ofxSvg improved compatibility (#6303)

Added support for the SVG "use" command, a common feature that allows multiple instances of the same graphic elements. 

Also fixed an issue where line weights less that 1 unit would not render. 

#changelog #addons #ofxSvg

CHANGELOG.md

@@ -1,4 +1,9 @@
 
+CORE
+----
+### utils
+- ofXML - provided access to the underlying pugi::xml_node method "getParent()" 
+
 PLATFORM/IDE SPECIFIC
 -----------------
 
@@ -9,7 +14,10 @@ ADDONS
 ------
 ### ofxOpenCv
 - added support for OpenCV4 : deprecated C functions replaced by their C++ counterpart. Also fix issue due to incorrect pkg-config package [commit](https://github.com/openframeworks/openFrameworks/commit/)
-
+
+### ofxSVG
+- added support for the SVG "use" command, a common feature that allows multiple instances of the same graphic elements. Also fixed an issue where line weights less that 1 unit would not render. This increased compatibility can be disabled if required by using the ofxSVG::setImprovedCompatibilityMode(bool mode) method. [commit](https://github.com/openframeworks/openFrameworks/commit/)
+- 
 --------------------------------------
 
 ```

addons/ofxSvg/src/ofxSvg.cpp

@@ -10,7 +10,22 @@ ofxSVG::~ofxSVG(){
 	paths.clear();
 }
 
-void ofxSVG::load(string path){
+float ofxSVG::getWidth() const {
+	return width;
+}
+
+float ofxSVG::getHeight() const {
+	return height;
+}
+
+int ofxSVG::getNumPath(){
+	return paths.size();
+}
+ofPath & ofxSVG::getPathAt(int n){
+	return paths[n];
+}
+
+void ofxSVG::load(std::string path){
 	path = ofToDataPath(path);
 
 	if(path.compare("") == 0){
@@ -19,10 +34,22 @@ void ofxSVG::load(string path){
 	}
 
 	ofBuffer buffer = ofBufferFromFile(path);
-	size_t size = buffer.size();
+
+	loadFromString(buffer.getText(), path);
+
+}
+
+void ofxSVG::loadFromString(std::string stringdata, std::string urlstring){
+
+	// goes some way to improving SVG compatibility
+	fixSvgString(stringdata);
+
+	const char* data = stringdata.c_str();
+	int size = stringdata.size();
+	const char* url = urlstring.c_str();
 
 	struct svgtiny_diagram * diagram = svgtiny_create();
-	svgtiny_code code = svgtiny_parse(diagram, buffer.getText().c_str(), size, path.c_str(), 0, 0);
+	svgtiny_code code = svgtiny_parse(diagram, data, size, url, 0, 0);
 
 	if(code != svgtiny_OK){
 		string msg;
@@ -47,21 +74,90 @@ void ofxSVG::load(string path){
 			 msg = "unknown svgtiny_code " + ofToString(code);
 			 break;
 		}
-		ofLogError("ofxSVG") << "load(): couldn't parse \"" << path << "\": " << msg;
+		ofLogError("ofxSVG") << "load(): couldn't parse \"" << urlstring << "\": " << msg;
 	}
 
 	setupDiagram(diagram);
 
 	svgtiny_free(diagram);
 }
 
+void ofxSVG::fixSvgString(std::string& xmlstring) {
+
+	ofXml xml;
+
+	xml.parse(xmlstring);
+
+	// so it turns out that if the stroke width is <1 it rounds it down to 0,
+	// and makes it disappear because svgtiny stores strokewidth as an integer!
+	ofXml::Search strokeWidthElements = xml.find("//*[@stroke-width]");
+	if(!strokeWidthElements.empty()) {
+
+		for(ofXml & element: strokeWidthElements){
+			//cout << element.toString() << endl;
+			float strokewidth = element.getAttribute("stroke-width").getFloatValue();
+			strokewidth = MAX(1,round(strokewidth));
+			element.getAttribute("stroke-width").set(strokewidth);
+
+		}
+	}
+
+	//lib svgtiny doesn't remove elements with display = none, so this code fixes that
+
+	bool finished = false;
+	while(!finished) {
+
+		ofXml::Search invisibleElements  = xml.find("//*[@display=\"none\"]");
+
+		if(invisibleElements.empty()) {
