Demonstrates loading and saving of configurations via XML

Author:: Y.M. Bosman <yoran.bosman@gmail.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 so

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

    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;
}