darkfi/bin/darkwallet/src/ui/chatview.rs

/* This file is part of DarkFi (https://dark.fi)
 *
 * Copyright (C) 2020-2024 Dyne.org foundation
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

use darkfi_serial::{deserialize, Decodable, Encodable, SerialDecodable, SerialEncodable};
use miniquad::TouchPhase;
use rand::{rngs::OsRng, Rng};
use std::{
    collections::BTreeMap,
    hash::{DefaultHasher, Hash, Hasher},
    sync::{Arc, Mutex as SyncMutex, Weak},
};

use crate::{
    error::Result,
    gfx2::{
        DrawCall, DrawInstruction, DrawMesh, GraphicsEventPublisherPtr, Point, Rectangle,
        RenderApi, RenderApiPtr, Vertex,
    },
    mesh::{Color, MeshBuilder, MeshInfo, COLOR_BLUE, COLOR_GREY, COLOR_WHITE},
    prop::{
        PropertyBool, PropertyColor, PropertyFloat32, PropertyPtr, PropertyStr, PropertyUint32,
    },
    pubsub::Subscription,
    scene::{Pimpl, SceneGraph, SceneGraphPtr2, SceneNodeId},
    text2::{self, Glyph, GlyphPositionIter, SpritePtr, TextShaper, TextShaperPtr},
    util::zip3,
};

use super::{eval_rect, get_parent_rect, read_rect, DrawUpdate, OnModify, Stoppable};

const DEBUG_RENDER: bool = false;

fn is_whitespace(s: &str) -> bool {
    s.chars().all(char::is_whitespace)
}

#[derive(Clone, Debug, SerialEncodable, SerialDecodable)]
pub struct ChatMsg {
    pub nick: String,
    pub text: String,
}

type Timestamp = u32;

#[derive(Clone)]
struct Message {
    timest: Timestamp,
    chatmsg: ChatMsg,
    glyphs: Vec<Glyph>,
}

const LINES_PER_PAGE: usize = 10;
const PRELOAD_PAGES: usize = 10;

#[derive(Clone)]
struct Page {
    msgs: Vec<Message>,
    atlas: text2::RenderedAtlas,
}

#[derive(Clone)]
struct PageMeshInfo {
    px_height: f32,
    mesh: DrawMesh,
}

type Page2Ptr = Arc<Page2>;

struct Page2 {
    msgs: Vec<Message>,
    atlas: text2::RenderedAtlas,
    // One draw call per page.
    // Resizing the canvas means we recalc wrapping and the mesh changes
    mesh_inf: SyncMutex<Option<PageMeshInfo>>,
}

impl Page2 {
    async fn new(msgs: Vec<Message>, render_api: &RenderApi) -> Arc<Self> {
        let mut atlas = text2::Atlas::new(render_api);
        for msg in &msgs {
            atlas.push(&msg.glyphs);
        }
        let Ok(atlas) = atlas.make().await else {
            // what else should I do here?
            panic!("unable to make atlas!");
        };

        Arc::new(Self { msgs, atlas, mesh_inf: SyncMutex::new(None) })
    }

    /// Regenerates the mesh, returning the old mesh which should be freed
    async fn regen_mesh(
        &self,
        clip: &Rectangle,
        render_api: &RenderApi,
        font_size: f32,
        line_height: f32,
        baseline: f32,
        nick_colors: &[Color],
        timestamp_color: Color,
        text_color: Color,
    ) -> (PageMeshInfo, Option<DrawMesh>) {
        let mut wrapped_line_idx = 0;

        let mut mesh = MeshBuilder::new();

        for msg in &self.msgs {
            let glyphs = &msg.glyphs;

            let nick_color = select_nick_color(&msg.chatmsg.nick, nick_colors);

            // Keep track of the 'section'
            // Section 0 is the timestamp
            // Section 1 is the nickname (colorized)
            // Finally is just the message itself
            let mut section = 2;

            let mut lines = text2::wrap(clip.w, font_size, glyphs);
            // We are drawing bottom up but line wrap gives us lines in normal order
            lines.reverse();
            let last_idx = lines.len() - 1;
            for (i, line) in lines.into_iter().enumerate() {
                let off_y = (wrapped_line_idx + 1) as f32 * line_height;

                if i == last_idx {
                    section = 0;
                }

                // debug draw baseline
                //let y = baseline - off_y;
                //mesh.draw_filled_box(&Rectangle { x: 0., y: y - 1., w: clip.w, h: 1. }, COLOR_BLUE);

