Fix page down behavior, resolves #1

src/Document.php

@@ -230,6 +230,10 @@ class Document {
 
 			// Add a new row with the contents of the previous row at the point of the split
 			$this->insertRow($at->y + 1, substr($chars, $at->x));
+
+			// Highlight the two changed rows
+			$row->update();
+			$this->rows[$at->y + 1]->update();
 		}
 
 		$this->dirty = true;

src/Editor.php

@@ -56,6 +56,11 @@ class Editor {
 	 */
 	protected bool $shouldQuit = false;
 
+	/**
+	 * @var int The amount to move the cursor off the left
+	 */
+	protected int $cursorLeftOffset = 0;
+
 	/**
 	 * @var int The number of times to confirm you wish to quit
 	 */
@@ -87,6 +92,8 @@ class Editor {
 	{
 		$this->statusMessage = StatusMessage::from('HELP: Ctrl-S = save | Ctrl-Q = quit | Ctrl-F = find');
 		$this->cursor = Point::new();
+		$this->cursor->x += $this->cursorLeftOffset;
+
 		$this->offset = Point::new();
 		$this->terminalSize = Terminal::size();
 
@@ -385,13 +392,13 @@ class Editor {
 
 			($fileRow >= $this->document->numRows)
 				? $this->drawPlaceholderRow($y)
-				: $this->drawRow($fileRow);
+				: $this->drawRow($fileRow, true);
 
 			$this->outputBuffer .= "\r\n";
 		}
 	}
 
-	protected function drawRow(int $rowIdx): void
+	protected function drawRow(int $rowIdx, bool $lineNumbers): void
 	{
 		$row = $this->document->row($rowIdx);
 		if ( ! $row->isValid())
@@ -409,8 +416,46 @@ class Editor {
 			$len = $this->terminalSize->cols;
 		}
 
-		$chars = substr($row->render, $this->offset->x, (int)$len);
-		$hl = array_slice($row->hl, $this->offset->x, (int)$len);
+		if ($lineNumbers)
+		{
+			$this->drawLineNumbers($rowIdx);
+		}
+
+		$this->drawRowHighlighting($row, $len);
+
+		$this->outputBuffer .= ANSI::RESET_TEXT;
+		$this->outputBuffer .= ANSI::color(Color::FG_WHITE);
+	}
+
+	protected function drawLineNumbers(int $rowIdx): void
+	{
+		$rawColCount = match (true) {
+			$this->document->numRows > 50 => 3,
+			$this->document->numRows > 500 => 4,
+			$this->document->numRows > 5_000 => 5,
+			$this->document->numRows > 50_000 => 6,
+			$this->document->numRows > 500_000 => 7,
+			default => 2,
+		};
+
+		$rowNumber = $rowIdx + 1;
+		$digitLen = strlen("$rowNumber");
+		$frontPadding = str_repeat(' ', $rawColCount - $digitLen);
+		$rearPadding = str_repeat(' ', 2);
+
+		$output = sprintf("%s%d%s", $frontPadding, $rowNumber, $rearPadding);
+
+		$this->outputBuffer .= ANSI::RESET_TEXT;
+		$this->outputBuffer .= ANSI::color(Color::FG_WHITE);
+		$this->outputBuffer .= $output;
+
+		$this->cursorLeftOffset = strlen($output);
+	}
+
+	protected function drawRowHighlighting(Row $row, int $len): void
+	{
+		$chars = substr($row->render, $this->offset->x, $len);
+		$hl = array_slice($row->hl, $this->offset->x, $len);
 
 		$currentColor = -1;
 
@@ -454,9 +499,6 @@ class Editor {
 				$this->outputBuffer .= $ch;
 			}
 		}
-
-		$this->outputBuffer .= ANSI::RESET_TEXT;
-		$this->outputBuffer .= ANSI::color(Color::FG_WHITE);
 	}
 
 	protected function drawPlaceholderRow(int $y): void
@@ -548,9 +590,10 @@ class Editor {
 		$this->drawMessageBar();
 
