video/gtk4: Implement support for GLTextures when possible.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs/-/merge_requests/588>

ci/generate-static-test.py

@@ -8,7 +8,7 @@ from utils import iterate_plugins
 
 # the csound version used on ci does not ship a .pc file
 # threadshare we skip in meson static build as well
-IGNORE = ['csound', 'threadshare']
+IGNORE = ['csound', 'threadshare', 'gtk4']
 
 outdir = sys.argv[1]
 

ci/run_windows_tests.ps1

@@ -17,11 +17,18 @@ function Run-Tests {
     param (
         $Features
     )
+    $local_exclude = $exclude_crates;
+
+    # In this case the plugin will pull x11/wayland features
+    # which will fail to build on windows.
+    if (($Features -eq '--all-features') -or ($Features -eq '')) {
+        $local_exclude += @("--exclude", "gst-plugin-gtk4")
+    }
 
     Write-Host "Features: $Features"
-    Write-Host "Exclude string: $exclude_crates"
+    Write-Host "Exclude string: $local_exclude"
 
-    cargo build --color=always --workspace $exclude_crates --all-targets $Features
+    cargo build --color=always --workspace $local_exclude --all-targets $Features
 
     if (!$?) {
         Write-Host "Build failed"
@@ -29,7 +36,7 @@ function Run-Tests {
     }
 
     $env:G_DEBUG="fatal_warnings"
-    cargo test --no-fail-fast --color=always --workspace $exclude_crates --all-targets $Features
+    cargo test --no-fail-fast --color=always --workspace $local_exclude --all-targets $Features
 
     if (!$?) {
         Write-Host "Tests failed"

docs/plugins/gst_plugins_cache.json

@@ -1940,7 +1940,7 @@
                 "long-name": "GTK 4 Paintable Sink",
                 "pad-templates": {
                     "sink": {
-                        "caps": "video/x-raw:\n         format: { BGRA, ARGB, RGBA, ABGR, RGB, BGR }\n          width: [ 1, 2147483647 ]\n         height: [ 1, 2147483647 ]\n      framerate: [ 0/1, 2147483647/1 ]\n\nvideo/x-raw(memory:SystemMemory, meta:GstVideoOverlayComposition):\n         format: { BGRA, ARGB, RGBA, ABGR, RGB, BGR }\n          width: [ 1, 2147483647 ]\n         height: [ 1, 2147483647 ]\n      framerate: [ 0/1, 2147483647/1 ]\n\nvideo/x-raw(meta:GstVideoOverlayComposition):\n         format: { BGRA, ARGB, RGBA, ABGR, RGB, BGR }\n          width: [ 1, 2147483647 ]\n         height: [ 1, 2147483647 ]\n      framerate: [ 0/1, 2147483647/1 ]\n",
+                        "caps": "video/x-raw:\n         format: { BGRA, ARGB, RGBA, ABGR, RGB, BGR }\n          width: [ 1, 2147483647 ]\n         height: [ 1, 2147483647 ]\n      framerate: [ 0/1, 2147483647/1 ]\n\nvideo/x-raw(memory:GLMemory, meta:GstVideoOverlayComposition):\n         format: { BGRA, ARGB, RGBA, ABGR, RGB, BGR }\n          width: [ 1, 2147483647 ]\n         height: [ 1, 2147483647 ]\n      framerate: [ 0/1, 2147483647/1 ]\n texture-target: 2D\n\nvideo/x-raw(memory:GLMemory):\n         format: { BGRA, ARGB, RGBA, ABGR, RGB, BGR }\n          width: [ 1, 2147483647 ]\n         height: [ 1, 2147483647 ]\n      framerate: [ 0/1, 2147483647/1 ]\n texture-target: 2D\n\nvideo/x-raw(memory:SystemMemory, meta:GstVideoOverlayComposition):\n         format: { BGRA, ARGB, RGBA, ABGR, RGB, BGR }\n          width: [ 1, 2147483647 ]\n         height: [ 1, 2147483647 ]\n      framerate: [ 0/1, 2147483647/1 ]\n\nvideo/x-raw(meta:GstVideoOverlayComposition):\n         format: { BGRA, ARGB, RGBA, ABGR, RGB, BGR }\n          width: [ 1, 2147483647 ]\n         height: [ 1, 2147483647 ]\n      framerate: [ 0/1, 2147483647/1 ]\n",
                         "direction": "sink",
                         "presence": "always"
                     }

meson.build

@@ -140,7 +140,7 @@ else
   message('csound not found, disabling its plugin')
 endif
 
-if dependency('gtk4', required : get_option('gtk4')).found()
+if dependency('gtk4', version: '>= 4.6.0', required : get_option('gtk4')).found()
   plugins += {'gst-plugin-gtk4' : 'libgstgtk4',}
 endif
 
@@ -278,7 +278,7 @@ foreach plugin : plugins
   )
   meson.override_dependency(plugin_name, dep)
 
-  if static_build and plugin_name in ['gstcsound', 'gstthreadshare']
+  if static_build and plugin_name in ['gstcsound', 'gstthreadshare', 'gstgtk4']
     warning('Static plugin @0@ is known to fail. It will not be included in libgstreamer-full.'.format(plugin_name))
   else
     gst_plugins += dep

video/gtk4/Cargo.toml

@@ -9,11 +9,18 @@ rust-version = "1.63"
 description = "GStreamer GTK 4 Sink element and Paintable widget"
 
 [dependencies]
-gtk = { package = "gtk4", git = "https://github.com/gtk-rs/gtk4-rs" }
+gtk = { package = "gtk4", git = "https://github.com/gtk-rs/gtk4-rs", features = ["v4_6"] }
+gdk_wayland = { package = "gdk4-wayland", git = "https://github.com/gtk-rs/gtk4-rs", features = ["v4_4"], optional = true}
+gdk_x11 = { package = "gdk4-x11", git = "https://github.com/gtk-rs/gtk4-rs", features = ["v4_4"], optional = true}
 
 gst = { package = "gstreamer", git = "https://gitlab.freedesktop.org/gstreamer/gstreamer-rs", features = ["v1_16"] }
 gst_base = { package = "gstreamer-base", git = "https://gitlab.freedesktop.org/gstreamer/gstreamer-rs" }
 gst_video = { package = "gstreamer-video", git = "https://gitlab.freedesktop.org/gstreamer/gstreamer-rs" }
+gst_gl = { package = "gstreamer-gl", git = "https://gitlab.freedesktop.org/gstreamer/gstreamer-rs", features = ["v1_16"] }
+
+gst_gl_wayland = { package = "gstreamer-gl-wayland", git = "https://gitlab.freedesktop.org/gstreamer/gstreamer-rs", features = ["v1_16"], optional = true }
+gst_gl_x11 = { package = "gstreamer-gl-x11", git = "https://gitlab.freedesktop.org/gstreamer/gstreamer-rs", features = ["v1_16"], optional = true }
+gst_gl_egl = { package = "gstreamer-gl-egl", git = "https://gitlab.freedesktop.org/gstreamer/gstreamer-rs", features = ["v1_16"], optional = true }
 
 once_cell = "1.0"
 fragile = "2"
@@ -27,7 +34,11 @@ path = "src/lib.rs"
 gst-plugin-version-helper = { path="../../version-helper" }
 