                // Render line
                let mut glyph_pos_iter = GlyphPositionIter::new(font_size, &line, baseline);
                for (mut glyph_rect, glyph) in glyph_pos_iter.zip(line.iter()) {
                    let uv_rect =
                        self.atlas.fetch_uv(glyph.glyph_id).expect("missing glyph UV rect");
                    glyph_rect.y -= off_y;

                    let color = match section {
                        0 => timestamp_color,
                        1 => nick_color,
                        _ => text_color,
                    };

                    //mesh.draw_outline(&glyph_rect, COLOR_BLUE, 2.);
                    mesh.draw_box(&glyph_rect, color, uv_rect);

                    if section < 2 && is_whitespace(&glyph.substr) {
                        section += 1;
                    }
                }
                wrapped_line_idx += 1;
            }
        }

        let px_height = wrapped_line_idx as f32 * line_height;

        let mesh = mesh.alloc(render_api).await.unwrap();
        let mesh = mesh.draw_with_texture(self.atlas.texture_id);

        let mesh_inf = PageMeshInfo { px_height, mesh };

        let old = std::mem::replace(&mut *self.mesh_inf.lock().unwrap(), Some(mesh_inf.clone()));
        let old = old.map(|v| v.mesh);

        (mesh_inf, old)
    }
}

fn select_nick_color(nick: &str, nick_colors: &[Color]) -> Color {
    let mut hasher = DefaultHasher::new();
    nick.hash(&mut hasher);
    let i = hasher.finish() as usize;
    let color = nick_colors[i % nick_colors.len()];
    color
}

struct TouchInfo {
    start_scroll: f32,
    start_y: f32,
    start_instant: std::time::Instant,
    last_y: f32,
}

impl TouchInfo {
    fn new() -> Self {
        Self { start_scroll: 0., start_y: 0., start_instant: std::time::Instant::now(), last_y: 0. }
    }
}

pub type ChatViewPtr = Arc<ChatView>;

pub struct ChatView {
    node_id: SceneNodeId,
    tasks: Vec<smol::Task<()>>,
    sg: SceneGraphPtr2,
    render_api: RenderApiPtr,
    text_shaper: TextShaperPtr,
    tree: sled::Tree,

    pages: SyncMutex<Vec<Page>>,
    pages2: SyncMutex<Vec<Page2Ptr>>,
    drawcalls: SyncMutex<Vec<DrawMesh>>,
    dc_key: u64,

    /// Used for detecting when scrolling view
    mouse_pos: SyncMutex<Point>,
    /// Touch scrolling
    touch_info: SyncMutex<TouchInfo>,

    rect: PropertyPtr,
    scroll: PropertyFloat32,
    font_size: PropertyFloat32,
    line_height: PropertyFloat32,
    baseline: PropertyFloat32,
    timestamp_color: PropertyColor,
    text_color: PropertyColor,
    nick_colors: PropertyPtr,
    z_index: PropertyUint32,
}

impl ChatView {
    pub async fn new(
        ex: Arc<smol::Executor<'static>>,
        sg: SceneGraphPtr2,
        node_id: SceneNodeId,
        render_api: RenderApiPtr,
        event_pub: GraphicsEventPublisherPtr,
        text_shaper: TextShaperPtr,
        tree: sled::Tree,
    ) -> Pimpl {
        debug!(target: "ui::chatview", "ChatView::new()");
        let scene_graph = sg.lock().await;
        let node = scene_graph.get_node(node_id).unwrap();
        let node_name = node.name.clone();

