var pageClass = {

    new : func (d) {

        var m = { parents : [pageClass] };

        m.page = d.display.screen;

        m.window = {};

        m.state = {};

        m.selected = '';

        return m;

    },

    del : func (id = nil) {

        if (id != nil and typeof(id) == 'scalar') {

            delete(me.state, id);

            id = [ id ];

        }

        else {

            foreach (var s; keys(me.state))

                delete(me.state, s);

            id = keys(me.window);

        }

        foreach (var w; id) {

            me.window[w]

                .hide()

                .del();

            delete(me.window, w);

        }

    },

    _selected_text : func (id, text, x, y) {

        me.selected = id;

        me.window[id]

            .setFontSize(16)

            .setFont('LiberationFonts/LiberationMono-Regular.ttf')

            .setTranslation(x, y)

            .setDrawMode(0x01 + 0x04)

            .setText(text)

            .setColorFill(0,1,1)

            .setColor(0,0,0);

    },

    _editable_text : func (id, text, x, y) {

        me.window[id]

            .setFontSize(16)

            .setFont('LiberationFonts/LiberationMono-Regular.ttf')

            .setTranslation(x, y)

            .setText(text)

            .setColorFill(0,0,0)

            .setColor(0,1,1);

    },

    _normal_text : func (id, text, x, y) {

        me.window[id]

            .setFontSize(16)

            .setFont('LiberationFonts/LiberationMono-Regular.ttf')

            .setTranslation(x, y)

            .setText(text)

            .setColorFill(0,0,0)

            .setColor(1,1,1);

    },

    _title_text : func (id, text, x, y) {

        me.window[id]

            .setFontSize(16)

            .setFont('LiberationFonts/LiberationMono-Regular.ttf')

            .setTranslation(x, y)

            .setAlignment('center-center')

            .setText(text)

            .setColorFill(0,0,0)

            .setColor(0,1,1);

    },

    fill : func (id, scroll = nil) {

        var state = me.state[id];

        state.scroll = {

            offset : 0,           # offset between canvas element and state element

            last : 9999,          # last scrollgroup

            begin: -9999,         # first canvas element of the scrolling area

            end: 9999,            # last canvas element of the scrolling area

            upper: -9999,         # group printed on the top of the scrolling area

            lower: 9999,          # group printed at the bottom of the scrolling area

            lines : scroll != nil ? scroll.lines : 0, # number of lines for the scrolling area

            columns : scroll != nil ? scroll.columns : 0, # number of objects on each scrolling lines

        };

        var scrollgroup = {};

        forindex (var line; state.objects) {

            if (find('separator', state.objects[line].type) > -1) {

                me.window[id ~ '-' ~ (line - state.scroll.offset)] = me.page.createChild('path')

                    .setStrokeLineWidth(1)

                    .moveTo(state.x_base, state.geometry.y - 12)

                    .horiz(state.geometry.w - 20)

                    .setColor(1,1,1);

                state.geometry.x = state.x_base;

                state.geometry.y += 8;

            }

            else {

                if (contains(state.objects[line], 'scrollgroup')) {

                    state.scroll.last = state.objects[line].scrollgroup;

                    scrollgroup[state.objects[line].scrollgroup] = 1;

                    if (state.scroll.begin == -9999) {

                        state.scroll.begin = line;

                        state.scroll.upper = state.objects[line].scrollgroup;

                    }

                    if (size(keys(scrollgroup)) > state.scroll.lines) {

                        if (state.scroll.end == 9999) {

                            state.scroll.end = line - 1;

                            state.scroll.lower = state.objects[line - 1].scrollgroup;

                        }

                        else

                            state.scroll.last = state.objects[line].scrollgroup;

                        state.scroll.offset += 1;

                        continue;

                    }

                }

                me.window[id ~ '-' ~ (line - state.scroll.offset)] = me.page.createChild('text');

                if (find('normal', state.objects[line].type) > -1)

                    me._normal_text(

                            id ~ '-' ~ (line - state.scroll.offset),

                            state.objects[line].text,

                            state.geometry.x,

                            state.geometry.y,

                            );

                elsif (find('selected', state.objects[line].type) > -1)

                    me._selected_text(

                            id ~ '-' ~ (line - state.scroll.offset),

                            state.objects[line].text,

                            state.geometry.x,

                            state.geometry.y,

                            );

                elsif (find('editable', state.objects[line].type) > -1)

                    me._editable_text(

                            id ~ '-' ~ (line - state.scroll.offset),

                            state.objects[line].text,

                            state.geometry.x,

                            state.geometry.y,

                            );

                elsif (find('title', state.objects[line].type) > -1)

                    me._title_text(

                            id ~ '-' ~ (line - state.scroll.offset),

                            state.objects[line].text,

                            state.x_base - 10 + state.geometry.w / 2,

                            state.geometry.y

                        );

                if (find('end-of-line', state.objects[line].type) > -1

                or  find('title', state.objects[line].type) > -1) {

                    state.geometry.x = state.x_base;

                    state.geometry.y += 24;

                }

                else

                    state.geometry.x += size(state.objects[line].text) * 10 + 8;

            }

        }

        # reset the scrolling offset before the first move

        state.scroll.offset = 0;

    },

    draw : func (id, geometry, objects, scroll = nil) {

        if (contains(me.window, id ~ '-bg')) {

            printlog('debug', 'objet ' ~ id ~ ' already exists');

            return;

        }

        if (!contains(geometry, 'h') and !contains(geometry, 'l')) {

            printlog('debug', 'missing parameter l or h');

            return;

        }

        var save_x = geometry.x;

        var save_y = geometry.y;

        me.state[id] = {

            objects: objects,

            geometry: geometry,

            x_base : geometry.x + 10,

            h_max : contains(geometry, 'h') ? h : geometry.l * 24 + 8 + geometry.sep * 16,

        };

        me.state[id].y_max = me.state[id].h_max + me.state[id].geometry.y;

        me.window[id ~ '-bg'] = me.page.createChild('path');

        me.window[id ~ '-bg']

            .rect(geometry.x, geometry.y,

                  geometry.w, me.state[id].h_max)

            .setColor(1,1,1)

            .setColorFill(0,0,0);

        me.state[id].geometry.x += 10;

        me.state[id].geometry.y += 16;

        me.fill(id, scroll);

        geometry.x = save_x;

        geometry.y = save_y;

    },

};