Customizable/configurable status line (#2434)

* feat(statusline): add the file type (language id) to the status line

* refactor(statusline): move the statusline implementation into an own struct

* refactor(statusline): split the statusline implementation into different functions

* refactor(statusline): Append elements using a consistent API

This is a preparation for the configurability which is about to be
implemented.

* refactor(statusline): implement render_diagnostics()

This avoid cluttering the render() function and will simplify
configurability.

* feat(statusline): make the status line configurable

* refactor(statusline): make clippy happy

* refactor(statusline): avoid intermediate StatusLineObject

Use a more functional approach to obtain render functions and write to
the buffers, and avoid an intermediate StatusLineElement object.

* fix(statusline): avoid rendering the left elements twice

* refactor(statusline): make clippy happy again

* refactor(statusline): rename `buffer` into `parts`

* refactor(statusline): ensure the match is exhaustive

* fix(statusline): avoid an overflow when calculating the maximal center width

* chore(statusline): Describe the statusline configurability in the book

* chore(statusline): Correct and add documentation

* refactor(statusline): refactor some code following the code review

Avoid very small helper functions for the diagnositcs and inline them
instead.
Rename the config field `status_line` to `statusline` to remain
consistent with `bufferline`.

* chore(statusline): adjust documentation following the config field refactoring

* revert(statusline): revert regression introduced by c0a1870

* chore(statusline): slight adjustment in the configuration documentation

* feat(statusline): integrate changes from #2676 after rebasing

* refactor(statusline): remove the StatusLine struct

Because none of the functions need `Self` and all of them are in an own
file, there is no explicit need for the struct.

* fix(statusline): restore the configurability of color modes

The configuration was ignored after reintegrating the changes of #2676
in 8d28f95.

* fix(statusline): remove the spinner padding

* refactor(statusline): remove unnecessary format!()

1 files changed, 8 insertions, 155 deletions

diff --git a/helix-term/src/ui/editor.rs b/helix-term/src/ui/editor.rs
index a7c67a21..9b8bf8eb 100644
--- a/helix-term/src/ui/editor.rs
+++ b/helix-term/src/ui/editor.rs
@@ -7,7 +7,6 @@ use crate::{
 };
 
 use helix_core::{
-    coords_at_pos, encoding,
     graphemes::{
         ensure_grapheme_boundary_next_byte, next_grapheme_boundary, prev_grapheme_boundary,
     },
@@ -17,7 +16,7 @@ use helix_core::{
     LineEnding, Position, Range, Selection, Transaction,
 };
 use helix_view::{
-    document::{Mode, SCRATCH_BUFFER_NAME},
+    document::Mode,
     editor::{CompleteAction, CursorShapeConfig},
     graphics::{Color, CursorKind, Modifier, Rect, Style},
     input::KeyEvent,
@@ -29,6 +28,8 @@ use std::borrow::Cow;
 use crossterm::event::{Event, MouseButton, MouseEvent, MouseEventKind};
 use tui::buffer::Buffer as Surface;
 
+use super::statusline;
+
 pub struct EditorView {
     pub keymaps: Keymaps,
     on_next_key: Option<Box<dyn FnOnce(&mut commands::Context, KeyEvent)>>,
@@ -161,7 +162,11 @@ impl EditorView {
             .area
             .clip_top(view.area.height.saturating_sub(1))
             .clip_bottom(1); // -1 from bottom to remove commandline
-        self.render_statusline(editor, doc, view, statusline_area, surface, is_focused);
+
+        let mut context =
+            statusline::RenderContext::new(editor, doc, view, is_focused, &self.spinners);
+
+        statusline::render(&mut context, statusline_area, surface);
     }
 