        let rect = node.get_property("rect").expect("ChatView::rect");
        let scroll = PropertyFloat32::wrap(node, "scroll", 0).unwrap();
        let font_size = PropertyFloat32::wrap(node, "font_size", 0).unwrap();
        let line_height = PropertyFloat32::wrap(node, "line_height", 0).unwrap();
        let baseline = PropertyFloat32::wrap(node, "baseline", 0).unwrap();
        let timestamp_color = PropertyColor::wrap(node, "timestamp_color").unwrap();
        let text_color = PropertyColor::wrap(node, "text_color").unwrap();
        let nick_colors = node.get_property("nick_colors").expect("ChatView::nick_colors");
        let z_index = PropertyUint32::wrap(node, "z_index", 0).unwrap();

        drop(scene_graph);

        let self_ = Arc::new_cyclic(|me: &Weak<Self>| {
            let ev_sub = event_pub.subscribe_mouse_wheel();
            let me2 = me.clone();
            let mouse_wheel_task = ex.spawn(async move {
                loop {
                    Self::process_mouse_wheel(&me2, &ev_sub).await;
                }
            });

            let ev_sub = event_pub.subscribe_mouse_move();
            let me2 = me.clone();
            let mouse_move_task = ex.spawn(async move {
                loop {
                    Self::process_mouse_move(&me2, &ev_sub).await;
                }
            });

            let ev_sub = event_pub.subscribe_touch();
            let me2 = me.clone();
            let touch_task = ex.spawn(async move {
                loop {
                    Self::process_touch(&me2, &ev_sub).await;
                }
            });

            let mut on_modify = OnModify::new(ex, node_name, node_id, me.clone());

            //on_modify.when_change(scroll.prop(), Self::scrollview);

            async fn redraw(self_: Arc<ChatView>) {
                self_.redraw().await;
            }
            on_modify.when_change(rect.clone(), redraw);

            let mut tasks = vec![mouse_wheel_task, mouse_move_task, touch_task];
            tasks.append(&mut on_modify.tasks);

            Self {
                node_id,
                tasks,
                sg,
                render_api,
                text_shaper,
                tree,

                pages: SyncMutex::new(Vec::new()),
                pages2: SyncMutex::new(Vec::new()),
                drawcalls: SyncMutex::new(Vec::new()),
                dc_key: OsRng.gen(),

                mouse_pos: SyncMutex::new(Point::from([0., 0.])),
                touch_info: SyncMutex::new(TouchInfo::new()),

                rect,
                scroll,
                font_size,
                line_height,
                baseline,
                timestamp_color,
                text_color,
                nick_colors,
                z_index,
            }
        });

        let timer = std::time::Instant::now();
        self_.populate().await;
        debug!(target: "ui::chatview", "populate() took {:?}", timer.elapsed());

        Pimpl::ChatView(self_)
    }

    async fn process_mouse_wheel(me: &Weak<Self>, ev_sub: &Subscription<(f32, f32)>) {
        let Ok((wheel_x, wheel_y)) = ev_sub.receive().await else {
            debug!(target: "ui::chatview", "Event relayer closed");
            return
        };

        let Some(self_) = me.upgrade() else {
            // Should not happen
            panic!("self destroyed before mouse_wheel_task was stopped!");
        };

        self_.handle_mouse_wheel(wheel_x, wheel_y).await;
    }

    async fn process_mouse_move(me: &Weak<Self>, ev_sub: &Subscription<(f32, f32)>) {
        let Ok((mouse_x, mouse_y)) = ev_sub.receive().await else {
            debug!(target: "ui::chatview", "Event relayer closed");
            return
        };

        let Some(self_) = me.upgrade() else {
            // Should not happen
            panic!("self destroyed before mouse_move_task was stopped!");
        };

        self_.handle_mouse_move(mouse_x, mouse_y).await;
    }

    async fn process_touch(me: &Weak<Self>, ev_sub: &Subscription<(TouchPhase, u64, f32, f32)>) {
        let Ok((phase, id, touch_x, touch_y)) = ev_sub.receive().await else {
            debug!(target: "ui::chatview", "Event relayer closed");
            return
        };

        let Some(self_) = me.upgrade() else {
            // Should not happen
            panic!("self destroyed before touch_task was stopped!");
        };

        self_.handle_touch(phase, id, touch_x, touch_y).await;
    }

    async fn handle_mouse_wheel(&self, wheel_x: f32, wheel_y: f32) {
        debug!(target: "ui::chatview", "handle_mouse_wheel({wheel_x}, {wheel_y})");