 [features]
+default = []
 static = []
+wayland = ["gdk_wayland", "gst_gl_wayland"]
+x11glx = ["gdk_x11", "gst_gl_x11"]
+x11egl = ["gdk_x11", "gst_gl_egl"]
 capi = []
 doc = ["gst/v1_18"]
 

video/gtk4/README.md

@@ -2,3 +2,6 @@
 
 GTK 4 provides `gtk::Video` & `gtk::Picture` for rendering media such as videos. As the default `gtk::Video` widget doesn't
 offer the possibility to use a custom `gst::Pipeline`. The plugin provides a `gst_video::VideoSink` along with a `gdk::Paintable` that's capable of rendering the sink's frames.
+
+The Sink can generate GL Textures if the system is capable of it, but it needs to be compiled
+with either `wayland`, `x11glx` or `x11egl` cargo features.

video/gtk4/examples/gtksink.rs

@@ -6,30 +6,6 @@ use gtk::{gdk, gio, glib};
 use std::cell::RefCell;
 
 fn create_ui(app: &gtk::Application) {
-    let pipeline = gst::Pipeline::default();
-    let src = gst::ElementFactory::make("videotestsrc").build().unwrap();
-
-    let overlay = gst::ElementFactory::make("clockoverlay")
-        .property("font-desc", "Monospace 42")
-        .build()
-        .unwrap();
-
-    let sink = gst::ElementFactory::make("gtk4paintablesink")
-        .build()
-        .unwrap();
-    let paintable = sink.property::<gdk::Paintable>("paintable");
-
-    pipeline.add_many(&[&src, &overlay, &sink]).unwrap();
-    src.link_filtered(
-        &overlay,
-        &gst_video::VideoCapsBuilder::new()
-            .width(640)
-            .height(480)
-            .build(),
-    )
-    .unwrap();
-    overlay.link(&sink).unwrap();
-
     let window = gtk::ApplicationWindow::new(app);
     window.set_default_size(640, 480);
 
@@ -37,6 +13,48 @@ fn create_ui(app: &gtk::Application) {
     let picture = gtk::Picture::new();
     let label = gtk::Label::new(Some("Position: 00:00:00"));
 
+    let pipeline = gst::Pipeline::new(None);
+
+    let overlay = gst::ElementFactory::make("clockoverlay")
+        .property("font-desc", "Monospace 42")
+        .build()
+        .unwrap();
+
+    let gtksink = gst::ElementFactory::make("gtk4paintablesink")
+        .build()
+        .unwrap();
+
+    // Need to set state to Ready to get a GL context
+    gtksink.set_state(gst::State::Ready).unwrap();
+    let paintable = gtksink.property::<gdk::Paintable>("paintable");
+
+    // TODO: future plans to provide a bin-like element that works with less setup
+    let (src, sink) = if paintable
+        .property::<Option<gdk::GLContext>>("gl-context")
+        .is_some()
+    {
+        let src = gst::ElementFactory::make("gltestsrc").build().unwrap();
+
+        let sink = gst::ElementFactory::make("glsinkbin")
+            .property("sink", &gtksink)
+            .build()
+            .unwrap();
+        (src, sink)
+    } else {
+        let src = gst::ElementFactory::make("videotestsrc").build().unwrap();
+        (src, gtksink)
+    };
+
+    pipeline.add_many(&[&src, &overlay, &sink]).unwrap();
+    let caps = gst_video::VideoCapsBuilder::new()
+        .width(640)
+        .height(480)
+        .any_features()
+        .build();
+
+    src.link_filtered(&overlay, &caps).unwrap();
+    overlay.link(&sink).unwrap();
+
     picture.set_paintable(Some(&paintable));
     vbox.append(&picture);
     vbox.append(&label);
@@ -115,12 +133,10 @@ fn main() {
 
     gstgtk4::plugin_register_static().expect("Failed to register gstgtk4 plugin");
 
-    {
+    let app = gtk::Application::new(None, gio::ApplicationFlags::FLAGS_NONE);
-        let app = gtk::Application::new(None, gio::ApplicationFlags::FLAGS_NONE);
 
-        app.connect_activate(create_ui);
+    app.connect_activate(create_ui);
-        app.run();
+    app.run();
-    }
 
     unsafe {
         gst::deinit();

video/gtk4/src/lib.rs

@@ -18,6 +18,7 @@
 use gst::glib;
 
 mod sink;
+mod utils;
 pub use sink::PaintableSink;
 
 fn plugin_init(plugin: &gst::Plugin) -> Result<(), glib::BoolError> {

video/gtk4/src/sink/frame.rs

@@ -9,7 +9,7 @@
 //
 // SPDX-License-Identifier: MPL-2.0
 
-use gtk::prelude::*;
+use gst_gl::prelude::*;
 use gtk::{gdk, glib};
 use std::collections::{HashMap, HashSet};
 
@@ -17,6 +17,7 @@ use std::collections::{HashMap, HashSet};
 pub(crate) struct Frame {
     frame: gst_video::VideoFrame<gst_video::video_frame::Readable>,
     overlays: Vec<Overlay>,
+    gst_context: Option<gst_gl::GLContext>,
 }
 
 #[derive(Debug)]
@@ -31,7 +32,6 @@ struct Overlay {
 
 #[derive(Debug)]
 pub(crate) struct Texture {
-    //FIXME: create getters instead of having the fields public
     pub texture: gdk::Texture,
     pub x: f32,
     pub y: f32,
@@ -90,15 +90,63 @@ fn video_frame_to_memory_texture(
     (texture, pixel_aspect_ratio)
 }
 