+			finished = true;
+		} else {
+			const ofXml& element = invisibleElements[0];
+			ofXml parent = element.getParent();
+			if(parent && element) parent.removeChild(element);
+		}
+
+	}
+
+	// implement the SVG "use" element by expanding out those elements into
+	// XML that svgtiny will parse correctly.
+	ofXml::Search useElements = xml.find("//use");
+	if(!useElements.empty()) {
+
+		for(ofXml & element: useElements){
+
+			// get the id attribute
+			string id = element.getAttribute("xlink:href").getValue();
+			// remove the leading "#" from the id
+			id.erase(id.begin());
+
+			// find the original definition of that element - TODO add defs into path?
+			string searchstring ="//*[@id='"+id+"']";
+			ofXml idelement = xml.findFirst(searchstring);
+
+			// if we found one then use it! (find first returns an empty xml on failure)
+			if(idelement.getAttribute("id").getValue()!="") {
+
+				// make a copy of that element
+				element.appendChild(idelement);
+
+				// then turn the use element into a g element
+				element.setName("g");
+
+			}
+		}
+	}
+
+	xmlstring = xml.toString();
+
+}
+
 void ofxSVG::draw(){
 	for(int i = 0; i < (int)paths.size(); i++){
 		paths[i].draw();
 	}
 }
 
-
 void ofxSVG::setupDiagram(struct svgtiny_diagram * diagram){
 
 	width = diagram->width;

addons/ofxSvg/src/ofxSvg.h

@@ -3,31 +3,50 @@
 //#include "ofMain.h"
 #include "ofPath.h"
 #include "ofTypes.h"
+#include "ofXml.h"
+
+
+/// \file
+/// ofxSVG is used for loading and rendering SVG files. It's a wrapper
+/// for the open source C library [Libsvgtiny](https://www.netsurf-browser.org/projects/libsvgtiny/ "Libsvgtiny website"),
+/// and it supports files in the [SVG Tiny format](https://www.w3.org/TR/SVGMobile/ "SVG Tiny 1.2
+/// format specification at the W3C").
+///
+/// Libsvgtiny supports a subset of SVG elements, (for a full list, see the Libsvgtiny readme file)
+/// but we have gone some way to improving this by manually implementing some extra features (such as the
+/// SVG "use" element).
 
 class ofxSVG {
 	public: ~ofxSVG();
 
-
-		float getWidth() const {
-			return width;
-		}
-		float getHeight() const {
-			return height;
-		}
+		float getWidth() const ;
+		float getHeight() const;
+
+		/// \brief Loads an SVG file from the provided filename.
+		///
+		/// ~~~~
 		void load(std::string path);
+
+		/// \brief Loads an SVG from a text string.
+		///
+		/// Useful for parsing SVG text from sources other than a file. As the
+		/// underlying SVG parsing library requires a url, this method gives
+		/// you the option of providing one.
+		///
+		/// ~~~~
+		void loadFromString(std::string data, std::string url="local");
+
 		void draw();
 
-		int getNumPath(){
-			return paths.size();
-		}
-		ofPath & getPathAt(int n){
-			return paths[n];
-		}
-
+		int getNumPath();
+		ofPath & getPathAt(int n);
+
 		const std::vector <ofPath> & getPaths() const;
 
 	private:
 
+		void fixSvgString(std::string& xmlstring);
+
 		float width, height;
 
 		std::vector <ofPath> paths;

libs/openFrameworks/utils/ofXml.cpp

@@ -150,6 +150,9 @@ ofXml ofXml::getLastChild() const{
 	return ofXml(doc, this->xml.last_child());
 }
 
+ofXml ofXml::getParent() const {
+	return ofXml(doc, this->xml.parent());
+}
 
 ofXml::Attribute ofXml::getAttribute(const std::string & name) const{
 	return this->xml.attribute(name.c_str());

libs/openFrameworks/utils/ofXml.h

@@ -135,6 +135,8 @@ class ofXml{
 
 	ofXml getFirstChild() const;
 	ofXml getLastChild() const;
+
+	ofXml getParent() const;
 
 
 	Attribute getAttribute(const std::string & name) const;