Method doUpdateVisibility

valdi/src/valdi/runtime/Context/ViewNode.cpp:685–801

    if (visibilityChanged) {
        _viewNodeTree->flushVisibilityObservers();
    }
}

bool ViewNode::doUpdateVisibility(const Valdi::Frame& viewport,
                                  bool parentHasChanged,
                                  bool parentIsVisible,
                                  int& visitedNodes) {
    visitedNodes++;

    auto needsUpdate = calculatedViewportNeedsUpdate() || parentHasChanged;
    auto childrenNeedsUpdate = calculatedViewportHasChildNeedsUpdate();
    auto viewportChanged = false;
    auto changed = false;

    if (needsUpdate) {
        Frame clipRect;

        auto visibleInViewport = parentIsVisible;

        // Only bother calculating the viewport if the parent is visible,
        // otherwise viewport is assumed to be empty frame.
        if (parentIsVisible) {
            auto bounds = calculateSelfViewport();

            if (VALDI_UNLIKELY(ignoreParentViewport())) {
                clipRect = bounds;
            } else {
                visibleInViewport = bounds.intersects(viewport);
                if (visibleInViewport) {
                    clipRect = bounds.intersection(viewport);
                }
            }

            if (visibleInViewport) {
                clipRect.x -= bounds.x;
                clipRect.y -= bounds.y;

                // Reverse-map the clip rect from visual (scaled) space back into
                // the local coordinate space so children see the correct visible
                // range. Negative scale also flips the axis; positive scale != 1
                // only compresses/expands without flipping.
                if (_scaleX < 0.0f) {
                    const float absScaleX = -_scaleX;
                    clipRect.x = (bounds.width - (clipRect.x + clipRect.width)) / absScaleX;
                    clipRect.width = clipRect.width / absScaleX;
                } else if (_scaleX > 0.0f && _scaleX != 1.0f) {
                    clipRect.x /= _scaleX;
                    clipRect.width /= _scaleX;
                }
                if (_scaleY < 0.0f) {
                    const float absScaleY = -_scaleY;
                    clipRect.y = (bounds.height - (clipRect.y + clipRect.height)) / absScaleY;
                    clipRect.height = clipRect.height / absScaleY;
                } else if (_scaleY > 0.0f && _scaleY != 1.0f) {
                    clipRect.y /= _scaleY;
                    clipRect.height /= _scaleY;
                }