feat: add configurable line_height setting

crates/config_core/src/constants.rs

@@ -11,6 +11,15 @@ pub(crate) const DEFAULT_TMUX_BINARY: &str = "tmux";
 pub(crate) const DEFAULT_TMUX_PERSISTENCE: bool = true;
 pub(crate) const DEFAULT_TMUX_SHOW_ACTIVE_PANE_BORDER: bool = false;
 pub(crate) const DEFAULT_MOUSE_SCROLL_MULTIPLIER: f32 = 3.0;
+/// Unitless multiplier applied to the font's natural cell height to produce the
+/// terminal row height. `1.0` means no extra vertical space; `2.0` doubles it.
+pub const DEFAULT_LINE_HEIGHT: f32 = 1.4;
+/// Lowest accepted line-height multiplier. Values below this cause rows to
+/// visually overlap.
+pub const MIN_LINE_HEIGHT: f32 = 0.8;
+/// Highest accepted line-height multiplier. Values above this make the grid
+/// unusably sparse.
+pub const MAX_LINE_HEIGHT: f32 = 2.5;
 pub(crate) const DEFAULT_SCROLLBACK_HISTORY: usize = 2000;
 pub(crate) const MAX_SCROLLBACK_HISTORY: usize = 100_000;
 pub(crate) const DEFAULT_INACTIVE_TAB_SCROLLBACK: Option<usize> = None;

crates/config_core/src/default_config.txt

@@ -73,6 +73,8 @@ window_height = 820
 font_family = JetBrains Mono
 # Terminal font size in pixels
 font_size = 14
+# Terminal line height multiplier (0.8 to 2.5)
+line_height = 1.4
 # Shape of the terminal cursor
 cursor_style = block
 # Enable blinking cursor animation

crates/config_core/src/lib.rs

@@ -9,7 +9,10 @@ mod schema;
 mod types;
 
 pub use color_keys::{ColorEntryError, apply_color_entry, canonical_color_key};
-pub use constants::{SHELL_DECIDE_THEME_ID, VALID_ROOT_KEYS, VALID_SECTIONS};
+pub use constants::{
+    DEFAULT_LINE_HEIGHT, MAX_LINE_HEIGHT, MIN_LINE_HEIGHT, SHELL_DECIDE_THEME_ID, VALID_ROOT_KEYS,
+    VALID_SECTIONS,
+};
 pub use diagnostics::{ConfigDiagnostic, ConfigDiagnosticKind, ConfigParseReport};
 pub use document::{
     ColorSettingUpdate, apply_color_updates, remove_raw_root_key, remove_root_setting,
@@ -32,5 +35,9 @@ pub use types::{
     TerminalScrollbarStyle, TerminalScrollbarVisibility, ThemeId, WorkingDirFallback,
 };
 
+pub fn format_line_height(value: f32) -> String {
+    format!("{value:.2}")
+}
+
 #[cfg(test)]
 mod parser_tests;

crates/config_core/src/parser.rs

@@ -2,8 +2,8 @@ use std::collections::{BTreeMap, HashMap};
 
 use crate::color_keys::{ColorEntryError, apply_color_entry};
 use crate::constants::{
-    MAX_MOUSE_SCROLL_MULTIPLIER, MAX_PANE_FOCUS_STRENGTH, MAX_SCROLLBACK_HISTORY,
-    MIN_MOUSE_SCROLL_MULTIPLIER, SHELL_DECIDE_THEME_ID, VALID_SECTIONS,
+    MAX_LINE_HEIGHT, MAX_MOUSE_SCROLL_MULTIPLIER, MAX_PANE_FOCUS_STRENGTH, MAX_SCROLLBACK_HISTORY,
+    MIN_LINE_HEIGHT, MIN_MOUSE_SCROLL_MULTIPLIER, SHELL_DECIDE_THEME_ID, VALID_SECTIONS,
 };
 use crate::diagnostics::{ConfigDiagnostic, ConfigDiagnosticKind, ConfigParseReport};
 use crate::schema::{RootSettingId, root_setting_from_key, root_setting_spec};
@@ -519,6 +519,29 @@ impl AppConfig {
                         config.font_size = parsed;
                     }
                 }
+                RootSettingId::LineHeight => {
+                    if let Some(parsed) = parse_f32_field(
+                        &mut diagnostics,
+                        line_number,
+                        key,
+                        value,
+                        "a finite number between 0.8 and 2.5",
+                    ) {
+                        if parsed.is_finite()
+                            && (MIN_LINE_HEIGHT..=MAX_LINE_HEIGHT).contains(&parsed)
+                        {
+                            config.line_height = parsed;
+                        } else {
+                            push_invalid_value(
+                                &mut diagnostics,
+                                line_number,
+                                key,
+                                value,
+                                "a finite number between 0.8 and 2.5",
+                            );
+                        }
+                    }
+                }
                 RootSettingId::CursorStyle => {
                     if let Some(parsed) = CursorStyle::from_str(value) {
                         config.cursor_style = parsed;

