Enhance the glutin breakout example

examples/glutin_breakout.rs

@@ -4,9 +4,11 @@ use mini_gl_fb::{glutin, GlutinBreakout};
 
 use glutin::GlContext;
 
+use std::cmp::{min, max};
+
 fn main() {
     let mut fb = mini_gl_fb::gotta_go_fast("Hello world!", 800.0, 600.0);
-    let buffer = vec![[128u8, 0, 0, 255]; 800 * 600];
+    let mut buffer = vec![[128u8, 0, 0, 255]; 800 * 600];
     fb.update_buffer(&buffer);
 
     let GlutinBreakout {
@@ -16,6 +18,9 @@ fn main() {
     } = fb.glutin_breakout();
 
     let mut running = true;
+    let mut mouse_x = 0;
+    let mut mouse_y = 0;
+    let mut mouse_down = false;
     while running {
         events_loop.poll_events(|event| {
             use glutin::{Event, ElementState, VirtualKeyCode};
@@ -36,6 +41,23 @@ fn main() {
                     let dpi_factor = gl_window.get_hidpi_factor();
                     gl_window.resize(logical_size.to_physical(dpi_factor));
                 }
+                Event::WindowEvent { event: CursorMoved { position, .. }, .. } => {
+                    let dpi_factor = gl_window.get_hidpi_factor();
+                    let (x, y) = position.to_physical(dpi_factor).into();
+                    mouse_x = min(max(x, 0), 800 - 1);
+                    mouse_y = min(max(y, 0), 600 - 1);
+                    if mouse_down {
+                        buffer[(mouse_x + mouse_y * 800) as usize] = [64, 128, 255, 255];
+                        fb.update_buffer(&buffer);
+                    }
+                }
+                Event::WindowEvent { event: MouseInput { state, .. }, .. } => {
+                    if state == ElementState::Pressed {
+                        mouse_down = true;
+                    } else {
+                        mouse_down = false;
+                    }
+                }
                 _ => {}
             }
         });