Library for shared applet code; use in battery applet

Creates window, button, and popover with correct properties and CSS
style.

Cargo.lock

@@ -356,6 +356,7 @@ version = "0.1.0"
 dependencies = [
  "futures",
  "gtk4",
+ "libcosmic-applet",
  "relm4",
  "zbus",
 ]
@@ -502,7 +503,7 @@ dependencies = [
 [[package]]
 name = "cosmic-panel-config"
 version = "0.1.0"
-source = "git+https://github.com/pop-os/cosmic-panel#49b8d8c84f9db93c72ef06778b76ccb38329a8c4"
+source = "git+https://github.com/pop-os/cosmic-panel/#49b8d8c84f9db93c72ef06778b76ccb38329a8c4"
 dependencies = [
  "anyhow",
  "gtk4",
@@ -1560,6 +1561,16 @@ dependencies = [
  "x11",
 ]
 
+[[package]]
+name = "libcosmic-applet"
+version = "0.1.0"
+dependencies = [
+ "cosmic-panel-config",
+ "gtk4",
+ "once_cell",
+ "relm4-macros",
+]
+
 [[package]]
 name = "libcosmic-widgets"
 version = "0.1.0"

Cargo.toml

@@ -11,4 +11,5 @@ members = [
     "applets/cosmic-applet-time",
     "applets/cosmic-app-list",
     "applets/cosmic-panel-button",
+    "libcosmic-applet",
 ]

applets/cosmic-applet-battery/Cargo.toml

@@ -6,5 +6,6 @@ edition = "2021"
 [dependencies]
 futures = "0.3"
 gtk4 = { git = "https://github.com/gtk-rs/gtk4-rs" }
+libcosmic-applet = { path = "../../libcosmic-applet" }
 relm4 = { git = "https://github.com/relm4/relm4", branch = "next", features = ["macros"] }
 zbus = { version = "2", no-default-features = true }

applets/cosmic-applet-battery/src/main.rs

@@ -77,19 +77,11 @@ impl SimpleComponent for AppModel {
     type Output = ();
 
     view! {
-        gtk4::Window {
+        libcosmic_applet::Applet {
-            set_decorated: false,
-            set_resizable: false,
-            set_width_request: 1,
-            set_height_request: 1,
-            gtk4::MenuButton {
-                set_has_frame: false,
             #[watch]
-                set_icon_name: &model.icon_name,
+            set_button_icon_name: &model.icon_name,
             #[wrap(Some)]
-                set_popover = &gtk4::Popover {
+            set_popover_child = &gtk4::Box {
-                    #[wrap(Some)]
-                    set_child = &gtk4::Box {
                 set_orientation: gtk4::Orientation::Vertical,
 
                 // Battery
@@ -199,8 +191,6 @@ impl SimpleComponent for AppModel {
             }
         }
     }
-        }
-    }
 
     fn init(
         _params: Self::InitParams,

libcosmic-applet/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "libcosmic-applet"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+cosmic-panel-config = { git = "https://github.com/pop-os/cosmic-panel/", features = ["gtk4"] }
+gtk4 = { git = "https://github.com/gtk-rs/gtk4-rs", features = ["v4_6"] }
+once_cell = "1.12.0"
+relm4-macros = { git = "https://github.com/Relm4/Relm4.git", branch = "next" }

libcosmic-applet/src/deref_cell.rs

@@ -0,0 +1,31 @@
+use once_cell::unsync::OnceCell;
+
+/// Wrapper around `OnceCell` implementing `Deref`, and thus also panicking
+/// when not set (or set twice).
+///
+/// To be used in place of `gtk::TemplateChild`, but without xml.
+pub struct DerefCell<T>(OnceCell<T>);
+
+impl<T> DerefCell<T> {
+    #[track_caller]
+    pub fn set(&self, value: T) {
+        if self.0.set(value).is_err() {
+            panic!("Initialized twice");
+        }
+    }
+}
+
+impl<T> Default for DerefCell<T> {
+    fn default() -> Self {
+        Self(OnceCell::default())
+    }
+}
+
+impl<T> std::ops::Deref for DerefCell<T> {
+    type Target = T;
+
+    #[track_caller]
+    fn deref(&self) -> &T {
+        self.0.get().unwrap()
+    }
+}

libcosmic-applet/src/lib.rs

@@ -0,0 +1,111 @@
+use gtk4::{glib, prelude::*, subclass::prelude::*};
+use relm4_macros::view;
+
+mod deref_cell;
+use deref_cell::DerefCell;
+
+// TODO make sure style fits different panel colors?
+// TODO abstraction to start main loop? Work with relm4.
+// TODO gir bindings
+// TODO orientation, etc.
+// TODO make image size dependent on CosmicPanelConfig?
+
+static STYLE: &str = "
+window.cosmic_applet_window {
+        background: transparent;
+}
+
+button.cosmic_applet_button {
+    border-radius: 12px;
+    transition: 100ms;
+    padding: 4px;
+    border-color: transparent;
+    background: transparent;
+    outline-color: transparent;
+}
+";
+
+#[derive(Default)]
+pub struct AppletInner {
+    menu_button: DerefCell<gtk4::MenuButton>,
+    popover: DerefCell<gtk4::Popover>,
+}
+
+#[glib::object_subclass]
+impl ObjectSubclass for AppletInner {
+    const NAME: &'static str = "CosmicApplet";
+    type Type = Applet;
+    type ParentType = gtk4::Window;
+}
+
+impl ObjectImpl for AppletInner {
+    fn constructed(&self, obj: &Applet) {
+        let window = || obj;
+        view! {
+            window() {
+                add_css_class: "cosmic_applet_window",
+                set_decorated: false,
+                set_resizable: false,
+                set_width_request: 1,
+                set_height_request: 1,
+                #[wrap(Some)]
+                set_child: menu_button = &gtk4::MenuButton {
+                    add_css_class: "cosmic_applet_button",
+                    set_has_frame: false,
+                    #[wrap(Some)]
+                    set_popover: popover = &gtk4::Popover {
+                        // TODO: change if it can be positioned correctly?
+                        set_has_arrow: false,
+                    }
+                }
+            }
+        }
+
+        let provider = gtk4::CssProvider::new();
+        provider.load_from_data(STYLE.as_bytes());
+        obj.style_context().add_provider(&provider, gtk4::STYLE_PROVIDER_PRIORITY_APPLICATION);
+
+        self.menu_button.set(menu_button);
+        self.popover.set(popover);
+    }
+}
+
+impl WidgetImpl for AppletInner {}
+impl WindowImpl for AppletInner {}
+
+glib::wrapper! {
+    pub struct Applet(ObjectSubclass<AppletInner>)
+        @extends gtk4::Widget, gtk4::Window;
+}
+
+impl Default for Applet {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl Applet {
+    pub fn new() -> Self {
+        glib::Object::new(&[]).unwrap()
+    }
+
+    fn inner(&self) -> &AppletInner {
+        AppletInner::from_instance(self)
+    }
+
+    pub fn set_button_child(&self, child: Option<&impl IsA<gtk4::Widget>>) {
+        self.inner().menu_button.set_child(child);
+    }
+
+    pub fn set_button_icon_name(&self, name: &str) {
+        self.inner().menu_button.set_icon_name(name);
+    }
+
+    pub fn set_button_label(&self, label: &str) {
+        self.inner().menu_button.set_label(label);
+    }
+
+    pub fn set_popover_child(&self, child: Option<&impl IsA<gtk4::Widget>>) {
+        self.inner().popover.set_child(child);
+    }
+}