 		// Specify the current cursor position
+		// The current 'x' position takes into account the length of the line number column
 		$this->outputBuffer .= ANSI::moveCursor(
 			$this->cursor->y - $this->offset->y,
-			$this->renderX - $this->offset->x
+			$this->renderX - $this->offset->x + $this->cursorLeftOffset,
 		);
 
 		$this->outputBuffer .= ANSI::SHOW_CURSOR;
@@ -666,7 +709,7 @@ class Editor {
 
 	protected function moveCursor(string $key): void
 	{
-		$x = $this->cursor->x;
+		$x = saturating_sub($this->cursor->x, $this->cursorLeftOffset);
 		$y = $this->cursor->y;
 		$row = $this->document->row($y);
 		if ( ! $row->isValid())
@@ -685,7 +728,7 @@ class Editor {
 				{
 					// Beginning of a line, go to end of previous line
 					$y--;
-					$x = $row->size - 1;
+					$x = $this->document->row($y)->size - 1;
 				}
 				break;
 
@@ -735,7 +778,7 @@ class Editor {
 				break;
 
 			default:
-				// Do nothing
+				return;
 		}
 
 		// Snap cursor to the end of a row when moving
@@ -749,8 +792,9 @@ class Editor {
 			}
 
 			$this->cursor->x = $x;
-			$this->cursor->y = $y;
 		}
+
+		$this->cursor->y = ($y >= $this->document->numRows) ? $this->document->numRows - 1 : $y;
 	}
 
 	protected function insertChar(string $c): void
@@ -766,7 +810,7 @@ class Editor {
 			$this->document->delete($this->cursor);
 		}
 
-		if ($ch === KeyType::BACKSPACE && ($this->cursor->x > 0 || $this->cursor->y > 0))
+		if ($ch === KeyType::BACKSPACE && ($this->cursor->x > $this->cursorLeftOffset || $this->cursor->y > 0))
 		{
 			$this->moveCursor(KeyType::ARROW_LEFT);
 			$this->document->delete($this->cursor);

src/FileType.php

@@ -115,7 +115,7 @@ class FileType {
 					'usize', '&str', 'Copy', 'Drop', 'From', 'Into', 'None', 'Self', 'Send', 'Some',
 					'Sync', 'bool', 'char', 'i128', 'u128', 'Box', 'Err', 'Ord', 'Vec', 'dyn', 'f32',
 					'f64', 'i16', 'i32', 'i64', 'str', 'u16', 'u32', 'u64', 'Eq', 'Fn', 'Ok', 'i8', 'u8',
-					'&mut self', '&mut', '&self', 'self',
+					'&mut self', '&mut', '&self', 'self', '()',
 				],
 				[
 					'...', '=>', '..', '>>=', '<<=', '--', '%=', '>>', ':=', '++', '/=', '<<', '>=',

src/Row.php

@@ -263,8 +263,15 @@ class Row {
 				|| $this->highlightCommonOperators($i, $syntax)
 				|| $this->highlightNumber($i, $syntax)
 			) {
+				if ($i >= $this->rsize)
+				{
+					break;
+				}
+				else
+				{
 					continue;
 				}
+			}
 
 			$i++;
 		}

src/functions.php

@@ -189,6 +189,12 @@ function tabs_to_spaces(string $str, int $number = KILO_TAB_STOP): string
 	return str_replace(RawKeyCode::TAB, str_repeat(RawKeyCode::SPACE, $number), $str);
 }
 
+/**
+ * Get an understandable name for the type of error code
+ *
+ * @param int $code
+ * @return string
+ */
 function error_code_name(int $code): string
 {
 	return 	match ($code) {
@@ -210,11 +216,28 @@ function error_code_name(int $code): string
 	};
 }
 
+/**
+ * Add two integers, returning the sum, or if the
+ * sum is greater than $max, returning $max
+ *
+ * @param int $a
+ * @param int $b
+ * @param int $max
+ * @return int
+ */
 function saturating_add(int $a, int $b, int $max): int
 {
 	return ($a + $b > $max) ? $max : $a + $b;
 }
 
+/**
+ * Subtract $b from $a, returning the difference
+ * or 0, whichever is greater
+ *
+ * @param int $a
+ * @param int $b
+ * @return int
+ */
 function saturating_sub(int $a, int $b): int
 {
 	if ($b > $a)