added tab to insert mode

helix-term/src/editor.rs

@@ -1,5 +1,5 @@
 use clap::ArgMatches as Args;
-use helix_core::{state::coords_at_pos, state::Mode, syntax::HighlightEvent, Range, State};
+use helix_core::{state::Mode, syntax::HighlightEvent, Range, State};
 use helix_view::{commands, keymap, View};
 
 use std::{
@@ -24,6 +24,8 @@ use crossterm::{
 
 use tui::{backend::CrosstermBackend, buffer::Buffer as Surface, layout::Rect, style::Style};
 
+const TAB_WIDTH: usize = 4;
+
 type Terminal = tui::Terminal<CrosstermBackend<std::io::Stdout>>;
 
 static EX: smol::Executor = smol::Executor::new();
@@ -85,10 +87,7 @@ impl Editor {
                 // TODO: inefficient, should feed chunks.iter() to tree_sitter.parse_with(|offset, pos|)
                 let source_code = view.state.doc().to_string();
 
-                let last_line = std::cmp::min(
-                    (view.first_line + viewport.height - 1) as usize,
-                    view.state.doc().len_lines() - 1,
-                );
+                let last_line = view.last_line(viewport);
 
                 let range = {
                     // calculate viewport byte ranges
@@ -172,6 +171,8 @@ impl Editor {
                                     if line >= viewport.height {
                                         break 'outer;
                                     }
+                                } else if grapheme == "\t" {
+                                    visual_x += (TAB_WIDTH as u16);
                                 } else {
                                     // Cow will prevent allocations if span contained in a single slice
                                     // which should really be the majority case
@@ -281,12 +282,16 @@ impl Editor {
 
                 // render the cursor
                 let pos = view.state.selection().cursor();
-                let coords = coords_at_pos(&view.state.doc().slice(..), pos);
+
+                let pos = view
+                    .screen_coords_at_pos(&view.state.doc().slice(..), pos, area)
+                    .expect("Cursor is out of bounds.");
+
                 execute!(
                     stdout,
                     cursor::MoveTo(
-                        coords.col as u16 + viewport.x,
-                        coords.row as u16 - view.first_line + viewport.y,
+                        pos.col as u16 + viewport.x,
+                        pos.row as u16 - view.first_line + viewport.y,
                     )
                 );
             }

helix-view/src/commands.rs

@@ -301,6 +301,10 @@ pub fn insert_char(view: &mut View, c: char) {
     // TODO: need to store into history if successful
 }
 
+pub fn insert_tab(view: &mut View, _count: usize) {
+    insert_char(view, '\t');
+}
+
 pub fn insert_newline(view: &mut View, _count: usize) {
     insert_char(view, '\n');
 }

helix-view/src/keymap.rs

@@ -157,6 +157,10 @@ pub fn default() -> Keymaps {
                     code: KeyCode::Enter,
                     modifiers: Modifiers::NONE
                 }] => commands::insert_newline,
+                vec![Key {
+                    code: KeyCode::Tab,
+                    modifiers: Modifiers::NONE
+                }] => commands::insert_tab,
             )
     )
 }

helix-view/src/view.rs

@@ -1,9 +1,13 @@
 use anyhow::Error;
 
-use std::path::PathBuf;
+use std::{borrow::Cow, path::PathBuf};
 
 use crate::theme::Theme;
-use helix_core::State;
+use helix_core::{
+    graphemes::{grapheme_width, RopeGraphemes},
+    Position, RopeSlice, State,
+};
+use tui::layout::Rect;
 
 pub struct View {
     pub state: State,
@@ -44,4 +48,48 @@ impl View {
             self.first_line = line.saturating_sub(padding);
         }
     }
+
+    /// Calculates the last visible line on screen
+    #[inline]
+    pub fn last_line(&self, viewport: Rect) -> usize {
+        std::cmp::min(
+            (self.first_line + viewport.height - 1) as usize,
+            self.state.doc().len_lines() - 1,
+        )
+    }
+
+    /// Translates a document position to an absolute position in the terminal.
+    /// Returns a (line, col) position if the position is visible on screen.
+    // TODO: Could return width as well for the character width at cursor.
+    pub fn screen_coords_at_pos(
+        &self,
+        text: &RopeSlice,
+        pos: usize,
+        viewport: Rect,
+    ) -> Option<Position> {
+        let line = text.char_to_line(pos);
+
+        if line < self.first_line as usize || line > self.last_line(viewport) {
+            // Line is not visible on screen
+            return None;
+        }
+
+        let line_start = text.line_to_char(line);
+        let line_slice = text.slice(line_start..pos);
+        let mut col = 0;
+
+        for grapheme in RopeGraphemes::new(&line_slice) {
+            if grapheme == "\t" {
+                // TODO: this should be const TAB_WIDTH
+                col += 4;
+            } else {
+                let grapheme = Cow::from(grapheme);
+                col += grapheme_width(&grapheme);
+            }
+        }
+
+        let row = line - self.first_line as usize;
+
+        Some(Position::new(row, col))
+    }
 }