Attempt to refactor as a step towards moving gstreamer integration in…

examples/gstreamer-player/Cargo.toml

@@ -16,13 +16,13 @@ name = "gstreamer-player"
 
 [dependencies]
 slint = { path = "../../api/rs/slint" }
-anyhow = { version = "1.0" }
 futures = { version = "0.3.28" }
 
 gst = {package = "gstreamer", version = "0.21.3"}
 gst-audio = {package = "gstreamer-audio", version = "0.21.3" }
 gst-video = {package = "gstreamer-video", version = "0.21.2" }
 gst-app = {package = "gstreamer-app", version = "0.21.2" }
+thiserror = "1.0.57"
 
 
 [build-dependencies]

examples/gstreamer-player/main.rs

@@ -3,33 +3,59 @@
 
 slint::include_modules!();
 
-use anyhow::{bail, Result};
-
 use gst::prelude::*;
+use gst_app::AppSink;
 
-fn try_gstreamer_video_frame_to_pixel_buffer(
-    frame: &gst_video::VideoFrame<gst_video::video_frame::Readable>,
-) -> Result<slint::SharedPixelBuffer<slint::Rgb8Pixel>> {
-    match frame.format() {
-        gst_video::VideoFormat::Rgb => {
-            let mut slint_pixel_buffer =
-                slint::SharedPixelBuffer::<slint::Rgb8Pixel>::new(frame.width(), frame.height());
-            frame
-                .buffer()
-                .copy_to_slice(0, slint_pixel_buffer.make_mut_bytes())
-                .expect("Unable to copy to slice!"); // Copies!
-            Ok(slint_pixel_buffer)
-        }
-        _ => {
-            bail!(
-                "Cannot convert frame to a slint RGB frame because it is format {}",
-                frame.format().to_str()
-            )
-        }
-    }
+#[derive(thiserror::Error, Debug)]
+enum GStreamerSlintError {
+    #[error("wrong video type")]
+    WrongVideoFormatError(String)
 }
 
-fn main() {
+//  This code would be moved to a rust crate that
+// TODO make width and height work dynamically without passing them
+fn set_callback_that_updates_a_slint_image<F>(app_sink: &mut AppSink, callback: F, width:u32, height:u32) -> Result<(), GStreamerSlintError>
+where F: FnOnce(&slint::Image) + Send
+{
+    app_sink.set_callbacks(
+        gst_app::AppSinkCallbacks::builder()
+            .new_sample(move |appsink| {
+                let sample = appsink.pull_sample().map_err(|_| gst::FlowError::Eos)?;
+                let buffer = sample.buffer_owned().unwrap(); // Probably copies!
+                let video_info =
+                    gst_video::VideoInfo::builder(gst_video::VideoFormat::Rgb, width, height)
+                        .build()
+                        .expect("couldn't build video info!");
+                let video_frame =
+                    gst_video::VideoFrame::from_buffer_readable(buffer, &video_info).unwrap();
+
+                let slint_frame = match video_frame.format() {
+                    gst_video::VideoFormat::Rgb => {
+                        let mut slint_pixel_buffer =
+                            slint::SharedPixelBuffer::<slint::Rgb8Pixel>::new(video_frame.width(), video_frame.height());
+                        video_frame
+                            .buffer()
+                            .copy_to_slice(0, slint_pixel_buffer.make_mut_bytes())
+                            .expect("Unable to copy to slice!"); // Copies!
+                        Ok(slint_pixel_buffer)
+                    }
+                    _ => {
+                        Err(format!("Cannot convert frame to a slint RGB8 images because it is format {}", video_frame.format().to_str()))
+                    }
+                }.expect("Unable to convert the video frame to a slint video frame!");
+                let slint_image = slint::Image::from_rgb8(slint_frame);
+                callback(&slint_image);
+
+                Ok(gst::FlowSuccess::Ok)
+            })
+            .build()
+    );
+    Ok(())
+}
+
+
+
+fn main() -> Result<(), GStreamerSlintError> {
     let app = App::new().unwrap();
     let app_weak = app.as_weak();
 
@@ -43,7 +69,7 @@ fn main() {
     let width: u32 = 1024;
     let height: u32 = 1024;
 
-    let appsink = gst_app::AppSink::builder()
+    let mut app_sink = AppSink::builder()
         .caps(
             &gst_video::VideoCapsBuilder::new()
                 .format(gst_video::VideoFormat::Rgb)
@@ -55,37 +81,26 @@ fn main() {
 
     let pipeline = gst::Pipeline::with_name("test-pipeline");
 
-    pipeline.add_many([&source, &appsink.upcast_ref()]).unwrap();
-    source.link(&appsink).expect("Elements could not be linked.");
-
-    appsink.set_callbacks(
-        gst_app::AppSinkCallbacks::builder()
-            .new_sample(move |appsink| {
-                let sample = appsink.pull_sample().map_err(|_| gst::FlowError::Eos)?;
-                let buffer = sample.buffer_owned().unwrap(); // Probably copies!
-                let video_info =
-                    gst_video::VideoInfo::builder(gst_video::VideoFormat::Rgb, width, height)
-                        .build()
-                        .expect("couldn't build video info!");
-                let video_frame =
-                    gst_video::VideoFrame::from_buffer_readable(buffer, &video_info).unwrap();
-                let slint_frame = try_gstreamer_video_frame_to_pixel_buffer(&video_frame)
-                    .expect("Unable to convert the video frame to a slint video frame!");
+    pipeline.add_many([&source, &app_sink.upcast_ref()]).unwrap();
+    source.link(&app_sink).expect("Elements could not be linked.");
 
-                app_weak
-                    .upgrade_in_event_loop(|app| {
-                        app.set_video_frame(slint::Image::from_rgb8(slint_frame))
-                    })
-                    .unwrap();
 
-                Ok(gst::FlowSuccess::Ok)
+    // Library user has to write this closure because app and set_video_frame are both codegenned.
+    // Captures app_weak
+    let set_video_frame = |image: & slint::Image| {
+        // app.set_video_frame(image);
+        app_weak
+            .upgrade_in_event_loop(|app| {
+                app.set_video_frame(*image)
             })
-            .build(),
-    );
+            .unwrap();
+    };
+    set_callback_that_updates_a_slint_image(&mut app_sink, set_video_frame, 256, 256)?;
 
     pipeline
         .set_state(gst::State::Playing)
         .expect("Unable to set the pipeline to the `Playing` state");
 
     app.run().unwrap();
+    Ok(())
 }