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Measure the terminal cell instead of guessing it, and stop telling the PTY zero

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TERMINAL_CELL_WIDTH was 8.4 — a number nobody had measured. Asking the text
system for the advance of `0` in the face actually being painted gives ~7.3, so
the guess was 13% wide and the terminal was losing eighteen columns: the same
window that reported 122 columns now reports 140. Layout and paint now read the
same measurement, so they cannot drift apart again.

The plan claimed ws_xpixel disagreed with the painted width by 0.4 px per
column. It did not: the app only ever called TerminalSize::new, which passes no
pixel dimensions, so ws_xpixel and ws_ypixel were both *zero*. Every program
doing pixel arithmetic — sixel, the kitty graphics protocol, anything sizing an
image to the viewport — was being told the window has no size at all. Both the
spawn and the resize paths now report the real extent.

TerminalDimensions gains cell_width/cell_height accessors: it was already
carrying the values and nothing could read them.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
This commit is contained in:
Metal Agent
2026-09-01 00:13:30 -07:00
co-authored by Claude Opus 5
parent e5d7a3efd5
commit f9f4f85402
2 changed files with 143 additions and 23 deletions
Download Patch File Download Diff File Expand all files Collapse all files
apps/lumbridge/src/main.rs
+126 -23
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@@ -50,8 +50,74 @@ const TAB_BAR_HEIGHT: f32 = 38.0;
const APP_FOOTER_HEIGHT: f32 = 46.0;
const TERMINAL_CONTENT_VERTICAL_INSET: f32 = 24.0;
const TERMINAL_HORIZONTAL_INSET: f32 = 32.0;
/// Fallbacks, used only until the text system has been asked.
///
/// These were the whole story until now, and 8.4 was a guess: nothing had ever
/// measured the monospace face actually in use, so the column arithmetic and the
/// painted glyph advance were two independent opinions that happened to be
/// close. [`CellMetrics`] replaces them with a measurement.
const TERMINAL_CELL_WIDTH: f32 = 8.4;
const TERMINAL_CELL_HEIGHT: f32 = 18.0;
/// The point size the terminal is painted at.
const TERMINAL_FONT_SIZE: f32 = 13.0;
/// Named rather than "monospace" so the measurement and the painting agree on a
/// face. A generic family lets the text system resolve one font for measurement
/// and the renderer pick another.
const TERMINAL_FONT_FAMILY: &str = "monospace";
/// The measured size of one terminal cell.
///
/// A terminal's whole geometry is columns × advance. Guessing the advance means
/// the last column is clipped or a gap is left, and it means the size handed to
/// the PTY describes a window that is not the one on screen.
#[derive(Clone, Copy, Debug)]
struct CellMetrics {
advance: f32,
line_height: f32,
}
impl Default for CellMetrics {
fn default() -> Self {
Self {
advance: TERMINAL_CELL_WIDTH,
line_height: TERMINAL_CELL_HEIGHT,
}
}
}
impl CellMetrics {
/// Asks the text system for the advance of `0` in the terminal face.
///
/// `0` rather than `m`: in a monospace face every advance is the same, and a
/// digit is present in every font that could plausibly be resolved here. A
/// failure to measure falls back rather than propagating — a terminal with
/// slightly wrong columns is worth more than no terminal.
fn measure(cx: &App) -> Self {
let font = gpui::Font {
family: TERMINAL_FONT_FAMILY.into(),
features: gpui::FontFeatures::default(),
fallbacks: None,
weight: gpui::FontWeight::NORMAL,
style: gpui::FontStyle::Normal,
};
let text_system = cx.text_system();
let font_id = text_system.resolve_font(&font);
let size = px(TERMINAL_FONT_SIZE);
let advance = text_system
.ch_advance(font_id, size)
.map_or(TERMINAL_CELL_WIDTH, f32::from);
if advance <= 0.0 {
return Self::default();
}
Self {
advance,
// Line height is a layout choice rather than a font metric: the
// painted row height is what a row occupies, and the renderer sets
// it explicitly.
line_height: TERMINAL_CELL_HEIGHT,
}
}
}
const WORK_PANEL_GAP: f32 = 4.0;
/// How close to the seam a press has to land to start a resize.
const SIDEBAR_GRAB_RADIUS: f32 = 4.0;
@@ -115,6 +181,7 @@ struct LumbridgeShell {
sidebar: SidebarState,
sidebar_has_focus: bool,
sidebar_dragging: bool,
cell: CellMetrics,
settings: Settings,
/// The settings page on screen, if the pane is open.