+fn video_frame_to_gl_texture(
+    frame: &gst_video::VideoFrame<gst_video::video_frame::Readable>,
+    cached_textures: &mut HashMap<usize, gdk::Texture>,
+    used_textures: &mut HashSet<usize>,
+    gdk_context: &gdk::GLContext,
+    gst_context: &gst_gl::GLContext,
+) -> (gdk::Texture, f64) {
+    let texture_id = frame.texture_id(0).expect("Invalid texture id") as usize;
+
+    let pixel_aspect_ratio =
+        (frame.info().par().numer() as f64) / (frame.info().par().denom() as f64);
+
+    if let Some(texture) = cached_textures.get(&(texture_id)) {
+        used_textures.insert(texture_id);
+        return (texture.clone(), pixel_aspect_ratio);
+    }
+
+    let width = frame.width();
+    let height = frame.height();
+
+    let sync_meta = frame.buffer().meta::<gst_gl::GLSyncMeta>().unwrap();
+    sync_meta.wait(gst_context);
+
+    let texture = unsafe {
+        gdk::GLTexture::new(gdk_context, texture_id as u32, width as i32, height as i32)
+            .upcast::<gdk::Texture>()
+    };
+
+    cached_textures.insert(texture_id, texture.clone());
+    used_textures.insert(texture_id);
+
+    (texture, pixel_aspect_ratio)
+}
+
 impl Frame {
-    pub fn into_textures(self, cached_textures: &mut HashMap<usize, gdk::Texture>) -> Vec<Texture> {
+    pub(crate) fn into_textures(
+        self,
+        gdk_context: Option<&gdk::GLContext>,
+        cached_textures: &mut HashMap<usize, gdk::Texture>,
+    ) -> Vec<Texture> {
         let mut textures = Vec::with_capacity(1 + self.overlays.len());
         let mut used_textures = HashSet::with_capacity(1 + self.overlays.len());
 
         let width = self.frame.width();
         let height = self.frame.height();
         let (texture, pixel_aspect_ratio) =
-            video_frame_to_memory_texture(self.frame, cached_textures, &mut used_textures);
+            if let (Some(gdk_ctx), Some(gst_ctx)) = (gdk_context, self.gst_context.as_ref()) {
+                video_frame_to_gl_texture(
+                    &self.frame,
+                    cached_textures,
+                    &mut used_textures,
+                    gdk_ctx,
+                    gst_ctx,
+                )
+            } else {
+                video_frame_to_memory_texture(self.frame, cached_textures, &mut used_textures)
+            };
 
         textures.push(Texture {
             texture,
@@ -131,9 +179,48 @@ impl Frame {
 }
 
 impl Frame {
-    pub fn new(buffer: &gst::Buffer, info: &gst_video::VideoInfo) -> Result<Self, gst::FlowError> {
+    pub(crate) fn new(
-        let frame = gst_video::VideoFrame::from_buffer_readable(buffer.clone(), info)
+        buffer: &gst::Buffer,
-            .map_err(|_| gst::FlowError::Error)?;
+        info: &gst_video::VideoInfo,
+        have_gl_context: bool,
+    ) -> Result<Self, gst::FlowError> {
+        let mut gst_context = None;
+
+        // Empty buffers get filtered out in show_frame
+        debug_assert!(buffer.n_memory() > 0);
+
+        let is_buffer_gl = buffer
+            .peek_memory(0)
+            .downcast_memory_ref::<gst_gl::GLBaseMemory>()
+            .is_some();
+
+        let frame = if !is_buffer_gl || !have_gl_context {
+            gst_video::VideoFrame::from_buffer_readable(buffer.clone(), info)
+                .map_err(|_| gst::FlowError::Error)?
+        } else {
+            let gst_ctx = buffer
+                .peek_memory(0)
+                .downcast_memory_ref::<gst_gl::GLBaseMemory>()
+                .map(|m| m.context())
+                .expect("Failed to retrieve the GstGL Context.");
+
+            gst_context = Some(gst_ctx.clone());
+
+            if let Some(meta) = buffer.meta::<gst_gl::GLSyncMeta>() {
+                meta.set_sync_point(gst_ctx);
+                gst_video::VideoFrame::from_buffer_readable_gl(buffer.clone(), info)
+                    .map_err(|_| gst::FlowError::Error)?
+            } else {
+                let mut buffer = buffer.clone();
+                {
+                    let buffer = buffer.make_mut();
+                    let meta = gst_gl::GLSyncMeta::add(buffer, gst_ctx);
+                    meta.set_sync_point(gst_ctx);
+                }
+                gst_video::VideoFrame::from_buffer_readable_gl(buffer, info)
+                    .map_err(|_| gst::FlowError::Error)?
+            }
+        };
 
         let overlays = frame
             .buffer()
@@ -171,6 +258,10 @@ impl Frame {
             })
             .collect();
 
-        Ok(Self { frame, overlays })
+        Ok(Self {
+            frame,
+            overlays,
+            gst_context,
+        })
     }
 }

video/gtk4/src/sink/imp.rs

@@ -13,21 +13,26 @@ use super::SinkEvent;
 use crate::sink::frame::Frame;
 use crate::sink::paintable::Paintable;
 
-use glib::prelude::*;
+use glib::translate::*;
 use glib::Sender;
+use gtk::prelude::*;
+use gtk::{gdk, glib};
 
+use gst::prelude::*;
 use gst::subclass::prelude::*;
 use gst_base::subclass::prelude::*;
+use gst_gl::prelude::GLContextExt as GstGLContextExt;
+use gst_gl::prelude::*;
 use gst_video::subclass::prelude::*;
 
-use gtk::glib;
-
 use once_cell::sync::Lazy;
-use std::sync::Mutex;
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::{Mutex, MutexGuard};
 
+use crate::utils;
 use fragile::Fragile;
 
-pub(super) static CAT: Lazy<gst::DebugCategory> = Lazy::new(|| {
+static CAT: Lazy<gst::DebugCategory> = Lazy::new(|| {
     gst::DebugCategory::new(
         "gstgtk4paintablesink",
         gst::DebugColorFlags::empty(),
@@ -35,25 +40,24 @@ pub(super) static CAT: Lazy<gst::DebugCategory> = Lazy::new(|| {
     )
 });
 
