Kordophone/src/transcript/transcript-drawing-area.vala

using Gtk;
using Gee;

private class TranscriptDrawingArea : Widget 
{
    private SortedSet<Message> _messages = new TreeSet<Message>();
    private ArrayList<ChatItemLayout> _chat_items = new ArrayList<ChatItemLayout>();

    private const float bubble_padding = 10.0f;
    private const float bubble_margin = 18.0f;

    public TranscriptDrawingArea() {
        add_css_class("transcript-drawing-area");
    }

    public void set_messages(SortedSet<Message> messages) {
        _messages = messages;
        recompute_message_layouts();
    }

    public override SizeRequestMode get_request_mode() {
        return SizeRequestMode.HEIGHT_FOR_WIDTH;
    }
    
    public override void measure(Orientation orientation, int for_size, out int minimum, out int natural, out int minimum_baseline, out int natural_baseline) 
    {
        if (orientation == Orientation.HORIZONTAL) {
            // Horizontal, so we take up the full width provided
            minimum = 0;
            natural = for_size;
        } else {
            // compute total message layout height 
            float total_height = 0.0f;
            _chat_items.foreach((chat_item) => {
                total_height += chat_item.get_height() + bubble_padding;
                return true;
            });

            minimum = (int)total_height;
            natural = (int)total_height;
        }
        
        minimum_baseline = -1;
        natural_baseline = -1;
    }

    public override void size_allocate(int width, int height, int baseline) {
        base.size_allocate(width, height, baseline);
        recompute_message_layouts();
    }
    
    public override void snapshot(Snapshot snapshot) {
        var container_width = get_width();
        float y_offset = 0;
        _chat_items.foreach((chat_item) => {
            var item_width = chat_item.get_width();
            var item_height = chat_item.get_height();

            snapshot.save();
            
            // Flip the y-axis, since our parent is upside down (so newest messages are at the bottom)
            snapshot.scale(1.0f, -1.0f);

            // Translate to the correct position
            snapshot.translate(Graphene.Point() { 
                x = (chat_item.from_me ? (container_width - item_width - bubble_margin) : bubble_margin), 
                y = y_offset 
            });

            // Undo the y-axis flip, origin is top left 
            snapshot.translate(Graphene.Point() { x = 0, y = -item_height });

            chat_item.draw(snapshot);
            snapshot.restore();

            y_offset -= item_height + bubble_padding;

            return true;
        });
    }

    private void recompute_message_layouts() {
        var container_width = get_width();
        float max_width = container_width * 0.90f;
        
        _chat_items.clear();

        var reversed_messages = _messages
            .order_by((a, b) => b.date.compare(a.date)); // reverse order
        
        DateTime? last_date = null;
        reversed_messages.foreach((message) => {
            // Remember everything in here is backwards.

            if (last_date == null) {
                last_date = message.date;
            } else if (last_date.difference(message.date) > (TimeSpan.MINUTE * 25)) {
                var date_item = new DateItemLayout(last_date.to_local().format("%b %d, %Y at %H:%M"), this, max_width);
                _chat_items.add(date_item);
                last_date = message.date;
            }

            var text_bubble = new TextBubbleLayout(message, this, max_width);
            _chat_items.add(text_bubble);

            return true;
        });
        
        queue_draw();
        queue_resize();
    }
}