Tutorial 25: Xml Handling

Demonstrates loading and saving of configurations via XML

Author
  Y.M. Bosman <yoran.nosp@m..bos.nosp@m.man@g.nosp@m.mail.nosp@m..com>

This demo features a fully usable system for configuration handling. The code can easily be integrated into own apps.

#include <irrlicht.h>
using namespace irr;
using namespace core;
using namespace scene;
using namespace video;
using namespace io;
using namespace gui;
#ifdef _IRR_WINDOWS_
#pragma comment(lib, "Irrlicht.lib")
#endif

SettingManager class.

This class loads and writes the settings and manages the options.

The class makes use of irrMap which is a an associative arrays using a red-black tree it allows easy mapping of a key to a value, along the way there is some information on how to use it.

class SettingManager
{
public:
// Construct setting managers and set default settings
SettingManager(const stringw& settings_file): SettingsFile(settings_file), NullDevice(0)
{
// Irrlicht null device, we want to load settings before we actually created our device, therefore, nulldevice
NullDevice = irr::createDevice(irr::video::EDT_NULL);
//DriverOptions is an irrlicht map,
//we can insert values in the map in two ways by calling insert(key,value) or by using the [key] operator
//the [] operator overrides values if they already exist
DriverOptions.insert(L"Software", EDT_SOFTWARE);
DriverOptions.insert(L"OpenGL", EDT_OPENGL);
DriverOptions.insert(L"Direct3D9", EDT_DIRECT3D9);
//some resolution options
ResolutionOptions.insert(L"640x480", dimension2du(640,480));
ResolutionOptions.insert(L"800x600", dimension2du(800,600));
ResolutionOptions.insert(L"1024x768", dimension2du(1024,768));
//our preferred defaults
SettingMap.insert(L"driver", L"Direct3D9");
SettingMap.insert(L"resolution", L"640x480");
SettingMap.insert(L"fullscreen", L"0"); //0 is false
}
// Destructor, you could store settings automatically on exit of your
// application if you wanted to in our case we simply drop the
// nulldevice
~SettingManager()
{
if (NullDevice)
{
NullDevice->closeDevice();
NullDevice->drop();
}
};

Load xml from disk, overwrite default settings The xml we are trying to load has the following structure settings nested in sections nested in the root node, like:

        <pre>
            <?xml version="1.0"?>
            <mygame>
                <video>
                    <setting name="driver" value="Direct3D9" />
                    <setting name="fullscreen" value="0" />
                    <setting name="resolution" value="1024x768" />
                </video>
            </mygame>
        </pre>

bool load()
{
//if not able to create device don't attempt to load
if (!NullDevice)
return false;
irr::io::IXMLReader* xml = NullDevice->getFileSystem()->createXMLReader(SettingsFile); //create xml reader
if (!xml)
return false;
const stringw settingTag(L"setting"); //we'll be looking for this tag in the xml
stringw currentSection; //keep track of our current section
const stringw videoTag(L"video"); //constant for videotag
//while there is more to read
while (xml->read())
{
//check the node type
switch (xml->getNodeType())
{
//we found a new element
case irr::io::EXN_ELEMENT:
{
//we currently are in the empty or mygame section and find the video tag so we set our current section to video
if (currentSection.empty() && videoTag.equals_ignore_case(xml->getNodeName()))
{
currentSection = videoTag;
}
//we are in the video section and we find a setting to parse
else if (currentSection.equals_ignore_case(videoTag) && settingTag.equals_ignore_case(xml->getNodeName() ))
{
//read in the key
stringw key = xml->getAttributeValueSafe(L"name");
//if there actually is a key to set
if (!key.empty())
{
//set the setting in the map to the value,
//the [] operator overrides values if they already exist or inserts a new key value
//pair into the settings map if it was not defined yet
SettingMap[key] = xml->getAttributeValueSafe(L"value");
}
}
//..
// You can add your own sections and tags to read in here
//..
}
break;
//we found the end of an element
case irr::io::EXN_ELEMENT_END:
//we were at the end of the video section so we reset our tag
currentSection=L"";
break;
}
}
// don't forget to delete the xml reader
xml->drop();
return true;
}
// Save the xml to disk. We use the nulldevice.
bool save()
{
//if not able to create device don't attempt to save
if (!NullDevice)
return false;
//create xml writer
irr::io::IXMLWriter* xwriter = NullDevice->getFileSystem()->createXMLWriter( SettingsFile );
if (!xwriter)
return false;
//write out the obligatory xml header. Each xml-file needs to have exactly one of those.
xwriter->writeXMLHeader();
//start element mygame, you replace the label "mygame" with anything you want
xwriter->writeElement(L"mygame");
xwriter->writeLineBreak(); //new line
//start section with video settings
xwriter->writeElement(L"video");
xwriter->writeLineBreak(); //new line
// getIterator gets us a pointer to the first node of the settings map
// every iteration we increase the iterator which gives us the next map node
// until we reach the end we write settings one by one by using the nodes key and value functions
map<stringw, stringw>::Iterator i = SettingMap.getIterator();
for(; !i.atEnd(); i++)
{
//write element as <setting name="key" value="x" />
//the second parameter indicates this is an empty element with no children, just attributes
xwriter->writeElement(L"setting",true, L"name", i->getKey().c_str(), L"value",i->getValue().c_str() );
xwriter->writeLineBreak();
}
xwriter->writeLineBreak();
//close video section
xwriter->writeClosingTag(L"video");
xwriter->writeLineBreak();
//..
// You can add writing sound settings, savegame information etc
//..
//close mygame section
xwriter->writeClosingTag(L"mygame");
//delete xml writer
xwriter->drop();
return true;
}
// Set setting in our manager
void setSetting(const stringw& name, const stringw& value)
{
SettingMap[name]=value;
}
// set setting overload to quickly assign integers to our setting map
void setSetting(const stringw& name, s32 value)
{
SettingMap[name]=stringw(value);
}
// Get setting as string
stringw getSetting(const stringw& key) const
{
//the find function or irrmap returns a pointer to a map Node
//if the key can be found, otherwise it returns null
//the map node has the function getValue and getKey, as we already know the key, we return node->getValue()
map<stringw, stringw>::Node* n = SettingMap.find(key);
if (n)
return n->getValue();
else
return L"";
}
//
bool getSettingAsBoolean(const stringw& key ) const
{
stringw s = getSetting(key);
if (s.empty())
return false;
return s.equals_ignore_case(L"1");
}
//
s32 getSettingAsInteger(const stringw& key) const
{
//we implicitly cast to string instead of stringw because strtol10 does not accept wide strings
const stringc s = getSetting(key);
if (s.empty())
return 0;
return strtol10(s.c_str());
}
public:
map<stringw, s32> DriverOptions; //available options for driver config
map<stringw, dimension2du> ResolutionOptions; //available options for resolution config
private:
SettingManager(const SettingManager& other); // defined but not implemented
SettingManager& operator=(const SettingManager& other); // defined but not implemented
map<stringw, stringw> SettingMap; //current config
stringw SettingsFile; // location of the xml, usually the
irr::IrrlichtDevice* NullDevice;
};

