在superview中定位具有任意定位点的子视图

我很难想出正确的算法。我有一个超级视图(绿色)和一个子视图(黄色)。具有任意的锚定点(只是一个选择点,不与层的 anchor 属性)在此子视图(红色)中,我必须按照放置此红色点的方式放置子视图并调整其大小 子视图的大小也会随之调整 按比例地 如果需要(如果在移动其帧后超出superview的边界)。没有使用自动布局。看看我想要什么。

所以基本上我写了一个C++测试例程,其中一个新的比例矩形被计算为“新的点”(因此,这个点得到这个新矩形的中心),但是我不知道接下来要做什么来处理一个不在子视图中心的点。 Rect 基本上是一个具有 x, y, width, height 成员。

    Rect
    calculateRectInBounds(const Rect &boundingRect, const Rect &initialRect, const Point &translationPoint)
    {
        double boundsWidth = boundingRect.getWidth();
        double boundsHeight = boundingRect.getHeight();
        double distanceX, distanceY;
        Size sizeByWidth, sizeByHeight;

        // detect part where point is

        /*
         * UL | UR
         * ---C---
         * LL | LR
         */

        // -- upper left - check left & top borders

        if (translationPoint.x <= boundsWidth / 2 && translationPoint.y < boundsHeight / 2) {
            distanceX = translationPoint.x;
            distanceY = translationPoint.y;

            sizeByWidth = scaleSizeToWidth(initialRect.getSize(), distanceX);
            sizeByHeight = scaleSizeToHeight(initialRect.getSize(), distanceY);

            if (sizeByWidth.height > distanceY) {
                return {translationPoint.x - sizeByHeight.width,
                        0,
                        sizeByHeight.width * 2,
                        sizeByHeight.height * 2};
            }

            return {0,
                    translationPoint.y - sizeByWidth.height,
                    sizeByWidth.width * 2,
                    sizeByWidth.height * 2};
        }

        // -- upper right - check top & right borders

        if (translationPoint.x > boundsWidth / 2 && translationPoint.y <= boundsHeight / 2) {
            distanceX = boundsWidth - translationPoint.x;
            distanceY = translationPoint.y;

            sizeByWidth = scaleSizeToWidth(initialRect.getSize(), distanceX);
            sizeByHeight = scaleSizeToHeight(initialRect.getSize(), distanceY);

            if (sizeByWidth.height > distanceY) {
                return {translationPoint.x - sizeByHeight.width,
                        0,
                        sizeByHeight.width * 2,
                        sizeByHeight.height * 2};
            }

            return {translationPoint.x - sizeByWidth.width,
                    translationPoint.y - sizeByWidth.height,
                    sizeByWidth.width * 2,
                    sizeByWidth.height * 2};
        }

        // -- lower right - check right & bottom borders

        if (translationPoint.x >= boundsWidth / 2 && translationPoint.y > boundsHeight / 2) {
            distanceX = boundsWidth - translationPoint.x;
            distanceY = boundsHeight - translationPoint.y;

            sizeByWidth = scaleSizeToWidth(initialRect.getSize(), distanceX);
            sizeByHeight = scaleSizeToHeight(initialRect.getSize(), distanceY);

            if (sizeByWidth.height > distanceY) {
                return {translationPoint.x - sizeByHeight.width,
                        translationPoint.y - sizeByHeight.height,
                        sizeByHeight.width * 2,
                        sizeByHeight.height * 2};
            }

            return {translationPoint.x - sizeByWidth.width,
                    translationPoint.y - sizeByWidth.height,
                    sizeByWidth.width * 2,
                    sizeByWidth.height * 2};
        }

        // -- lower left - check bottom & left borders

        if (translationPoint.x < boundsWidth / 2 && translationPoint.y >= boundsHeight / 2) {
            distanceX = translationPoint.x;
            distanceY = boundsHeight - translationPoint.y;

            sizeByWidth = scaleSizeToWidth(initialRect.getSize(), distanceX);
            sizeByHeight = scaleSizeToHeight(initialRect.getSize(), distanceY);

            if (sizeByWidth.height > distanceY) {
                return {translationPoint.x - sizeByHeight.width,
                        translationPoint.y - sizeByHeight.height,
                        sizeByHeight.width * 2,
                        sizeByHeight.height * 2};
            }

            return {0,
                    translationPoint.y - sizeByWidth.height,
                    sizeByWidth.width * 2,
                    sizeByWidth.height * 2};
        }

        // -- center

        return initialRect;
    }

Size
scaleSizeToWidth(Size size, double newWidth)
{
    return {newWidth, (std::min(size.width, newWidth) / std::max(size.width, newWidth)) * size.height};
}

Size
scaleSizeToHeight(Size size, double newHeight)
{
    return {(std::min(size.height, newHeight) / std::max(size.height, newHeight)) * size.width, newHeight};
}

    Rect
    calculateRectInBounds(const Rect &boundingRect, const Rect &initialRect, const Point &anchorPoint)
    {
        auto lDist = anchorPoint.x - initialRect.getX();
        auto rDist = initialRect.getWidth() - lDist;
        auto tDist = anchorPoint.y - initialRect.getY();
        auto bDist = initialRect.getHeight() - tDist;

        auto lRatio = (lDist * 2) / boundingRect.getWidth();
        auto rRatio = (rDist * 2) / boundingRect.getWidth();
        auto tRatio = (tDist * 2) / boundingRect.getHeight();
        auto bRatio = (bDist * 2) / boundingRect.getHeight();

        auto scale = 1 / std::max({lRatio, rRatio, tRatio, bRatio});

        auto x = initialRect.getWidth() / 2 - lDist * scale + initialRect.getX();
        auto y = initialRect.getHeight() / 2 - tDist * scale + initialRect.getY();
        auto width = initialRect.getWidth() * scale;
        auto height = initialRect.getHeight() * scale;

        return {x, y, width, height};
    }