add initial scanning from a camera stream

closes #107

Cargo.lock

@@ -252,6 +252,8 @@ dependencies = [
  "diesel_migrations",
  "futures",
  "gettext-rs",
+ "gstreamer",
+ "gstreamer-base",
  "gtk-macros",
  "gtk4",
  "hex",
@@ -1254,6 +1256,63 @@ dependencies = [
  "system-deps",
 ]
 
+[[package]]
+name = "gstreamer"
+version = "0.17.0"
+source = "git+https://gitlab.freedesktop.org/gstreamer/gstreamer-rs#beee75dabec062d35533c3d785b55d6c9301ca73"
+dependencies = [
+ "bitflags",
+ "cfg-if 1.0.0",
+ "futures-channel",
+ "futures-core",
+ "futures-util",
+ "glib",
+ "gstreamer-sys",
+ "libc",
+ "muldiv",
+ "num-rational",
+ "once_cell",
+ "paste",
+ "pretty-hex",
+ "thiserror",
+]
+
+[[package]]
+name = "gstreamer-base"
+version = "0.17.0"
+source = "git+https://gitlab.freedesktop.org/gstreamer/gstreamer-rs#beee75dabec062d35533c3d785b55d6c9301ca73"
+dependencies = [
+ "bitflags",
+ "cfg-if 1.0.0",
+ "glib",
+ "gstreamer",
+ "gstreamer-base-sys",
+ "libc",
+]
+
+[[package]]
+name = "gstreamer-base-sys"
+version = "0.17.0"
+source = "git+https://gitlab.freedesktop.org/gstreamer/gstreamer-rs#beee75dabec062d35533c3d785b55d6c9301ca73"
+dependencies = [
+ "glib-sys",
+ "gobject-sys",
+ "gstreamer-sys",
+ "libc",
+ "system-deps",
+]
+
+[[package]]
+name = "gstreamer-sys"
+version = "0.17.0"
+source = "git+https://gitlab.freedesktop.org/gstreamer/gstreamer-rs#beee75dabec062d35533c3d785b55d6c9301ca73"
+dependencies = [
+ "glib-sys",
+ "gobject-sys",
+ "libc",
+ "system-deps",
+]
+
 [[package]]
 name = "gtk-macros"
 version = "0.2.0"
@@ -1747,6 +1806,12 @@ dependencies = [
  "autocfg",
 ]
 
+[[package]]
+name = "muldiv"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b5136edda114182728ccdedb9f5eda882781f35fa6e80cc360af12a8932507f3"
+
 [[package]]
 name = "nb-connect"
 version = "1.0.2"
@@ -1982,6 +2047,12 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "paste"
+version = "1.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c5d65c4d95931acda4498f675e332fcbdc9a06705cd07086c510e9b6009cd1c1"
+
 [[package]]
 name = "percent-encoding"
 version = "2.1.0"
@@ -2074,6 +2145,12 @@ version = "0.2.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ac74c624d6b2d21f425f752262f42188365d7b8ff1aff74c82e45136510a4857"
 
+[[package]]
+name = "pretty-hex"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bc5c99d529f0d30937f6f4b8a86d988047327bb88d04d2c4afc356de74722131"
+
 [[package]]
 name = "pretty_env_logger"
 version = "0.4.0"

Cargo.toml

@@ -13,6 +13,8 @@ diesel = {version = "1.4", features = ["sqlite", "r2d2"]}
 diesel_migrations = {version = "1.4", features = ["sqlite"]}
 futures = "0.3"
 gettext-rs = {version = "0.5", features = ["gettext-system"]}
+gst = {package = "gstreamer", git = "https://gitlab.freedesktop.org/gstreamer/gstreamer-rs"}
+gst_base = {package = "gstreamer-base", git = "https://gitlab.freedesktop.org/gstreamer/gstreamer-rs"}
 gtk = {git = "https://github.com/gtk-rs/gtk4-rs", package = "gtk4"}
 gtk-macros = "0.2"
 hex = "0.4"

