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/*************************************************************************
** GroupCollapser.cpp **
** **
** This file is part of dvisvgm -- a fast DVI to SVG converter **
** Copyright (C) 2005-2023 Martin Gieseking <martin.gieseking@uos.de> **
** **
** This program is free software; you can redistribute it and/or **
** modify it under the terms of the GNU General Public License as **
** published by the Free Software Foundation; either version 3 of **
** the License, or (at your option) any later version. **
** **
** This program is distributed in the hope that it will be useful, but **
** WITHOUT ANY WARRANTY; without even the implied warranty of **
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the **
** GNU General Public License for more details. **
** **
** You should have received a copy of the GNU General Public License **
** along with this program; if not, see <http://www.gnu.org/licenses/>. **
*************************************************************************/
#include <algorithm>
#include <array>
#include <string>
#include <vector>
#include "GroupCollapser.hpp"
#include "TransformSimplifier.hpp"
#include "../XMLNode.hpp"
using namespace std;
bool GroupCollapser::COMBINE_TRANSFORMS = true;
const char* GroupCollapser::info () const {
return "join nested group elements";
}
/** Checks if there's only a single child element and optional whitespace
* siblings in a given element.
* @param[in] elem element to check
* @return pointer to the only child element or nullptr */
static XMLElement* only_child_element (XMLElement *elem) {
XMLElement *firstChildElement=nullptr;
for (XMLNode *child : *elem) {
if (XMLElement *childElement = child->toElement()) {
if (firstChildElement)
return nullptr;
firstChildElement = childElement;
}
else if (!child->toWSNode())
return nullptr;
}
return firstChildElement;
}
/** Removes all whitespace child nodes from a given element. */
static void remove_ws_nodes (XMLElement *elem) {
XMLNode *node = elem->firstChild();
while (node) {
if (!node->toWSNode())
node = node->next();
else {
XMLNode *next = node->next();
XMLElement::detach(node);
node = next;
}
}
}
/** Recursively removes all redundant group elements from the given context element
* and moves their attributes to the corresponding parent elements.
* @param[in] context root of the subtree to process
* @param[in] depth depth of tree node being processed (0 = root of local tree) */
void GroupCollapser::execute (XMLElement *context, int depth) {
if (!context)
return;
XMLNode *child=context->firstChild();
while (child) {
XMLNode *next=child->next();
if (XMLElement *childElement = child->toElement()) {
execute(childElement, depth+1);
// remove empty groups and groups without attributes
if (childElement->name() == "g" && (childElement->attributes().empty() || (!childElement->hasAttribute("id") && childElement->empty(true)))) {
remove_ws_nodes(childElement);
if (XMLNode *firstUnwrappedNode = XMLElement::unwrap(childElement))
next = firstUnwrappedNode;
}
}
child = next;
}
if (XMLElement *childElement = only_child_element(context)) {
if (collapsible(*context)) {
if (childElement->name() == "g" && unwrappable(*childElement, *context) && moveAttributes(*childElement, *context)) {
remove_ws_nodes(context);
XMLElement::unwrap(childElement);
}
}
}
if (depth == 0 && COMBINE_TRANSFORMS && _transformCombined) {
TransformSimplifier().execute(context);
_transformCombined = false;
}
}
/** Moves all attributes from an element to another one. Attributes already
* present in the destination element are overwritten or combined.
* @param[in] source element the attributes are taken from
* @param[in] dest element that receives the attributes
* @return true if all attributes have been moved */
bool GroupCollapser::moveAttributes (XMLElement &source, XMLElement &dest) {
vector<string> movedAttributes;
for (const auto &attr : source.attributes()) {
if (attr.name == "transform") {
string transform;
if (const char *destvalue = dest.getAttributeValue("transform")) {
transform = destvalue+attr.value;
_transformCombined = true;
}
else {
transform = attr.value;
}
dest.addAttribute("transform", transform);
movedAttributes.emplace_back("transform");
}
else if (attr.inheritable()) {
dest.addAttribute(attr.name, attr.value);
movedAttributes.emplace_back(attr.name);
}
}
for (const string &attrname : movedAttributes)
source.removeAttribute(attrname);
return source.attributes().empty();
}
/** Returns true if a given element is allowed to take the inheritable attributes
* and children of a child group without changing the semantics.
* @param[in] element group element to check */
bool GroupCollapser::collapsible (const XMLElement &element) {
// the 'fill' attribute of animation elements has different semantics than
// that of graphics elements => don't collapse them
static const char *names[] = {
"animate", "animateColor", "animateMotion", "animateTransform", "set"
};
auto it = find_if(begin(names), end(names), [&](const string &name) {
return element.name() == name;
});
return it == end(names);
}
/** Returns true if a given group element is allowed to be unwrapped, i.e. its
* attributes and children can be moved to the parent without changing the semantics.
* @param[in] source element whose children and attributes should be moved
* @param[in] dest element that should receive the children and attributes */
bool GroupCollapser::unwrappable (const XMLElement &source, const XMLElement &dest) {
const char *cp1 = source.getAttributeValue("clip-path");
const char *cp2 = dest.getAttributeValue("clip-path");
if (cp2) {
// check for colliding clip-path attributes
if (cp1 && string(cp1) != string(cp2))
return false;
// don't apply inner transformations to outer clipping paths
if (source.hasAttribute("transform"))
return false;
}
// these attributes prevent a group from being unwrapped
static const char *attribs[] = {
"class", "id", "filter", "mask", "style"
};
auto it = find_if(begin(attribs), end(attribs), [&](const string &name) {
return source.hasAttribute(name) || dest.hasAttribute(name);
});
return it == end(attribs);
}
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