-#[derive(Default)]
+#[derive(Default, Debug)]
 pub struct PaintableSink {
-    pub(super) paintable: Mutex<Option<Fragile<Paintable>>>,
+    paintable: Mutex<Option<Fragile<Paintable>>>,
     info: Mutex<Option<gst_video::VideoInfo>>,
-    pub(super) sender: Mutex<Option<Sender<SinkEvent>>>,
+    sender: Mutex<Option<Sender<SinkEvent>>>,
-    pub(super) pending_frame: Mutex<Option<Frame>>,
+    pending_frame: Mutex<Option<Frame>>,
+    gst_display: Mutex<Option<gst_gl::GLDisplay>>,
+    gst_app_context: Mutex<Option<gst_gl::GLContext>>,
+    gst_context: Mutex<Option<gst_gl::GLContext>>,
+    cached_caps: Mutex<Option<gst::Caps>>,
+    have_gl_context: AtomicBool,
 }
 
 impl Drop for PaintableSink {
     fn drop(&mut self) {
         let mut paintable = self.paintable.lock().unwrap();
-
-        // Drop the paintable from the main thread
         if let Some(paintable) = paintable.take() {
-            let context = glib::MainContext::default();
+            glib::MainContext::default().invoke(|| drop(paintable))
-
-            context.invoke(move || {
-                drop(paintable);
-            });
         }
     }
 }
@@ -69,7 +73,7 @@ impl ObjectImpl for PaintableSink {
     fn properties() -> &'static [glib::ParamSpec] {
         static PROPERTIES: Lazy<Vec<glib::ParamSpec>> = Lazy::new(|| {
             vec![
-                glib::ParamSpecObject::builder::<gtk::gdk::Paintable>("paintable")
+                glib::ParamSpecObject::builder::<gdk::Paintable>("paintable")
                     .nick("Paintable")
                     .blurb("The Paintable the sink renders to")
                     .read_only()
@@ -85,14 +89,14 @@ impl ObjectImpl for PaintableSink {
             "paintable" => {
                 let mut paintable = self.paintable.lock().unwrap();
                 if paintable.is_none() {
-                    self.obj().initialize_paintable(&mut paintable);
+                    self.create_paintable(&mut paintable);
                 }
 
                 let paintable = match &*paintable {
                     Some(ref paintable) => paintable,
                     None => {
                         gst::error!(CAT, imp: self, "Failed to create paintable");
-                        return None::<&gtk::gdk::Paintable>.to_value();
+                        return None::<&gdk::Paintable>.to_value();
                     }
                 };
 
@@ -105,7 +109,7 @@ impl ObjectImpl for PaintableSink {
                             imp: self,
                             "Can't retrieve Paintable from non-main thread"
                         );
-                        None::<&gtk::gdk::Paintable>.to_value()
+                        None::<&gdk::Paintable>.to_value()
                     }
                 }
             }
@@ -139,6 +143,8 @@ impl ElementImpl for PaintableSink {
 
                 for features in [
                     None,
+                    Some(&["memory:GLMemory", "meta:GstVideoOverlayComposition"][..]),
+                    Some(&["memory:GLMemory"][..]),
                     Some(&["memory:SystemMemory", "meta:GstVideoOverlayComposition"][..]),
                     Some(&["meta:GstVideoOverlayComposition"][..]),
                 ] {
@@ -156,6 +162,12 @@ impl ElementImpl for PaintableSink {
                         c.get_mut()
                             .unwrap()
                             .set_features_simple(Some(gst::CapsFeatures::new(features)));
+
+                        if features.contains(&"memory:GLMemory") {
+                            c.get_mut()
+                                .unwrap()
+                                .set_simple(&[("texture-target", &"2D")])
+                        }
                     }
 
                     caps.append(c);
@@ -182,8 +194,9 @@ impl ElementImpl for PaintableSink {
         match transition {
             gst::StateChange::NullToReady => {
                 let mut paintable = self.paintable.lock().unwrap();
+
                 if paintable.is_none() {
-                    self.obj().initialize_paintable(&mut paintable);
+                    self.create_paintable(&mut paintable);
                 }
 
                 if paintable.is_none() {
@@ -209,6 +222,35 @@ impl ElementImpl for PaintableSink {
 }
 
 impl BaseSinkImpl for PaintableSink {
+    fn caps(&self, filter: Option<&gst::Caps>) -> Option<gst::Caps> {
+        let cached_caps = self
+            .cached_caps
+            .lock()
+            .expect("Failed to lock cached caps mutex")
+            .clone();
+
+        let mut tmp_caps = cached_caps.unwrap_or_else(|| {
+            let templ = Self::pad_templates();
+            templ[0].caps().clone()
+        });
+
+        gst::debug!(CAT, imp: self, "Advertising our own caps: {:?}", &tmp_caps);
+
+        if let Some(filter_caps) = filter {
+            gst::debug!(
+                CAT,
+                imp: self,
+                "Intersecting with filter caps: {:?}",
+                &filter_caps
+            );
+
+            tmp_caps = filter_caps.intersect_with_mode(&tmp_caps, gst::CapsIntersectMode::First);
+        };
+
+        gst::debug!(CAT, imp: self, "Returning caps: {:?}", &tmp_caps);
+        Some(tmp_caps)
+    }
+
     fn set_caps(&self, caps: &gst::Caps) -> Result<(), gst::LoggableError> {
         gst::debug!(CAT, imp: self, "Setting caps {:?}", caps);
 
@@ -224,12 +266,113 @@ impl BaseSinkImpl for PaintableSink {
         &self,
         query: &mut gst::query::Allocation,
     ) -> Result<(), gst::LoggableError> {
-        query.add_allocation_meta::<gst_video::VideoMeta>(None);
+        gst::debug!(CAT, imp: self, "Proposing Allocation query");
 
+        self.parent_propose_allocation(query)?;
+
+        query.add_allocation_meta::<gst_video::VideoMeta>(None);
         // TODO: Provide a preferred "window size" here for higher-resolution rendering
         query.add_allocation_meta::<gst_video::VideoOverlayCompositionMeta>(None);
 