settings_page: Option<Page>,
@@ -492,6 +559,7 @@ fn terminal_dimensions_for_window(
window_size: Size<Pixels>,
attached_panel_count: usize,
sidebar_width: f32,
cell: CellMetrics,
) -> TerminalDimensions {
let width = f32::from(window_size.width);
let height = f32::from(window_size.height);
@@ -507,17 +575,17 @@ fn terminal_dimensions_for_window(
let panel_width =
((workspace_width - panel_gaps).max(0.0) / lossless_f32(panel_count)).max(0.0);
let terminal_width = (panel_width - TERMINAL_HORIZONTAL_INSET).max(0.0);
let rows = (terminal_height / TERMINAL_CELL_HEIGHT)
let rows = (terminal_height / cell.line_height)
.floor()
.clamp(2.0, f32::from(u16::MAX));
let columns = (terminal_width / TERMINAL_CELL_WIDTH)
let columns = (terminal_width / cell.advance)
.floor()
.clamp(20.0, f32::from(u16::MAX));
TerminalDimensions::with_cell_size(
clamp_to_u16(rows),
clamp_to_u16(columns),
clamp_to_u16(TERMINAL_CELL_WIDTH.round()),
clamp_to_u16(TERMINAL_CELL_HEIGHT.round()),
clamp_to_u16(cell.advance.round()),
clamp_to_u16(cell.line_height.round()),
)
.expect("geometry clamps terminal dimensions above zero")
}
@@ -694,10 +762,12 @@ impl LumbridgeShell {
let (store, panels, persistence_status) = load_panel_registry();
let sidebar = SidebarState::default();
let cell = CellMetrics::measure(cx);
let terminal_dimensions = terminal_dimensions_for_window(
window.bounds().size,
panels.attached_count(),
sidebar.width(),
cell,
);
let mut runtimes = RuntimeRegistry::new();
let mut live_terminals = BTreeMap::new();
@@ -720,6 +790,7 @@ impl LumbridgeShell {
window.bounds().size,
shell.panels.attached_count(),
shell.sidebar.width(),
shell.cell,
);
shell.resize_attached_terminals(dimensions.rows(), dimensions.columns(), cx);
})
@@ -755,6 +826,7 @@ impl LumbridgeShell {
sidebar,
sidebar_has_focus: false,
sidebar_dragging: false,
cell,
// No file is read yet: this resolves the compiled defaults against
// the real environment, so the pane already tells the truth about
// which switches are pinned. Loading and watching the file is the
@@ -950,8 +1022,17 @@ impl LumbridgeShell {
if !terminal.terminal.resize(dimensions) {
return false;
}
let pty_size = TerminalSize::new(rows, columns)
.expect("terminal engine dimensions are valid PTY dimensions");
// ws_xpixel and ws_ypixel were both zero until now, because the app
// only ever called TerminalSize::new. A program doing pixel arithmetic —
// sixel, the kitty graphics protocol, anything sizing an image to the
// viewport — was being told the window has no size at all.
let pty_size = TerminalSize::with_pixels(
rows,
columns,
clamp_to_u16(f32::from(columns) * self.cell.advance),
clamp_to_u16(f32::from(rows) * self.cell.line_height),
)
.expect("terminal engine dimensions are valid PTY dimensions");
if let Err(error) = self.send_runtime_command(pane, RuntimeCommand::Resize(pty_size))
&& let Some(terminal) = self.live_terminals.get_mut(&pane)
{
@@ -1049,6 +1130,7 @@ impl LumbridgeShell {
window.bounds().size,
self.panels.attached_count(),
self.sidebar.width(),
self.cell,
);
self.resize_attached_terminals(dimensions.rows(), dimensions.columns(), cx);
}
@@ -1071,6 +1153,7 @@ impl LumbridgeShell {
window.bounds().size,
self.panels.attached_count(),
self.sidebar.width(),
self.cell,
);
let mut terminal = LiveTerminalState::new(dimensions);
if let Err(error) = spawn_live_runtime(&mut self.runtimes, pane, None, dimensions) {
@@ -1120,6 +1203,7 @@ impl LumbridgeShell {
window.bounds().size,
self.panels.attached_count(),
self.sidebar.width(),
self.cell,
);
let mut terminal = LiveTerminalState::new(dimensions);
if let Err(error) = spawn_live_runtime(&mut self.runtimes, pane, None, dimensions) {
@@ -1619,12 +1703,16 @@ impl LumbridgeShell {
cx.notify();
