render_video/src/question.rs

use crate::{iotro::Language, Resolution};
use fontconfig::Fontconfig;
use harfbuzz_rs::{Face, Font, Owned, UnicodeBuffer};
use std::sync::OnceLock;
use svgwriter::{
	tags::{Group, Path, Rect, TSpan, TagWithPresentationAttributes as _, Text},
	Data, Graphic, Transform
};

pub(crate) struct Question {
	res: Resolution,
	g: Group
}

impl Question {
	pub(crate) fn new(res: Resolution, lang: &Language<'_>, str: String) -> Self {
		static FONT: OnceLock<Owned<Font<'static>>> = OnceLock::new();
		let font = FONT.get_or_init(|| {
			let fc = Fontconfig::new().unwrap();
			let font_path = fc.find("Noto Sans", None).unwrap().path;
			let face = Face::from_file(font_path, 0).unwrap();
			Font::new(face)
		});
		let upem = font.face().upem();

		// constants
		let border_r = 12;
		let font_size = 44;
		let line_height = font_size * 6 / 5;
		let padding = font_size / 2;
		let margin_x = 240;
		let margin_y = padding * 3 / 2;
		let question_offset = 64;
		let question_width = 240;

		// calculated
		let box_width = 1920 - 2 * margin_x;
		let text_width = box_width - 2 * padding;

		// calculates the width of the given string
		let width_of = |s: &str| {
			let width: i32 =
				harfbuzz_rs::shape(font, UnicodeBuffer::new().add_str(s), &[])
					.get_glyph_positions()
					.iter()
					.map(|glyph_pos| glyph_pos.x_advance)
					.sum();
			(width * font_size) / upem as i32
		};
		let space_width = width_of(" ");

		// lay out the text
		let mut text = Text::new()
			.with_dominant_baseline("hanging")
			.with_transform(
				Transform::new().translate(padding, padding + font_size / 2 + border_r)
			);
		let words = str.split_whitespace();
		let mut text_height = 0;
		let mut text_x = 0;
		for word in words {
			let word_width = width_of(word);
			if text_x + word_width > text_width {
				text_x = 0;
				text_height += line_height;
			}
			text.push(
				TSpan::new()
					.with_x(text_x)
					.with_y(text_height)
					.append(word.to_owned())
			);
			text_x += word_width + space_width;
		}
		text_height += font_size;

		// calculated
		let box_height = text_height + 2 * padding + font_size / 2 + border_r;

		let mut g = Group::new()
			.with_fill("white")
			.with_font_family("Noto Sans")
			.with_font_size(font_size)
			.with_transform(
				Transform::new().translate(margin_x, 1080 - margin_y - box_height)
			);

		let mut outline = Data::new();
		outline.move_by(border_r, 0).horiz_line_to(question_offset);
		outline
			.vert_line_by(-font_size / 2)
			.arc_by(border_r, border_r, 0, false, true, border_r, -border_r)
			.horiz_line_by(question_width)
			.arc_by(border_r, border_r, 0, false, true, border_r, border_r)
			.vert_line_by(font_size)
			.arc_by(border_r, border_r, 0, false, true, -border_r, border_r)
			.horiz_line_by(-question_width)
			.arc_by(border_r, border_r, 0, false, true, -border_r, -border_r)
			.vert_line_by(-font_size / 2)
			.move_by(question_width + 2 * border_r, 0);
		outline
			.horiz_line_to(box_width - border_r)
			.arc_by(border_r, border_r, 0, false, true, border_r, border_r)
			.vert_line_by(box_height - 2 * border_r)
			.arc_by(border_r, border_r, 0, false, true, -border_r, border_r)
			.horiz_line_to(border_r)
			.arc_by(border_r, border_r, 0, false, true, -border_r, -border_r)
			.vert_line_to(border_r)
			.arc_by(border_r, border_r, 0, false, true, border_r, -border_r);
		g.push(
			Path::new()
				.with_stroke("#fff")
				.with_stroke_width(3)
				.with_fill("#000")
				.with_fill_opacity(".3")
				.with_d(outline)
		);
		g.push(
			Text::new()
				.with_x(question_offset + question_width / 2 + border_r)
				.with_y(0)
				.with_dominant_baseline("middle")
				.with_text_anchor("middle")
				.with_font_weight(600)
				.append("Question")
		);
		g.push(text);

		Self { res, g }
	}

	pub(crate) fn finish(self) -> Graphic {
		let mut svg = Graphic::new();
		svg.set_width(self.res.width());
		svg.set_height(self.res.height());
		svg.set_view_box("0 0 1920 1080");
		svg.push(
			Rect::new()
				.with_fill("#040")
				.with_x(0)
				.with_y(0)
				.with_width(1920)
				.with_height(1080)
		);
		svg.push(self.g);
		svg
	}
}

#[cfg(test)]
#[test]
fn question() {
	let svg = Question::new(
		Resolution::FullHD,
		&Language::default(),
		"Hallo Welt! Dies ist eine sehr kluge Frage aus dem Publikum. Die Frage ist nämlich: Was ist eigentlich die Frage?".into()
	)
	.finish();
	std::fs::write("question.svg", svg.to_string_pretty()).unwrap();
}