pub unsafe trait ElementClass<T: ObjectType>
+where
+    T::RsType: IsA<gst::Element>,
+    T::ImplType: ElementImpl,
+{
     fn add_pad_template(&mut self, pad_template: gst::PadTemplate) {
         unsafe {
             gst_ffi::gst_element_class_add_pad_template(
@@ -80,14 +84,21 @@ pub unsafe trait ElementClass {
             );
         }
     }
+
+    fn override_vfuncs(&mut self) {
+        unsafe {
+            let klass = &mut *(self as *const Self as *mut gst_ffi::GstElementClass);
+            klass.change_state = Some(element_change_state::<T>);
+        }
+    }
 }
 
 glib_wrapper! {
-    pub struct RsElement(Object<ffi::RsElement>): [gst::Element => gst_ffi::GstElement,
+    pub struct RsElement(Object<InstanceStruct<RsElement>>): [gst::Element => gst_ffi::GstElement,
                                                               gst::Object => gst_ffi::GstObject];
 
     match fn {
-        get_type => || ffi::rs_element_get_type(),
+        get_type => || get_type::<RsElement>(),
     }
 }
 
@@ -95,211 +106,59 @@ impl RsElement {
     pub fn get_impl(&self) -> &ElementImpl {
         unsafe {
             let stash = self.to_glib_none();
-            let ptr: *const ffi::RsElement = stash.0;
+            let ptr: *mut InstanceStruct<RsElement> = stash.0;
-            (*ptr).get_impl()
+            (*ptr).get_impl().as_ref()
         }
     }
 }
 
 unsafe impl<T: IsA<gst::Element>> Element for T {}
-unsafe impl ElementClass for RsElementClass {}
+pub type RsElementClass = ClassStruct<RsElement>;
+unsafe impl ElementClass<RsElement> for RsElementClass {}
+unsafe impl ElementClass<RsElement> for gst_ffi::GstElementClass {}
 
-struct ElementData {
+// FIXME: Boilerplate
-    class_init: Box<Fn(&mut RsElementClass) + Send + 'static>,
+impl ElementImpl for Box<ElementImpl> {
-    init: Box<Fn(&RsElement) -> Box<ElementImpl> + Send + Sync + 'static>,
+    fn change_state(
+        &self,
+        element: &gst::Element,
+        transition: gst::StateChange,
+    ) -> gst::StateChangeReturn {
+        let imp: &ElementImpl = self.as_ref();
+        imp.change_state(element, transition)
+    }
 }
 
-pub mod ffi {
+impl ObjectType for RsElement {
-    use super::*;
+    const NAME: &'static str = "RsElement";
-    use super::RsElement as RsElementWrapper;
+    type GlibType = gst_ffi::GstElement;
+    type GlibClassType = gst_ffi::GstElementClass;
+    type RsType = RsElement;
+    type ImplType = Box<ElementImpl>;
 
-    #[repr(C)]
+    fn glib_type() -> glib::Type {
-    pub struct RsElement {
+        unsafe { from_glib(gst_ffi::gst_element_get_type()) }
-        parent: gst_ffi::GstElement,
-        imp: *const Box<ElementImpl>,
-        panicked: AtomicBool,
     }
 
-    impl RsElement {
+    fn class_init(klass: &mut Self::GlibClassType) {
-        pub fn get_impl(&self) -> &ElementImpl {
+        klass.override_vfuncs();
-            unsafe {
-                assert!(!self.imp.is_null());
-                &*(*self.imp)
-            }
-        }
     }
+}
 
