paintStartMarker function

void paintStartMarker(Canvas canvas, Offset offset, Color color, double iconSize,)

Renders a location pin icon to indicate the start point of a contract.

This function draws a location pin icon (from Material Icons) at the specified position on the canvas. The pin visually marks the starting point of a contract or trade on a financial chart, making it easy for users to identify where a contract began.

The function uses Flutter's TextPainter to render the icon, which is an efficient way to draw icons from icon fonts. The icon is rendered with the specified color and size, allowing for consistent styling with other chart elements.

This marker is typically used in conjunction with other visual elements like vertical lines (paintStartLine) to provide a complete visual representation of contract start points.

@param canvas The canvas on which to paint the marker. @param offset The position on the canvas where the marker should be drawn. @param color The color to use for the marker. @param iconSize The size of the icon in logical pixels.

Implementation

void paintStartMarker(
  Canvas canvas,
  Offset offset,
  Color color,
  double iconSize,
) {
  // Use the location_on icon from Material Icons as the pin marker
  const IconData icon = Icons.location_on;

  // Create a TextPainter to render the icon
  // TextPainter is used because it's an efficient way to render
  // icons from icon fonts like Material Icons
  TextPainter(textDirection: TextDirection.ltr)
    // Configure the text span with the icon character and styling
    ..text = TextSpan(
      // Convert the icon's code point to a character
      text: String.fromCharCode(icon.codePoint),
      style: TextStyle(
        fontSize: iconSize,
        fontFamily: icon.fontFamily,
        color: color,
      ),
    )
    // Calculate the layout of the icon
    ..layout()
    // Paint the icon at the specified offset
    ..paint(canvas, offset);
}