feather_ui/render/

textbox.rs

// SPDX-License-Identifier: Apache-2.0
// SPDX-FileCopyrightText: 2025 Fundament Research Institute <https://fundament.institute>

use std::cell::RefCell;
use std::rc::Rc;

use cosmic_text::Cursor;
use unicode_segmentation::UnicodeSegmentation;

use crate::Error;
use crate::color::sRGB;
use crate::render::compositor::DataFlags;
use crate::render::{compositor, text};

pub struct Instance {
    pub text_buffer: Rc<RefCell<cosmic_text::Buffer>>,
    pub padding: crate::PxPerimeter,
    pub cursor: Cursor,
    pub selection: Option<(Cursor, Cursor)>,
    pub selection_bg: sRGB,
    pub selection_color: sRGB,
    pub color: sRGB,
    pub cursor_color: sRGB,
    pub scale: f32,
}

impl Instance {
    fn draw_box(
        x: f32,
        y: f32,
        mut w: f32,
        mut h: f32,
        bounds: crate::PxRect,
        color: sRGB,
    ) -> compositor::Data {
        // When we are drawing boxes that need to line up with each other, this is a
        // worst-case scenario for the compositor's antialiasing. The only way
        // to antialias arbitrary selection boxes correctly is to use a texture
        // cache or a custom shader. Instead of doing that, we just pixel-snap
        // everything.
        w = w.min((bounds.bottomright().x - x).max(0.0));
        h = h.min((bounds.bottomright().y - y).max(0.0));
        let bx = x.max(bounds.topleft().x);
        let by = y.max(bounds.topleft().y);
        w -= bx - x;
        h -= by - y;

        compositor::Data {
            pos: [bx.round(), by.round()].into(),
            dim: [w.round(), h.round()].into(),
            uv: [0.0, 0.0].into(),
            uvdim: [0.0, 0.0].into(),
            color: color.as_32bit().rgba,
            flags: DataFlags::new().with_tex(u8::MAX).with_raw(true).into(),
            ..Default::default()
        }
    }
}

impl crate::render::Renderable for Instance {
    fn render(
        &self,
        area: crate::PxRect,
        driver: &crate::graphics::Driver,
        compositor: &mut compositor::CompositorView<'_>,
    ) -> Result<(), Error> {
        let buffer = self.text_buffer.borrow();
        // Padding works differently in a textbox than in a static text field, because a
        // textbox cannot having non-clipping regions outside the text area, or
        // you'll get rendering errors when scrolling.
        let area = area + self.padding;
        let pos = area.topleft();

        let bounds = area.intersect(compositor.current_clip());

        let bounds_top = bounds.topleft().y as i32;
        let bounds_bottom = bounds.bottomright().y as i32;
        let bounds_min_x = (bounds.topleft().x as i32).max(0);
        let bounds_min_y = bounds_top.max(0);
        let bounds_max_x = bounds.bottomright().x as i32;
        let bounds_max_y = bounds_bottom;
        let color = self.color.into();
        let selection_color = self.selection_color.into();

        let is_run_visible = |run: &cosmic_text::LayoutRun| {
            let start_y_physical = (pos.y + (run.line_top * self.scale)) as i32;
            let end_y_physical = start_y_physical + (run.line_height * self.scale) as i32;

            start_y_physical <= bounds_bottom && bounds_top <= end_y_physical
        };

        for run in buffer
            .layout_runs()
            .skip_while(|run| !is_run_visible(run))
            .take_while(is_run_visible)
        {
            let line_i = run.line_i;
            let line_top = run.line_top;
            let line_height = run.line_height;

            // Highlight selection
            if let Some((start, end)) = &self.selection
                && line_i >= start.line
                && line_i <= end.line
            {
                let mut range_opt = None;
                for glyph in run.glyphs.iter() {
                    // Guess x offset based on characters
                    let cluster = &run.text[glyph.start..glyph.end];
                    let total = cluster.grapheme_indices(true).count();
                    let mut c_x = glyph.x;
                    let c_w = glyph.w / total as f32;
                    for (i, c) in cluster.grapheme_indices(true) {
                        let c_start = glyph.start + i;
                        let c_end = glyph.start + i + c.len();
                        if (start.line != line_i || c_end > start.index)
                            && (end.line != line_i || c_start < end.index)
                        {
                            range_opt = match range_opt.take() {
                                Some((min, max)) => Some((
                                    std::cmp::min(min, c_x as i32),
                                    std::cmp::max(max, (c_x + c_w) as i32),
                                )),
                                None => Some((c_x as i32, (c_x + c_w) as i32)),
                            };
                        } else if let Some((min, max)) = range_opt.take() {
                            compositor.preprocessed(Self::draw_box(
                                min as f32 + pos.x,
                                line_top + pos.y,
                                std::cmp::max(0, max - min) as f32,
                                line_height,
                                bounds,
                                self.selection_bg,
                            ));
                        }
                        c_x += c_w;
                    }
                }

                if run.glyphs.is_empty() && end.line > line_i {
                    // Highlight all of internal empty lines
                    range_opt = Some((0, buffer.size().0.unwrap_or(0.0) as i32));
                }

                if let Some((mut min, mut max)) = range_opt.take() {
                    if end.line > line_i {
                        // Draw to end of line
                        if run.rtl {
                            min = 0;
                        } else if let (Some(w), _) = buffer.size() {
                            max = w.round() as i32;
                        } else if max == 0 {
                            max = (buffer.metrics().font_size * 0.5) as i32;
                        }
                    }
                    compositor.preprocessed(Self::draw_box(
                        min as f32 + pos.x,
                        line_top + pos.y,
                        std::cmp::max(0, max - min) as f32,
                        line_height,
                        bounds,
                        self.selection_bg,
                    ));
                }
            }

            // Draw text
            for glyph in run.glyphs.iter() {
                let physical_glyph = glyph.physical((pos.x, pos.y), self.scale);

                let mut color = match glyph.color_opt {
                    Some(some) => some,
                    None => color,
                };

                if let Some((start, end)) = self.selection
                    && line_i >= start.line
                    && line_i <= end.line
                    && (start.line != line_i || glyph.end > start.index)
                    && (end.line != line_i || glyph.start < end.index)
                {
                    color = selection_color;
                }

                text::Instance::write_glyph(
                    physical_glyph.cache_key,
                    &mut driver.font_system.write(),
                    &mut driver.glyphs.write(),
                    &driver.device,
                    &driver.queue,
                    &mut driver.atlas.write(),
                    &mut driver.swash_cache.write(),
                )?;

                if let Some(data) = text::Instance::prepare_glyph(
                    physical_glyph.x,
                    physical_glyph.y,
                    run.line_y,
                    self.scale,
                    color,
                    bounds_min_x,
                    bounds_min_y,
                    bounds_max_x,
                    bounds_max_y,
                    text::Instance::get_glyph(physical_glyph.cache_key, &driver.glyphs.read())
                        .ok_or(Error::GlyphCacheFailure)?,
                )? {
                    compositor.preprocessed(data);
                }
            }

            // Draw cursor
            if let Some((x, y)) = crate::editor::cursor_position(&self.cursor, &run) {
                compositor.preprocessed(Self::draw_box(
                    x as f32 + pos.x,
                    y as f32 + pos.y,
                    1.0,
                    line_height,
                    bounds,
                    self.cursor_color,
                ));
            }
        }

        Ok(())
    }
}