-    #[repr(C)]
+unsafe extern "C" fn element_change_state<T: ObjectType>(
-    pub struct RsElementClass {
-        parent_class: gst_ffi::GstElementClass,
-        element_data: *const ElementData,
-    }
-
-    pub unsafe fn rs_element_get_type() -> glib_ffi::GType {
-        use std::sync::{Once, ONCE_INIT};
-
-        static mut TYPE: glib_ffi::GType = gobject_ffi::G_TYPE_INVALID;
-        static ONCE: Once = ONCE_INIT;
-
-        ONCE.call_once(|| {
-            let type_info = gobject_ffi::GTypeInfo {
-                class_size: mem::size_of::<RsElementClass>() as u16,
-                base_init: None,
-                base_finalize: None,
-                class_init: Some(element_class_init),
-                class_finalize: None,
-                class_data: ptr::null_mut(),
-                instance_size: mem::size_of::<RsElement>() as u16,
-                n_preallocs: 0,
-                instance_init: None,
-                value_table: ptr::null(),
-            };
-
-            let type_name = {
-                let mut idx = 0;
-
-                loop {
-                    let type_name = CString::new(format!("RsElement-{}", idx)).unwrap();
-                    if gobject_ffi::g_type_from_name(type_name.as_ptr()) ==
-                        gobject_ffi::G_TYPE_INVALID
-                    {
-                        break type_name;
-                    }
-                    idx += 1;
-                }
-            };
-
-            TYPE = gobject_ffi::g_type_register_static(
-                gst_ffi::gst_element_get_type(),
-                type_name.as_ptr(),
-                &type_info,
-                gobject_ffi::GTypeFlags::empty(),
-            );
-        });
-
-        TYPE
-    }
-
-    unsafe extern "C" fn element_finalize(obj: *mut gobject_ffi::GObject) {
-        callback_guard!();
-        let element = &mut *(obj as *mut RsElement);
-
-        drop(Box::from_raw(element.imp as *mut Box<ElementImpl>));
-        element.imp = ptr::null_mut();
-
-        let klass = *(obj as *const glib_ffi::gpointer);
-        let parent_klass = gobject_ffi::g_type_class_peek_parent(klass);
-        let parent_klass = &*(gobject_ffi::g_type_class_peek_parent(parent_klass) as
-            *const gobject_ffi::GObjectClass);
-        parent_klass.finalize.map(|f| f(obj));
-    }
-
-    unsafe extern "C" fn element_sub_class_init(
-        klass: glib_ffi::gpointer,
-        klass_data: glib_ffi::gpointer,
-    ) {
-        callback_guard!();
-        let element_data = &*(klass_data as *const ElementData);
-
-        {
-            let klass = &mut *(klass as *mut RsElementClass);
-
-            klass.element_data = element_data;
-
-            (element_data.class_init)(klass);
-        }
-    }
-
-    unsafe extern "C" fn element_class_init(
-        klass: glib_ffi::gpointer,
-        _klass_data: glib_ffi::gpointer,
-    ) {
-        callback_guard!();
-        {
-            let gobject_klass = &mut *(klass as *mut gobject_ffi::GObjectClass);
-
-            gobject_klass.finalize = Some(element_finalize);
-        }
-
-        {
-            let element_klass = &mut *(klass as *mut gst_ffi::GstElementClass);
-
-            element_klass.change_state = Some(element_change_state);
-        }
-    }
-
-    unsafe extern "C" fn element_change_state(
     ptr: *mut gst_ffi::GstElement,
     transition: gst_ffi::GstStateChange,
-    ) -> gst_ffi::GstStateChangeReturn {
+) -> gst_ffi::GstStateChangeReturn
+where
+    T::RsType: IsA<gst::Element>,
+    T::ImplType: ElementImpl,
+{
     callback_guard!();
-        let element = &*(ptr as *mut RsElement);
+    let element = &*(ptr as *mut InstanceStruct<T>);
-        let wrap: RsElementWrapper = from_glib_borrow(ptr as *mut RsElement);
+    let wrap: gst::Element = from_glib_borrow(ptr as *mut gst_ffi::GstElement);
     let imp = &*element.imp;
 
