function OnGUI()
{
    if(displayed)
    {
        GUI.skin = skillInfoStyle;

        var posBookX:float = Screen.width/2 -960/2;
        var posBookY:float = Screen.height/2 -960/2;
        var sizePageX:int = 960/2-150;
        var sizePageY:int = 960-310-250;
        var rectTree:Rect = new Rect(posBookX+960/2+50, posBookY+350, sizePageX, sizePageY);
        var sizeCase:int = 64;

        var posCaseX:int[] = new int[5];
        var posCaseY:int[] = new int[5];
        var posCaseYBase:int = 100;
        posCaseX[0] = sizePageX/6;  //Offensif 1
        posCaseY[0] = posCaseYBase;
        posCaseX[1] = sizePageX/6;  //Offensif 2
        posCaseY[1] = posCaseYBase*2;
        posCaseX[2] = sizePageX/2;  //Defensif 1
        posCaseY[2] = posCaseY[0];
        posCaseX[3] = sizePageX/2;  //Defensif 2
        posCaseY[3] = posCaseY[1];
        posCaseX[4] = sizePageX/3;  //Defensif/Offensif
        posCaseY[4] = posCaseYBase*3;

        GUI.BeginGroup(rectTree);  //From here, nothing shows up
        print("ok"); //This message works perfectly fine
        GUI.Box(new Rect(0,0,960,960),"");

        for(i = 0; i < fireSkills.length; i++)
        {
            GUI.DrawTexture(new Rect(posCaseX[i], posCaseY[i]-posCaseYBase/2, sizeCase, sizeCase), caseST);
            GUI.Button(new Rect(posCaseX[i], posCaseY[i]-posCaseYBase/2, sizeCase, sizeCase), "");
        }

        GUI.EndGroup(); //From here, everything works fine

    }
}