Score, Lives, and Game Over

A playable game needs feedback: a visible score, a limited number of lives, and a clear end condition.

Drawing text

sf::Font font;
if (!font.loadFromFile("arial.ttf")) {
    // handle missing font file
}

sf::Text scoreText;
scoreText.setFont(font);
scoreText.setCharacterSize(20);
scoreText.setFillColor(sf::Color::White);
scoreText.setPosition(10.f, 10.f);

// Each frame:
scoreText.setString("Score: " + std::to_string(score) + "  Lives: " + std::to_string(lives));
window.draw(scoreText);

Losing a life

When the ball's position goes past the bottom edge, it's a miss, not a wall bounce:

if (ball.shape.getPosition().y > windowHeight) {
    lives--;

    if (lives <= 0) {
        gameOver = true;
    } else {
        // Reset the ball above the paddle to keep playing
        ball.shape.setPosition(windowWidth / 2.f, windowHeight / 2.f);
        ball.velocity = sf::Vector2f(200.f, -200.f);
    }
}

Winning

if (bricks.empty()) {
    won = true;
}

The pieces

• sf::Font and sf::Text need a real .ttf file, on Linux /usr/share/fonts/truetype/dejavu/DejaVuSans.ttf usually exists, on other platforms bundle a font file with your project.
• std::to_string(score) converts a number to a std::string so it can be concatenated with + onto other strings.
• Losing a life resets the ball instead of ending the game immediately, the game should only end once lives reaches 0.
• Checking bricks.empty() is a clean win condition, once every brick is destroyed, the vector naturally has no elements left.