gl: wrapper for gst_gl_framebuffer_draw_to_texture

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer-rs/-/merge_requests/1314>

gstreamer-gl/Gir.toml

@@ -415,6 +415,7 @@ status = "generate"
 [[object]]
 name = "GstGL.GLFramebuffer"
 status = "generate"
+manual_traits = ["GLFramebufferExtManual"]
 
     [[object.function]]
     name = "attach"
@@ -423,8 +424,7 @@ status = "generate"
 
     [[object.function]]
     name = "draw_to_texture"
-    # needs to be manually implemented for correct types/mutability
+    manual = true
-    ignore = true
 
 [[object]]
 name = "GstGL.GLOverlayCompositor"

gstreamer-gl/src/gl_framebuffer.rs

@@ -0,0 +1,35 @@
+use glib::{prelude::*, translate::*};
+
+use crate::{GLFramebuffer, GLMemoryRef};
+
+mod sealed {
+    pub trait Sealed {}
+    impl<T: super::IsA<super::GLFramebuffer>> Sealed for T {}
+}
+
+pub trait GLFramebufferExtManual: sealed::Sealed + IsA<GLFramebuffer> + 'static {
+    #[doc(alias = "gst_gl_framebuffer_draw_to_texture")]
+    fn draw_to_texture<F: FnOnce()>(&self, mem: &mut GLMemoryRef, func: F) {
+        let mut func = std::mem::ManuallyDrop::new(func);
+        let user_data: *mut F = &mut *func;
+
+        unsafe extern "C" fn trampoline<F: FnOnce()>(
+            data: glib::ffi::gpointer,
+        ) -> glib::ffi::gboolean {
+            let func = std::ptr::read(data as *mut F);
+            func();
+            glib::ffi::GTRUE
+        }
+
+        unsafe {
+            ffi::gst_gl_framebuffer_draw_to_texture(
+                self.as_ref().to_glib_none().0,
+                mem.as_mut_ptr(),
+                Some(trampoline::<F>),
+                user_data as glib::ffi::gpointer,
+            );
+        }
+    }
+}
+
+impl<O: IsA<GLFramebuffer>> GLFramebufferExtManual for O {}

gstreamer-gl/src/lib.rs

@@ -42,6 +42,7 @@ mod gl_base_memory;
 pub use self::gl_base_memory::*;
 mod gl_memory;
 pub use crate::gl_memory::*;
+mod gl_framebuffer;
 mod gl_memory_pbo;
 pub use crate::gl_memory_pbo::*;
 
@@ -53,7 +54,8 @@ pub mod prelude {
 
     pub use crate::{
         auto::traits::*, context::ContextGLExt, gl_context::GLContextExtManual,
-        gl_display::GLDisplayExtManual, gl_video_frame::VideoFrameGLExt,
+        gl_display::GLDisplayExtManual, gl_framebuffer::GLFramebufferExtManual,
+        gl_video_frame::VideoFrameGLExt,
     };
 }