-        self.parent_propose_allocation(query)
+        {
+            // Early return if there is no context initialized
+            let gst_context_guard = self.gst_context.lock().unwrap();
+            if gst_context_guard.is_none() {
+                gst::debug!(
+                    CAT,
+                    imp: self,
+                    "Found no GL Context during propose_allocation."
+                );
+                return Ok(());
+            }
+        }
+
+        // GL specific things
+        let (caps, need_pool) = query.get_owned();
+
+        if caps.is_empty() {
+            return Err(gst::loggable_error!(CAT, "No caps where specified."));
+        }
+
+        if let Some(f) = caps.features(0) {
+            if !f.contains("memory:GLMemory") {
+                gst::debug!(
+                    CAT,
+                    imp: self,
+                    "No 'memory:GLMemory' feature in caps: {}",
+                    caps
+                )
+            }
+        }
+
+        let info = gst_video::VideoInfo::from_caps(&caps)
+            .map_err(|_| gst::loggable_error!(CAT, "Failed to get VideoInfo from caps"))?;
+
+        let size = info.size() as u32;
+
+        {
+            let gst_context = { self.gst_context.lock().unwrap().clone().unwrap() };
+            let buffer_pool = gst_gl::GLBufferPool::new(&gst_context);
+
+            if need_pool {
+                gst::debug!(CAT, imp: self, "Creating new Pool");
+
+                let mut config = buffer_pool.config();
+                config.set_params(Some(&caps), size, 0, 0);
+                config.add_option("GstBufferPoolOptionGLSyncMeta");
+
+                if let Err(err) = buffer_pool.set_config(config) {
+                    return Err(gst::loggable_error!(
+                        CAT,
+                        format!("Failed to set config in the GL BufferPool.: {}", err)
+                    ));
+                }
+            }
+
+            // we need at least 2 buffer because we hold on to the last one
+            query.add_allocation_pool(Some(&buffer_pool), size, 2, 0);
+
+            if gst_context.check_feature("GL_ARB_sync")
+                || gst_context.check_feature("GL_EXT_EGL_sync")
+            {
+                query.add_allocation_meta::<gst_gl::GLSyncMeta>(None)
+            }
+        }
+
+        Ok(())
+    }
+
+    fn query(&self, query: &mut gst::QueryRef) -> bool {
+        gst::log!(CAT, imp: self, "Handling query {:?}", query);
+
+        match query.view_mut() {
+            gst::QueryViewMut::Context(q) => {
+                // Avoid holding the locks while we respond to the query
+                // The objects are ref-counted anyway.
+                let gst_display = { self.gst_display.lock().unwrap().clone() };
+                if let Some(display) = gst_display {
+                    let (app_ctx, gst_ctx) = {
+                        (
+                            self.gst_app_context.lock().unwrap().clone(),
+                            self.gst_context.lock().unwrap().clone(),
+                        )
+                    };
+                    assert_ne!(app_ctx, None);
+                    assert_ne!(gst_ctx, None);
+
+                    return gst_gl::functions::gl_handle_context_query(
+                        &*self.instance(),
+                        q,
+                        Some(&display),
+                        gst_ctx.as_ref(),
+                        app_ctx.as_ref(),
+                    );
+                }
+
+                BaseSinkImplExt::parent_query(self, query)
+            }
+            _ => BaseSinkImplExt::parent_query(self, query),
+        }
     }
 }
 
@@ -237,16 +380,27 @@ impl VideoSinkImpl for PaintableSink {
     fn show_frame(&self, buffer: &gst::Buffer) -> Result<gst::FlowSuccess, gst::FlowError> {
         gst::trace!(CAT, imp: self, "Rendering buffer {:?}", buffer);
 
+        // Empty buffer, nothing to render
+        if buffer.n_memory() == 0 {
+            gst::trace!(
+                CAT,
+                imp: self,
+                "Empty buffer, nothing to render. Returning."
+            );
+            return Ok(gst::FlowSuccess::Ok);
+        };
+
         let info = self.info.lock().unwrap();
         let info = info.as_ref().ok_or_else(|| {
             gst::error!(CAT, imp: self, "Received no caps yet");
             gst::FlowError::NotNegotiated
         })?;
 
-        let frame = Frame::new(buffer, info).map_err(|err| {
+        let frame = Frame::new(buffer, info, self.have_gl_context.load(Ordering::Relaxed))
-            gst::error!(CAT, imp: self, "Failed to map video frame");
+            .map_err(|err| {
-            err
+                gst::error!(CAT, imp: self, "Failed to map video frame");
-        })?;
+                err
+            })?;
         self.pending_frame.lock().unwrap().replace(frame);
 