        let Some(rect) = self.get_cached_world_rect().await else { return };

        let mouse_pos = self.mouse_pos.lock().unwrap().clone();
        if !rect.contains(&mouse_pos) {
            //debug!(target: "ui::chatview", "not inside rect");
            return
        }
        //debug!(target: "ui::chatview", "inside rect");
        let scroll = self.scroll.get() + wheel_y * 50.;
        self.scrollview(scroll).await;
    }

    async fn handle_mouse_move(&self, mouse_x: f32, mouse_y: f32) {
        //debug!(target: "ui::chatview", "handle_mouse_move({mouse_x}, {mouse_y})");
        let mut mouse_pos = self.mouse_pos.lock().unwrap();
        mouse_pos.x = mouse_x;
        mouse_pos.y = mouse_y;
    }

    async fn handle_touch(&self, phase: TouchPhase, id: u64, touch_x: f32, touch_y: f32) {
        // Ignore multi-touch
        if id != 0 {
            return
        }
        // Simulate mouse events
        match phase {
            TouchPhase::Started => {
                let mut touch_info = self.touch_info.lock().unwrap();
                touch_info.start_scroll = self.scroll.get();
                touch_info.start_y = touch_y;
                touch_info.start_instant = std::time::Instant::now();
                touch_info.last_y = touch_y;
            }
            TouchPhase::Moved => {
                let (start_scroll, start_y) = {
                    let mut touch_info = self.touch_info.lock().unwrap();
                    touch_info.last_y = touch_y;
                    (touch_info.start_scroll, touch_info.start_y)
                };

                let dist = touch_y - start_y;
                // TODO the line selected should be fixed and move exactly that distance
                // No use of multipliers
                // TODO we are maybe doing too many updates so make a widget to 'slow down'
                // how often we move to fixed intervals.
                // draw a poly shape and eval each line segment.
                let scroll = start_scroll + dist;
                self.scrollview(scroll).await;
            }
            TouchPhase::Ended => {
                // Now calculate scroll acceleration
            }
            TouchPhase::Cancelled => {}
        }
    }

    /// Descent = line height - baseline
    fn descent(&self) -> f32 {
        self.line_height.get() - self.baseline.get()
    }

    /// Beware of this method. Here be dragons.
    /// Possibly racy so we limit it just to mouse stuff (for now).
    fn cached_rect(&self) -> Option<Rectangle> {
        let Ok(rect) = read_rect(self.rect.clone()) else {
            error!(target: "ui::chatview", "cached_rect is None");
            return None
        };
        Some(rect)
    }
    async fn get_parent_rect(&self) -> Option<Rectangle> {
        let sg = self.sg.lock().await;
        let node = sg.get_node(self.node_id).unwrap();
        let Some(parent_rect) = get_parent_rect(&sg, node) else {
            return None;
        };
        drop(sg);
        Some(parent_rect)
    }
    async fn get_cached_world_rect(&self) -> Option<Rectangle> {
        // NBD if it's slightly wrong
        let mut rect = self.cached_rect()?;

        // If layers can be nested and we use offsets for (x, y)
        // then this will be incorrect for nested layers.
        // For now we don't allow nesting of layers.
        let parent_rect = self.get_parent_rect().await?;

        // Offset rect which is now in world coords
        rect.x += parent_rect.x;
        rect.y += parent_rect.y;

        Some(rect)
    }

    async fn populate(&self) {
        let iter = self.tree.iter().rev();
        self.load_n_pages(iter, PRELOAD_PAGES).await;
    }

    /// Load extra pages
    async fn preload_pages(&self) -> usize {
        // Get last page
        let last_page = self.pages2.lock().unwrap().last().unwrap().clone();
        // get the current earliest timestamp
        let last_timest = last_page.msgs.last().unwrap().timest;

