fix(ui): resolve terminal split-screen sizing alignment and remainder margin gap

src/app/constants.rs

@@ -2,7 +2,12 @@ pub(crate) const DEFAULT_COLS: u16 = 100;
 pub(crate) const DEFAULT_ROWS: u16 = 30;
 pub(crate) const SIDEBAR_WIDTH: f32 = 306.0;
 pub(crate) const COLLAPSED_SIDEBAR_WIDTH: f32 = 52.0;
+
+#[allow(dead_code)]
 pub(crate) const TAB_BAR_HEIGHT: f32 = 52.0;
+#[allow(dead_code)]
 pub(crate) const TERMINAL_PADDING_X: f32 = 32.0;
+#[allow(dead_code)]
 pub(crate) const TERMINAL_PADDING_Y: f32 = 32.0;
+
 pub(crate) const TERMINAL_KEY_CONTEXT: &str = "AshellTerminal";

src/app/ui.rs

@@ -2270,8 +2270,11 @@ impl Ashell {
                 div()
                     .size_full()
                     .on_prepaint(move |bounds, _window, cx| {
-                        let _ = view.update(cx, |this, _| {
-                            this.terminal_panel_bounds = Some(bounds);
+                        let _ = view.update(cx, |this, cx| {
+                            if this.terminal_panel_bounds != Some(bounds) {
+                                this.terminal_panel_bounds = Some(bounds);
+                                cx.notify();
+                            }
                         });
                     })
                     .overflow_hidden()
@@ -2320,8 +2323,6 @@ impl Ashell {
                 let Some(snapshot) = snapshot else {
                     return div().into_any_element();
                 };
-                let view = cx.entity();
-                let tab_id_clone = tab_id.clone();
                 let tab_id_clone2 = tab_id.clone();
                 let focus_handle = this.focus_handle.clone();
                 let marked_text = if is_focused {
@@ -2336,11 +2337,6 @@ impl Ashell {
                 let mut el = div()
                     .size_full()
                     .overflow_hidden()
-                    .on_prepaint(move |bounds, _window, cx| {
-                        let _ = view.update(cx, |this, _| {
-                            this.terminal_bounds.insert(tab_id_clone.clone(), bounds);
-                        });
-                    })
                     .on_mouse_down(
                         MouseButton::Left,
                         cx.listener(move |this, _, _, cx| {
@@ -2357,6 +2353,7 @@ impl Ashell {
                         font_size,
                         line_height,
                         cell_width,
+                        tab_id.to_string(),
                         this.search_highlight_map(
                             tab_id,
                             cx.theme().danger.opacity(0.35),
@@ -2433,10 +2430,10 @@ impl Ashell {
                     el = el.opacity(0.85);
                 }
 
+                let mut wrapper = div().size_full();
                 if has_multiple_panes {
                     if is_focused {
-                        el = div()
-                            .size_full()
+                        wrapper = wrapper
                             .relative()
                             .child(
                                 div()
@@ -2477,11 +2474,13 @@ impl Ashell {
                             .p(px(4.))
                             .child(el);
                     } else {
-                        el = div().size_full().p(px(4.)).child(el);
+                        wrapper = wrapper.p(px(4.)).child(el);
                     }
+                } else {
+                    wrapper = wrapper.child(el);
                 }
 
-                el.into_any_element()
+                wrapper.into_any_element()
             }
             PaneLayout::Horizontal(children, ratio) => {
                 v_flex()
@@ -2596,7 +2595,7 @@ impl Render for Ashell {
             self.active_tab = self.tabs.first().map(|tab| tab.id.clone());
         }
         self.sync_sftp_path_input(window, cx);
-        self.sync_terminal_size(window, cx);
+
         if self.show_transfers_dialog {
             self.show_transfers_dialog = false;
             self.show_transfers_dialog(window, cx);

src/session/mod.rs

@@ -1,7 +1,7 @@
 pub mod config;
 