         let sender = self.sender.lock().unwrap();
@@ -263,3 +417,392 @@ impl VideoSinkImpl for PaintableSink {
         Ok(gst::FlowSuccess::Ok)
     }
 }
+
+impl PaintableSink {
+    fn pending_frame(&self) -> Option<Frame> {
+        self.pending_frame.lock().unwrap().take()
+    }
+
+    fn do_action(&self, action: SinkEvent) -> glib::Continue {
+        let paintable = self.paintable.lock().unwrap().clone();
+        let paintable = match paintable {
+            Some(paintable) => paintable,
+            None => return glib::Continue(false),
+        };
+
+        match action {
+            SinkEvent::FrameChanged => {
+                gst::trace!(CAT, imp: self, "Frame changed");
+                paintable.get().handle_frame_changed(self.pending_frame())
+            }
+        }
+
+        glib::Continue(true)
+    }
+
+    fn configure_caps(&self) {
+        let mut tmp_caps = Self::pad_templates()[0].caps().clone();
+
+        // Filter out GL caps from the template pads if we have no context
+        if !self.have_gl_context.load(Ordering::Relaxed) {
+            tmp_caps = tmp_caps
+                .iter_with_features()
+                .filter(|(_, features)| !features.contains("memory:GLMemory"))
+                .map(|(s, c)| (s.to_owned(), c.to_owned()))
+                .collect::<gst::Caps>();
+        }
+
+        self.cached_caps
+            .lock()
+            .expect("Failed to lock Mutex")
+            .replace(tmp_caps);
+    }
+
+    fn create_paintable(&self, paintable_storage: &mut MutexGuard<Option<Fragile<Paintable>>>) {
+        let ctx = self.realize_context();
+
+        let ctx = if let Some(c) = ctx {
+            if let Ok(c) = self.initialize_gl_wrapper(c) {
+                self.have_gl_context.store(true, Ordering::Relaxed);
+                Some(c)
+            } else {
+                None
+            }
+        } else {
+            None
+        };
+
+        self.configure_caps();
+        self.initialize_paintable(ctx, paintable_storage);
+    }
+
+    fn initialize_paintable(
+        &self,
+        gl_context: Option<Fragile<gdk::GLContext>>,
+        paintable_storage: &mut MutexGuard<Option<Fragile<Paintable>>>,
+    ) {
+        gst::debug!(CAT, imp: self, "Initializing paintable");
+
+        let paintable = utils::invoke_on_main_thread(|| {
+            // grab the context out of the fragile
+            let ctx = gl_context.map(|f| f.into_inner());
+            Fragile::new(Paintable::new(ctx))
+        });
+
+        // The channel for the SinkEvents
+        let (sender, receiver) = glib::MainContext::channel(glib::PRIORITY_DEFAULT);
+        let sink = self.instance();
+        receiver.attach(
+            None,
+            glib::clone!(
+                @weak sink => @default-return glib::Continue(false),
+                move |action| sink.imp().do_action(action)
+            ),
+        );
+
+        **paintable_storage = Some(paintable);
+
+        *self.sender.lock().unwrap() = Some(sender);
+    }
+
+    fn realize_context(&self) -> Option<Fragile<gdk::GLContext>> {
+        gst::debug!(CAT, imp: self, "Realizing GDK GL Context");
+
+        let weak = self.instance().downgrade();
+        let cb = move || -> Option<Fragile<gdk::GLContext>> {
+            let obj = weak
+                .upgrade()
+                .expect("Failed to upgrade Weak ref during gl initialization.");
+
+            gst::debug!(CAT, obj: &obj, "Realizing GDK GL Context from main context");
+
+            // This can return NULL but only happens in 2 situations:
+            // * If the function is called before gtk_init
+            // * If the function is called after gdk_display_close(default_display)
+            // Both of which are treated as programming errors.
+            //
+            // However, when we are building the docs, gtk_init doesn't get called
+            // and this would cause the documentation generation to error.
+            // Thus its okayish to return None here and fallback to software
+            // rendering, since this path isn't going to be used by applications
+            // anyway.
+            //
+            // FIXME: add a couple more gtk_init checks across the codebase where
+            // applicable since this is no longer going to panic.
+            let display = gdk::Display::default()?;
+            let ctx = display.create_gl_context();
+
+            if let Ok(ctx) = ctx {
+                gst::info!(CAT, obj: &obj, "Realizing GDK GL Context",);
+
+                if ctx.realize().is_ok() {
+                    gst::info!(CAT, obj: &obj, "Successfully realized GDK GL Context",);
+                    return Some(Fragile::new(ctx));
+                } else {
+                    gst::warning!(CAT, obj: &obj, "Failed to realize GDK GL Context",);
+                }
+            } else {
+                gst::warning!(CAT, obj: &obj, "Failed to create GDK GL Context",);
+            };
+
+            None
+        };
+
+        utils::invoke_on_main_thread(cb)
+    }
+
+    fn initialize_gl_wrapper(
+        &self,
+        context: Fragile<gdk::GLContext>,
+    ) -> Result<Fragile<gdk::GLContext>, glib::Error> {
+        gst::info!(CAT, imp: self, "Initializing GDK GL Context");
+        let self_ = self.instance().clone();
+        utils::invoke_on_main_thread(move || self_.imp().initialize_gl(context))
+    }
+
+    fn initialize_gl(
+        &self,
+        context: Fragile<gdk::GLContext>,
+    ) -> Result<Fragile<gdk::GLContext>, glib::Error> {
+        let ctx = context.get();
+        let display = gtk::prelude::GLContextExt::display(ctx)
+            .expect("Failed to get GDK Display from GDK Context.");
+        ctx.make_current();
+
+        let mut app_ctx_guard = self.gst_app_context.lock().unwrap();
+        let mut display_ctx_guard = self.gst_display.lock().unwrap();
+
+        match ctx.type_().name() {
+            #[cfg(all(target_os = "linux", feature = "x11egl"))]
+            "GdkX11GLContextEGL" => {
+                self.initialize_x11egl(display, &mut display_ctx_guard, &mut app_ctx_guard)?;
+            }
+            #[cfg(all(target_os = "linux", feature = "x11glx"))]
+            "GdkX11GLContextGLX" => {
+                self.initialize_x11glx(display, &mut display_ctx_guard, &mut app_ctx_guard)?;
+            }
+            #[cfg(all(target_os = "linux", feature = "wayland"))]
+            "GdkWaylandGLContext" => {
+                self.initialize_waylandegl(display, &mut display_ctx_guard, &mut app_ctx_guard)?;
+            }
+            _ => {
+                gst::error!(
+                    CAT,
+                    imp: self,
+                    "Unsupported GDK display {} for GL",
+                    &display,
+                );
+                return Err(glib::Error::new(
+                    gst::ResourceError::Failed,
+                    &format!("Unsupported GDK display {display} for GL"),
+                ));
+            }
+        };
+
+        // This should have been initialized once we are done with the platform checks
+        assert!(app_ctx_guard.is_some());
+
+        match app_ctx_guard.as_ref().unwrap().activate(true) {
+            Ok(_) => gst::info!(CAT, imp: self, "Successfully activated GL Context."),
+            Err(_) => {
+                gst::error!(CAT, imp: self, "Failed to activate GL context",);
+                return Err(glib::Error::new(
+                    gst::ResourceError::Failed,
+                    "Failed to activate GL context",
