adding default workspaces hook

src/core/hooks.rs

@@ -56,7 +56,7 @@
 //!
 //! ### Layout Hooks
 //!
-//! Finally we have [`LayoutHook`]s which operate a little differently, in that they have
+//! Next we have [`LayoutHook`]s which operate a little differently, in that they have
 //! two methods to implement. Layout hooks are run _around_ whatever [Layout][1] is active
 //! for the focused workspace, allowing you to modify the screen dimensions available for the
 //! layout algorithm before it runs and editing the list of window positions it generates

src/extensions/hooks/default_workspaces.rs

@@ -0,0 +1,58 @@
+//! Configure workspaces to auto-spawn a set of windows if they are empty when they gain focus
+use crate::{
+    core::{hooks::StateHook, State},
+    util::spawn,
+    x::XConn,
+    Result,
+};
+
+/// Specify a workspace by `tag` and use a named layout to spawn a set of default programs
+/// on it if it gains focus while currently empty.
+///
+/// The programs are spawned in the order they are specified in [DefaultWorkspace::boxed] meaning
+/// that the final program `progs` will have focus.
+#[derive(Debug, Clone)]
+pub struct DefaultWorkspace {
+    tag: String,
+    layout_name: String,
+    progs: Vec<String>,
+}
+
+impl DefaultWorkspace {
+    /// Create a new boxed `DefaultWorkspace` that can be added to your Config as a refresh hook.
+    pub fn boxed<X>(
+        tag: impl Into<String>,
+        layout_name: impl Into<String>,
+        progs: Vec<impl Into<String>>,
+    ) -> Box<dyn StateHook<X>>
+    where
+        X: XConn,
+    {
+        Box::new(Self {
+            tag: tag.into(),
+            layout_name: layout_name.into(),
+            progs: progs.into_iter().map(|p| p.into()).collect(),
+        })
+    }
+}
+
+impl<X> StateHook<X> for DefaultWorkspace
+where
+    X: XConn,
+{
+    fn call(&mut self, state: &mut State<X>, _x: &X) -> Result<()> {
+        let on_screen_and_empty = matches!(state.diff.after.visible.iter().find(|s| s.tag == self.tag), Some(s) if s.clients.is_empty());
+
+        if on_screen_and_empty
+            && !state
+                .diff
+                .previous_visible_tags()
+                .contains(&self.tag.as_str())
+        {
+            state.client_set.set_layout_by_name(&self.layout_name);
+            self.progs.iter().try_for_each(spawn)?;
+        }
+
+        Ok(())
+    }
+}

src/extensions/hooks/mod.rs

@@ -1,4 +1,5 @@
 //! Hook implementations and helpers for adding to your Penrose window manager
+pub mod default_workspaces;
 pub mod ewmh;
 pub mod manage;
 pub mod named_scratchpads;

src/pure/stack_set.rs

@@ -553,6 +553,17 @@ where
         self.screens.focus.workspace.previous_layout()
     }
 
+    /// Attempt to set the current [Layout][crate::core::layout::Layout] by name.
+    ///
+    /// This is a no-op if the requested layout is already active or if no layout with the given name
+    /// is available for the active workspace.
+    pub fn set_layout_by_name(&mut self, layout: impl AsRef<str>) {
+        self.screens
+            .focus
+            .workspace
+            .set_layout_by_name(layout.as_ref())
+    }
+
     /// Move focus to the next [Screen]
     pub fn next_screen(&mut self) {
         if self.screens.len() == 1 {