Fix cursor alignment on long lines

src/usr/editor.rs

@@ -236,6 +236,36 @@ impl Editor {
  self.highlighted.clear();
  }
 
+ // Align cursor that is past the end of line,
+ // to the end of line or to the left of the screen.
+ //
+ // If the cursor is at the end of the long line
+ // that takes two screens in the following diagram:
+ //
+ // +----------------------+----------------------+
+ // | | |
+ // | This is a short line | |
+ // | | |
+ // | This is a loooooooooo|oooooong line |
+ // | | |
+ // +----------------------+----------------------+
+ //
+ // Going up should move the cursor to the left of
+ // the second screen, then going left should move
+ // to the left of the first screen. If going up
+ // another time before going left, the cursor
+ // should be at the end of the short line.
+ fn align_cursor(&mut self) {
+ let eol = self.lines[self.offset.y + self.cursor.y].chars().count();
+ if eol <= self.offset.x + self.cursor.x {
+ if eol <= self.offset.x {
+ self.cursor.x = 0;
+ } else {
+ self.cursor.x = eol - self.offset.x - 1;
+ }
+ }
+ }
+
  pub fn run(&mut self) -> Result<(), ExitCode> {
  print!("\x1b[2J\x1b[1;1H"); // Clear screen and move cursor to top
  self.print_screen();
@@ -319,7 +349,7 @@ impl Editor {
  self.offset.y -= 1;
  self.print_screen();
  }
- self.cursor.x = self.next_pos(self.cursor.x, self.cursor.y);
+ self.align_cursor();
  },
  'B' if csi => { // Arrow Down
  let is_eof = self.offset.y + self.cursor.y == self.lines.len() - 1;
@@ -333,7 +363,7 @@ impl Editor {
  } else {
  self.cursor.y += 1;
  }
- self.cursor.x = self.next_pos(self.cursor.x, self.cursor.y);
+ self.align_cursor();
  }
  },
  'C' if csi => { // Arrow Right
@@ -361,7 +391,7 @@ impl Editor {
  self.offset.x -= self.cols();
  self.cursor.x += self.cols() - 1;
  self.print_screen();
- self.cursor.x = self.next_pos(self.cursor.x, self.cursor.y);
+ self.align_cursor();
  } else {
  self.cursor.x -= 1;
  }
@@ -521,20 +551,6 @@ impl Editor {
  Ok(())
  }
 
- // Move cursor past end of line to end of line or left of the screen
- fn next_pos(&self, x: usize, y: usize) -> usize {
- let eol = self.lines[self.offset.y + y].chars().count();
- if eol <= self.offset.x + x {
- if eol <= self.offset.x {
- 0
- } else {
- eol - 1
- }
- } else {
- x
- }
- }
-
  fn rows(&self) -> usize {
  sys::console::rows() - 1 // Leave out one line for status line
  }