build-aux/com.belmoussaoui.Authenticator.Devel.json

@@ -6,15 +6,17 @@
     "sdk-extensions": ["org.freedesktop.Sdk.Extension.rust-stable"],
     "command": "authenticator",
     "finish-args": [
+        "--socket=pulseaudio",
+        "--device=all",
         "--share=network",
         "--share=ipc",
-        "--device=dri",
         "--socket=fallback-x11",
         "--socket=wayland",
         "--talk-name=org.a11y.Bus",
         "--talk-name=org.freedesktop.secrets",
         "--env=RUST_LOG=authenticator=debug",
-        "--env=G_MESSAGES_DEBUG=none"
+        "--env=G_MESSAGES_DEBUG=none",
+        "--env=GST_PLUGIN_SYSTEM_PATH=/app/lib/gstreamer-1.0"
     ],
     "build-options": {
         "append-path": "/usr/lib/sdk/rust-stable/bin",
@@ -30,7 +32,7 @@
     },
     "modules": [
         {
-            "name": "libhandy",
+            "name": "libadwaita",
             "buildsystem": "meson",
             "config-opts": [
                 "-Dintrospection=disabled",
@@ -47,8 +49,7 @@
                     "branch": "main"
                 }
             ]
-        },
+        },{
-        {
             "name": "zbar",
             "config-opts": [
                 "--without-qt",
@@ -76,6 +77,82 @@
                 }
             ]
         },
+        {
+            "name" : "gstreamer",
+            "buildsystem" : "meson",
+            "config-opts" : [
+                "-Dexamples=disabled",
+                "-Dtests=disabled",
+                "-Ddoc=disabled"
+            ],
+            "sources" : [
+                {
+                    "type" : "git",
+                    "branch" : "1.18",
+                    "url" : "https://gitlab.freedesktop.org/gstreamer/gstreamer.git"
+                }
+            ]
+        },
+        {
+            "name" : "gst-plugins-base",
+            "buildsystem" : "meson",
+            "config-opts" : [
+                "-Ddoc=disabled",
+                "-Dexamples=disabled",
+                "-Dtests=disabled",
+                "-Dorc=enabled",
+                "--wrap-mode=nodownload"
+            ],
+            "sources" : [
+                {
+                    "type" : "git",
+                    "branch" : "1.18",
+                    "url" : "https://gitlab.freedesktop.org/gstreamer/gst-plugins-base.git"
+                }
+            ]
+        },
+        {
+            "name" : "gst-plugins-good",
+            "buildsystem" : "meson",
+            "config-opts" : [
+                "-Dgtk3=disabled",
+                "-Dgtk4=enabled",
+                "-Dgtk4-experiments=true",
+                "-Ddoc=disabled",
+                "-Dexamples=disabled",
+                "-Dtests=disabled"
+            ],
+            "sources" : [
+                {
+                    "type" : "git",
+                    "branch" : "1.18",
+                    "url" : "https://gitlab.freedesktop.org/gstreamer/gst-plugins-good.git"
+                },
+                {
+                    "type" : "patch",
+                    "path" : "767.patch"
+                }
+            ]
+	    },
+        {
+            "name" : "gst-bad-plugins",
+            "buildsystem": "meson",
+            "config-opts" : [
+            	"-Dzbar=enabled",
+            	"-Drsvg=disabled",
+            	"-Dvulkan=disabled",
+            	"-Dexamples=disabled",
+            	"-Dtests=disabled",
+            	"-Dintrospection=disabled"
+            ],
+            "sources" : [
+                {
+                    "type" : "git",
+                    "url" : "https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad.git",
+                    "branch" : "1.18"
+                }
+            ]
+        },
         {
             "name": "authenticator",
             "buildsystem": "meson",

data/resources.gresource.xml

@@ -18,6 +18,9 @@
     <!-- UI Files -->
     <file compressed="true" preprocess="xml-stripblanks" alias="preferences.ui">resources/ui/preferences.ui</file>
     <file compressed="true" preprocess="xml-stripblanks" alias="preferences_password_page.ui">resources/ui/preferences_password_page.ui</file>
+
+    <file compressed="true" preprocess="xml-stripblanks" alias="camera.ui">resources/ui/camera.ui</file>
+
     <file compressed="true" preprocess="xml-stripblanks" alias="shortcuts.ui">resources/ui/shortcuts.ui</file>
     <file compressed="true" preprocess="xml-stripblanks" alias="window.ui">resources/ui/window.ui</file>
   </gresource>

