Clip text correctly when out-of-bounds

src/font.rs

@@ -44,12 +44,17 @@ impl<'a> FontRenderer<'a> {
         text: T,
         pos: Position,
     ) {
+        if pos.x > 240 || pos.y > 240 {
+            // Everything would be out-of-bounds
+            return;
+        }
+
         let glyphs = self
             .font
             .layout(&text.into(), self.scale, self.offset)
             .collect::<Vec<_>>();
 
-        let width = libm::ceil(
+        let text_width = libm::ceil(
             glyphs
                 .iter()
                 .rev()
@@ -58,14 +63,17 @@ impl<'a> FontRenderer<'a> {
                 .unwrap_or(0.0) as f64,
         ) as usize;
 
-        let mut pixel_data = vec![Rgb565::white(); self.height as usize * width];
+        let width = (text_width + pos.x as usize).min(240) - pos.x as usize;
+        let height = (self.height + pos.y as u32).min(240) - pos.y as u32;
+
+        let mut pixel_data = vec![Rgb565::white(); height as usize * width];
 
         for g in glyphs {
             if let Some(bb) = g.pixel_bounding_box() {
                 g.draw(|x, y, cov| {
                     let x = bb.min.x + x as i32;
                     let y = bb.min.y + y as i32;
-                    if x >= 0 && y >= 0 && x < width as i32 && y < self.height as i32 {
+                    if x >= 0 && y >= 0 && x < width as i32 && y < height as i32 {
                         let col = 255 - (255. * cov) as u8;
                         pixel_data[(x + y * width as i32) as usize] = Rgb565(col, col, col);
                     }
@@ -77,7 +85,7 @@ impl<'a> FontRenderer<'a> {
             pos,
             Position {
                 x: pos.x + width as u16 - 1,
-                y: pos.y + self.height as u16 - 1,
+                y: pos.y + height as u16 - 1,
             },
         );
         display.write(display::Writeable::Data(

src/main.rs

@@ -112,7 +112,7 @@ fn main() -> ! {
 
     let font_renderer = FontRenderer::create(30);
 
-    font_renderer.render(&mut display, "Hello World!", Position::new(0, 0));
+    font_renderer.render(&mut display, "Hello World!", Position::new(70, 220));
 
     loop {
         let delay_start = Instant::now();