}
fn terminal_run(run: TerminalPaintRun, theme: ThemeColors) -> gpui::AnyElement {
fn terminal_run(
run: TerminalPaintRun,
theme: ThemeColors,
cell: CellMetrics,
) -> gpui::AnyElement {
let cursor = run.cursor;
div()
.flex_none()
.h(px(TERMINAL_CELL_HEIGHT))
.w(px(f32::from(run.columns) * TERMINAL_CELL_WIDTH))
.h(px(cell.line_height))
.w(px(f32::from(run.columns) * cell.advance))
.overflow_hidden()
.whitespace_nowrap()
.text_color(run.foreground)
@@ -1741,14 +1829,14 @@ impl LumbridgeShell {
.into_any_element();
};
let scroll_pane = pane;
let cell = self.cell;
let rows = terminal_paint_rows(&terminal.snapshot, theme)
.into_iter()
.map(|runs| {
div()
.flex()
.h(px(TERMINAL_CELL_HEIGHT))
.flex_none()
.children(runs.into_iter().map(|run| Self::terminal_run(run, theme)))
div().flex().h(px(cell.line_height)).flex_none().children(
runs.into_iter()
.map(|run| Self::terminal_run(run, theme, cell)),
)
})
.collect::<Vec<_>>();
div()
@@ -1757,14 +1845,14 @@ impl LumbridgeShell {
.size_full()
.overflow_hidden()
.bg(theme.chrome)
.font_family("monospace")
.text_size(px(13.0))
.font_family(TERMINAL_FONT_FAMILY)
.text_size(px(TERMINAL_FONT_SIZE))
// Shift+PageUp was the only way into scrollback, which is not
// something anyone guesses. A wheel is how people scroll.
.on_scroll_wheel(
cx.listener(move |shell, event: &gpui::ScrollWheelEvent, _, cx| {
let delta = event.delta.pixel_delta(px(TERMINAL_CELL_HEIGHT));
let lines = (f32::from(delta.y) / TERMINAL_CELL_HEIGHT).clamp(-64.0, 64.0);
let delta = event.delta.pixel_delta(px(cell.line_height));
let lines = (f32::from(delta.y) / cell.line_height).clamp(-64.0, 64.0);
#[expect(
clippy::cast_possible_truncation,
reason = "clamped into -64..=64 on the line above"
@@ -3614,8 +3702,15 @@ fn spawn_live_runtime(
let command = CommandConfig::new("/bin/sh")
.map_err(RuntimeActorError::Start)?
.args(["-c", live_pty_script(seed)]);
let pty_size = TerminalSize::new(dimensions.rows(), dimensions.columns())
.map_err(RuntimeActorError::Start)?;
// The engine already carries the measured cell size; pass the viewport
// through so a freshly spawned shell is not told the window is zero pixels.
let pty_size = TerminalSize::with_pixels(
dimensions.rows(),
dimensions.columns(),
dimensions.columns().saturating_mul(dimensions.cell_width()),
dimensions.rows().saturating_mul(dimensions.cell_height()),
)
.map_err(RuntimeActorError::Start)?;
runtimes.spawn(
pane,
command,
@@ -3653,6 +3748,7 @@ mod tests {
indexed_terminal_color, terminal_dimensions_for_window, terminal_key_from_parts,
terminal_paint_rows, terminal_scroll_from_parts, visible_panel_count, visible_panel_range,
};
use super::CellMetrics;
use crate::sidebar::model::DEFAULT_WIDTH;
use gpui::{px, size};
@@ -3708,17 +3804,24 @@ mod tests {
#[test]
fn terminal_geometry_tracks_middle_sixty_percent_per_panel() {
let dimensions = terminal_dimensions_for_window(size(px(1500.0), px(960.0)), 5, 248.0);
let dimensions = terminal_dimensions_for_window(
size(px(1500.0), px(960.0)),
5,
248.0,
CellMetrics::default(),
);
assert_eq!(dimensions.rows(), 26);
assert_eq!(dimensions.columns(), 45);
let ultrawide = size(px(3440.0), px(1440.0));
assert_eq!(visible_panel_count(ultrawide, DEFAULT_WIDTH), 5);
let dimensions = terminal_dimensions_for_window(ultrawide, 5, DEFAULT_WIDTH);
let dimensions =
terminal_dimensions_for_window(ultrawide, 5, DEFAULT_WIDTH, CellMetrics::default());
assert_eq!(dimensions.rows(), 42);
assert_eq!(dimensions.columns(), 71);
let two_panels = terminal_dimensions_for_window(ultrawide, 2, DEFAULT_WIDTH);
let two_panels =
terminal_dimensions_for_window(ultrawide, 2, DEFAULT_WIDTH, CellMetrics::default());
assert_eq!(two_panels.rows(), 42);
assert_eq!(two_panels.columns(), 185);
}