feat(window): add configurable separator_px

CHANGELOG.md

@@ -6,6 +6,7 @@ Format follows [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 ## [Unreleased]
 
 ### Added
+- add `window.separator_px` to configure the width of the separator between panes
 - add `--maximized` and `--fullscreen` flags to start the window in that mode
 - persist and restore window size, maximized, and fullscreen state per session
 - REP (`CSI Ps b`): repeat the last printed character `Ps` times

README.md

@@ -159,6 +159,7 @@ width           = 800
 height          = 600
 title           = "mmterm"
 cursor_blink_ms = 500
+separator_px    = 1        # width in px of the separator between panes (DPI-scaled)
 
 [shell]
 # program = "/bin/zsh"   # defaults to $SHELL

assets/config.toml

@@ -11,6 +11,7 @@ title           = "mmterm"
 cursor_blink_ms = 500
 inactive_dim    = 0.55
 detect_urls     = true
+separator_px    = 1
 
 [shell]
 # program = "/bin/zsh"

doc/SPEC.md

@@ -221,6 +221,7 @@ Screenshot capture is a two-step flow: region selection followed by a name promp
 | window | cursor_blink_ms | uint | `500` |
 | window | inactive_dim | float | `0.55` |
 | window | detect_urls | bool | `true` |
+| window | separator_px | uint | `1` |
 | terminal | scrollback_lines | uint | `10000` (min 100) |
 | shell | program | string? | `$SHELL` |
 | logging | auto_log | bool | `false` |

src/app_event.rs

@@ -461,8 +461,14 @@ impl App {
     fn separator_at_pixel(&self, px: u32, py: u32) -> Option<crate::ui::layout::SeparatorHandle> {
         let tab = &self.state.tabs[self.state.active_tab];
         if !tab.zoomed {
-            tab.layout
-                .separator_at_pixel_scaled(px, py, 4, self.tab_h(), self.status_h())
+            tab.layout.separator_at_pixel_scaled(
+                px,
+                py,
+                4,
+                self.tab_h(),
+                self.status_h(),
+                self.separator_px(),
+            )
         } else {
             None
         }
@@ -601,7 +607,8 @@ impl App {
         let tab_h = self.tab_h();
         let status_h = self.status_h();
         let pane_padding = self.pane_padding();
-        Self::sync_pane_sizes_tab(&mut self.state.tabs[ai], tab_h, status_h, pane_padding);
+        let sep = self.separator_px();
+        Self::sync_pane_sizes_tab(&mut self.state.tabs[ai], tab_h, status_h, sep, pane_padding);
         let icon = match handle.dir {
             SplitDir::H => CursorIcon::ColResize,
             SplitDir::V => CursorIcon::RowResize,

src/config/mod.rs

@@ -147,6 +147,9 @@ fn default_inactive_dim() -> f32 {
 fn default_detect_urls() -> bool {
     true
 }
+fn default_separator_px() -> u32 {
+    1
+}
 
 #[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
 pub struct WindowConfig {
@@ -158,6 +161,8 @@ pub struct WindowConfig {
     pub inactive_dim: f32,
     #[serde(default = "default_detect_urls")]
     pub detect_urls: bool,
+    #[serde(default = "default_separator_px")]
+    pub separator_px: u32,
 }
 
 #[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]

src/config/tui_config.rs

@@ -90,6 +90,8 @@ pub struct ConfigPanel {
     /// Section names that are currently collapsed (body fields hidden).
     pub collapsed: HashSet<&'static str>,
     pub version: &'static str,
+    /// Preserved verbatim from the loaded config (not exposed as an editable field).
+    pub separator_px: u32,
 }
 
 impl ConfigPanel {
@@ -313,6 +315,7 @@ impl ConfigPanel {
             status: None,
             collapsed,
             version: env!("MMTERM_VERSION"),
+            separator_px: cfg.window.separator_px,
         }
     }
 