 use gpui::{
-    App, AppContext as _, Context, Entity, KeyDownEvent, MouseButton, MouseDownEvent,
+    AppContext as _, Context, Entity, KeyDownEvent, MouseButton, MouseDownEvent,
     MouseMoveEvent, SharedString, Window, px,
 };
 use gpui_component::{Theme, WindowExt as _, input::InputState};
@@ -13,8 +13,7 @@ use self::config::{AuthMethod, Session};
 use crate::{
     Ashell, PaneLayout, SelectorEntry, TabGroup,
     app::constants::{
-        DEFAULT_COLS, DEFAULT_ROWS, SIDEBAR_WIDTH, TAB_BAR_HEIGHT, TERMINAL_PADDING_X,
-        TERMINAL_PADDING_Y,
+        DEFAULT_COLS, DEFAULT_ROWS,
     },
     backend::{local, ssh},
     terminal::{BackendCommand, RenderSnapshot, TabKind, TerminalTab},
@@ -959,64 +958,9 @@ impl Ashell {
         format!("{}@{}:{}", session.user, session.host, session.port)
     }
 
-    pub(crate) fn sync_terminal_size(&mut self, window: &Window, cx: &App) {
-        let viewport = window.viewport_size();
-        let sidebar_width = self
-            .workspace_panels
-            .read(cx)
-            .sizes()
-            .first()
-            .map(|size| size.as_f32())
-            .unwrap_or(SIDEBAR_WIDTH);
 
-        // Use the whole terminal panel bounds for PTY sizing.
-        // Individual pane bounds are smaller when split, so using them here
-        // would shrink the root PTY dimensions a second time.
-        let (width, height) = if let Some(bounds) = self.terminal_panel_bounds {
-            (bounds.size.width.as_f32(), bounds.size.height.as_f32())
-        } else {
-            let terminal_height = self
-                .body_panels
-                .read(cx)
-                .sizes()
-                .first()
-                .map(|size| size.as_f32())
-                .unwrap_or(viewport.height.as_f32() - TAB_BAR_HEIGHT - 248.0);
-            (
-                (viewport.width.as_f32() - sidebar_width - TERMINAL_PADDING_X - 8.0)
-                    .max(self.terminal_cell_width()),
-                (terminal_height - TERMINAL_PADDING_Y).max(self.terminal_line_height()),
-            )
-        };
-        let total_cols = (width / self.terminal_cell_width()).floor().max(1.0) as u16;
-        let total_rows = (height / self.terminal_line_height()).floor().max(1.0) as u16;
 
-        Self::resize_pane_tree(&mut self.tabs, &self.pane_root, total_cols, total_rows);
-    }
 
-    fn resize_pane_tree(tabs: &mut [TerminalTab], layout: &PaneLayout, cols: u16, rows: u16) {
-        match layout {
-            PaneLayout::Single(id) => {
-                if let Some(tab) = tabs.iter_mut().find(|t| t.id == *id) {
-                    tab.resize(cols.max(1), rows.max(1));
-                }
-            }
-            PaneLayout::Horizontal(children, _) => {
-                let n = children.len() as u16;
-                let each_rows = (rows / n).max(1);
-                for child in children {
-                    Self::resize_pane_tree(tabs, child, cols, each_rows);
-                }
-            }
-            PaneLayout::Vertical(children, _) => {
-                let n = children.len() as u16;
-                let each_cols = (cols / n).max(1);
-                for child in children {
-                    Self::resize_pane_tree(tabs, child, each_cols, rows);
-                }
-            }
-        }
-    }
 
     pub(crate) fn split_current_pane(&mut self, direction: &str, cx: &mut Context<Self>) {
         tracing::info!(

src/terminal/element.rs

@@ -132,6 +132,7 @@ pub struct TerminalElement {
     font_size: Pixels,
     line_height: Pixels,
     cell_width: Pixels,
+    tab_id: String,
     search_highlights: Option<std::collections::HashMap<(i32, i32), Hsla>>,
 }
 