data/resources/ui/account_add.ui

@@ -1,5 +1,17 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
+  <menu id="scan_menu">
+    <section>
+      <item>
+        <attribute name="label" translatable="yes">_Camera</attribute>
+        <attribute name="action">add.camera</attribute>
+      </item>
+      <item>
+        <attribute name="label" translatable="yes">_Screenshot</attribute>
+        <attribute name="action">add.screenshot</attribute>
+      </item>
+    </section>
+  </menu>
   <object class="GtkAdjustment" id="counter_adjustment">
     <property name="upper">60</property>
     <property name="step-increment">1</property>
@@ -11,9 +23,12 @@
     <property name="default-height">550</property>
     <property name="title" translatable="yes">Add a new account</property>
     <child>
-      <object class="AdwLeaflet">
+      <object class="AdwLeaflet" id="deck">
+        <property name="can-unfold">False</property>
+        <property name="can-swipe-back">True</property>
         <child>
           <object class="AdwLeafletPage">
+            <property name="name">main</property>
             <property name="child">
               <object class="GtkBox">
                 <property name="orientation">vertical</property>
@@ -41,10 +56,9 @@
                       </object>
                     </child>
                     <child type="end">
-                      <object class="GtkButton" id="scan_btn">
+                      <object class="GtkMenuButton" id="scan_btn">
-                        <property name="receives-default">True</property>
                         <property name="tooltip-text" translatable="yes">Scan QR Code</property>
-                        <property name="action-name">add.scan-qr</property>
+                        <property name="menu-model">scan_menu</property>
                         <property name="icon-name">qrscanner-symbolic</property>
                       </object>
                     </child>
@@ -219,6 +233,14 @@
             </property>
           </object>
         </child>
+        <child>
+          <object class="AdwLeafletPage">
+            <property name="name">camera</property>
+            <property name="child">
+              <object class="Camera" id="camera" />
+            </property>
+          </object>
+        </child>
       </object>
     </child>
     <child>

data/resources/ui/camera.ui

@@ -0,0 +1,87 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<interface>
+  <template parent="GtkWidget" class="Camera">
+    <child>
+      <object class="GtkStack" id="stack">
+        <property name="transition-type">crossfade</property>
+        <property name="hhomogeneous">False</property>
+        <child>
+          <object class="GtkStackPage">
+            <property name="name">loading</property>
+            <property name="child">
+              <object class="GtkSpinner" id="spinner">
+                <property name="halign">center</property>
+                <property name="vexpand">True</property>
+                <property name="valign">center</property>
+                <property name="width-request">48</property>
+                <property name="height-request">48</property>
+              </object>
+            </property>
+          </object>
+        </child>
+        <child>
+          <object class="GtkStackPage">
+            <property name="name">not-found</property>
+            <property name="child">
+              <object class="AdwStatusPage">
+                <property name="icon-name">camera-hardware-disabled-symbolic</property>
+                <property name="title" translatable="yes">No Camera Found</property>
+                <property name="description" translatable="yes"></property>
+                <property name="child">
+                  <object class="GtkButton">
+                    <property name="label" translatable="yes">_From A Screenshot</property>
+                    <property name="action-name">add.screenshot</property>
+                    <property name="halign">center</property>
+                    <property name="margin-top">24</property>
+                    <property name="use-underline">True</property>
+                    <style>
+                      <class name="large-button" />
+                      <class name="pill-button" />
+                      <class name="suggested-action" />
+                    </style>
+                  </object>
+                </property>
+              </object>
+            </property>
+          </object>
+        </child>
+        <child>
+          <object class="GtkStackPage">
+            <property name="name">stream</property>
+            <property name="child">
+              <object class="GtkOverlay" id="overlay">
+                <child type="overlay">
+                  <object class="GtkBox">
+                    <property name="orientation">horizontal</property>
+                    <property name="valign">end</property>
+                    <property name="halign">fill</property>
+                    <property name="margin-start">18</property>
+                    <property name="margin-end">18</property>
+                    <property name="margin-bottom">18</property>
+                    <property name="spacing">8</property>
+                    <child>
+                      <object class="GtkButton">
+                        <property name="icon-name">qrscanner-symbolic</property>
+                        <property name="tooltip-text" translatable="yes">Capture from a screenshot</property>
+                        <property name="width-request">44</property>
+                        <property name="height-request">44</property>
+                        <property name="halign">end</property>
+                        <property name="hexpand">True</property>
+                        <property name="valign">center</property>
+                        <property name="action-name">camera.screenshot-scan</property>
+                        <style>
+                          <class name="osd" />
+                          <class name="circular-button" />
+                        </style>
+                      </object>
+                    </child>
+                  </object>
+                </child>
+              </object>
+            </property>
+          </object>
+        </child>
+      </object>
+    </child>
+  </template>
+</interface>

