pugixml spritesheet navigation

Question

I have an xml file that describes sprites located in a sprite sheet:

<?xml version="1.0"?>
<!-- Generated by darkFunction Editor (www.darkfunction.com) -->
<img name="PaddleGfx.png" w="350" h="340">
  <definitions>
    <dir name="PaddleGfx">
      <dir name="Normal">
        <spr name="0" x="0" y="0" w="74" h="20"/>
        <spr name="1" x="74" y="0" w="74" h="20"/>
        <spr name="2" x="148" y="0" w="74" h="20"/>
        <spr name="3" x="222" y="0" w="74" h="20"/>
        <spr name="4" x="0" y="20" w="74" h="20"/>
        <spr name="5" x="74" y="20" w="74" h="20"/>
        <spr name="6" x="148" y="20" w="74" h="20"/>
        <spr name="7" x="252" y="40" w="74" h="20"/>
      </dir>
      <dir name="Big">
        <spr name="0" x="222" y="20" w="126" h="20"/>
        <spr name="1" x="0" y="40" w="126" h="20"/>
        <spr name="2" x="126" y="40" w="126" h="20"/>
        <spr name="3" x="0" y="60" w="126" h="20"/>
        <spr name="4" x="126" y="60" w="126" h="20"/>
        <spr name="5" x="0" y="80" w="126" h="19"/>
        <spr name="6" x="0" y="99" w="126" h="20"/>
        <spr name="7" x="126" y="99" w="126" h="20"/>
      </dir>
      <dir name="Small">
        <spr name="0" x="252" y="60" w="58" h="20"/>
        <spr name="1" x="252" y="99" w="58" h="20"/>
        <spr name="2" x="0" y="119" w="58" h="20"/>
        <spr name="3" x="126" y="80" w="58" h="19"/>
        <spr name="4" x="0" y="139" w="58" h="20"/>
        <spr name="5" x="258" y="80" w="58" h="19"/>
        <spr name="6" x="0" y="159" w="58" h="20"/>
        <spr name="7" x="0" y="179" w="58" h="20"/>
      </dir>
      <dir name="Normal2">
        <spr name="0" x="58" y="119" w="74" h="20"/>
        <spr name="1" x="58" y="139" w="74" h="20"/>
        <spr name="2" x="58" y="159" w="74" h="20"/>
        <spr name="3" x="184" y="80" w="74" h="19"/>
        <spr name="4" x="58" y="179" w="74" h="20"/>
        <spr name="5" x="58" y="199" w="74" h="20"/>
        <spr name="6" x="58" y="219" w="74" h="20"/>
        <spr name="7" x="58" y="239" w="74" h="20"/>
      </dir>
      <dir name="Normal3">
        <spr name="0" x="58" y="259" w="74" h="20"/>
        <spr name="1" x="58" y="279" w="74" h="20"/>
        <spr name="2" x="58" y="299" w="74" h="21"/>
        <spr name="3" x="58" y="320" w="74" h="20"/>
        <spr name="4" x="132" y="119" w="74" h="21"/>
        <spr name="5" x="206" y="119" w="74" h="20"/>
        <spr name="6" x="132" y="140" w="74" h="20"/>
        <spr name="7" x="206" y="140" w="74" h="20"/>
      </dir>
      <dir name="NormalToSmall">
        <spr name="0" x="132" y="160" w="74" h="20"/>
        <spr name="1" x="206" y="160" w="72" h="20"/>
        <spr name="2" x="280" y="119" w="70" h="20"/>
        <spr name="3" x="280" y="140" w="68" h="20"/>
        <spr name="4" x="278" y="160" w="66" h="20"/>
        <spr name="5" x="132" y="180" w="64" h="20"/>
        <spr name="6" x="132" y="200" w="62" h="20"/>
        <spr name="7" x="132" y="220" w="60" h="20"/>
      </dir>
      <dir name="NormalToBig">
        <spr name="0" x="196" y="180" w="74" h="20"/>
        <spr name="1" x="270" y="180" w="80" h="20"/>
        <spr name="2" x="196" y="200" w="86" h="20"/>
        <spr name="3" x="196" y="220" w="93" h="19"/>
        <spr name="4" x="196" y="239" w="100" h="18"/>
        <spr name="5" x="196" y="257" w="106" h="19"/>
        <spr name="6" x="196" y="276" w="112" h="20"/>
        <spr name="7" x="197" y="296" w="118" h="20"/>
      </dir>
    </dir>
  </definitions>
</img>

