C++ (Cpp) StyleContext::setGlobal示例

void Tile::build(StyleContext& _ctx, const Scene& _scene, const TileData& _data, const DataSource& _source) {

    const auto& layers = _scene.layers();

    _ctx.setGlobal("$zoom", m_id.z);

    for (auto& style : _scene.styles()) {
        style->onBeginBuildTile(*this);
    }

    for (const auto& datalayer : layers) {

        if (datalayer.source() != _source.name()) { continue; }

        for (const auto& collection : _data.layers) {

            if (!collection.name.empty() && collection.name != datalayer.collection()) { continue; }

            for (const auto& feat : collection.features) {
                _ctx.setFeature(feat);

                std::vector<DrawRule> rules;
                datalayer.match(feat, _ctx, rules);

                for (auto& rule : rules) {
                    auto* style = _scene.findStyle(rule.style);

                    if (style) {
                        rule.eval(_ctx);
                        style->buildFeature(*this, feat, rule);
                    }
                }
            }
        }
    }

    for (auto& style : _scene.styles()) {
        style->onEndBuildTile(*this);
    }

    for (auto& geometry : m_geometry) {
        geometry.second->compileVertexBuffer();
    }
}