meson.build

@@ -9,6 +9,12 @@ dependency('gio-2.0', version: '>= 2.56')
 dependency('gdk-pixbuf-2.0')
 dependency('gtk4', version: '>= 4.0.0')
 dependency('libadwaita-1', version: '>=1.0.0')
+dependency('zbar', version: '>= 0.20')
+dependency('gstreamer-1.0', version: '>= 1.18')
+dependency('gstreamer-base-1.0', version: '>= 1.18')
+dependency('gstreamer-plugins-base-1.0', version: '>= 1.18')
+dependency('gstreamer-plugins-bad-1.0', version: '>= 1.18')
+
 
 cargo = find_program('cargo', required: true)
 glib_compile_schemas = find_program('glib-compile-schemas', required: true)

po/POTFILES.in

@@ -4,6 +4,7 @@ data/com.belmoussaoui.Authenticator.metainfo.xml.in.in
 data/resources/ui/account_add.ui
 data/resources/ui/account_details_page.ui
 data/resources/ui/account_row.ui
+data/resources/ui/camera.ui
 data/resources/ui/preferences_password_page.ui
 data/resources/ui/preferences.ui
 data/resources/ui/provider_page.ui

src/main.rs

@@ -22,6 +22,7 @@ use config::{GETTEXT_PACKAGE, LOCALEDIR};
 fn main() {
     pretty_env_logger::init();
     gtk::init().expect("failed to init gtk4 ");
+    gst::init().expect("failed to init gstreamer");
     // Prepare i18n
     setlocale(LocaleCategory::LcAll, "");
     bindtextdomain(GETTEXT_PACKAGE, LOCALEDIR);

src/meson.build

@@ -71,6 +71,7 @@ sources = files(
   'widgets/providers/mod.rs',
   'widgets/providers/page.rs',
   'widgets/providers/row.rs',
+  'widgets/camera.rs',
 	'widgets/mod.rs',
 	'widgets/url_row.rs',
 	'widgets/window.rs',

src/widgets/accounts/add.rs

@@ -1,13 +1,13 @@
 use crate::{
-    helpers::qrcode,
     models::{Account, OTPMethod, OTPUri, Provider, ProvidersModel},
-    widgets::{ProviderImage, UrlRow},
+    widgets::{Camera, ProviderImage, UrlRow},
 };
 use anyhow::Result;
 use glib::{clone, signal::Inhibit};
 use gtk::{gio, glib, prelude::*, subclass::prelude::*, CompositeTemplate};
 use gtk_macros::{action, get_action};
 use once_cell::sync::OnceCell;
+use std::str::FromStr;
 
 mod imp {
     use super::*;
@@ -20,6 +20,10 @@ mod imp {
         pub selected_provider: RefCell<Option<Provider>>,
         pub actions: gio::SimpleActionGroup,
         #[template_child]
+        pub camera: TemplateChild<Camera>,
+        #[template_child]
+        pub deck: TemplateChild<adw::Leaflet>,
+        #[template_child]
         pub image: TemplateChild<ProviderImage>,
         #[template_child]
         pub provider_website_row: TemplateChild<UrlRow>,
@@ -79,12 +83,15 @@ mod imp {
                 algorithm_label: TemplateChild::default(),
                 counter_row: TemplateChild::default(),
                 period_row: TemplateChild::default(),
+                deck: TemplateChild::default(),
+                camera: TemplateChild::default(),
             }
         }
 
         fn class_init(klass: &mut Self::Class) {
             UrlRow::static_type();
             ProviderImage::static_type();
+            Camera::static_type();
             klass.set_template_from_resource("/com/belmoussaoui/Authenticator/account_add.ui");
             Self::bind_template_children(klass);
             klass.add_signal("added", glib::SignalFlags::ACTION, &[], glib::Type::Unit);
@@ -137,20 +144,21 @@ impl AccountAddDialog {
             .connect_changed(clone!(@weak self as win => move |_| win.validate()));
     }
 