        // iterate from there
        let key = last_timest.to_be_bytes();
        debug!(target: "ui::chatview", "preloading from {key:?}");
        let iter = self.tree.range(..key).rev();

        self.load_n_pages(iter, PRELOAD_PAGES).await
    }

    async fn load_n_pages<I: Iterator<Item = sled::Result<(sled::IVec, sled::IVec)>>>(
        &self,
        iter: I,
        n: usize,
    ) -> usize {
        let mut pages_len = 0;
        let mut msgs = vec![];

        for entry in iter {
            let Ok((k, v)) = entry else { break };
            assert_eq!(k.len(), 4);
            let key_bytes: [u8; 4] = k.as_ref().try_into().unwrap();
            let timest = Timestamp::from_be_bytes(key_bytes);
            let chatmsg: ChatMsg = deserialize(&v).unwrap();
            debug!(target: "ui::chatview", "{k:?} {chatmsg:?}");

            let timestr = timest.to_string();
            // left pad with zeros
            let mut timestr = format!("{:0>4}", timestr);
            timestr.insert(2, ':');

            let text = format!("{} {} {}", timestr, chatmsg.nick, chatmsg.text);
            let glyphs = self.text_shaper.shape(text, self.font_size.get()).await;

            msgs.push(Message { timest, chatmsg, glyphs });

            if msgs.len() >= LINES_PER_PAGE {
                let msgs = std::mem::take(&mut msgs);
                let page = Page2::new(msgs, &self.render_api).await;

                self.pages2.lock().unwrap().push(page);
                pages_len += 1;

                if pages_len >= n {
                    break
                }
            }
        }

        // Any remaining messages added to a short page
        if !msgs.is_empty() {
            let page = Page2::new(msgs, &self.render_api).await;

            self.pages2.lock().unwrap().push(page);
            pages_len += 1;
        }

        debug!(target: "ui::chatview", "populated {} pages", pages_len);

        pages_len
    }

    async fn get_total_height(&self, rect: &Rectangle, pages: &Vec<Page2Ptr>) -> f32 {
        let font_size = self.font_size.get();
        let line_height = self.line_height.get();
        let baseline = self.baseline.get();

        let timest_color = self.timestamp_color.get();
        let text_color = self.text_color.get();
        let nick_colors = self.read_nick_colors();

        // Nudge the bottom line up slightly, otherwise chars like p will cross the bottom.
        let mut current_height = self.descent();

        for page in pages {
            let mesh_inf = page.mesh_inf.lock().unwrap().clone();
            let mesh_inf = match mesh_inf {
                Some(mesh_inf) => mesh_inf,
                None => {
                    let (mesh_inf, old_drawmesh) = page
                        .regen_mesh(
                            &rect,
                            &self.render_api,
                            font_size,
                            line_height,
                            baseline,
                            &nick_colors,
                            timest_color.clone(),
                            text_color.clone(),
                        )
                        .await;
                    assert!(old_drawmesh.is_none());
                    mesh_inf
                }
            };

            current_height += mesh_inf.px_height;
        }

        current_height
    }

    async fn draw_cached(&self, mut rect: Rectangle, scroll: &mut f32) -> Vec<DrawInstruction> {
        let mut instrs = vec![];

        if *scroll < 0. {
            *scroll = 0.;
        }

        // Make sure we have enough pages loaded.
        // If there's no more to load then adjust the scroll.
        let mut pages = self.pages2.lock().unwrap().clone();
        while self.get_total_height(&rect, &pages).await < *scroll + rect.h {
            debug!(target: "ui::chatview", "draw_cached() loading more pages");

            if self.preload_pages().await == 0 {
                // No more pages available to load
                pages = self.pages2.lock().unwrap().clone();
                let new_height = self.get_total_height(&rect, &pages).await;
                *scroll = new_height - rect.h;
                break
            }
        }

        let descent = self.descent();
        let mut current_height = 0.;
        for page in pages {
            if current_height > *scroll + rect.h {
                break
            }

            let mesh_inf = page.mesh_inf.lock().unwrap().clone();
            let mesh_inf = mesh_inf.expect("preload above should've regen_mesh()");

