Add terminal example

examples/terminal/Cargo.toml

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+[package]
+name = "terminal"
+version = "0.1.0"
+authors = ["Jeremy Soller <jeremy@system76.com>"]
+edition = "2021"
+license = "MIT OR Apache-2.0"
+publish = false
+
+[dependencies]
+cosmic-text = { path = "../../" }
+env_logger = "0.9"
+fontdb = "0.9"
+log = "0.4"
+termion = "2.0"

examples/terminal/src/main.rs

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+use cosmic_text::{Attrs, Color, FontSystem, SwashCache, TextBuffer, TextMetrics};
+use std::cmp;
+use termion::{
+    color,
+    cursor,
+};
+
+fn main() {
+    // A FontSystem provides access to detected system fonts, create one per application
+    let font_system = FontSystem::new();
+
+    // A SwashCache stores rasterized glyphs, create one per application
+    let mut swash_cache = SwashCache::new(&font_system);
+
+    // Text metrics indicate the font size and line height of a buffer
+    let metrics = TextMetrics::new(14, 20);
+
+    // A TextBuffer provides shaping and layout for a UTF-8 string, create one per text widget
+    let mut text_buffer = TextBuffer::new(&font_system, metrics);
+
+    // Set a size for the text buffer, in pixels
+    let width = 80u16;
+    let height = 25u16;
+    text_buffer.set_size(width as i32, height as i32);
+
+    // Attributes indicate what font to choose
+    let attrs = Attrs::new();
+
+    // Add some text!
+    text_buffer.set_text(" Hi, Rust! 🦀", attrs);
+
+    // Perform shaping as desired
+    text_buffer.shape_until_cursor();
+
+    // Default text color (0xFF, 0xFF, 0xFF is white)
+    let text_color = Color::rgb(0xFF, 0xFF, 0xFF);
+
+    // Start on a new line
+    println!();
+
+    // Clear buffer with black background
+    for _y in 0..height {
+        for _x in 0..text_buffer.size().0 {
+            print!(
+                "{} {}",
+                color::Bg(color::Rgb(0, 0, 0)),
+                color::Bg(color::Reset),
+            );
+        }
+        println!();
+    }
+
+    // Go back to start
+    print!("{}", cursor::Up(height));
+
+    // Print the buffer
+    let mut last_x = 0;
+    let mut last_y = 0;
+    text_buffer.draw(&mut swash_cache, text_color, |x, y, w, h, color| {
+        let a = color.a();
+        if a == 0 || x < 0 || y < 0 || w != 1 || h != 1 {
+            // Ignore alphas of 0, or invalid x, y coordinates, or unimplemented sizes
+            return;
+        }
+
+        // Scale by alpha (mimics blending with black)
+        let scale = |c: u8| {
+            cmp::max(0, cmp::min(255,
+                ((c as i32) * (a as i32)) / 255
+            )) as u8
+        };
+
+        // Navigate to x coordinate
+        if x > last_x {
+            print!("{}", cursor::Right((x - last_x) as u16));
+            last_x = x;
+        } else if x < last_x {
+            print!("{}", cursor::Left((last_x - x) as u16));
+            last_x = x;
+        }
+
+        // Navigate to y coordinate
+        if y > last_y {
+            print!("{}", cursor::Down((y - last_y) as u16));
+            last_y = y;
+        } else if y < last_y {
+            print!("{}", cursor::Up((last_y - y) as u16));
+            last_y = y;
+        }
+
+        // Print a space with the expected color as the background
+        print!(
+            "{} {}",
+            color::Bg(color::Rgb(
+                scale(color.b()),
+                scale(color.g()),
+                scale(color.r()),
+            )),
+            color::Bg(color::Reset),
+        );
+
+        // Printing a space increases x coordinate
+        last_x += 1;
+    });
+
+    // Skip over output
+    if last_x > 0 {
+        print!("{}", cursor::Left(last_x as u16));
+    }
+    if (last_y as u16) < height {
+        print!("{}", cursor::Down(height - last_y as u16));
+    }
+}

terminal.sh

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+RUST_LOG=cosmic_text=debug,terminal=debug cargo run --release --package terminal -- "$@"