-    fn scan_qr(&self) -> Result<()> {
+    fn scan_from_screenshot(&self) {
-        qrcode::screenshot_area(
+        let self_ = imp::AccountAddDialog::from_instance(self);
-            self.clone().upcast::<gtk::Window>(),
+        self_.camera.from_screenshot();
-            clone!(@weak self as dialog => move |screenshot| {
+    }
-                if let Ok(otp_uri) = qrcode::scan(&screenshot) {
+
-                    dialog.set_from_otp_uri(otp_uri);
+    fn scan_from_camera(&self) {
-                }
+        let self_ = imp::AccountAddDialog::from_instance(self);
-            }),
+        self_.deck.set_visible_child_name("camera");
-        )?;
+
-        Ok(())
+        self_.camera.start();
     }
 
     fn set_from_otp_uri(&self, otp_uri: OTPUri) {
         let self_ = imp::AccountAddDialog::from_instance(self);
+        self_.deck.set_visible_child_name("main"); // Switch back the form view
 
         self_.token_entry.set_text(&otp_uri.secret);
         self_.username_entry.set_text(&otp_uri.label);
@@ -234,7 +242,7 @@ impl AccountAddDialog {
             self_.actions,
             "back",
             clone!(@weak self as dialog => move |_, _| {
-                dialog.destroy();
+                dialog.close();
             })
         );
         action!(
@@ -249,11 +257,17 @@ impl AccountAddDialog {
 
         action!(
             self_.actions,
-            "scan-qr",
+            "camera",
             clone!(@weak self as dialog => move |_, _| {
-                if let Err(err) = dialog.scan_qr() {
+                dialog.scan_from_camera();
-                    warn!("Failed to scan a QR code {}", err)
+            })
-                }
+        );
+
+        action!(
+            self_.actions,
+            "screenshot",
+            clone!(@weak self as dialog => move |_, _| {
+                dialog.scan_from_screenshot();
             })
         );
         self.insert_action_group("add", Some(&self_.actions));
@@ -268,12 +282,28 @@ impl AccountAddDialog {
 
         self_.provider_completion.connect_match_selected(
             clone!(@weak self as dialog, @strong self_.model as model => move |_, store, iter| {
-                let provider_id = store.get_value(iter, 0). get_some::<i32>().unwrap();
+                let provider_id = store.get_value(iter, 0).get_some::<i32>().unwrap();
                 let provider = model.get().unwrap().find_by_id(provider_id).unwrap();
                 dialog.set_provider(provider);
 
                 Inhibit(false)
             }),
         );
+
+        self_
+            .camera
+            .connect_local(
+                "code-detected",
+                false,
+                clone!(@weak self as dialog => move |args| {
+                    let code = args.get(1).unwrap().get::<String>().unwrap().unwrap();
+                    if let Ok(otp_uri) = OTPUri::from_str(&code) {
+                        dialog.set_from_otp_uri(otp_uri);
+                    }
+
+                    None
+                }),
+            )
+            .unwrap();
     }
 }