            // Apply scroll and scissor
            // We use the scissor for scrolling
            // Because we use the scissor, our actual rect is now rect instead of parent_rect
            let off_x = 0.;
            // This calc decides whether scroll is in terms of pages or pixels
            let off_y = (*scroll - current_height + rect.h) / rect.h;
            let scale_x = 1. / rect.w;
            let scale_y = 1. / rect.h;
            let model = glam::Mat4::from_translation(glam::Vec3::new(off_x, off_y, 0.)) *
                glam::Mat4::from_scale(glam::Vec3::new(scale_x, scale_y, 1.));

            instrs.push(DrawInstruction::ApplyMatrix(model));
            instrs.push(DrawInstruction::Draw(mesh_inf.mesh));

            current_height += mesh_inf.px_height;
        }

        instrs
    }

    /// Basically a version of redraw() where regen_mesh() is never called.
    /// Instead we use the cached version.
    async fn scrollview(&self, mut scroll: f32) {
        debug!(target: "ui::chatview", "scrollview()");
        let sg = self.sg.lock().await;
        let node = sg.get_node(self.node_id).unwrap();

        let Some(parent_rect) = get_parent_rect(&sg, node) else {
            return;
        };

        if let Err(err) = eval_rect(self.rect.clone(), &parent_rect) {
            panic!("Node {:?} bad rect property: {}", node, err);
        }

        let Ok(mut rect) = read_rect(self.rect.clone()) else {
            panic!("Node {:?} bad rect property", node);
        };

        let mut mesh_instrs = self.draw_cached(rect.clone(), &mut scroll).await;
        let mut instrs = vec![DrawInstruction::ApplyViewport(rect)];
        instrs.append(&mut mesh_instrs);

        let draw_calls =
            vec![(self.dc_key, DrawCall { instrs, dcs: vec![], z_index: self.z_index.get() })];

        self.render_api.replace_draw_calls(draw_calls).await;

        self.scroll.set(scroll);
    }

    async fn redraw(&self) {
        debug!(target: "ui::chatview", "redraw()");
        let sg = self.sg.lock().await;
        let node = sg.get_node(self.node_id).unwrap();

        let Some(parent_rect) = get_parent_rect(&sg, node) else {
            return;
        };

        let Some(draw_update) = self.draw(&sg, &parent_rect).await else {
            error!(target: "ui::chatview", "ChatView {:?} failed to draw", node);
            return;
        };
        self.render_api.replace_draw_calls(draw_update.draw_calls).await;
        debug!(target: "ui::chatview", "replace draw calls done");
        for buffer_id in draw_update.freed_buffers {
            self.render_api.delete_buffer(buffer_id);
        }
        for texture_id in draw_update.freed_textures {
            self.render_api.delete_texture(texture_id);
        }
    }

    async fn regen_mesh(&self, mut rect: Rectangle) -> (Vec<DrawInstruction>, Vec<DrawMesh>) {
        let font_size = self.font_size.get();
        let line_height = self.line_height.get();
        let baseline = self.baseline.get();
        let descent = self.descent();

        let mut instrs = vec![];
        let mut old_drawmesh = vec![];

        let timest_color = self.timestamp_color.get();
        let text_color = self.text_color.get();
        let nick_colors = self.read_nick_colors();

        let pages = self.pages2.lock().unwrap().clone();

        let mut mesh_infs = vec![];
        // First pass is to measure the height and generate the meshes
        let mut current_height = 0.;
        for page in pages {
            // We should be able to count lines and perform wrapping without having to
            // generate the mesh and alloc buffers.
            // We need to separate both these ops.
            let (mesh_inf, old) = page
                .regen_mesh(
                    &rect,
                    &self.render_api,
                    font_size,
                    line_height,
                    baseline,
                    &nick_colors,
                    timest_color.clone(),
                    text_color.clone(),
                )
                .await;

            current_height += mesh_inf.px_height;

            if let Some(old) = old {
                old_drawmesh.push(old);
            }
            mesh_infs.push(mesh_inf);
        }

        let total_height = current_height + descent;

