split screen logic into seprate crate for testing

shared/Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "shared"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+embedded-graphics = "0.8.1"

shared/src/lib.rs

@@ -0,0 +1,97 @@
+#![feature(ascii_char)]
+
+use embedded_graphics::{
+    mono_font::{
+        MonoFont, MonoTextStyle,
+        ascii::{FONT_6X9, FONT_10X20},
+    },
+    pixelcolor::{BinaryColor, Rgb565},
+    prelude::{Point, WebColors, *},
+    primitives::{Circle, Line, PrimitiveStyle, Rectangle},
+    text::{Alignment, Baseline, Text, TextStyle},
+};
+
+pub const SCREEN_WIDTH: usize = 320;
+pub const SCREEN_HEIGHT: usize = 320;
+const SCREEN_ROWS: usize = 15;
+const SCREEN_COLS: usize = 31;
+const FONT: MonoFont = FONT_10X20;
+const COLOR: Rgb565 = Rgb565::CSS_LAWN_GREEN;
+
+pub struct Cursor {
+    x: u16,
+    y: u16,
+}
+
+impl Cursor {
+    fn new(x: u16, y: u16) -> Self {
+        Self { x, y }
+    }
+}
+
+pub struct TextBuffer {
+    grid: [[Option<char>; SCREEN_COLS]; SCREEN_ROWS],
+    cursor: Cursor,
+}
+
+impl TextBuffer {
+    pub fn new() -> Self {
+        Self {
+            grid: [[None; SCREEN_COLS]; SCREEN_ROWS],
+            cursor: Cursor { x: 0, y: 0 },
+        }
+    }
+
+    /// writes char at cursor
+    pub fn write_char(&mut self, ch: char) {
+        for (i, row) in self.grid.iter_mut().enumerate() {
+            for (j, col) in row.iter_mut().enumerate() {
+                if i as u16 == self.cursor.x && j as u16 == self.cursor.y {
+                    *col = Some(ch)
+                }
+            }
+        }
+    }
+
+    /// fills text buffer with char
+    pub fn fill(&mut self, ch: char) {
+        for i in 0..SCREEN_ROWS {
+            for j in 0..SCREEN_COLS {
+                self.cursor = Cursor::new(i as u16, j as u16);
+                self.write_char(ch);
+            }
+        }
+    }
+
+    pub fn scroll_up(&mut self) {
+        let (top, bottom) = self.grid.split_at_mut(SCREEN_ROWS - 1);
+        for (dest, src) in top.iter_mut().zip(&bottom[1..]) {
+            dest.copy_from_slice(src);
+        }
+
+        self.grid[SCREEN_ROWS - 1].fill(None);
+    }
+
+    pub fn draw<D: DrawTarget<Color = Rgb565>>(&mut self, target: &mut D) {
+        let style = MonoTextStyle::new(&FONT, COLOR);
+
+        for (i, row) in self.grid.iter().enumerate() {
+            for (j, col) in row[1..].iter().enumerate() {
+                if let Some(ch) = col {
+                    let pos = Point::new(
+                        (j as i32) * FONT.character_size.width as i32,
+                        (i as i32) * FONT.character_size.height as i32,
+                    );
+
+                    let _ = Text::with_baseline(
+                        ch.as_ascii().unwrap().as_str(),
+                        pos,
+                        style,
+                        Baseline::Top,
+                    )
+                    .draw(target);
+                }
+            }
+        }
+    }
+}