事件

要怎麼跟視窗互動呢？使用者在視窗上互動時，SFML 會產生事件(Event)，進而接收窗口的事件，並針對發生的事件（例如：滑鼠移動、點擊，鍵盤點擊等）做相對應的處理。

sf::Event event;
while (window.pollEvent(event))
{
    switch (event.type)
    {
        case sf::Event::Closed:
            window.close();
            break;

        case sf::Event::KeyPressed:
            // ...
            break;

        default:
            break;
    }
}

SFML 總共有以下這幾種事件：

• sf::Event::Closed

  • 視窗關閉

• sf::Event::LostFocus, sf::Event::GainedFocus

  • 選擇/隱藏 視窗

• sf::Event::Resized

  • 視窗大小調整
  • 資料 event.size
    • event.size.width 寬
    • event.size.height 高

• sf::Event::TextEntered

  • 文字輸入

if (event.type == sf::Event::TextEntered)
{
    if (event.text.unicode < 128)
        std::cout << "ASCII character typed: " << static_cast<char>(event.text.unicode) << std::endl;
}

• sf::Event::KeyPressed, sf::Event::KeyReleased
  • 鍵盤按下/放開按鍵
  • 會有延遲（跟在文字編輯器上打字一樣），如果不希望有延遲請用 Real-time Input
  • 可以把關閉重複的事件（當按鍵持續按下）
    • window.setKeyRepeatEnabled(false)

if (event.type == sf::Event::KeyPressed)
{
    if (event.key.code == sf::Keyboard::Escape)
    {
        std::cout << "the escape key was pressed" << std::endl;
        std::cout << "control:" << event.key.control << std::endl;
        std::cout << "alt:" << event.key.alt << std::endl;
        std::cout << "shift:" << event.key.shift << std::endl;
        std::cout << "system:" << event.key.system << std::endl;
    }
}

• sf::Event::MouseWheelScrolled
  • 滾動滑鼠滾輪
  • 資料： event.mouseWheelScroll
    • wheel 哪種滾輪
      • sf::Mouse::Wheel::VerticalWheel
      • sf::Mouse::Wheel::HorizontalWheel
    • delta 位移量 （正代表上、左，負相反）
    • x, y 座標

if (event.type == sf::Event::MouseWheelScrolled)
{
    if (event.mouseWheelScroll.wheel == sf::Mouse::VerticalWheel)
        std::cout << "wheel type: vertical" << std::endl;
    else if (event.mouseWheelScroll.wheel == sf::Mouse::HorizontalWheel)
        std::cout << "wheel type: horizontal" << std::endl;
    else
        std::cout << "wheel type: unknown" << std::endl;
    std::cout << "wheel movement: " << event.mouseWheelScroll.delta << std::endl;
    std::cout << "mouse x: " << event.mouseWheelScroll.x << std::endl;
    std::cout << "mouse y: " << event.mouseWheelScroll.y << std::endl;
}

• sf::Event::MouseButtonPressed, sf::Event::MouseButtonReleased
  • 滑鼠按鍵
  • 資料：event.mouseButton
    • button 按鍵
    • x, y 座標

if (event.type == sf::Event::MouseButtonPressed)
{
    if (event.mouseButton.button == sf::Mouse::Right)
    {
        std::cout << "the right button was pressed" << std::endl;
        std::cout << "mouse x: " << event.mouseButton.x << std::endl;
        std::cout << "mouse y: " << event.mouseButton.y << std::endl;
    }
}

• sf::Event::MouseMoved
  • 滑鼠移動
  • 只有在視窗內才會產生此事件

if (event.type == sf::Event::MouseMoved)
{
    std::cout << "new mouse x: " << event.mouseMove.x << std::endl;
    std::cout << "new mouse y: " << event.mouseMove.y << std::endl;
}

• sf::Event::MouseEntered, sf::Event::MouseMouseLeft

  • 滑鼠進入視窗、離開視窗

• 此外還有跟搖桿有關的事件，但這裡省略