     pub fn render_rulers(
@@ -730,158 +735,6 @@ impl EditorView {
         }
     }
 
-    pub fn render_statusline(
-        &self,
-        editor: &Editor,
-        doc: &Document,
-        view: &View,
-        viewport: Rect,
-        surface: &mut Surface,
-        is_focused: bool,
-    ) {
-        use tui::text::{Span, Spans};
-
-        //-------------------------------
-        // Left side of the status line.
-        //-------------------------------
-
-        let theme = &editor.theme;
-        let (mode, mode_style) = match doc.mode() {
-            Mode::Insert => (" INS ", theme.get("ui.statusline.insert")),
-            Mode::Select => (" SEL ", theme.get("ui.statusline.select")),
-            Mode::Normal => (" NOR ", theme.get("ui.statusline.normal")),
-        };
-        let progress = doc
-            .language_server()
-            .and_then(|srv| {
-                self.spinners
-                    .get(srv.id())
-                    .and_then(|spinner| spinner.frame())
-            })
-            .unwrap_or("");
-
-        let base_style = if is_focused {
-            theme.get("ui.statusline")
-        } else {
-            theme.get("ui.statusline.inactive")
-        };
-        // statusline
-        surface.set_style(viewport.with_height(1), base_style);
-        if is_focused {
-            let color_modes = editor.config().color_modes;
-            surface.set_string(
-                viewport.x,
-                viewport.y,
-                mode,
-                if color_modes { mode_style } else { base_style },
-            );
-        }
-        surface.set_string(viewport.x + 5, viewport.y, progress, base_style);
-
-        //-------------------------------
-        // Right side of the status line.
-        //-------------------------------
-
-        let mut right_side_text = Spans::default();
-
-        // Compute the individual info strings and add them to `right_side_text`.
-
-        // Diagnostics
-        let diags = doc.diagnostics().iter().fold((0, 0), |mut counts, diag| {
-            use helix_core::diagnostic::Severity;
-            match diag.severity {
-                Some(Severity::Warning) => counts.0 += 1,
-                Some(Severity::Error) | None => counts.1 += 1,
-                _ => {}
-            }
-            counts
-        });
-        let (warnings, errors) = diags;
-        let warning_style = theme.get("warning");
-        let error_style = theme.get("error");
-        for i in 0..2 {
-            let (count, style) = match i {
-                0 => (warnings, warning_style),
-                1 => (errors, error_style),
-                _ => unreachable!(),
-            };
-            if count == 0 {
-                continue;
-            }
-            let style = base_style.patch(style);
-            right_side_text.0.push(Span::styled("●", style));
-            right_side_text
-                .0
-                .push(Span::styled(format!(" {} ", count), base_style));
-        }
-
-        // Selections
-        let sels_count = doc.selection(view.id).len();
-        right_side_text.0.push(Span::styled(
-            format!(
-                " {} sel{} ",
-                sels_count,
-                if sels_count == 1 { "" } else { "s" }
-            ),
-            base_style,
-        ));
-
-        // Position
-        let pos = coords_at_pos(
-            doc.text().slice(..),
-            doc.selection(view.id)
-                .primary()
-                .cursor(doc.text().slice(..)),
-        );
-        right_side_text.0.push(Span::styled(
-            format!(" {}:{} ", pos.row + 1, pos.col + 1), // Convert to 1-indexing.
-            base_style,
-        ));
-
-        let enc = doc.encoding();
-        if enc != encoding::UTF_8 {
-            right_side_text
-                .0
-                .push(Span::styled(format!(" {} ", enc.name()), base_style));
-        }
-
-        // Render to the statusline.
-        surface.set_spans(
-            viewport.x
-                + viewport
-                    .width
-                    .saturating_sub(right_side_text.width() as u16),
-            viewport.y,
-            &right_side_text,
-            right_side_text.width() as u16,
-        );
-
-        //-------------------------------
-        // Middle / File path / Title
-        //-------------------------------
-        let title = {
-            let rel_path = doc.relative_path();
-            let path = rel_path
-                .as_ref()
-                .map(|p| p.to_string_lossy())
-                .unwrap_or_else(|| SCRATCH_BUFFER_NAME.into());
-            format!("{}{}", path, if doc.is_modified() { "[+]" } else { "" })
-        };
-
-        surface.set_string_truncated(
-            viewport.x + 8, // 8: 1 space + 3 char mode string + 1 space + 1 spinner + 1 space
-            viewport.y,
-            &title,
-            viewport
-                .width
-                .saturating_sub(6)
-                .saturating_sub(right_side_text.width() as u16 + 1) as usize, // "+ 1": a space between the title and the selection info
-            |_| base_style,
-            true,
-            true,
-        );
-    }
-
     /// Handle events by looking them up in `self.keymaps`. Returns None
     /// if event was handled (a command was executed or a subkeymap was
     /// activated). Only KeymapResult::{NotFound, Cancelled} is returned