crates/config_core/src/parser_tests.rs

@@ -1,8 +1,8 @@
 use crate::{
-    AiProvider, AppConfig, ConfigDiagnosticKind, ConfigParseReport, CursorStyle, PaneFocusEffect,
-    Rgb8, RootSettingId, RootSettingValueKind, TabCloseVisibility, TabTitleMode, TabTitleSource,
-    TabWidthMode, TerminalScrollbarStyle, TerminalScrollbarVisibility, WorkingDirFallback,
-    root_setting_specs,
+    AiProvider, AppConfig, ConfigDiagnosticKind, ConfigParseReport, CursorStyle,
+    DEFAULT_LINE_HEIGHT, PaneFocusEffect, Rgb8, RootSettingId, RootSettingValueKind,
+    TabCloseVisibility, TabTitleMode, TabTitleSource, TabWidthMode, TerminalScrollbarStyle,
+    TerminalScrollbarVisibility, WorkingDirFallback, root_setting_specs,
 };
 
 fn parse(input: &str) -> AppConfig {
@@ -21,6 +21,7 @@ fn defaults_enable_tmux_persistence_and_raise_pane_focus_strength() {
     assert!(!defaults.background_opacity_cells);
     assert!(!defaults.chrome_contrast);
     assert!((defaults.pane_focus_strength - 0.6).abs() < f32::EPSILON);
+    assert!((defaults.line_height - DEFAULT_LINE_HEIGHT).abs() < f32::EPSILON);
 }
 
 #[test]
@@ -390,6 +391,26 @@ fn numeric_keys_parse_table_driven() {
         assert_eq!(parsed, fallback);
     }
 
+    assert_eq!(parse("line_height = 0.8\n").line_height, 0.8);
+    assert_eq!(parse("line_height = 1.25\n").line_height, 1.25);
+    assert_eq!(parse("line_height = 2.5\n").line_height, 2.5);
+    assert_eq!(
+        parse("line_height = 0.79\n").line_height,
+        defaults.line_height
+    );
+    assert_eq!(
+        parse("line_height = 2.51\n").line_height,
+        defaults.line_height
+    );
+    assert_eq!(
+        parse("line_height = inf\n").line_height,
+        defaults.line_height
+    );
+    assert_eq!(
+        parse("line_height = NaN\n").line_height,
+        defaults.line_height
+    );
+
     let non_negative_float_cases = [("padding_x", 2.0), ("padding_y", 4.0)];
     for (key, expected) in non_negative_float_cases {
         let valid = parse(&format!("{} = {}\n", key, expected));

crates/config_core/src/schema.rs

@@ -333,6 +333,7 @@ define_root_settings! {
     (WindowHeight, "window_height", [], Advanced, "WINDOW", "Window Height", "Default startup window height in pixels", ["window", "height", "startup", "size"], RootSettingValueKind::Numeric, false),
     (FontFamily, "font_family", [], Appearance, "FONT", "Font Family", "Font family used in terminal UI", ["font", "typeface", "text"], RootSettingValueKind::Special, false),
     (FontSize, "font_size", [], Appearance, "FONT", "Font Size", "Terminal font size in pixels", ["font", "size", "text"], RootSettingValueKind::Numeric, false),
+    (LineHeight, "line_height", [], Appearance, "FONT", "Line Height", "Terminal line height multiplier (0.8 to 2.5)", ["font", "line", "height", "spacing", "rows"], RootSettingValueKind::Numeric, false),
     (CursorStyle, "cursor_style", [], Terminal, "CURSOR", "Cursor Style", "Shape of the terminal cursor", ["cursor", "shape", "block", "line"], RootSettingValueKind::Enum, false),
     (CursorBlink, "cursor_blink", [], Terminal, "CURSOR", "Cursor Blink", "Enable blinking cursor animation", ["cursor", "blink", "animation"], RootSettingValueKind::Boolean, false),
     (BackgroundOpacity, "background_opacity", [], Appearance, "WINDOW", "Background Opacity", "Window background opacity (0.0 to 1.0)", ["background", "opacity", "transparency"], RootSettingValueKind::Numeric, false),
@@ -478,6 +479,7 @@ pub fn root_setting_default_value(config: &AppConfig, id: RootSettingId) -> Opti
         RootSettingId::WindowHeight => Some(config.window_height.to_string()),
         RootSettingId::FontFamily => Some(config.font_family.clone()),
         RootSettingId::FontSize => Some(config.font_size.to_string()),
+        RootSettingId::LineHeight => Some(crate::format_line_height(config.line_height)),
         RootSettingId::CursorStyle => Some(match config.cursor_style {
             CursorStyle::Line => "line".to_string(),
             CursorStyle::Block => "block".to_string(),
@@ -641,4 +643,13 @@ mod tests {
             Some("false".to_string())
         );
     }
+
+    #[test]
+    fn line_height_default_value_matches_app_config() {
+        let defaults = AppConfig::default();
+        assert_eq!(
+            root_setting_default_value(&defaults, RootSettingId::LineHeight),
+            Some(crate::format_line_height(defaults.line_height))
+        );
+    }
 }