@@ -687,6 +690,7 @@ impl ConfigPanel {
                 cursor_blink_ms: blink_ms,
                 inactive_dim,
                 detect_urls,
+                separator_px: self.separator_px,
             },
             shell: ShellConfig { program: shell },
             terminal: TerminalConfig { scrollback_lines },

src/config/tui_config_test.rs

@@ -305,6 +305,7 @@ fn distinct_config() -> Config {
             cursor_blink_ms: 523,
             inactive_dim: 0.42,
             detect_urls: true,
+            separator_px: 7,
         },
         shell: ShellConfig {
             program: Some("/bin/xyzsh".into()),

src/input/mouse_ops.rs

@@ -50,7 +50,10 @@ impl App {
 
     pub(crate) fn pane_at_pixel(&self, px: f64, py: f64) -> Option<usize> {
         let (tab_h, status_h) = (self.tab_h(), self.status_h());
-        let rects = self.tab().layout.rects_scaled(tab_h, status_h);
+        let rects = self
+            .tab()
+            .layout
+            .rects_scaled(tab_h, status_h, self.separator_px());
         geometry::pane_at_pixel(&rects, px, py)
     }
 

src/input_ops.rs

@@ -103,10 +103,11 @@ impl App {
         let active = self.tab().active;
         let tab_h = self.tab_h();
         let status_h = self.status_h();
+        let sep = self.separator_px();
         let rect = self
             .tab()
             .layout
-            .rects_scaled(tab_h, status_h)
+            .rects_scaled(tab_h, status_h, sep)
             .into_iter()
             .find(|(id, _)| *id == active)
             .map(|(_, r)| r)
@@ -128,7 +129,8 @@ impl App {
         let tab_h = self.tab_h();
         let status_h = self.status_h();
         let pane_padding = self.pane_padding();
-        Self::sync_pane_sizes_tab(&mut self.state.tabs[ai], tab_h, status_h, pane_padding);
+        let sep = self.separator_px();
+        Self::sync_pane_sizes_tab(&mut self.state.tabs[ai], tab_h, status_h, sep, pane_padding);
         if let Some(w) = &self.window {
             w.request_redraw();
         }
@@ -140,7 +142,8 @@ impl App {
         let tab_h = self.tab_h();
         let status_h = self.status_h();
         let pane_padding = self.pane_padding();
-        Self::sync_pane_sizes_tab(&mut self.state.tabs[ai], tab_h, status_h, pane_padding);
+        let sep = self.separator_px();
+        Self::sync_pane_sizes_tab(&mut self.state.tabs[ai], tab_h, status_h, sep, pane_padding);
         self.request_redraw();
     }
 
@@ -233,9 +236,16 @@ impl App {
         let tab_h = self.tab_h();
         let status_h = self.status_h();
         let pane_padding = self.pane_padding();
+        let sep = self.separator_px();
         // Re-grids only the active pane: sibling metrics + rects are unchanged,
         // so their cols/rows don't change and they are left alone.
-        Self::sync_pane_sizes_tab(&mut self.state.tabs[idx], tab_h, status_h, pane_padding);
+        Self::sync_pane_sizes_tab(
+            &mut self.state.tabs[idx],
+            tab_h,
+            status_h,
+            sep,
+            pane_padding,
+        );
     }
 
     pub(crate) fn should_swallow_key(&mut self, event: &KeyEvent) -> bool {

src/main.rs

@@ -208,6 +208,14 @@ impl App {
         self.scale.chrome(crate::ui::layout::PANE_PADDING)
     }
 
+    /// DPI-scaled pane separator width from config. `.max(1)` keeps hit-testing
+    /// and rendering sane even when the configured value is 0.
+    pub(crate) fn separator_px(&self) -> u32 {
+        self.scale
+            .chrome(self.state.config.window.separator_px)
+            .max(1)
+    }
+
     fn handle_resize(&mut self, w: u32, h: u32) {
         for tab in &mut self.state.tabs {
             tab.layout.resize(w, h);

