From c656dc0931be5ef9b34302042e58d4bf25bb9181 Mon Sep 17 00:00:00 2001
From: CrispyPin <crispin@tasa.se>
Date: Sun, 26 Feb 2023 01:02:10 +0100
Subject: [PATCH] render cursor position properly after tabs

---
 .gitignore    |  2 +-
 src/editor.rs | 20 ++++++++++++++++----
 2 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/.gitignore b/.gitignore
index e49dec6..9f2a7dd 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,2 @@
 /target
-err
+err.log
diff --git a/src/editor.rs b/src/editor.rs
index 0b46b54..86ab9e1 100644
--- a/src/editor.rs
+++ b/src/editor.rs
@@ -9,6 +9,8 @@ use termion::{
 	raw::IntoRawMode,
 };
 
+const TAB_SIZE: usize = 4;
+
 pub struct Editor {
 	text: String,
 	lines: Vec<Line>,
@@ -100,8 +102,8 @@ impl Editor {
 		}
 	}
 
-	fn current_line(&self) -> &Line {
-		self.lines.get(self.cursor.line).unwrap_or(&(0..0))
+	fn current_line(&self) -> Line {
+		self.lines.get(self.cursor.line).unwrap_or(&(0..0)).clone()
 	}
 
 	fn find_lines(&mut self) {
@@ -124,12 +126,15 @@ impl Editor {
 			print!(
 				"{}{}",
 				cursor::Goto(1, row as u16 + 1),
-				text.replace('\t', "    ")
+				text.replace('\t', &" ".repeat(TAB_SIZE))
 			);
 		}
 		print!(
 			"{}",
-			cursor::Goto(self.cursor.column as u16 + 1, self.cursor.line as u16 + 1)
+			cursor::Goto(
+				self.physical_column() as u16 + 1,
+				self.cursor.line as u16 + 1
+			)
 		);
 		stdout().flush().unwrap();
 	}
@@ -154,4 +159,11 @@ impl Editor {
 	fn index(&self) -> usize {
 		self.current_line().start + self.cursor.column
 	}
+
+	fn physical_column(&self) -> usize {
+		let start = self.current_line().start;
+		let end = self.current_line().start + self.cursor.column;
+		let preceding_tabs = self.text[start..end].chars().filter(|&c| c == '\t').count();
+		self.cursor.column + preceding_tabs * (TAB_SIZE - 1)
+	}
 }