crates/config_core/src/types.rs

@@ -286,6 +286,10 @@ pub struct AppConfig {
     pub window_height: f32,
     pub font_family: String,
     pub font_size: f32,
+    /// Unitless multiplier on the font cell height that controls vertical row
+    /// spacing. Clamped to [`MIN_LINE_HEIGHT`]..=[`MAX_LINE_HEIGHT`] at the
+    /// use-site in `TerminalView`.
+    pub line_height: f32,
     pub cursor_style: CursorStyle,
     pub cursor_blink: bool,
     pub background_opacity: f32,
@@ -360,6 +364,7 @@ impl Default for AppConfig {
             window_height: 820.0,
             font_family: "JetBrains Mono".to_string(),
             font_size: 14.0,
+            line_height: crate::constants::DEFAULT_LINE_HEIGHT,
             cursor_style: CursorStyle::default(),
             cursor_blink: DEFAULT_CURSOR_BLINK,
             background_opacity: 1.0,

crates/terminal_ui/src/grid.rs

@@ -1058,11 +1058,6 @@ impl TerminalGrid {
         self.cells.iter().map(|row| row.len()).sum()
     }
 
-    #[cfg(test)]
-    fn iter_cells(&self) -> impl Iterator<Item = &CellRenderInfo> {
-        self.cells.iter().flat_map(|row| row.iter())
-    }
-
     fn cell_is_drawable_text(cell: &CellRenderInfo) -> bool {
         cell.render_text && cell.char != ' ' && cell.char != '\0' && !cell.char.is_control()
     }
@@ -1107,7 +1102,7 @@ impl TerminalGrid {
         let mut ops = Vec::with_capacity(self.cell_count());
         let mut current: Option<TextBatch> = None;
 
-        for cell in self.iter_cells() {
+        for cell in self.cells.iter().flat_map(|row| row.iter()) {
             if !Self::cell_is_drawable_text(cell) {
                 Self::push_pending_text_batch(&mut current, &mut ops);
                 continue;

docs/configuration.md

@@ -28,6 +28,11 @@ Tmux integration is an add-on. Set `tmux_enabled = true` to start in tmux mode b
 - Terminal font size in pixels
 - Group: `FONT`
 
+`line_height`
+- Default: `1.4`
+- Terminal line height multiplier (0.8 to 2.5)
+- Group: `FONT`
+
 `background_opacity`
 - Default: `1`
 - Window background opacity (0.0 to 1.0)

src/settings_view/mod.rs

@@ -21,7 +21,7 @@ use std::time::{Duration, Instant};
 use termy_command_core::CommandId;
 use termy_config_core::{
     RootSettingId, RootSettingValueKind, SettingsSection as CoreSettingsSection,
-    color_setting_from_key, color_setting_specs, root_setting_default_value,
+    color_setting_from_key, color_setting_specs, format_line_height, root_setting_default_value,
     root_setting_enum_choices, root_setting_from_key, root_setting_specs, root_setting_value_kind,
 };
 

src/settings_view/sections.rs

@@ -89,12 +89,14 @@ impl SettingsWindow {
         let chrome_contrast = self.config.chrome_contrast;
         let font_family = self.config.font_family.clone();
         let font_size = self.config.font_size;
+        let line_height = self.config.line_height;
         let padding_x = self.config.padding_x;
         let padding_y = self.config.padding_y;
         let theme_meta = Self::setting_metadata_or_fallback("theme");
         let opacity_meta = Self::setting_metadata_or_fallback("background_opacity");
         let font_family_meta = Self::setting_metadata_or_fallback("font_family");
         let font_size_meta = Self::setting_metadata_or_fallback("font_size");
+        let line_height_meta = Self::setting_metadata_or_fallback("line_height");
         let padding_x_meta = Self::setting_metadata_or_fallback("padding_x");
         let padding_y_meta = Self::setting_metadata_or_fallback("padding_y");
 