src/pane_ops.rs

@@ -137,9 +137,10 @@ impl App {
             .and_then(|e| e.pty.cwd());
         let tab_h = self.tab_h();
         let status_h = self.status_h();
+        let sep = self.separator_px();
         let layout = Layout::new(0, win_w, win_h);
         let initial_rect = layout
-            .rects_scaled(tab_h, status_h)
+            .rects_scaled(tab_h, status_h, sep)
             .first()
             .map(|(_, r)| *r)
             .unwrap_or([0, tab_h, win_w, win_h]);
@@ -244,17 +245,25 @@ impl App {
         let tab_h = self.tab_h();
         let status_h = self.status_h();
         let pane_padding = self.pane_padding();
-        Self::sync_pane_sizes_tab(&mut self.state.tabs[tab_idx], tab_h, status_h, pane_padding);
+        let sep = self.separator_px();
+        Self::sync_pane_sizes_tab(
+            &mut self.state.tabs[tab_idx],
+            tab_h,
+            status_h,
+            sep,
+            pane_padding,
+        );
     }
 
     pub(crate) fn sync_pane_sizes_tab(
         tab: &mut TabState,
         tab_h: u32,
         status_h: u32,
+        sep: u32,
         pane_padding: u32,
     ) {
         // rows*cell_height may be < pane_h by up to (cell_height-1)px — intentional bottom gutter; do not force equality.
-        let rects = tab.layout.rects_scaled(tab_h, status_h);
+        let rects = tab.layout.rects_scaled(tab_h, status_h, sep);
         for (id, rect) in rects {
             if let Some(entry) = tab.panes.get_mut(&id) {
                 let [_, _, w, h] = rect;
@@ -290,8 +299,9 @@ impl App {
         let tab_h = self.tab_h();
         let status_h = self.status_h();
         let pane_padding = self.pane_padding();
+        let sep = self.separator_px();
         for tab in &mut self.state.tabs {
-            Self::sync_pane_sizes_tab(tab, tab_h, status_h, pane_padding);
+            Self::sync_pane_sizes_tab(tab, tab_h, status_h, sep, pane_padding);
         }
     }
 
@@ -300,10 +310,11 @@ impl App {
         let active = self.tab().active;
         let tab_h = self.tab_h();
         let status_h = self.status_h();
+        let sep = self.separator_px();
         let active_rect = self
             .tab()
             .layout
-            .rects_scaled(tab_h, status_h)
+            .rects_scaled(tab_h, status_h, sep)
             .into_iter()
             .find(|(id, _)| *id == active)
             .map(|(_, r)| r)
@@ -330,7 +341,13 @@ impl App {
         tab.active = new_id;
         let idx = self.state.active_tab;
         let pane_padding = self.pane_padding();
-        Self::sync_pane_sizes_tab(&mut self.state.tabs[idx], tab_h, status_h, pane_padding);
+        Self::sync_pane_sizes_tab(
+            &mut self.state.tabs[idx],
+            tab_h,
+            status_h,
+            sep,
+            pane_padding,
+        );
     }
 
     pub(crate) fn do_close_pane(&mut self, event_loop: &ActiveEventLoop) {
@@ -358,7 +375,14 @@ impl App {
         let tab_h = self.tab_h();
         let status_h = self.status_h();
         let pane_padding = self.pane_padding();
-        Self::sync_pane_sizes_tab(&mut self.state.tabs[idx], tab_h, status_h, pane_padding);
+        let sep = self.separator_px();
+        Self::sync_pane_sizes_tab(
+            &mut self.state.tabs[idx],
+            tab_h,
+            status_h,
+            sep,
+            pane_padding,
+        );
     }
 }
 

src/pane_ops_test.rs

@@ -104,7 +104,7 @@ fn sync_uses_per_pane_metrics() {
         AppState::test_pane_entry(Logical(32.0), metrics(32.0, 16, 32)),
     );
 
-    App::sync_pane_sizes_tab(&mut tab, 22, 22, 0);
+    App::sync_pane_sizes_tab(&mut tab, 22, 22, 1, 0);
 
     // sync_pane_sizes_tab writes target dimensions to pending_resize; the parser
     // thread applies them asynchronously. Test the contract that sync_pane_sizes_tab

src/renderer/overlays_test.rs

@@ -18,6 +18,7 @@ fn make_panel(value: &str, kind: FieldKind) -> ConfigPanel {
         status: None,
         collapsed: HashSet::new(),
         version: "",
+        separator_px: 1,
     }
 }
 