+                ));
+            }
+        };
+
+        match app_ctx_guard.as_ref().unwrap().fill_info() {
+            Ok(_) => {
+                match app_ctx_guard.as_ref().unwrap().activate(true) {
+                    Ok(_) => gst::info!(
+                        CAT,
+                        imp: self,
+                        "Successfully activated GL Context after fill_info"
+                    ),
+                    Err(_) => {
+                        gst::error!(CAT, imp: self, "Failed to activate GL context",);
+                        return Err(glib::Error::new(
+                            gst::ResourceError::Failed,
+                            "Failed to activate GL context after fill_info",
+                        ));
+                    }
+                };
+            }
+            Err(err) => {
+                gst::error!(
+                    CAT,
+                    imp: self,
+                    "Failed to fill info on the GL Context: {}",
+                    &err
+                );
+                return Err(err);
+            }
+        };
+
+        match display_ctx_guard
+            .as_ref()
+            .unwrap()
+            .create_context(app_ctx_guard.as_ref().unwrap())
+        {
+            Ok(gst_context) => {
+                let mut gst_ctx_guard = self.gst_context.lock().unwrap();
+                gst::info!(CAT, imp: self, "Successfully initialized GL Context");
+                gst_ctx_guard.replace(gst_context);
+                Ok(context)
+            }
+            Err(err) => {
+                gst::error!(CAT, imp: self, "Could not create GL context: {}", &err);
+                Err(err)
+            }
+        }
+    }
+
+    #[cfg(all(target_os = "linux", feature = "x11egl"))]
+    fn initialize_x11egl(
+        &self,
+        display: gdk::Display,
+        display_ctx_guard: &mut Option<gst_gl::GLDisplay>,
+        app_ctx_guard: &mut Option<gst_gl::GLContext>,
+    ) -> Result<(), glib::Error> {
+        gst::info!(
+            CAT,
+            imp: self,
+            "Initializing GL with for x11 EGL backend and display."
+        );
+
+        let platform = gst_gl::GLPlatform::EGL;
+        let (gl_api, _, _) = gst_gl::GLContext::current_gl_api(platform);
+        let gl_ctx = gst_gl::GLContext::current_gl_context(platform);
+
+        if gl_ctx != 0 {
+            unsafe {
+                let d = display.downcast::<gdk_x11::X11Display>().unwrap();
+                let x11_display = gdk_x11::ffi::gdk_x11_display_get_egl_display(d.to_glib_none().0);
+                assert!(!x11_display.is_null());
+
+                let gst_display =
+                    gst_gl_egl::ffi::gst_gl_display_egl_new_with_egl_display(x11_display);
+                assert!(!gst_display.is_null());
+                let gst_display: gst_gl::GLDisplay =
+                    from_glib_full(gst_display as *mut gst_gl::ffi::GstGLDisplay);
+
+                let gst_app_context =
+                    gst_gl::GLContext::new_wrapped(&gst_display, gl_ctx, platform, gl_api);
+
+                assert!(gst_app_context.is_some());
+
+                display_ctx_guard.replace(gst_display);
+                app_ctx_guard.replace(gst_app_context.unwrap());
+
+                Ok(())
+            }
+        } else {
+            gst::error!(CAT, imp: self, "Failed to get handle from GdkGLContext",);
+            Err(glib::Error::new(
+                gst::ResourceError::Failed,
+                "Failed to get handle from GdkGLContext",
+            ))
+        }
+    }
+
+    #[cfg(all(target_os = "linux", feature = "x11glx"))]
+    fn initialize_x11glx(
+        &self,
+        display: gdk::Display,
+        display_ctx_guard: &mut Option<gst_gl::GLDisplay>,
+        app_ctx_guard: &mut Option<gst_gl::GLContext>,
+    ) -> Result<(), glib::Error> {
+        gst::info!(
+            CAT,
+            imp: self,
+            "Initializing GL with for x11 GLX backend and display."
+        );
+
+        let platform = gst_gl::GLPlatform::GLX;
+        let (gl_api, _, _) = gst_gl::GLContext::current_gl_api(platform);
+        let gl_ctx = gst_gl::GLContext::current_gl_context(platform);
+
+        if gl_ctx != 0 {
+            unsafe {
+                let d = display.downcast::<gdk_x11::X11Display>().unwrap();
+                let x11_display = gdk_x11::ffi::gdk_x11_display_get_xdisplay(d.to_glib_none().0);
+                assert!(!x11_display.is_null());
+
+                let gst_display = gst_gl_x11::ffi::gst_gl_display_x11_new_with_display(x11_display);
+                assert!(!gst_display.is_null());
+                let gst_display: gst_gl::GLDisplay =
+                    from_glib_full(gst_display as *mut gst_gl::ffi::GstGLDisplay);
+
+                let gst_app_context =
+                    gst_gl::GLContext::new_wrapped(&gst_display, gl_ctx, platform, gl_api);
+
+                assert!(gst_app_context.is_some());
+
+                display_ctx_guard.replace(gst_display);
+                app_ctx_guard.replace(gst_app_context.unwrap());
+
+                Ok(())
+            }
+        } else {
+            gst::error!(CAT, imp: self, "Failed to get handle from GdkGLContext",);
+            Err(glib::Error::new(
+                gst::ResourceError::Failed,
+                "Failed to get handle from GdkGLContext",
+            ))
+        }
+    }
+
+    #[cfg(all(target_os = "linux", feature = "wayland"))]
+    fn initialize_waylandegl(
+        &self,
+        display: gdk::Display,
+        display_ctx_guard: &mut Option<gst_gl::GLDisplay>,
+        app_ctx_guard: &mut Option<gst_gl::GLContext>,
+    ) -> Result<(), glib::Error> {
+        gst::info!(
+            CAT,
+            imp: self,
+            "Initializing GL with for Wayland EGL backend and display."
+        );
+
+        let platform = gst_gl::GLPlatform::EGL;
+        let (gl_api, _, _) = gst_gl::GLContext::current_gl_api(platform);
+        let gl_ctx = gst_gl::GLContext::current_gl_context(platform);
+
+        // FIXME: bindings
+        if gl_ctx != 0 {
+            unsafe {
+                // let wayland_display = gdk_wayland::WaylandDisplay::wl_display(display.downcast());
+                // get the ptr directly since we are going to use it raw
+                let d = display.downcast::<gdk_wayland::WaylandDisplay>().unwrap();
+                let wayland_display =
+                    gdk_wayland::ffi::gdk_wayland_display_get_wl_display(d.to_glib_none().0);
+                assert!(!wayland_display.is_null());
+
+                let gst_display =
+                    gst_gl_wayland::ffi::gst_gl_display_wayland_new_with_display(wayland_display);
+                assert!(!gst_display.is_null());
+                let gst_display: gst_gl::GLDisplay =
+                    from_glib_full(gst_display as *mut gst_gl::ffi::GstGLDisplay);
+
+                let gst_app_context =
+                    gst_gl::GLContext::new_wrapped(&gst_display, gl_ctx, platform, gl_api);
+
+                assert!(gst_app_context.is_some());
+
+                display_ctx_guard.replace(gst_display);
+                app_ctx_guard.replace(gst_app_context.unwrap());
+
+                Ok(())
+            }
+        } else {
+            gst::error!(CAT, imp: self, "Failed to get handle from GdkGLContext",);
+            Err(glib::Error::new(
+                gst::ResourceError::Failed,
+                "Failed to get handle from GdkGLContext",
+            ))
+        }
+    }
+}