src/widgets/camera.rs

@@ -0,0 +1,370 @@
+use glib::{Receiver, Sender};
+use gst::prelude::*;
+use gtk::{
+    gio,
+    glib::{self, clone},
+    prelude::*,
+    subclass::prelude::*,
+    CompositeTemplate,
+};
+use gtk_macros::send;
+use once_cell::sync::Lazy;
+/// Fancy Camera with QR code detection using ZBar
+///
+/// Pipeline:
+///                            queue -- videoconvert -- zbar -- fakesink
+///                         /
+///     device sink -- tee
+///                         \
+///                            queue -- glsinkbin
+///
+///
+
+static PIPELINE_NAME: Lazy<glib::GString> = Lazy::new(|| glib::GString::from("camera"));
+
+mod screenshot {
+    use anyhow::Result;
+    use ashpd::{
+        desktop::screenshot::{Screenshot, ScreenshotOptions, ScreenshotProxy},
+        zbus, RequestProxy, Response, WindowIdentifier,
+    };
+    use gtk::{gio, prelude::*};
+    use image::GenericImageView;
+    use zbar_rust::ZBarImageScanner;
+
+    pub fn scan(screenshot: &gio::File) -> Result<String> {
+        let (data, _) = screenshot.load_contents(gio::NONE_CANCELLABLE)?;
+
+        let img = image::load_from_memory(&data)?;
+
+        let (width, height) = img.dimensions();
+        let img_data: Vec<u8> = img.to_luma8().to_vec();
+
+        let mut scanner = ZBarImageScanner::new();
+
+        let results = scanner
+            .scan_y800(&img_data, width, height)
+            .map_err(|e| anyhow::format_err!(e))?;
+
+        if let Some(ref result) = results.get(0) {
+            let content = String::from_utf8(result.data.clone())?;
+            return Ok(content);
+        }
+        anyhow::bail!("Invalid QR code")
+    }
+
+    pub fn capture<F: FnOnce(gio::File)>(window: gtk::Window, callback: F) -> Result<()> {
+        let connection = zbus::Connection::new_session()?;
+        let proxy = ScreenshotProxy::new(&connection)?;
+        let handle = proxy.screenshot(
+            WindowIdentifier::from(window),
+            ScreenshotOptions::default().interactive(true).modal(true),
+        )?;
+        let request = RequestProxy::new(&connection, &handle)?;
+        request.on_response(move |response: Response<Screenshot>| {
+            if let Ok(screenshot) = response {
+                callback(gio::File::new_for_uri(&screenshot.uri));
+            }
+        })?;
+        Ok(())
+    }
+}
+
+#[derive(Debug)]
+pub enum CameraEvent {
+    CodeDetected(String),
+    DeviceAdded(gst::Device),
+    DeviceRemoved(gst::Device),
+    StreamStarted,
+}
+
+#[derive(Debug)]
+pub enum CameraState {
+    Loading,
+    NotFound,
+    Ready,
+    Paused,
+}
+
+mod imp {
+    use super::*;
+    use glib::subclass;
+    use std::cell::RefCell;
+
+    #[derive(Debug, CompositeTemplate)]
+    pub struct Camera {
+        pub actions: gio::SimpleActionGroup,
+        pub sender: Sender<CameraEvent>,
+        pub receiver: RefCell<Option<Receiver<CameraEvent>>>,
+        pub pipeline: gst::Pipeline,
+        pub sink: gst::Element,
+        pub devices: gio::ListStore,
+        pub monitor: gst::DeviceMonitor,
+        #[template_child]
+        pub stack: TemplateChild<gtk::Stack>,
+        #[template_child]
+        pub overlay: TemplateChild<gtk::Overlay>,
+        #[template_child]
+        pub spinner: TemplateChild<gtk::Spinner>,
+    }
+
+    impl ObjectSubclass for Camera {
+        const NAME: &'static str = "Camera";
+        type Type = super::Camera;
+        type ParentType = gtk::Widget;
+        type Instance = subclass::simple::InstanceStruct<Self>;
+        type Class = subclass::simple::ClassStruct<Self>;
+
+        glib::object_subclass!();
+
+        fn class_init(klass: &mut Self::Class) {
+            klass.set_template_from_resource("/com/belmoussaoui/Authenticator/camera.ui");
+            Self::bind_template_children(klass);
+            klass.set_layout_manager_type::<gtk::BinLayout>();
+            klass.add_signal(
+                "code-detected",
+                glib::SignalFlags::RUN_FIRST,
+                &[String::static_type()],
+                glib::Type::Unit,
+            );
+        }
+
+        fn instance_init(obj: &subclass::InitializingObject<Self::Type>) {
+            obj.init_template();
+        }
+
+        fn new() -> Self {
+            let pipeline = gst::Pipeline::new(Some(&*PIPELINE_NAME));
+            let sink = gst::ElementFactory::make("gtk4glsink", None).unwrap();