@@ -331,6 +332,7 @@ fn make_section_panel(collapsed: bool) -> ConfigPanel {
         status: None,
         collapsed: c,
         version: "",
+        separator_px: 1,
     }
 }
 

src/renderer/render_ops.rs

@@ -102,6 +102,7 @@ impl App {
         // Compute scaled chrome heights before any mutable borrow of self.surface.
         let tab_h = self.tab_h();
         let status_h = self.status_h();
+        let sep = self.separator_px();
 
         let Some(surface) = &mut self.surface else {
             return;
@@ -137,7 +138,7 @@ impl App {
         let (separators, zoomed, active_id) = {
             let tab = &self.state.tabs[self.state.active_tab];
             (
-                tab.layout.separators_scaled(tab_h, status_h),
+                tab.layout.separators_scaled(tab_h, status_h, sep),
                 tab.zoomed,
                 tab.active,
             )
@@ -205,7 +206,7 @@ impl App {
                     }
                 })
                 .collect();
-            let views = views::collect_pane_views(&self.state, &guards, w, h, tab_h, status_h);
+            let views = views::collect_pane_views(&self.state, &guards, w, h, tab_h, status_h, sep);
 
             let draw_separators: &[[u32; 4]] = if zoomed { &[] } else { &separators };
             let right_text = statusbar::resolve(

src/renderer/views.rs

@@ -45,6 +45,7 @@ pub fn collect_pane_views<'a>(
     h: u32,
     tab_h: u32,
     status_h: u32,
+    sep: u32,
 ) -> Vec<PaneView<'a>> {
     if state.tabs.is_empty() {
         return vec![];
@@ -88,7 +89,7 @@ pub fn collect_pane_views<'a>(
             metrics: &entry.metrics,
         }]
     } else {
-        let rects = tab.layout.rects_scaled(tab_h, status_h);
+        let rects = tab.layout.rects_scaled(tab_h, status_h, sep);
         rects
             .iter()
             .filter_map(|(id, rect)| {

src/renderer/views_test.rs

@@ -24,7 +24,7 @@ fn views(state: &AppState, w: u32, h: u32) -> Vec<PaneView<'_>> {
     let guards = acquire_grid_guards(state);
     // We need to keep guards alive for the duration of use. Since we can't
     // return views that borrow guards in a test helper, call the fn inline.
-    let _views = collect_pane_views(state, &guards, w, h, TAB_BAR_H, STATUS_BAR_H);
+    let _views = collect_pane_views(state, &guards, w, h, TAB_BAR_H, STATUS_BAR_H, 1);
     drop(guards);
     // Return a simplified view of the data we need to test
     vec![]
@@ -41,7 +41,7 @@ struct ViewSnapshot {
 
 fn collect_snapshots(state: &AppState, w: u32, h: u32) -> Vec<ViewSnapshot> {
     let guards = acquire_grid_guards(state);
-    let views = collect_pane_views(state, &guards, w, h, TAB_BAR_H, STATUS_BAR_H);
+    let views = collect_pane_views(state, &guards, w, h, TAB_BAR_H, STATUS_BAR_H, 1);
     views
         .iter()
         .map(|v| ViewSnapshot {

src/restore.rs

@@ -110,7 +110,14 @@ impl App {
                 continue;
             }
             let pane_padding = self.pane_padding();
-            Self::sync_pane_sizes_tab(&mut self.state.tabs[tab_idx], tab_h, status_h, pane_padding);
+            let sep = self.separator_px();
+            Self::sync_pane_sizes_tab(
+                &mut self.state.tabs[tab_idx],
+                tab_h,
+                status_h,
+                sep,
+                pane_padding,
+            );
             for (slot, &pane_id) in slot_to_id.iter().enumerate() {
                 let path = session::scrollback_path_for(self.scope.as_deref(), tab_i, slot);
                 let lines = session::load_scrollback(&path);