@@ -271,6 +272,7 @@ impl TerminalElement {
         font_size: Pixels,
         line_height: Pixels,
         cell_width: Pixels,
+        tab_id: String,
         search_highlights: Option<std::collections::HashMap<(i32, i32), Hsla>>,
     ) -> Self {
         Self {
@@ -282,6 +284,7 @@ impl TerminalElement {
             font_size,
             line_height,
             cell_width,
+            tab_id,
             search_highlights,
         }
     }
@@ -541,6 +544,32 @@ impl Element for TerminalElement {
     ) -> Self::PrepaintState {
         let _ = self.base_text_style(cx);
         let (rects, runs, custom_blocks) = self.layout_grid(cx);
+
+        // Save the precise GPUI-rendered bounds of this terminal element.
+        // This is 100% accurate because it is recorded during layout prepaint.
+        let view = self.view.clone();
+        let tab_id = self.tab_id.clone();
+        let _ = view.update(cx, |this, cx| {
+            let old_bounds = this.terminal_bounds.insert(tab_id.clone(), bounds);
+            
+            // Sync PTY size unconditionally on every prepaint layout pass to ensure
+            // absolute synchronization with GPUI layout regardless of intermediate events.
+            let line_height = this.terminal_line_height();
+            let cell_width = this.terminal_cell_width();
+            let w = bounds.size.width.as_f32();
+            let h = bounds.size.height.as_f32();
+            let cols = (w / cell_width).floor().max(1.0) as u16;
+            let rows = (h / line_height).floor().max(1.0) as u16;
+            
+            if let Some(tab) = this.tabs.iter_mut().find(|t| t.id == tab_id) {
+                tab.resize(cols, rows);
+            }
+            
+            if old_bounds != Some(bounds) {
+                cx.notify();
+            }
+        });
+
         PrepaintState {
             bounds,
             metrics: TerminalMetrics {
@@ -564,18 +593,24 @@ impl Element for TerminalElement {
         window: &mut Window,
         cx: &mut App,
     ) {
+        // Compute a vertical offset to center the text grid vertically,
+        // distributing the leftover pixel remainder evenly to the top and bottom.
+        let grid_height = prepaint.metrics.line_height * (prepaint.bounds.size.height.as_f32() / prepaint.metrics.line_height.as_f32()).floor();
+        let y_offset = ((prepaint.bounds.size.height - grid_height) / 2.0).max(px(0.0));
+        let draw_origin = point(prepaint.bounds.origin.x, prepaint.bounds.origin.y + y_offset);
+
         for rect in &prepaint.rects {
-            rect.paint(prepaint.bounds.origin, prepaint.metrics, window);
+            rect.paint(draw_origin, prepaint.metrics, window);
         }
 
         for run in &prepaint.runs {
-            run.paint(prepaint.bounds.origin, prepaint.metrics, window, cx);
+            run.paint(draw_origin, prepaint.metrics, window, cx);
         }
 
         for block in &prepaint.custom_blocks {
-            let x = prepaint.bounds.origin.x.as_f32()
+            let x = draw_origin.x.as_f32()
                 + block.col as f32 * prepaint.metrics.cell_width.as_f32();
-            let y = prepaint.bounds.origin.y.as_f32()
+            let y = draw_origin.y.as_f32()
                 + block.row as f32 * prepaint.metrics.line_height.as_f32();
             paint_custom_block(
                 window,
@@ -592,7 +627,7 @@ impl Element for TerminalElement {
             &self.focus_handle,
             TerminalInputHandler {
                 view: self.view.clone(),
-                element_bounds: prepaint.bounds,
+                element_bounds: Bounds::new(draw_origin, prepaint.bounds.size),
                 cell_width: prepaint.metrics.cell_width.as_f32(),
                 line_height: prepaint.metrics.line_height.as_f32(),
             },
@@ -602,8 +637,8 @@ impl Element for TerminalElement {
         if let Some(marked_text) = self.marked_text.as_ref().filter(|text| !text.is_empty()) {
             if let Some(cursor) = prepaint.cursor {
                 let pos = point(
-                    prepaint.bounds.origin.x + prepaint.metrics.cell_width * cursor.col as f32,
-                    prepaint.bounds.origin.y + prepaint.metrics.line_height * cursor.row as f32,
+                    draw_origin.x + prepaint.metrics.cell_width * cursor.col as f32,
+                    draw_origin.y + prepaint.metrics.line_height * cursor.row as f32,
                 );
                 let mut base_style = self.base_text_style(cx);
                 base_style.underline = Some(UnderlineStyle {
@@ -650,8 +685,8 @@ impl Element for TerminalElement {
             {
                 return;
             }
-            let x = prepaint.bounds.origin.x + prepaint.metrics.cell_width * cursor.col as f32;
-            let y = prepaint.bounds.origin.y + prepaint.metrics.line_height * cursor.row as f32;
+            let x = draw_origin.x + prepaint.metrics.cell_width * cursor.col as f32;
+            let y = draw_origin.y + prepaint.metrics.line_height * cursor.row as f32;
             match cursor.shape {
                 CursorShape::Hidden => {}
                 CursorShape::Beam => {