     panic_to_error2!(&wrap, &element.panicked, gst::StateChangeReturn::Failure, {
         imp.change_state(&wrap, from_glib(transition))
     }).to_glib()
-    }
-
-    unsafe extern "C" fn element_sub_init(
-        instance: *mut gobject_ffi::GTypeInstance,
-        klass: glib_ffi::gpointer,
-    ) {
-        callback_guard!();
-        let element = &mut *(instance as *mut RsElement);
-        let wrap: RsElementWrapper = from_glib_borrow(instance as *mut RsElement);
-        let klass = &*(klass as *const RsElementClass);
-        let element_data = &*klass.element_data;
-
-        let imp = (element_data.init)(&wrap);
-        element.imp = Box::into_raw(Box::new(imp));
-    }
-
-    pub fn element_register<F, G>(
-        plugin: &gst::Plugin,
-        name: &str,
-        rank: u32,
-        class_init: F,
-        init: G,
-    ) where
-        F: Fn(&mut RsElementClass) + Send + 'static,
-        G: Fn(&RsElementWrapper) -> Box<ElementImpl> + Send + Sync + 'static,
-    {
-        unsafe {
-            let parent_type = rs_element_get_type();
-            let type_name = format!("RsElement-{}", name);
-
-            let element_data = ElementData {
-                class_init: Box::new(class_init),
-                init: Box::new(init),
-            };
-            let element_data = Box::into_raw(Box::new(element_data)) as glib_ffi::gpointer;
-
-            let type_info = gobject_ffi::GTypeInfo {
-                class_size: mem::size_of::<RsElementClass>() as u16,
-                base_init: None,
-                base_finalize: None,
-                class_init: Some(element_sub_class_init),
-                class_finalize: None,
-                class_data: element_data,
-                instance_size: mem::size_of::<RsElement>() as u16,
-                n_preallocs: 0,
-                instance_init: Some(element_sub_init),
-                value_table: ptr::null(),
-            };
-
-            let type_ = gobject_ffi::g_type_register_static(
-                parent_type,
-                type_name.to_glib_none().0,
-                &type_info,
-                gobject_ffi::GTypeFlags::empty(),
-            );
-
-            gst::Element::register(plugin, &name, rank, from_glib(type_));
-        }
-    }
 }
-
-pub use self::ffi::RsElementClass;
-pub use self::ffi::element_register;

gst-plugin/src/lib.rs

@@ -43,4 +43,6 @@ pub mod sink;
 pub mod demuxer;
 pub mod bytes;
 
+pub mod object;
 pub mod element;
+pub mod base_src;