I've been able to use the following to list the contents under img/definitions/dir/dir

pugi::xml_node panels = doc.child("img").child("definitions").child("dir").child("dir");
std::cout <<"panels.name: "<< panels.name() << std::endl;
for (pugi::xml_node panel = panels.first_child(); panel; panel = panel.next_sibling())
{
    std::cout <<"panel.name: " << panel.name() << std::endl;
    for (pugi::xml_attribute attr = panel.first_attribute(); attr; attr = attr.next_attribute())
    {
        std::cout << "  attr.name: " << attr.name() << "= attr.value: " << attr.value() << std::endl;
    }
    std::cout << std::endl;
}

Output:

panels.name: dir
panel.name: spr
  attr.name: name= attr.value: 0
  attr.name: x= attr.value: 0
  attr.name: y= attr.value: 0
  attr.name: w= attr.value: 74
  attr.name: h= attr.value: 20

panel.name: spr
  attr.name: name= attr.value: 1
  attr.name: x= attr.value: 74
  attr.name: y= attr.value: 0
  attr.name: w= attr.value: 74
  attr.name: h= attr.value: 20

panel.name: spr
  attr.name: name= attr.value: 2
  attr.name: x= attr.value: 148
  attr.name: y= attr.value: 0
  attr.name: w= attr.value: 74
  attr.name: h= attr.value: 20

panel.name: spr
  attr.name: name= attr.value: 3
  attr.name: x= attr.value: 222
  attr.name: y= attr.value: 0
  attr.name: w= attr.value: 74
  attr.name: h= attr.value: 20

panel.name: spr
  attr.name: name= attr.value: 4
  attr.name: x= attr.value: 0
  attr.name: y= attr.value: 20
  attr.name: w= attr.value: 74
  attr.name: h= attr.value: 20

panel.name: spr
  attr.name: name= attr.value: 5
  attr.name: x= attr.value: 74
  attr.name: y= attr.value: 20
  attr.name: w= attr.value: 74
  attr.name: h= attr.value: 20

panel.name: spr
  attr.name: name= attr.value: 6
  attr.name: x= attr.value: 148
  attr.name: y= attr.value: 20
  attr.name: w= attr.value: 74
  attr.name: h= attr.value: 20

panel.name: spr
  attr.name: name= attr.value: 7
  attr.name: x= attr.value: 252
  attr.name: y= attr.value: 40
  attr.name: w= attr.value: 74
  attr.name: h= attr.value: 20


Process returned 0 (0x0)   execution time : 0.109 s
Press any key to continue.

However, I'm finding it difficult to search for a specific paddle sprite e.g. "Big" + "spr name=0" then access the attribute values here i.e. x, y, w, h to allow me to then draw that particular sprite from the sprite sheet. Ultimately, I'm looking to place these values into the following sfml construct:

sf::IntRect(10, 10, 32, 32)))  //sprite x,y,width,height

I've tried using cout to test various methods from pugixml's documentation but I can't get any to do what I want e.g.

cout<<"test: "<<doc.find_child_by_attribute("spr","name","0").attribute("w").value()<<endl<<endl;

Answer 1

For your specific example, you can either use two find_child_by_attribute calls:

pugi::xml_node n1 = doc.child("img").child("definitions").child("dir").find_child_by_attribute("dir", "name", "Big").find_child_by_attribute("spr", "name", "0");
std::cout << n1.attribute("w").value() << std::endl;

Or use XPath:

pugi::xml_node n2 = doc.select_single_node("img/definitions/dir/dir[@name='Big']/spr[@name='0']").node();
std::cout << n2.attribute("w").value() << std::endl

Both output 126.

The reason find_child_by_attribute does not work in your example is because it only looks for a child of the node, not for any descendant within subtree.