Nixpkgs: Fractal crashes when displaying inline video

[tnias]

Describe the bug
Fractal crashes on opening a chat with an embedded video( or some other form of gstreamer thingy?).

To Reproduce
Steps to reproduce the behavior:

1. Get fractal nix-shell -p fractal
2. Start fractal fractal
3. (optional) create account and login.
4. Open a channel with an embedded video. (I tried the fractal channel #fractal-gtk:matrix.org)
5. See a few messages getting rendered, right before the crash. (This last step takes about 2 seconds)

Expected behavior

The channel's contents are displayed. The application does not crash.

Screenshots Output

% nix-shell -p fractal

[nix-shell:~/src/nixpkgs]$ RUST_BACKTRACE=1 fractal 
thread 'main' panicked at 'Missing dependency: element gtksink is needed (usually, in gstreamer-plugins-good or in gst-plugin-gtk).: BoolError { message: "Failed to create element from factory name", filename: "/build/fractal-4.4.0-vendor.tar.gz/gstreamer/src/auto/element_factory.rs", function: "gstreamer::auto::element_factory", line: 184 }', fractal-gtk/src/widgets/inline_player.rs:249:20
stack backtrace:
   0: <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt
   1: core::fmt::write
   2: std::io::Write::write_fmt
   3: std::panicking::default_hook::{{closure}}
   4: std::panicking::default_hook
   5: std::panicking::rust_panic_with_hook
   6: rust_begin_unwind
   7: core::panicking::panic_fmt
   8: core::result::unwrap_failed
   9: fractal_gtk::widgets::inline_player::VideoPlayerWidget::new
  10: fractal_gtk::widgets::message::MessageBox::build_room_msg_body_bx
  11: fractal_gtk::widgets::message::MessageBox::widget
  12: fractal_gtk::widgets::message::MessageBox::create
  13: fractal_gtk::widgets::room_history::create_row
  14: glib::source::trampoline
  15: g_main_context_dispatch
  16: g_main_context_iterate.isra.0
  17: g_main_context_iteration
  18: g_application_run
  19: <O as gio::application::ApplicationExtManual>::run
  20: fractal_gtk::main
  21: std::rt::lang_start::{{closure}}
  22: std::rt::lang_start_internal
  23: main
  24: __libc_start_main
  25: _start
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
Aborted (core dumped)

Additional context

I tried adding gst-plugins-good as the output suggests, but had no luck.

diff --git a/pkgs/applications/networking/instant-messengers/fractal/default.nix b/pkgs/applications/networking/instant-messengers/fractal/default.nix
index 2abd733b277..f36a51a800f 100644
--- a/pkgs/applications/networking/instant-messengers/fractal/default.nix
+++ b/pkgs/applications/networking/instant-messengers/fractal/default.nix
@@ -59,6 +59,7 @@ rustPlatform.buildRustPackage rec {
     gst_all_1.gst-editing-services
     gst_all_1.gst-plugins-bad
     gst_all_1.gst-plugins-base
+    gst_all_1.gst-plugins-good
     gst_all_1.gstreamer
     gst_all_1.gst-validate
     gtk3

Notify maintainers

@dtzWill @worldofpeace @jtojnar

Metadata

% nix-shell -p nix-info --run "nix-info -m"
 - system: `"x86_64-linux"`
 - host os: `Linux 5.4.59-hardened, NixOS, 20.09.git.c59ea8b8a0eM (Nightingale)`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.3.7`
 - channels(root): `"nixos-20.09pre239318.c59ea8b8a0e"`
 - channels(user): `""`
 - nixpkgs: `/nix/var/nix/profiles/per-user/root/channels/nixos`

Maintainer information:

# a list of nixpkgs attributes affected by the problem
attribute: pkgs.fractal
# a list of nixos modules affected by the problem
module:

[jtojnar]

gtksink is not build by default, you would need

(gst-plugins-good.override {
  gtkSupport = true;
})

[tnias]

The suggested fix works for me. :tada:
I created a PR so in the future installing fractal just works out of the box.