+            let (sender, r) = glib::MainContext::channel(glib::PRIORITY_DEFAULT);
+            let receiver = RefCell::new(Some(r));
+
+            Self {
+                actions: gio::SimpleActionGroup::new(),
+                sink,
+                sender,
+                receiver,
+                pipeline,
+                spinner: TemplateChild::default(),
+                stack: TemplateChild::default(),
+                overlay: TemplateChild::default(),
+                monitor: gst::DeviceMonitor::new(),
+                devices: gio::ListStore::new(gst::Device::static_type()),
+            }
+        }
+    }
+
+    impl ObjectImpl for Camera {
+        fn constructed(&self, obj: &Self::Type) {
+            obj.init_widgets();
+            obj.init_monitor();
+            self.parent_constructed(obj);
+        }
+        fn dispose(&self, _obj: &Self::Type) {
+            self.monitor.stop();
+            self.pipeline.set_state(gst::State::Null).unwrap();
+        }
+    }
+    impl WidgetImpl for Camera {}
+}
+
+glib::wrapper! {
+    pub struct Camera(ObjectSubclass<imp::Camera>) @extends gtk::Widget;
+}
+
+impl Camera {
+    pub fn new() -> Self {
+        glib::Object::new(&[]).expect("Failed to create a Camera")
+    }
+
+    fn init_monitor(&self) {
+        let self_ = imp::Camera::from_instance(self);
+        let caps = gst::Caps::new_simple("video/x-raw", &[]);
+        self_.monitor.add_filter(Some("Video/Source"), Some(&caps));
+
+        self_.monitor.start().unwrap();
+        let bus = self_.monitor.get_bus();
+        bus.add_watch_local(clone!(@strong self_.sender as sender => move |_, msg| {
+                use gst::MessageView;
+                match msg.view() {
+                    MessageView::DeviceAdded(event) => {
+                        let device = event.get_device();
+                        send!(sender, CameraEvent::DeviceAdded(device));
+                    }
+                    MessageView::DeviceRemoved(event) => {
+                        let device = event.get_device();
+                        send!(sender, CameraEvent::DeviceRemoved(device));
+                    }
+                    _ => (),
+                };
+
+            glib::Continue(true)
+        }))
+        .expect("Failed to attach a monitor");
+    }
+
+    fn init_pipelines(&self, source_element: gst::Element) {
+        let self_ = imp::Camera::from_instance(self);
+
+        let tee = gst::ElementFactory::make("tee", None).unwrap();
+        let queue = gst::ElementFactory::make("queue", None).unwrap();
+        let videoconvert = gst::ElementFactory::make("videoconvert", None).unwrap();
+        let zbar = gst::ElementFactory::make("zbar", None).unwrap();
+        let fakesink = gst::ElementFactory::make("fakesink", None).unwrap();
+        let queue2 = gst::ElementFactory::make("queue", None).unwrap();
+        let glsinkbin = gst::ElementFactory::make("glsinkbin", None).unwrap();
+        glsinkbin.set_property("sink", &self_.sink).unwrap();
+
+        self_
+            .pipeline
+            .add_many(&[
+                &source_element,
+                &tee,
+                &queue,
+                &videoconvert,
+                &zbar,
+                &fakesink,
+                &queue2,
+                &glsinkbin,
+            ])
+            .unwrap();
+
+        gst::Element::link_many(&[
+            &source_element,
+            &tee,
+            &queue,
+            &videoconvert,
+            &zbar,
+            &fakesink,
+        ])
+        .unwrap();
+        tee.link_pads(None, &queue2, None).unwrap();
+        gst::Element::link_many(&[&queue2, &glsinkbin]).unwrap();
+
+        let bus = self_.pipeline.get_bus().unwrap();
+        bus.add_watch_local(clone!(@strong self_.sender as sender => move |_, msg| {
+            use gst::MessageView;
+            match msg.view() {
+                MessageView::StateChanged(state) => {
+                    if Some(&*PIPELINE_NAME) == state.get_src().map(|s| s.get_name()).as_ref() {
+                        let structure = state.get_structure().unwrap();
+                        let new_state = structure.get::<gst::State>("new-state")
+                            .unwrap().unwrap();
+                        if new_state == gst::State::Playing {
+                            send!(sender, CameraEvent::StreamStarted);
+                        }
+                    }
+                }
