fix(tab-bar): prevent active tab from being hidden (#703)

3 files changed, 82 insertions, 96 deletions

diff --git a/default-plugins/tab-bar/src/line.rs b/default-plugins/tab-bar/src/line.rs
index 4cdc02c44..be5623ff9 100644
--- a/default-plugins/tab-bar/src/line.rs
+++ b/default-plugins/tab-bar/src/line.rs
@@ -8,39 +8,82 @@ fn get_current_title_len(current_title: &[LinePart]) -> usize {
     current_title.iter().map(|p| p.len).sum()
 }
 
+// move elements from before_active and after_active into tabs_to_render while they fit in cols
+// adds collapsed_tabs to the left and right if there's left over tabs that don't fit
 fn populate_tabs_in_tab_line(
     tabs_before_active: &mut Vec<LinePart>,
     tabs_after_active: &mut Vec<LinePart>,
     tabs_to_render: &mut Vec<LinePart>,
     cols: usize,
+    palette: Palette,
+    capabilities: PluginCapabilities,
 ) {
-    let mut take_next_tab_from_tabs_after = true;
+    let mut middle_size = get_current_title_len(tabs_to_render);
+
+    let mut total_left = 0;
+    let mut total_right = 0;
     loop {
-        if tabs_before_active.is_empty() && tabs_after_active.is_empty() {
-            break;
-        }
-        let current_title_len = get_current_title_len(tabs_to_render);
-        if current_title_len >= cols {
+        let left_count = tabs_before_active.len();
+        let right_count = tabs_after_active.len();
+        let collapsed_left = left_more_message(left_count, palette, tab_separator(capabilities));
+        let collapsed_right = right_more_message(right_count, palette, tab_separator(capabilities));
+
+        let total_size = collapsed_left.len + middle_size + collapsed_right.len;
+
+        if total_size > cols {
+            // break and dont add collapsed tabs to tabs_to_render, they will not fit
             break;
         }
-        let should_take_next_tab = take_next_tab_from_tabs_after;
-        let can_take_next_tab = !tabs_after_active.is_empty()
-            && tabs_after_active.get(0).unwrap().len + current_title_len <= cols;
-        let can_take_previous_tab = !tabs_before_active.is_empty()
-            && tabs_before_active.last().unwrap().len + current_title_len <= cols;
-        if should_take_next_tab && can_take_next_tab {
-            let next_tab = tabs_after_active.remove(0);
-            tabs_to_render.push(next_tab);
-            take_next_tab_from_tabs_after = false;
-        } else if can_take_previous_tab {
-            let previous_tab = tabs_before_active.pop().unwrap();
-            tabs_to_render.insert(0, previous_tab);
-            take_next_tab_from_tabs_after = true;
-        } else if can_take_next_tab {
-            let next_tab = tabs_after_active.remove(0);
-            tabs_to_render.push(next_tab);
-            take_next_tab_from_tabs_after = false;
+
+        let left = if let Some(tab) = tabs_before_active.last() {
+            tab.len
+        } else {
+            usize::MAX
+        };
+
+        let right = if let Some(tab) = tabs_after_active.first() {
+            tab.len
         } else {
+            usize::MAX
+        };
+
+        // total size is shortened if the next tab to be added is the last one, as that will remove the collapsed tab
+        let size_by_adding_left =
+            left.saturating_add(total_size)
+                .saturating_sub(if left_count == 1 {
+                    collapsed_left.len
+                } else {
+                    0
+                });
+        let size_by_adding_right =
+            right
+                .saturating_add(total_size)
+                .saturating_sub(if right_count == 1 {
+                    collapsed_right.len
+                } else {
+                    0
+                });
+
+        let left_fits = size_by_adding_left <= cols;
+        let right_fits = size_by_adding_right <= cols;
+        // active tab is kept in the middle by adding to the side that
+        // has less width, or if the tab on the other side doesn' fit
+        if (total_left <= total_right || !right_fits) && left_fits {
+            // add left tab
+            let tab = tabs_before_active.pop().unwrap();
+            middle_size += tab.len;
+            total_left += tab.len;
+            tabs_to_render.insert(0, tab);
+        } else if right_fits {
+            // add right tab
+            let tab = tabs_after_active.remove(0);
+            middle_size += tab.len;
+            total_right += tab.len;
+            tabs_to_render.push(tab);
+        } else {
+            // there's either no space to add more tabs or no more tabs to add, so we're done
+            tabs_to_render.insert(0, collapsed_left);
+            tabs_to_render.push(collapsed_right);
             break;
         }
     }
@@ -56,7 +99,8 @@ fn left_more_message(tab_count_to_the_left: usize, palette: Palette, separator:
         " ← +many ".to_string()
     };
     // 238
-    let more_text_len = more_text.chars().count() + 2; // 2 for the arrows
+    // chars length plus separator length on both sides
+    let more_text_len = more_text.chars().count() + 2 * separator.chars().count();
     let left_separator = style!(palette.cyan, palette.orange).paint(separator);
     let more_styled_text = style!(palette.black, palette.orange)
         .bold()
@@ -85,7 +129,8 @@ fn right_more_message(
     } else {
         " +many → ".to_string()
     };
-    let more_text_len = more_text.chars().count() + 1; // 2 for the arrow
+    // chars length plus separator length on both sides
+    let more_text_len = more_text.chars().count() + 2 * separator.chars().count();
     let left_separator = style!(palette.cyan, palette.orange).paint(separator);
     let more_styled_text = style!(palette.black, palette.orange)
         .bold()
@@ -101,48 +146,6 @@ fn right_more_message(
     }
 }
 
