remember-styles.h

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// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Remember what the current style context is and test for changes.
 *
 * Authors:
 *   Martin Owens <doctormo@geek-2.com>
 *
 * Copyright (C) 2025 Authors
 *
 * Released under GNU GPL v2+, read the file 'COPYING' for more information.
 */
 
#ifndef EXTENSION_INTERNAL_PDFOUTPUT_REMEMBERSTYLES_H
#define EXTENSION_INTERNAL_PDFOUTPUT_REMEMBERSTYLES_H
 
#include <set>
#include <stack>
#include <string>
 
#include "attributes.h"
#include "style.h"
#include "util/scope_exit.h"
 
class SPStyle;
 
namespace Inkscape::Extension::Internal {
 
using StyleMap = std::map<SPAttr, std::string>;
 
class StyleMemory
{
public:
    explicit StyleMemory(std::set<SPAttr> remember_attrs)
        : _attrs(std::move(remember_attrs))
    {
        _changes.emplace();
    }
 
    StyleMap get_changes(SPStyle const *style) const;
 
    StyleMap get_changes_and_remember(SPStyle const *style)
    {
        StyleMap changes = get_changes(style);
        _push(changes);
        return changes;
    }
 
    StyleMap get_ifset(SPStyle const *style) const;
 
    StyleMap const &get_state() const
    {
        return _changes.top();
    };
 
    [[nodiscard]] auto remember(StyleMap map)
    {
        _push(std::move(map));
        return scope_exit([this] { _changes.pop(); });
    }
 
private:
    // A list of CSS properties to watch for changes in
    std::set<SPAttr> const _attrs;
 
    // A stack of complete StyleMaps strings
    std::stack<StyleMap> _changes;
 
    void _push(StyleMap changes)
    {
        // The incoming map is a delta, but we must store a merge between the previous and the delta.
        auto current = get_state();
        changes.merge(std::move(current));
        _changes.push(std::move(changes));
    }
};
 
} // namespace Inkscape::Extension::Internal
 
#endif /* !EXTENSION_INTERNAL_PDFOUTPUT_REMEMBERSTYLES_H */
 
/*
  Local Variables:
  mode:c++
  c-file-style:"stroustrup"
  c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
  indent-tabs-mode:nil
  fill-column:99
  End:
*/
// vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:fileencoding=utf-8:textwidth=99 :