video/gtk4/src/sink/mod.rs

@@ -11,19 +11,11 @@
 
 use gtk::glib;
 use gtk::glib::prelude::*;
-use gtk::subclass::prelude::*;
-
-use fragile::Fragile;
-
-use std::sync::{mpsc, MutexGuard};
 
 mod frame;
 mod imp;
 mod paintable;
 
-use frame::Frame;
-use paintable::Paintable;
-
 enum SinkEvent {
     FrameChanged,
 }
@@ -35,74 +27,7 @@ glib::wrapper! {
 
 impl PaintableSink {
     pub fn new(name: Option<&str>) -> Self {
-        glib::Object::new(&[("name", &name)])
+        glib::Object::builder().property("name", &name).build()
-    }
-
-    fn pending_frame(&self) -> Option<Frame> {
-        let imp = self.imp();
-        imp.pending_frame.lock().unwrap().take()
-    }
-
-    fn initialize_paintable(
-        &self,
-        paintable_storage: &mut MutexGuard<Option<Fragile<SinkPaintable>>>,
-    ) {
-        gst::debug!(imp::CAT, obj: self, "Initializing paintable");
-
-        let context = glib::MainContext::default();
-
-        // The channel for the SinkEvents
-        let (sender, receiver) = glib::MainContext::channel(glib::PRIORITY_DEFAULT);
-
-        // This is an one time channel we send into the closure, so we can block until the paintable has been
-        // created.
-        let (send, recv) = mpsc::channel();
-        context.invoke(glib::clone!(
-            @weak self as sink =>
-            move || {
-                let paintable = Fragile::new(SinkPaintable::new());
-                send.send(paintable).expect("Somehow we dropped the receiver");
-
-                receiver.attach(
-                    None,
-                    glib::clone!(
-                        @weak sink => @default-return glib::Continue(false),
-                        move |action| sink.do_action(action)
-                    ),
-                );
-            }
-        ));
-
-        let paintable = recv.recv().expect("Somehow we dropped the sender");
-
-        **paintable_storage = Some(paintable);
-
-        let imp = self.imp();
-        *imp.sender.lock().unwrap() = Some(sender);
-    }
-
-    fn do_action(&self, action: SinkEvent) -> glib::Continue {
-        let imp = self.imp();
-        let paintable = imp.paintable.lock().unwrap().clone();
-        let paintable = match paintable {
-            Some(paintable) => paintable,
-            None => return glib::Continue(false),
-        };
-
-        match action {
-            SinkEvent::FrameChanged => {
-                gst::trace!(imp::CAT, obj: self, "Frame changed");
-                paintable.get().handle_frame_changed(self.pending_frame())
-            }
-        }
-
-        glib::Continue(true)
-    }
-}
-
-impl Default for PaintableSink {
-    fn default() -> Self {
-        PaintableSink::new(None)
     }
 }
 

video/gtk4/src/sink/paintable/imp.rs

@@ -20,7 +20,7 @@ use std::collections::HashMap;
 
 use once_cell::sync::Lazy;
 
-pub(super) static CAT: Lazy<gst::DebugCategory> = Lazy::new(|| {
+static CAT: Lazy<gst::DebugCategory> = Lazy::new(|| {
     gst::DebugCategory::new(
         "gstgtk4paintable",
         gst::DebugColorFlags::empty(),
@@ -28,21 +28,51 @@ pub(super) static CAT: Lazy<gst::DebugCategory> = Lazy::new(|| {
     )
 });
 
-#[derive(Default)]
+#[derive(Default, Debug)]
 pub struct Paintable {
     paintables: RefCell<Vec<Texture>>,
     cached_textures: RefCell<HashMap<usize, gdk::Texture>>,
+    gl_context: RefCell<Option<gdk::GLContext>>,
 }
 
 #[glib::object_subclass]
 impl ObjectSubclass for Paintable {
     const NAME: &'static str = "GstGtk4Paintable";
     type Type = super::Paintable;
-    type ParentType = glib::Object;
     type Interfaces = (gdk::Paintable,);
 }
 
-impl ObjectImpl for Paintable {}
+impl ObjectImpl for Paintable {
+    fn properties() -> &'static [glib::ParamSpec] {
+        static PROPERTIES: Lazy<Vec<glib::ParamSpec>> = Lazy::new(|| {
+            vec![
+                glib::ParamSpecObject::builder::<gdk::GLContext>("gl-context")
+                    .nick("GL Context")
+                    .blurb("GL context to use for rendering")
+                    .construct_only()
+                    .build(),
+            ]
+        });
+
+        PROPERTIES.as_ref()
+    }
+
+    fn property(&self, _id: usize, pspec: &glib::ParamSpec) -> glib::Value {
+        match pspec.name() {
+            "gl-context" => self.gl_context.borrow().to_value(),
+            _ => unimplemented!(),
+        }
+    }
+
+    fn set_property(&self, _id: usize, value: &glib::Value, pspec: &glib::ParamSpec) {
+        match pspec.name() {
+            "gl-context" => {
+                *self.gl_context.borrow_mut() = value.get::<Option<gtk::gdk::GLContext>>().unwrap();
+            }
+            _ => unimplemented!(),
+        }
+    }
+}
 
 impl PaintableImpl for Paintable {
     fn intrinsic_height(&self) -> i32 {
@@ -136,10 +166,12 @@ impl PaintableImpl for Paintable {
 
 impl Paintable {
     pub(super) fn handle_frame_changed(&self, frame: Option<Frame>) {
+        let context = self.gl_context.borrow();
         if let Some(frame) = frame {
             gst::trace!(CAT, imp: self, "Received new frame");
 
-            let new_paintables = frame.into_textures(&mut self.cached_textures.borrow_mut());
+            let new_paintables =
+                frame.into_textures(context.as_ref(), &mut self.cached_textures.borrow_mut());
             let new_size = new_paintables
                 .first()
                 .map(|p| (f32::round(p.width) as u32, f32::round(p.height) as u32))

video/gtk4/src/sink/paintable/mod.rs

@@ -22,20 +22,15 @@ glib::wrapper! {
 }
 
 impl Paintable {
-    pub fn new() -> Self {
+    pub fn new(context: Option<gdk::GLContext>) -> Self {
-        glib::Object::new(&[])
+        glib::Object::builder()
-    }
+            .property("gl-context", context)
-}
+            .build()
-
-impl Default for Paintable {
-    fn default() -> Self {
-        Self::new()
     }
 }
 
 impl Paintable {
     pub(crate) fn handle_frame_changed(&self, frame: Option<Frame>) {
-        let imp = self.imp();
+        self.imp().handle_frame_changed(frame);
-        imp.handle_frame_changed(frame);
     }
 }

video/gtk4/src/utils.rs

@@ -0,0 +1,16 @@
+use gtk::glib;
+use std::sync::mpsc;
+
+pub(crate) fn invoke_on_main_thread<F, T>(func: F) -> T
+where
+    F: FnOnce() -> T + Send + 'static,
+    T: Send + 'static,
+{
+    let context = glib::MainContext::default();
+
+    let (send, recv) = mpsc::channel();
+    context.invoke(move || {
+        send.send(func()).expect("Somehow we dropped the receiver");
+    });
+    recv.recv().expect("Somehow we dropped the sender")
+}