+                MessageView::Element(e) => {
+                    if let Some(s) = e.get_structure() {
+                        if let Ok(Some(symbol)) = s.get::<String>("symbol") {
+                           send!(sender, CameraEvent::CodeDetected(symbol));
+                        }
+                    }
+                }
+                MessageView::Error(err) => {
+                    error!(
+                        "Error from {:?}: {} ({:?})",
+                        err.get_src().map(|s| s.get_path_string()),
+                        err.get_error(),
+                        err.get_debug()
+                    );
+                }
+                _ => (),
+            };
+
+            glib::Continue(true)
+        }))
+        .expect("Failed to add bus watch");
+    }
+
+    fn set_state(&self, state: CameraState) {
+        let self_ = imp::Camera::from_instance(self);
+        info!("The camera state changed to {:#?}", state);
+        match state {
+            CameraState::NotFound => {
+                self_.stack.get().set_visible_child_name("not-found");
+            }
+            CameraState::Ready => {
+                self_.stack.get().set_visible_child_name("stream");
+                self_.spinner.get().stop();
+            }
+            CameraState::Loading => {
+                self_.stack.get().set_visible_child_name("loading");
+                self_.spinner.get().start();
+            }
+            CameraState::Paused => {}
+        }
+    }
+
+    fn do_event(&self, event: CameraEvent) -> glib::Continue {
+        let self_ = imp::Camera::from_instance(self);
+        match event {
+            CameraEvent::CodeDetected(code) => {
+                self.emit("code-detected", &[&code]).unwrap();
+            }
+            CameraEvent::DeviceAdded(device) => {
+                // TODO: allow selecting a device and update the sink on the pipeline
+                info!("Camera source added: {}", device.get_display_name());
+                self.set_state(CameraState::Loading);
+                let element = device.create_element(None).unwrap();
+                self.init_pipelines(element);
+                self_.devices.append(&device);
+            }
+            CameraEvent::DeviceRemoved(device) => {
+                info!("Camera source removed: {}", device.get_display_name());
+                self_.devices.append(&device);
+            }
+            CameraEvent::StreamStarted => {
+                self.set_state(CameraState::Ready);
+            }
+        }
+
+        glib::Continue(true)
+    }
+
+    pub fn start(&self) {
+        let self_ = imp::Camera::from_instance(self);
+        self_.pipeline.set_state(gst::State::Playing).unwrap();
+    }
+
+    pub fn stop(&self) {
+        let self_ = imp::Camera::from_instance(self);
+        self.set_state(CameraState::Paused);
+        self_.pipeline.set_state(gst::State::Null).unwrap();
+    }
+
+    pub fn from_screenshot(&self) {
+        let self_ = imp::Camera::from_instance(self);
+        let window = self.get_root().unwrap().downcast::<gtk::Window>().unwrap();
+        screenshot::capture(
+            window,
+            clone!(@strong self_.sender as sender => move |file| {
+                if let Ok(code) = screenshot::scan(&file) {
+                    send!(sender, CameraEvent::CodeDetected(code));
+                }
+            }),
+        )
+        .ok();
+    }
+
+    fn init_widgets(&self) {
+        let self_ = imp::Camera::from_instance(self);
+        self.set_state(CameraState::NotFound);
+        let receiver = self_.receiver.borrow_mut().take().unwrap();
+        receiver.attach(
+            None,
+            clone!(@weak self as camera => move |action| camera.do_event(action)),
+        );
+
+        let widget = self_
+            .sink
+            .get_property("widget")
+            .unwrap()
+            .get::<gtk::Widget>()
+            .unwrap()
+            .unwrap();
+        widget.set_property("force-aspect-ratio", &false).unwrap();
+        self_.overlay.get().set_child(Some(&widget));
+    }
+}

src/widgets/mod.rs

@@ -1,4 +1,5 @@
 mod accounts;
+mod camera;
 mod preferences;
 mod providers;
 mod url_row;
@@ -6,6 +7,7 @@ mod window;
 
 pub use self::{
     accounts::{AccountAddDialog, QRCodeData},
+    camera::Camera,
     preferences::PreferencesWindow,
     providers::{ProviderImage, ProvidersDialog, ProvidersList},
     url_row::UrlRow,