gst-plugin/src/object.rs

@@ -0,0 +1,188 @@
+// Copyright (C) 2017 Sebastian Dröge <sebastian@centricular.com>
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use std::ffi::CString;
+use std::ptr;
+use std::mem;
+use std::sync::atomic::AtomicBool;
+
+use glib_ffi;
+use gobject_ffi;
+
+use glib;
+use glib::translate::*;
+
+pub trait ImplTypeStatic<T: ObjectType>: Send + Sync + 'static {
+    fn get_name(&self) -> &str;
+    fn new(&self, &T::RsType) -> T::ImplType;
+    fn class_init(&self, &mut ClassStruct<T>);
+}
+
+pub trait ObjectType: 'static
+where
+    Self: Sized,
+{
+    const NAME: &'static str;
+    type GlibType;
+    type GlibClassType;
+    type RsType: FromGlibPtrBorrow<*mut InstanceStruct<Self>>;
+    type ImplType: 'static;
+
+    fn glib_type() -> glib::Type;
+
+    fn class_init(klass: &mut Self::GlibClassType);
+}
+
+#[repr(C)]
+pub struct InstanceStruct<T: ObjectType> {
+    pub parent: T::GlibType,
+    pub imp: *const T::ImplType,
+    pub panicked: AtomicBool,
+}
+
+impl<T: ObjectType> InstanceStruct<T> {
+    pub fn get_impl(&self) -> &T::ImplType {
+        unsafe { &*self.imp }
+    }
+}
+
+#[repr(C)]
+pub struct ClassStruct<T: ObjectType> {
+    pub parent: T::GlibClassType,
+    pub imp_static: *const Box<ImplTypeStatic<T>>,
+}
+
+unsafe extern "C" fn class_init<T: ObjectType>(
+    klass: glib_ffi::gpointer,
+    _klass_data: glib_ffi::gpointer,
+) {
+    callback_guard!();
+    {
+        let gobject_klass = &mut *(klass as *mut gobject_ffi::GObjectClass);
+
+        gobject_klass.finalize = Some(finalize::<T>);
+    }
+
+    T::class_init(&mut *(klass as *mut T::GlibClassType));
+}
+
+unsafe extern "C" fn finalize<T: ObjectType>(obj: *mut gobject_ffi::GObject) {
+    callback_guard!();
+    let instance = &mut *(obj as *mut InstanceStruct<T>);
+
+    drop(Box::from_raw(instance.imp as *mut T::ImplType));
+    instance.imp = ptr::null_mut();
+
+    let klass = *(obj as *const glib_ffi::gpointer);
+    let parent_klass = gobject_ffi::g_type_class_peek_parent(klass);
+    let parent_klass =
+        &*(gobject_ffi::g_type_class_peek_parent(parent_klass) as *const gobject_ffi::GObjectClass);
+    parent_klass.finalize.map(|f| f(obj));
+}
+
+pub unsafe fn get_type<T: ObjectType>() -> glib_ffi::GType {
+    use std::sync::{Once, ONCE_INIT};
+
+    static mut TYPE: glib_ffi::GType = gobject_ffi::G_TYPE_INVALID;
+    static ONCE: Once = ONCE_INIT;
+
+    ONCE.call_once(|| {
+        let type_info = gobject_ffi::GTypeInfo {
+            class_size: mem::size_of::<ClassStruct<T>>() as u16,
+            base_init: None,
+            base_finalize: None,
+            class_init: Some(class_init::<T>),
+            class_finalize: None,
+            class_data: ptr::null_mut(),
+            instance_size: mem::size_of::<InstanceStruct<T>>() as u16,
+            n_preallocs: 0,
+            instance_init: None,
+            value_table: ptr::null(),
+        };
+
+        let type_name = {
+            let mut idx = 0;
+
+            loop {
+                let type_name = CString::new(format!("{}-{}", T::NAME, idx)).unwrap();
+                if gobject_ffi::g_type_from_name(type_name.as_ptr()) == gobject_ffi::G_TYPE_INVALID
+                {
+                    break type_name;
+                }
+                idx += 1;
+            }
+        };
+
+        TYPE = gobject_ffi::g_type_register_static(
+            T::glib_type().to_glib(),
+            type_name.as_ptr(),
+            &type_info,
+            gobject_ffi::GTypeFlags::empty(),
+        );
+    });
+
+    TYPE
+}
+
+unsafe extern "C" fn sub_class_init<T: ObjectType>(
+    klass: glib_ffi::gpointer,
+    klass_data: glib_ffi::gpointer,
+) {
+    callback_guard!();
+    {
+        let klass = &mut *(klass as *mut ClassStruct<T>);
+        let imp_static = klass_data as *const Box<ImplTypeStatic<T>>;
+        klass.imp_static = imp_static;
+
+        (*imp_static).class_init(klass);
+    }
+}
+
+unsafe extern "C" fn sub_init<T: ObjectType>(
+    obj: *mut gobject_ffi::GTypeInstance,
+    _klass: glib_ffi::gpointer,
+) {
+    callback_guard!();
+    let instance = &mut *(obj as *mut InstanceStruct<T>);
+    let klass = &**(obj as *const *const ClassStruct<T>);
+    let rs_instance: T::RsType = from_glib_borrow(obj as *mut InstanceStruct<T>);
+
+    let imp = (*klass.imp_static).new(&rs_instance);
+    instance.imp = Box::into_raw(Box::new(imp));
+}
+
+pub fn register_type<T: ObjectType, I: ImplTypeStatic<T>>(imp: I) -> glib::Type {
+    unsafe {
+        let parent_type = get_type::<T>();
+        let type_name = format!("{}-{}", T::NAME, imp.get_name());
+
+        let imp: Box<ImplTypeStatic<T>> = Box::new(imp);
+
+        let type_info = gobject_ffi::GTypeInfo {
+            class_size: mem::size_of::<ClassStruct<T>>() as u16,
+            base_init: None,
+            base_finalize: None,
+            class_init: Some(sub_class_init::<T>),
+            class_finalize: None,
+            class_data: Box::into_raw(Box::new(imp)) as glib_ffi::gpointer,
+            instance_size: mem::size_of::<InstanceStruct<T>>() as u16,
+            n_preallocs: 0,
+            instance_init: Some(sub_init::<T>),
+            value_table: ptr::null(),
+        };
+
+        let type_ = gobject_ffi::g_type_register_static(
+            parent_type,
+            type_name.to_glib_none().0,
+            &type_info,
+            gobject_ffi::GTypeFlags::empty(),
+        );
+
+        from_glib(type_)
+    }
+}