        // If lines aren't enough to fill the available buffer then start from the top
        let start_pos = if total_height < rect.h { total_height } else { rect.h };

        let mut scroll = self.scroll.get();
        assert!(scroll >= 0.);
        // For when we resize the window and scroll is no longer valid
        let max_allowed_scroll = total_height - rect.h;
        debug!(
            "max_allowed_scroll = {max_allowed_scroll} = total_height={total_height} - rect.h={}",
            rect.h
        );
        if scroll > max_allowed_scroll {
            scroll = max_allowed_scroll;
            self.scroll.set(scroll);
        }

        let mut current_height = 0.;
        for mesh_inf in mesh_infs {
            if current_height > scroll + rect.h {
                break
            }

            // Apply scroll and scissor
            // We use the scissor for scrolling
            // Because we use the scissor, our actual rect is now rect instead of parent_rect
            let off_x = 0.;
            // This calc decides whether scroll is in terms of pages or pixels
            let off_y = (scroll + start_pos - current_height) / rect.h;
            let scale_x = 1. / rect.w;
            let scale_y = 1. / rect.h;
            let model = glam::Mat4::from_translation(glam::Vec3::new(off_x, off_y, 0.)) *
                glam::Mat4::from_scale(glam::Vec3::new(scale_x, scale_y, 1.));

            instrs.push(DrawInstruction::ApplyMatrix(model));

            instrs.push(DrawInstruction::Draw(mesh_inf.mesh));

            current_height += mesh_inf.px_height;
        }

        (instrs, old_drawmesh)

        /*
        if DEBUG_RENDER {
            let mut debug_mesh = MeshBuilder::new();
            debug_mesh.draw_outline(
                &Rectangle { x: 0., y: -clip.h, w: clip.w, h: clip.h },
                COLOR_BLUE,
                2.,
            );
            let mesh = debug_mesh.alloc(&self.render_api).await.unwrap();
            draws.push(DrawMesh {
                vertex_buffer: mesh.vertex_buffer,
                index_buffer: mesh.index_buffer,
                texture: None,
                num_elements: mesh.num_elements,
            });
        }

        draws
        */
    }

    fn read_nick_colors(&self) -> Vec<Color> {
        let mut colors = vec![];
        let mut color = [0f32; 4];
        for i in 0..self.nick_colors.get_len() {
            color[i % 4] = self.nick_colors.get_f32(i).expect("prop logic err");

            if i > 0 && i % 4 == 0 {
                let color = std::mem::take(&mut color);
                colors.push(color);
            }
        }
        colors
    }

    fn select_nick_color(&self, nick: &str, nick_colors: &[Color]) -> Color {
        let mut hasher = DefaultHasher::new();
        nick.hash(&mut hasher);
        let i = hasher.finish() as usize;
        let color = nick_colors[i % nick_colors.len()];
        color
    }

    pub async fn draw(&self, sg: &SceneGraph, parent_rect: &Rectangle) -> Option<DrawUpdate> {
        debug!(target: "ui::chatview", "ChatView::draw()");
        // Only used for debug messages
        let node = sg.get_node(self.node_id).unwrap();

        if let Err(err) = eval_rect(self.rect.clone(), parent_rect) {
            panic!("Node {:?} bad rect property: {}", node, err);
        }

        let Ok(mut rect) = read_rect(self.rect.clone()) else {
            panic!("Node {:?} bad rect property", node);
        };

        let timer = std::time::Instant::now();
        let (mut mesh_instrs, mut old_drawmesh) = self.regen_mesh(rect.clone()).await;
        debug!(target: "ui::chatview", "regen_mesh() took {:?}", timer.elapsed());

        let mut freed_textures = vec![];
        let mut freed_buffers = vec![];
        for old_mesh in old_drawmesh {
            freed_buffers.push(old_mesh.vertex_buffer);
            freed_buffers.push(old_mesh.index_buffer);
            //if let Some(texture_id) = old_dc.texture {
            //    freed_textures.push(texture_id);
            //}
        }

        debug!(target: "ui::chatview", "chatview rect = {:?}", rect);

        let mut instrs = vec![DrawInstruction::ApplyViewport(rect)];
        instrs.append(&mut mesh_instrs);

        Some(DrawUpdate {
            key: self.dc_key,
            draw_calls: vec![(
                self.dc_key,
                DrawCall { instrs, dcs: vec![], z_index: self.z_index.get() },
            )],
            freed_textures,
            freed_buffers,
        })
    }
}