-fn add_previous_tabs_msg(
-    tabs_before_active: &mut Vec<LinePart>,
-    tabs_to_render: &mut Vec<LinePart>,
-    title_bar: &mut Vec<LinePart>,
-    cols: usize,
-    palette: Palette,
-    separator: &str,
-) {
-    while get_current_title_len(tabs_to_render)
-        + left_more_message(tabs_before_active.len(), palette, separator).len
-        >= cols
-        && !tabs_to_render.is_empty()
-    {
-        tabs_before_active.push(tabs_to_render.remove(0));
-    }
-
-    let left_more_message = left_more_message(tabs_before_active.len(), palette, separator);
-    if left_more_message.len <= cols {
-        title_bar.push(left_more_message);
-    }
-}
-
-fn add_next_tabs_msg(
-    tabs_after_active: &mut Vec<LinePart>,
-    title_bar: &mut Vec<LinePart>,
-    cols: usize,
-    palette: Palette,
-    separator: &str,
-) {
-    while get_current_title_len(title_bar)
-        + right_more_message(tabs_after_active.len(), palette, separator).len
-        >= cols
-        && !title_bar.is_empty()
-    {
-        tabs_after_active.insert(0, title_bar.pop().unwrap());
-    }
-    let right_more_message = right_more_message(tabs_after_active.len(), palette, separator);
-    if right_more_message.len < cols {
-        title_bar.push(right_more_message);
-    }
-}
-
 fn tab_line_prefix(session_name: Option<&str>, palette: Palette, cols: usize) -> Vec<LinePart> {
     let prefix_text = " Zellij ".to_string();
 
@@ -184,7 +187,6 @@ pub fn tab_line(
     palette: Palette,
     capabilities: PluginCapabilities,
 ) -> Vec<LinePart> {
-    let mut tabs_to_render = Vec::new();
     let mut tabs_after_active = all_tabs.split_off(active_tab_index);
     let mut tabs_before_active = all_tabs;
     let active_tab = if !tabs_after_active.is_empty() {
@@ -194,38 +196,22 @@ pub fn tab_line(
     };
     let mut prefix = tab_line_prefix(session_name, palette, cols);
     let prefix_len = get_current_title_len(&prefix);
-    if prefix_len + active_tab.len <= cols {
-        tabs_to_render.push(active_tab);
+
+    // if active tab alone won't fit in cols, don't draw any tabs
+    if prefix_len + active_tab.len > cols {
+        return prefix;
     }
 
+    let mut tabs_to_render = vec![active_tab];
+
     populate_tabs_in_tab_line(
         &mut tabs_before_active,
         &mut tabs_after_active,
         &mut tabs_to_render,
         cols.saturating_sub(prefix_len),
+        palette,
+        capabilities,
     );
-
-    let mut tab_line: Vec<LinePart> = vec![];
-    if !tabs_before_active.is_empty() {
-        add_previous_tabs_msg(
-            &mut tabs_before_active,
-            &mut tabs_to_render,
-            &mut tab_line,
-            cols.saturating_sub(prefix_len),
-            palette,
-            tab_separator(capabilities),
-        );
-    }
-    tab_line.append(&mut tabs_to_render);
-    if !tabs_after_active.is_empty() {
-        add_next_tabs_msg(
-            &mut tabs_after_active,
-            &mut tab_line,
-            cols.saturating_sub(prefix_len),
-            palette,
-            tab_separator(capabilities),
-        );
-    }
-    prefix.append(&mut tab_line);
+    prefix.append(&mut tabs_to_render);
     prefix
 }
diff --git a/default-plugins/tab-bar/src/main.rs b/default-plugins/tab-bar/src/main.rs
index d4111cfae..850781261 100644
--- a/default-plugins/tab-bar/src/main.rs
+++ b/default-plugins/tab-bar/src/main.rs
@@ -65,7 +65,7 @@ impl ZellijPlugin for State {
             self.mode_info.session_name.as_deref(),
             all_tabs,
             active_tab_index,
-            cols,
+            cols.saturating_sub(1),
             self.mode_info.palette,
             self.mode_info.capabilities,
         );
diff --git a/default-plugins/tab-bar/src/tab.rs b/default-plugins/tab-bar/src/tab.rs
index 9edfba13f..dfa5ab776 100644
--- a/default-plugins/tab-bar/src/tab.rs
+++ b/default-plugins/tab-bar/src/tab.rs
@@ -5,7 +5,7 @@ use zellij_tile_utils::style;
 
 pub fn active_tab(text: String, palette: Palette, separator: &str) -> LinePart {
     let left_separator = style!(palette.cyan, palette.green).paint(separator);
-    let tab_text_len = text.chars().count() + 4; // 2 for left and right separators, 2 for the text padding
+    let tab_text_len = text.chars().count() + 2 + separator.chars().count() * 2; // 2 for left and right separators, 2 for the text padding
     let tab_styled_text = style!(palette.black, palette.green)
         .bold()
         .paint(format!(" {} ", text));
@@ -22,7 +22,7 @@ pub fn active_tab(text: String, palette: Palette, separator: &str) -> LinePart {
 
 pub fn non_active_tab(text: String, palette: Palette, separator: &str) -> LinePart {
     let left_separator = style!(palette.cyan, palette.fg).paint(separator);
-    let tab_text_len = text.chars().count() + 4; // 2 for left and right separators, 2 for the padding
+    let tab_text_len = text.chars().count() + 2 + separator.chars().count() * 2; // 2 for left and right separators, 2 for the text padding
     let tab_styled_text = style!(palette.black, palette.fg)
         .bold()
         .paint(format!(" {} ", text));