Extract addBlock in GdTrait so we can extend it to draw custom shapes

[xosofox]

As QR Codes do work with circles or partly rounded shapes, extracting the "addBlock" method allows to create custom writers, using the GdTrait but overwriting the addBlock method

example:

<?php

namespace App\Service;

use Endroid\QrCode\Writer\PngWriter;

readonly class PngShapeWriter extends PngWriter
{
    public function addBlock(
        \GdImage $baseImage,
        int $rowIndex,
        int $columnIndex,
        int $baseBlockSize,
        int $foregroundColor,
    ): void {

        // will draw a circle instead of a square
        imagefilledellipse(
            $baseImage,
            $columnIndex * $baseBlockSize + $baseBlockSize/2,
            $rowIndex * $baseBlockSize + $baseBlockSize/2,
            $baseBlockSize - 1,
            $baseBlockSize - 1,
            $foregroundColor
        );
    }
}

[Copilot]

Pull request overview

This PR enables customization of how individual QR “blocks” are rendered in GD-based writers by extracting the block-drawing logic into an overridable method, and by making PngWriter extendable so consumers can implement custom shapes (e.g., circles).

Changes:

• Removed final from PngWriter to allow extending it for custom rendering.
• Refactored GdTrait::writeGd() to delegate per-block drawing to a new addBlock() method.
• Added a default addBlock() implementation that draws the original square block via imagefilledrectangle().

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
src/Writer/PngWriter.php	Makes the PNG writer extendable to support custom writers overriding block rendering.
src/Writer/GdTrait.php	Extracts block rendering into addBlock() so subclasses can customize the rendered shape per matrix cell.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[endroid]

@Copilot what about composition over inheritance, why would I need to allow to extend it

[xosofox]

Are you asking me or copilot?

In case: I was just looking for a simple way to replace the block rendering with custom code and did not come up with a better solution (without code duplication)