Application context for global variables

struct SAppContext
{
SAppContext()
: Device(0),Gui(0), Driver(0), Settings(0), ShouldQuit(false),
ButtonSave(0), ButtonExit(0), ListboxDriver(0),
ListboxResolution(0), CheckboxFullscreen(0)
{
}
~SAppContext()
{
if (Settings)
delete Settings;
if (Device)
{
Device->closeDevice();
Device->drop();
}
}
IrrlichtDevice* Device;
IGUIEnvironment* Gui;
IVideoDriver* Driver;
SettingManager* Settings;
bool ShouldQuit;
//settings dialog
IGUIButton* ButtonSave;
IGUIButton* ButtonExit;
IGUIListBox* ListboxDriver;
IGUIListBox* ListboxResolution;
IGUICheckBox* CheckboxFullscreen;
};

A typical event receiver.

class MyEventReceiver : public IEventReceiver
{
public:
MyEventReceiver(SAppContext & a) : App(a) { }
virtual bool OnEvent(const SEvent& event)
{
if (event.EventType == EET_GUI_EVENT )
{
switch ( event.GUIEvent.EventType )
{
//handle button click events
case EGET_BUTTON_CLICKED:
{
//Our save button was called so we obtain the settings from our dialog and save them
if ( event.GUIEvent.Caller == App.ButtonSave )
{
//if there is a selection write it
if ( App.ListboxDriver->getSelected() != -1)
App.Settings->setSetting(L"driver", App.ListboxDriver->getListItem(App.ListboxDriver->getSelected()));
//if there is a selection write it
if ( App.ListboxResolution->getSelected() != -1)
App.Settings->setSetting(L"resolution", App.ListboxResolution->getListItem(App.ListboxResolution->getSelected()));
App.Settings->setSetting(L"fullscreen", App.CheckboxFullscreen->isChecked());
if (App.Settings->save())
{
App.Gui->addMessageBox(L"settings save",L"settings saved, please restart for settings to change effect","",true);
}
}
// cancel/exit button clicked, tell the application to exit
else if ( event.GUIEvent.Caller == App.ButtonExit)
{
App.ShouldQuit = true;
}
}
break;
}
}
return false;
}
private:
SAppContext & App;
};