@@ -161,6 +163,14 @@ impl SettingsWindow {
                 format!("{}px", font_size as i32),
                 cx,
             ),
+            self.render_editable_row(
+                "line_height",
+                EditableField::LineHeight,
+                line_height_meta.title,
+                line_height_meta.description,
+                format!("{line_height:.2}"),
+                cx,
+            ),
         ];
         let font_group = self.render_settings_group("FONT", font_rows);
 

src/settings_view/state.rs

@@ -11,6 +11,7 @@ pub(super) enum EditableField {
     BackgroundOpacity,
     FontFamily,
     FontSize,
+    LineHeight,
     PaddingX,
     PaddingY,
     Shell,
@@ -404,6 +405,7 @@ impl SettingsWindow {
             | EditableField::BackgroundOpacity
             | EditableField::FontFamily
             | EditableField::FontSize
+            | EditableField::LineHeight
             | EditableField::PaddingX
             | EditableField::PaddingY => Self::appearance_field_spec(field),
             EditableField::Shell
@@ -474,6 +476,16 @@ impl SettingsWindow {
                     max: 4096.0,
                 }),
             },
+            EditableField::LineHeight => FieldSpec {
+                root_setting: Some(RootSettingId::LineHeight),
+                codec: FieldCodec::Numeric,
+                dropdown_click_only: false,
+                numeric_step: Some(NumericStepSpec {
+                    delta: 0.05,
+                    min: termy_config_core::MIN_LINE_HEIGHT,
+                    max: termy_config_core::MAX_LINE_HEIGHT,
+                }),
+            },
             EditableField::PaddingX => FieldSpec {
                 root_setting: Some(RootSettingId::PaddingX),
                 codec: FieldCodec::Numeric,
@@ -822,6 +834,7 @@ impl SettingsWindow {
             ),
             EditableField::FontFamily => self.config.font_family.clone(),
             EditableField::FontSize => format!("{}", self.config.font_size.round() as i32),
+            EditableField::LineHeight => format_line_height(self.config.line_height),
             EditableField::PaddingX => format!("{}", self.config.padding_x.round() as i32),
             EditableField::PaddingY => format!("{}", self.config.padding_y.round() as i32),
             EditableField::Shell => self.config.shell.clone().unwrap_or_default(),
@@ -975,6 +988,18 @@ impl SettingsWindow {
                     &next.to_string(),
                 )
             }
+            EditableField::LineHeight => {
+                let next = (self.config.line_height + (delta as f32 * step.delta))
+                    .clamp(step.min, step.max);
+                let result = config::set_root_setting(
+                    termy_config_core::RootSettingId::LineHeight,
+                    &format_line_height(next),
+                );
+                if result.is_ok() {
+                    self.config.line_height = next;
+                }
+                result
+            }
             EditableField::PaddingX => {
                 let next =
                     (self.config.padding_x + (delta as f32 * step.delta)).clamp(step.min, step.max);
@@ -1172,6 +1197,7 @@ mod tests {
             EditableField::BackgroundOpacity,
             EditableField::FontFamily,
             EditableField::FontSize,
+            EditableField::LineHeight,
             EditableField::PaddingX,
             EditableField::PaddingY,
             EditableField::Shell,
@@ -1238,6 +1264,7 @@ mod tests {
         let numeric_fields = [
             EditableField::BackgroundOpacity,
             EditableField::FontSize,
+            EditableField::LineHeight,
             EditableField::PaddingX,
             EditableField::PaddingY,
             EditableField::ScrollbackHistory,
@@ -1254,6 +1281,14 @@ mod tests {
             assert_eq!(spec.codec, FieldCodec::Numeric);
             assert!(spec.numeric_step.is_some());
         }
+
+        let line_height_spec = SettingsWindow::field_spec(EditableField::LineHeight);
+        let step = line_height_spec
+            .numeric_step
+            .expect("missing line-height step");
+        assert!((step.delta - 0.05).abs() < f32::EPSILON);
+        assert!((step.min - termy_config_core::MIN_LINE_HEIGHT).abs() < f32::EPSILON);
+        assert!((step.max - termy_config_core::MAX_LINE_HEIGHT).abs() < f32::EPSILON);
     }
 
     #[test]