Add centerbox widget

crates/eww/src/app.rs

@@ -1,4 +1,7 @@
-use crate::{EwwPaths, config, daemon_response::DaemonResponseSender, display_backend, error_handling_ctx, eww_state, script_var_handler::*};
+use crate::{
+    config, daemon_response::DaemonResponseSender, display_backend, error_handling_ctx, eww_state, script_var_handler::*,
+    EwwPaths,
+};
 use anyhow::*;
 use debug_stub_derive::*;
 use eww_shared_util::VarName;

crates/eww/src/error_handling_ctx.rs

@@ -35,10 +35,8 @@ pub fn format_error(err: &anyhow::Error) -> String {
     for err in err.chain() {
         format!("chain: {}", err);
     }
-    match err.downcast_ref::<AstError>() {
-        Some(err) => stringify_diagnostic(err.to_diagnostic()).unwrap_or_else(|_| format!("{:?}", err)),
-        None => format!("{:?}", err),
-    }
+    let diag = anyhow_err_to_diagnostic(err);
+    stringify_diagnostic(diag).unwrap_or_else(|_| format!("{}", err))
 }
 
 pub fn anyhow_err_to_diagnostic(err: &anyhow::Error) -> Diagnostic<usize> {

crates/eww/src/widgets/mod.rs

@@ -70,17 +70,19 @@ fn build_builtin_gtk_widget(
 
     if let Some(gtk_widget) = gtk_widget.dynamic_cast_ref::<gtk::Container>() {
         resolve_container_attrs(&mut bargs, gtk_widget);
-        for child in &widget.children {
-            let child_widget = child.render(bargs.eww_state, window_name, widget_definitions).with_context(|| {
-                format!(
-                    "{}error while building child '{:#?}' of '{}'",
-                    format!("{} | ", widget.span),
-                    &child,
-                    &gtk_widget.get_widget_name()
-                )
-            })?;
-            gtk_widget.add(&child_widget);
-            child_widget.show();
+        if gtk_widget.get_children().is_empty() {
+            for child in &widget.children {
+                let child_widget = child.render(bargs.eww_state, window_name, widget_definitions).with_context(|| {
+                    format!(
+                        "{}error while building child '{:#?}' of '{}'",
+                        format!("{} | ", widget.span),
+                        &child,
+                        &gtk_widget.get_widget_name()
+                    )
+                })?;
+                gtk_widget.add(&child_widget);
+                child_widget.show();
+            }
         }
     }
 

crates/eww/src/widgets/widget_definitions.rs

@@ -1,14 +1,18 @@
 #![allow(clippy::option_map_unit_fn)]
 use super::{run_command, BuilderArgs};
-use crate::{enum_parse, error_handling_ctx, eww_state, resolve_block, util::list_difference, widgets::widget_node};
+use crate::{
+    enum_parse, error::DiagError, error_handling_ctx, eww_state, resolve_block, util::list_difference, widgets::widget_node,
+};
 use anyhow::*;
 use gdk::WindowExt;
 use glib;
 use gtk::{self, prelude::*, ImageExt};
+use itertools::Itertools;
 use std::{cell::RefCell, collections::HashMap, rc::Rc, time::Duration};
 use yuck::{
     config::validate::ValidationError,
     error::{AstError, AstResult, AstResultExt},
+    gen_diagnostic,
     parser::from_ast::FromAst,
 };
 
@@ -20,6 +24,7 @@ use yuck::{
 pub(super) fn widget_to_gtk_widget(bargs: &mut BuilderArgs) -> Result<gtk::Widget> {
     let gtk_widget = match bargs.widget.name.as_str() {
         "box" => build_gtk_box(bargs)?.upcast(),
+        "centerbox" => build_center_box(bargs)?.upcast(),
         "scale" => build_gtk_scale(bargs)?.upcast(),
         "progress" => build_gtk_progress(bargs)?.upcast(),
         "image" => build_gtk_image(bargs)?.upcast(),
@@ -494,6 +499,39 @@ fn build_gtk_box(bargs: &mut BuilderArgs) -> Result<gtk::Box> {
     Ok(gtk_widget)
 }
 
+/// @widget centerbox extends container
+/// @desc a box that must contain exactly three children, which will be layed out at the start, center and end of the container.
+fn build_center_box(bargs: &mut BuilderArgs) -> Result<gtk::Box> {
+    let gtk_widget = gtk::Box::new(gtk::Orientation::Horizontal, 0);
+    resolve_block!(bargs, gtk_widget, {
+        // @prop orientation - orientation of the centerbox. possible values: $orientation
+        prop(orientation: as_string) { gtk_widget.set_orientation(parse_orientation(&orientation)?) },
+    });
+
+    if bargs.widget.children.len() < 3 {
+        Err(DiagError::new(gen_diagnostic!("centerbox must contain exactly 3 elements", bargs.widget.span)))?
+    } else if bargs.widget.children.len() > 3 {
+        let (_, additional_children) = bargs.widget.children.split_at(3);
+        // we know that there is more than three children, so unwrapping on first and left here is fine.
+        let first_span = additional_children.first().unwrap().span();
+        let last_span = additional_children.last().unwrap().span();
+        Err(DiagError::new(gen_diagnostic!("centerbox must contain exactly 3 elements, but got more", first_span.to(last_span))))?
+    }
+
+    let mut children =
+        bargs.widget.children.iter().map(|child| child.render(bargs.eww_state, bargs.window_name, bargs.widget_definitions));
+    // we know that we have exactly three children here, so we can unwrap here.
+    let (first, center, end) = children.next_tuple().unwrap();
+    let (first, center, end) = (first?, center?, end?);
+    gtk_widget.pack_start(&first, true, true, 0);
+    gtk_widget.set_center_widget(Some(&center));
+    gtk_widget.pack_end(&end, true, true, 0);
+    first.show();
+    center.show();
+    end.show();
+    Ok(gtk_widget)
+}
+
 /// @widget label
 /// @desc A text widget giving you more control over how the text is displayed
 fn build_gtk_label(bargs: &mut BuilderArgs) -> Result<gtk::Label> {

crates/eww/src/widgets/widget_node.rs

@@ -9,7 +9,7 @@ use yuck::{
     error::{AstError, AstResult},
 };
 
-pub trait WidgetNode: std::fmt::Debug + dyn_clone::DynClone + Send + Sync {
+pub trait WidgetNode: Spanned + std::fmt::Debug + dyn_clone::DynClone + Send + Sync {
     fn get_name(&self) -> &str;
 
     /// Generate a [gtk::Widget] from a [element::WidgetUse].