perf: fast display (row runs, bulk fills, pixel scroll), terminal draws changed cells only + scrolls pixels, print! batched (was IPC per fmt fragment), snake sleeps on timer

crates/drivers/framebuffer/mock/src/lib.rs

@@ -10,6 +10,7 @@ pub struct MockFramebuffer {
     pixels: [(ScreenCoord, ScreenCoord, Color); 4096],
     pixel_count: usize,
     flushed: bool,
+    scrolls: usize,
 }
 
 impl MockFramebuffer {
@@ -20,6 +21,7 @@ impl MockFramebuffer {
             pixels: [(ScreenCoord::new(0), ScreenCoord::new(0), Color::from_raw(0)); 4096],
             pixel_count: 0,
             flushed: false,
+            scrolls: 0,
         }
     }
 
@@ -27,6 +29,11 @@ impl MockFramebuffer {
         self.pixel_count
     }
 
+    /// How many times the screen was scrolled.
+    pub fn scrolls(&self) -> usize {
+        self.scrolls
+    }
+
     pub fn was_flushed(&self) -> bool {
         self.flushed
     }
@@ -62,4 +69,8 @@ impl Framebuffer for MockFramebuffer {
     fn flush(&mut self) {
         self.flushed = true;
     }
+
+    fn scroll_up(&mut self, _top: ScreenCoord, _height: Dimension, _by: Dimension, _fill: Color) {
+        self.scrolls += 1;
+    }
 }