[2/n] [update-engine] add ( to the beginning of step indexes in the line displayer

update-engine/src/display/line_display_shared.rs

@@ -16,6 +16,7 @@ use owo_colors::OwoColorize;
 use swrite::{swrite, SWrite as _};
 
 use crate::{
+    display::StepIndexDisplay,
     events::{
         ProgressCounter, ProgressEvent, ProgressEventKind, StepEvent,
         StepEventKind, StepInfo, StepOutcome,
@@ -716,17 +717,16 @@ impl LineDisplayFormatter {
     ) {
         ld_step_info.nest_data.add_prefix(line);
 
-        // Print out "<step index>/<total steps>)". Leave space such that we
-        // print out e.g. "1/8)" and " 3/14)".
-        // Add 1 to the index to make it 1-based.
-        let step_index = ld_step_info.step_info.index + 1;
-        let step_index_width = ld_step_info.total_steps.to_string().len();
+        // Print out "(<current>/<total>)" in a padded way, so that successive
+        // steps are vertically aligned.
         swrite!(
             line,
-            "{:width$}/{:width$}) ",
-            step_index,
-            ld_step_info.total_steps,
-            width = step_index_width
+            "({}) ",
+            StepIndexDisplay::new(
+                ld_step_info.step_info.index,
+                ld_step_info.total_steps
+            )
+            .padded(true),
         );
 
         swrite!(

update-engine/src/display/mod.rs

@@ -11,11 +11,14 @@
 //! * [`LineDisplay`]: a line-oriented display suitable for the command line.
 //! * [`GroupDisplay`]: manages state and shows the results of several
 //!   [`LineDisplay`]s at once.
+//! * Some utility displayers which can be used to build custom displayers.
 
 mod group_display;
 mod line_display;
 mod line_display_shared;
+mod utils;
 
 pub use group_display::GroupDisplay;
 pub use line_display::{LineDisplay, LineDisplayStyles};
 use line_display_shared::*;
+pub use utils::*;

update-engine/src/display/utils.rs

@@ -0,0 +1,58 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+//! Utility displayers.
+
+use std::fmt;
+
+/// Given an index and a count of total steps, displays `{current}/{total}`.
+///
+/// Here:
+///
+/// * `current` is `index + 1`.
+/// * If `padded` is `true`, `current` is right-aligned and padded with spaces
+///   to the width of `total`.
+///
+/// # Examples
+///
+/// ```
+/// use update_engine::display::StepIndexDisplay;
+///
+/// let display = StepIndexDisplay::new(0, 8);
+/// assert_eq!(display.to_string(), "1/8");
+/// let display = StepIndexDisplay::new(82, 230);
+/// assert_eq!(display.to_string(), "83/230");
+/// let display = display.padded(true);
+/// assert_eq!(display.to_string(), " 83/230");
+/// ```
+#[derive(Debug)]
+pub struct StepIndexDisplay {
+    index: usize,
+    total: usize,
+    padded: bool,
+}
+
+impl StepIndexDisplay {
+    /// Create a new `StepIndexDisplay`.
+    ///
+    /// The index is 0-based (i.e. 1 is added to it when it is displayed).
+    pub fn new(index: usize, total: usize) -> Self {
+        Self { index, total, padded: false }
+    }
+
+    pub fn padded(self, padded: bool) -> Self {
+        Self { padded, ..self }
+    }
+}
+
+impl fmt::Display for StepIndexDisplay {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        if self.padded {
+            let width = self.total.to_string().len();
+            write!(f, "{:>width$}/{}", self.index + 1, self.total)
+        } else {
+            write!(f, "{}/{}", self.index + 1, self.total)
+        }
+    }
+}

wicket/src/ui/panes/update.rs

@@ -29,6 +29,7 @@ use ratatui::widgets::{
 use ratatui::Frame;
 use slog::{info, o, Logger};
 use tui_tree_widget::{Tree, TreeItem, TreeState};
+use update_engine::display::StepIndexDisplay;
 use update_engine::{
     AbortReason, CompletionReason, ExecutionStatus, FailureReason, StepKey,
     TerminalKind, WillNotBeRunReason,
@@ -1984,9 +1985,11 @@ impl ComponentUpdateListState {
                     ));
                     status_text.push(Span::styled(
                         format!(
-                            " (step {}/{})",
-                            step_key.index + 1,
-                            summary.total_steps,
+                            " (step {})",
+                            StepIndexDisplay::new(
+                                step_key.index,
+                                summary.total_steps,
+                            )
                         ),
                         style::plain_text(),
                     ));
@@ -2015,9 +2018,11 @@ impl ComponentUpdateListState {
                             ));
                             status_text.push(Span::styled(
                                 format!(
-                                    " at step {}/{}",
-                                    info.step_key.index + 1,
-                                    summary.total_steps,
+                                    " at step {}",
+                                    StepIndexDisplay::new(
+                                        info.step_key.index,
+                                        summary.total_steps,
+                                    )
                                 ),
                                 style::plain_text(),
                             ));
@@ -2033,9 +2038,11 @@ impl ComponentUpdateListState {
                             ));
                             status_text.push(Span::styled(
                                 format!(
-                                    " at step {}/{}",
-                                    info.step_key.index + 1,
-                                    summary.total_steps,
+                                    " at step {}",
+                                    StepIndexDisplay::new(
+                                        info.step_key.index,
+                                        summary.total_steps,
+                                    )
                                 ),
                                 style::plain_text(),
                             ));