《战车世界：闪电战》用户界面中的ECS

使用ECS（Entity-Component-System）架构而非传统继承进行用户界面开发

本文是Evgeny Zakharov在C ++俄罗斯夏季会议上的演讲的继续，他在该会议上描述了使用ECS（实体组件系统）体系结构而不是传统继承和UI of Tanks Blitz中的UI设备的一部分开发用户界面。 

Eugene在他的报告中详细介绍了当今世界上使用UI框架的基本原则，还讲述了如何结交ECS和UI朋友，以及由此带来的利弊。

在本文中，Eugene使用《战车世界：闪电战》中的一个小型UI示例，展示了UI中ECS体系结构的最大优点。

在研究本文之前，我们建议您观看报告的视频。

实施径向进度显示

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void RadialProgressSystem::RegisterControl(Control &control)
{
    auto *pieClippable = control.GetComponent<RadialProgressComponent>();
    if (pieClippable && control.GetComponent<TextureComponent>())
    {
        pieClippable->MarkAsDirty();
        this->registeredControls.insert(&control);
    }
}

, ,   TextureComponent  RadialProgressComponent. , , – Process. 

void RadialProgressSystem::UnregisterControl(Control &control)
{
    this->registeredControls.erase(&control);
}

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void RadialProgressSystem::Process(float elapsedTime)
{
    for (Control *control : this->registeredControls)
    {
        auto *pieClippable = control->GetComponent<UIRadialProgressComponent>();
        if (!pieClippable->IsDirty())
        {
            continue;
        }

        auto *polygon = control->GetComponent<ClipPolygonComponent>();
        if (!polygon)
        {
            ReportError(control, "You need UIClipPolygonComponent for UIRadialProgressComponent");
            continue;
        }

        auto *textureComponent = control->GetComponent<TextureComponent>();
        if (textureComponent != nullptr && textureComponent->GetSprite() != nullptr)
        {
            Polygon2 &polygonData = polygon->GetPolygon();
            polygonData.Clear();

            const Vector2 imageSize = textureComponent->GetSprite()->GetSize();
            const Vector2 pivot = CalcPivot(pieClippable);
            const Vector2 center = imageSize * pivot;

            const float progress = pieClippable->GetProgress();

            float startAngle = pieClippable->GetNormalizedStartAngle();
            float endAngle = pieClippable->GetNormalizedEndAngle();

            const float currentAngle = Interpolation::Linear(startAngle, endAngle, 0, progress, 1);

            const float width = pivot.x > 0 ? center.x : imageSize.x;
            const float height = pivot.y > 0 ? center.y : imageSize.y;
            const float initAngle = std::atan(width / height);

            polygonData.AddPoint(center);
            polygonData.AddPoint(CalcPointOnRectangle(startAngle, center, imageSize));

            int direction = startAngle < endAngle ? 1 : -1;
            float startOffset = direction > 0 ? 0 : PI_2 + pieClippable->GetAngleBias();

            float squareAngle = startOffset + direction * initAngle;

            const float directedStartAngle = direction * startAngle;
            const float directedEndAngle = direction * endAngle;
            const float directedCurrentAngle = direction * currentAngle;
            float directedSqureAngle = direction * squareAngle;
            const float doubledInitAngle = initAngle * 2.f;

            Vector<Vector2> squares {
                Vector2(imageSize.x, 0),
                Vector2(imageSize.x, imageSize.y),
                Vector2(0.f, imageSize.y),
                Vector2(0.f, 0.f)
            };

            int i = 0;
            while (directedSqureAngle < directedEndAngle)
            {
                if (directedSqureAngle < directedCurrentAngle && directedSqureAngle > directedStartAngle)
                {
                    int squareIndex = direction > 0 ? i % 4 : 3 - i % 4;
                    polygonData.AddPoint(squares[squareIndex]);
                }
                i++;
                int switcher = i % 2;
                squareAngle += direction * (PI * switcher - Sign(switcher - 0.5f) * doubledInitAngle);
                directedSqureAngle = direction * squareAngle;
            }

            polygonData.AddPoint(CalcPointOnRectangle(currentAngle, center, imageSize));

            pieClippable->ResetDirty();
        }
    }
}

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