htmlcss.cpp

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Copyright (c) 2021, Jan Koester jan.koester@gmx.net
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#include "htmlcss.h"
 
#include <algorithm>
#include <vector>
 
namespace {
 
    std::string lowerCopy(const std::string &s) {
        std::string t = s;
        std::transform(t.begin(), t.end(), t.begin(),
            [](unsigned char c) { return std::tolower(c); });
        return t;
    }
 
    // Strips a trailing "!important" (case-insensitive, any whitespace
    // before the "!") from a CSS declaration value -- see the identical
    // helper in css.cpp for why this matters; duplicated here (rather than
    // exposed from css.cpp) since it's a small, self-contained detail of
    // normalizing a single value string, not selector/cascade logic.
    void stripImportant(std::string &value) {
        size_t bang = value.rfind('!');
        if (bang == std::string::npos) return;
 
        size_t start = value.find_first_not_of(" \t\n\r", bang + 1);
        size_t end = value.find_last_not_of(" \t\n\r");
        if (start == std::string::npos || end == std::string::npos || start > end) return;
 
        std::string tail = value.substr(start, end - start + 1);
        std::transform(tail.begin(), tail.end(), tail.begin(),
            [](unsigned char c) { return std::tolower(c); });
        if (tail != "important") return;
 
        size_t valEnd = bang;
        while (valEnd > 0 && std::isspace(static_cast<unsigned char>(value[valEnd - 1]))) --valEnd;
        value.resize(valEnd);
    }
 
}
 
void libhtmlpp::collectStyleBlocks(CSSStyleSheet &sheet, Element &root)
{
    // Children discovered while walking a frame's sibling chain are
    // collected here and pushed in reverse at the end, so <style> blocks
    // end up appended to `sheet` in true document order (matters once two
    // rules for the same property fall back to "later one wins").
    std::vector<Element*> searchStack;
    searchStack.push_back(&root);
 
    while (!searchStack.empty()) {
        Element *cur = searchStack.back();
        searchStack.pop_back();
 
        std::vector<Element*> childFrames;
 
        while (cur) {
            int type = cur->getType();
            if (type == HtmlEl || type == SvgEL || type == TextAreaEL) {
                HtmlElement *hel = static_cast<HtmlElement*>(cur);
                if (lowerCopy(hel->getTagname()) == "style") {
                    std::string cssText;
                    Element *child = hel->firstChild();
                    while (child) {
                        if (child->getType() == TextEl) {
                            cssText += static_cast<TextElement*>(child)->getText();
                        }
                        child = child->nextElement();
                    }
                    if (!cssText.empty()) {
                        CSSStyleSheet partial;
                        partial.parse(cssText);
                        for (const auto &rule : partial.getRules()) {
                            sheet.addRule(rule);
                        }
                    }
                } else {
                    Element *child = hel->firstChild();
                    if (child) childFrames.push_back(child);
                }
            }
            cur = cur->nextElement();
        }
 
        for (auto it = childFrames.rbegin(); it != childFrames.rend(); ++it) {
            searchStack.push_back(*it);
        }
    }
}
 
libhtmlpp::CSSRuleResult libhtmlpp::getCSSRules(HtmlElement &target,
                                                  const CSSStyleSheet &sheet,
                                                  std::set<std::string> &seenMediaBlocks)
{
    CSSRuleResult result;
 
    CSSDeclaration inlineDecl = CSSStyleSheet::parseInlineStyle(target.getAtributte("style"));
    for (const auto &prop : inlineDecl.getProperties()) {
        std::string value = prop.getValue();
        stripImportant(value);
        result.properties[prop.getName()] = value;
    }
 
    std::string tag = lowerCopy(target.getTagname());
    std::string cssClass = target.getAtributte("class");
    std::string id = target.getAtributte("id");
 
    sheet.collectApproximateMatches(tag, cssClass, id, result.properties, result.mediaRules, seenMediaBlocks);
    return result;
}