[TD] make LineGroup selectable

At the moment one has to specify the LineGroup as string. But one doesn't know what groups exist. So one has to check the Wiki, learn there where the groups are defined and then open the definition file with a text editor.

This PR simplifies this by reading the existing groups out of the definition file and fill the combobox accordingly.
It also give the user info what the selected LineGroup defines via the tooltip.

A nice side effect is that no typos can occur since you don't have to enter the LineGroup name as text.

src/Mod/TechDraw/App/LineGroup.cpp

@@ -125,62 +125,49 @@ std::vector<double> LineGroup::split(std::string line)
     return result;
 }
 
-//static support function: find group defn in file
-std::string LineGroup::getRecordFromFile(std::string parmFile, std::string groupName)
+//static support function: find group definition in file
+std::string LineGroup::getRecordFromFile(std::string parmFile, int groupNumber)
 {
     std::string record;
-    std::string lineSpec;
     std::ifstream inFile;
     inFile.open (parmFile, std::ifstream::in);
     if(!inFile.is_open()) {
         Base::Console().Message( "Cannot open LineGroup file: %s\n",parmFile.c_str());
         return record;
     }
-
-    bool groupFound = false;
+    // parse file to get the groupNumber'th line
+    int counter = 0; // the combobox enums begin with 0
     while ( inFile.good() ){
          std::string line;
-         std::getline(inFile,line);
-         std::string nameTag = line.substr(0,1);
-         std::string foundName;
-         unsigned long int commaPos;
-         if ((nameTag == ";")  ||
-             (nameTag == " ")  ||
-             (line.empty()) )  {           //is cr/lf empty?
-             continue;
-         } else if (nameTag == "*") {
-             commaPos = line.find(',',1);
-             if (commaPos != std::string::npos) {
-                  foundName = line.substr(1,commaPos-1);
-             } else {
-                  foundName = line.substr(1);
-             }
-             if (foundName == groupName) {
-                 //this is our group
+         std::getline(inFile, line);
+         std::string nameTag = line.substr(0, 1);
+         if (nameTag == "*") { // we found a definition line
+             if (counter == groupNumber) {
                  record = line;
-                 groupFound = true;
-                 break;
+                 return record;
              }
+             ++counter;
         }
     }  //endwhile
-    if (!groupFound) {
-        Base::Console().Message("LineGroup - group: %s is not found\n", groupName.c_str());
-    }
-    return record;
+    // nothing was found
+    Base::Console().Error("LineGroup: the LineGroup file has only %s entries but entry number %s is set\n"
+        , std::to_string(counter).c_str()
+        , std::to_string(groupNumber).c_str());
+    return std::string(); // return an empty string
 }
 
 //static LineGroup maker
-LineGroup* LineGroup::lineGroupFactory(std::string groupName)
+LineGroup* LineGroup::lineGroupFactory(int groupNumber)
 {
-    LineGroup* lg = new LineGroup(groupName);
+    LineGroup* lg = new LineGroup();
 
     std::string lgFileName = Preferences::lineGroupFile();
 
-    std::string lgRecord = LineGroup::getRecordFromFile(lgFileName, groupName);
+    std::string lgRecord = LineGroup::getRecordFromFile(lgFileName, groupNumber);
 
     std::vector<double> values = LineGroup::split(lgRecord);
     if (values.size() < 4) {
-        Base::Console().Message( "LineGroup::invalid entry in %s\n",groupName.c_str() );
+        Base::Console().Error( "LineGroup::invalid entry in %s\n", lgFileName.c_str() );
     } else {
         lg->setWeight("Thin",values[0]);
         lg->setWeight("Graphic",values[1]);
@@ -191,16 +178,47 @@ LineGroup* LineGroup::lineGroupFactory(std::string groupName)
 }
 
 //valid weight names: Thick, Thin, Graphic, Extra
-double LineGroup::getDefaultWidth(std::string weightName, std::string groupName)
+double LineGroup::getDefaultWidth(std::string weightName, int groupNumber)
 {
     //default line weights
-    std::string lgName = groupName;
-    if (groupName.empty()) {
-        lgName = Preferences::lineGroup();
+    int lgNumber = groupNumber;
+    if (lgNumber == -1) {
+        lgNumber = Preferences::lineGroup();
     }
-    auto lg = TechDraw::LineGroup::lineGroupFactory(lgName);
+    auto lg = TechDraw::LineGroup::lineGroupFactory(lgNumber);
 
     double weight = lg->getWeight(weightName);
     delete lg;
     return weight;
 }
+
+//static support function: find group definition in file
+std::string LineGroup::getGroupNamesFromFile(std::string FileName)
+{
+    std::string record;
+    std::ifstream inFile;
+    inFile.open(FileName, std::ifstream::in);
+    if (!inFile.is_open()) {
+        Base::Console().Message("Cannot open LineGroup file: %s\n", FileName.c_str());
+        return record;
+    }
+    // parse the file
+    while (inFile.good()) {
+        std::string line;
+        std::getline(inFile, line);
+        std::string nameTag = line.substr(0, 1);
+        std::string found;
+        unsigned long int commaPos;
+        if (nameTag == "*") {
+            commaPos = line.find(',', 1);
+            if (commaPos != std::string::npos) {
+                found = line.substr(1, commaPos - 1);
+                record = record + found + ',';
+            }
+        }
+    }  //endwhile
+    if (record.empty()) {
+        Base::Console().Message("LineGroup error: no group found in file %s\n", FileName.c_str());
+    }
+    return record;
+}