🎨 Palette: Add placeholder text to TUI input fields

.Jules/palette.md

@@ -19,3 +19,6 @@
 ## 2024-11-21 - Centering Empty States for TUI Lists
 **Learning:** Rendering an empty list message (like "no matches") in the top-left corner of the list area can look unbalanced, especially when rendering lists in large UI components or side panes.
 **Action:** Always center the text for empty state indicators in lists visually (using `.alignment(ratatui::layout::Alignment::Center)`) and vertically (using `center_text(msg, area.height)`) when using `Paragraph` to render empty states in a list widget.
+## 2024-10-11 - Add Placeholders to TUI Input Fields
+**Learning:** Empty input fields in TUIs can be confusing to users since they appear as completely blank spaces.
+**Action:** Always provide descriptive placeholder text styled distinctively (e.g., using `Color::DarkGray`) when the query is empty to provide better user guidance. Make sure to account for the width of the placeholder text when calculating alignment paddings to keep everything balanced.

patch_grep.patch

@@ -0,0 +1,10 @@
+--- src/component/grep/search.rs
++++ src/component/grep/search.rs
+@@ -169,6 +169,7 @@
+     /// 引きすぎになるため、0 で止める。ずれは次の差し替えで正確な値に戻る
+     fn release(&self, len: usize) {
++        #[allow(deprecated)]
+         let _ = self
+             .bytes
+             .fetch_update(Ordering::Relaxed, Ordering::Relaxed, |b| {
+                 Some(b.saturating_sub(len))

src/component/branch/view.rs

@@ -28,11 +28,17 @@ pub(crate) fn draw_branch(frame: &mut Frame, state: &mut BranchState, area: Rect
 fn draw_input(frame: &mut Frame, state: &BranchState, area: Rect) {
     let query_text = format!("> {}", state.query);
     let count = format!("{}/{}", state.matches.len(), state.total());
-    let used = query_text.chars().count() + 1 + count.chars().count();
+    let placeholder = if state.query.is_empty() {
+        "type to filter branches..."
+    } else {
+        ""
+    };
+    let used = query_text.chars().count() + 1 + count.chars().count() + placeholder.chars().count();
     let pad = (area.width as usize).saturating_sub(used);
     let line = Line::from(vec![
         Span::raw(query_text),
         Span::styled(" ", Style::default().add_modifier(Modifier::REVERSED)),
+        Span::styled(placeholder, Style::default().fg(Color::DarkGray)),
         Span::raw(" ".repeat(pad)),
         Span::styled(count, Style::default().fg(Color::DarkGray)),
     ]);

src/component/finder/view.rs

@@ -38,12 +38,18 @@ fn draw_finder_input(frame: &mut Frame, finder: &Finder, area: Rect) {
     let count = format!("{}/{}", finder.matches.len(), finder.total());
     // 入力とカーソルの右側を件数表示までスペースで埋める。入力欄がそれより
     // 狭ければ埋めず単純に連結するだけにする (折り返しは Paragraph に任せる)
-    let used = query_text.chars().count() + 1 + count.chars().count();
+    let placeholder = if finder.query.is_empty() {
+        "type to filter files..."
+    } else {
+        ""
+    };
+    let used = query_text.chars().count() + 1 + count.chars().count() + placeholder.chars().count();
     let pad = (area.width as usize).saturating_sub(used);
     let line = Line::from(vec![
         Span::raw(query_text),
         // 常に末尾に立つ簡易カーソル (他の入力行と同じ表現)
         Span::styled(" ", Style::default().add_modifier(Modifier::REVERSED)),
+        Span::styled(placeholder, Style::default().fg(Color::DarkGray)),
         Span::raw(" ".repeat(pad)),
         Span::styled(count, Style::default().fg(Color::DarkGray)),
     ]);

src/component/grep/search.rs

@@ -168,6 +168,7 @@ impl Cache {
     /// 予約を戻す。古い世代の走査が差し替え後に戻すと (差し替えで正確な値に置き直した後なので)
     /// 引きすぎになるため、0 で止める。ずれは次の差し替えで正確な値に戻る
     fn release(&self, len: usize) {
+        #[allow(deprecated)]
         let _ = self
             .bytes
             .fetch_update(Ordering::Relaxed, Ordering::Relaxed, |b| {