Function to create a video settings dialog This dialog shows the current settings from the configuration xml and allows them to be changed

void createSettingsDialog(SAppContext& app)
{
// first get rid of alpha in gui
for (irr::s32 i=0; i<irr::gui::EGDC_COUNT ; ++i)
{
irr::video::SColor col = app.Gui->getSkin()->getColor((irr::gui::EGUI_DEFAULT_COLOR)i);
col.setAlpha(255);
app.Gui->getSkin()->setColor((irr::gui::EGUI_DEFAULT_COLOR)i, col);
}
//create video settings windows
gui::IGUIWindow* windowSettings = app.Gui->addWindow(rect<s32>(10,10,400,400),true,L"Videosettings");
app.Gui->addStaticText (L"Select your desired video settings", rect< s32 >(10,20, 200, 40), false, true, windowSettings);
// add listbox for driver choice
app.Gui->addStaticText (L"Driver", rect< s32 >(10,50, 200, 60), false, true, windowSettings);
app.ListboxDriver = app.Gui->addListBox(rect<s32>(10,60,220,120), windowSettings, 1,true);
//add all available options to the driver choice listbox
map<stringw, s32>::Iterator i = app.Settings->DriverOptions.getIterator();
for(; !i.atEnd(); i++)
app.ListboxDriver->addItem(i->getKey().c_str());
//set currently selected driver
app.ListboxDriver->setSelected(app.Settings->getSetting("driver").c_str());
// add listbox for resolution choice
app.Gui->addStaticText (L"Resolution", rect< s32 >(10,130, 200, 140), false, true, windowSettings);
app.ListboxResolution = app.Gui->addListBox(rect<s32>(10,140,220,200), windowSettings, 1,true);
//add all available options to the resolution listbox
map<stringw, dimension2du>::Iterator ri = app.Settings->ResolutionOptions.getIterator();
for(; !ri.atEnd(); ri++)
app.ListboxResolution->addItem(ri->getKey().c_str());
//set currently selected resolution
app.ListboxResolution->setSelected(app.Settings->getSetting("resolution").c_str());
//add checkbox to toggle fullscreen, initially set to loaded setting
app.CheckboxFullscreen = app.Gui->addCheckBox(
app.Settings->getSettingAsBoolean("fullscreen"),
rect<s32>(10,220,220,240), windowSettings, -1,
L"Fullscreen");
//last but not least add save button
app.ButtonSave = app.Gui->addButton(
rect<s32>(80,250,150,270), windowSettings, 2,
L"Save video settings");
//exit/cancel button
app.ButtonExit = app.Gui->addButton(
rect<s32>(160,250,240,270), windowSettings, 2,
L"Cancel and exit");
}

The main function. Creates all objects and does the XML handling.

int main()
{
//create new application context
SAppContext app;
//create device creation parameters that can get overwritten by our settings file
SIrrlichtCreationParameters param;
param.DriverType = EDT_SOFTWARE;
param.WindowSize.set(640,480);
// Try to load config.
// I leave it as an exercise of the reader to store the configuration in the local application data folder,
// the only logical place to store config data for games. For all other operating systems I redirect to your manuals
app.Settings = new SettingManager("../../media/settings.xml");
if ( !app.Settings->load() )
{
// ...
// Here add your own exception handling, for now we continue because there are defaults set in SettingManager constructor
// ...
}
else
{
//settings xml loaded from disk,
//map driversetting to driver type and test if the setting is valid
//the DriverOptions map contains string representations mapped to to irrlicht E_DRIVER_TYPE enum
//e.g "direct3d9" will become 4
//see DriverOptions in the settingmanager class for details
map<stringw, s32>::Node* driver = app.Settings->DriverOptions.find( app.Settings->getSetting("driver") );
if (driver)
{
if ( irr::IrrlichtDevice::isDriverSupported( static_cast<E_DRIVER_TYPE>( driver->getValue() )))
{
// selected driver is supported, so we use it.
param.DriverType = static_cast<E_DRIVER_TYPE>( driver->getValue());
}
}
//map resolution setting to dimension in a similar way as demonstrated above
map<stringw, dimension2du>::Node* res = app.Settings->ResolutionOptions.find( app.Settings->getSetting("resolution") );
if (res)
{
param.WindowSize = res->getValue();
}
//get fullscreen setting from config
param.Fullscreen = app.Settings->getSettingAsBoolean("fullscreen");
}
//create the irrlicht device using the settings
app.Device = createDeviceEx(param);
if (app.Device == 0)
{
// You can add your own exception handling on driver failure
exit(0);
}
app.Device->setWindowCaption(L"Xmlhandling - Irrlicht engine tutorial");
app.Driver = app.Device->getVideoDriver();
app.Gui = app.Device->getGUIEnvironment();
createSettingsDialog(app);
//set event receiver so we can respond to gui events
MyEventReceiver receiver(app);
app.Device->setEventReceiver(&receiver);
//enter main loop
while (!app.ShouldQuit && app.Device->run())
{
if (app.Device->isWindowActive())
{
app.Driver->beginScene(true, true, SColor(0,200,200,200));
app.Gui->drawAll();
app.Driver->endScene();
}
app.Device->sleep(10);
}
//app destroys device in destructor
return 0;
}