Change BasicInput::mouse_pos from usize to f64

examples/game_of_life.rs

@@ -4,7 +4,6 @@ use mini_gl_fb::{Config, BufferFormat};
 use mini_gl_fb::glutin::{MouseButton, VirtualKeyCode};
 
 use std::time::SystemTime;
-use std::cmp;
 
 const WIDTH: usize = 200;
 const HEIGHT: usize = 200;
@@ -46,9 +45,9 @@ fn main() {
 
         if input.mouse_is_down(MouseButton::Left) {
             // Mouse was pressed
-            let (mut x, mut y) = input.mouse_pos;
-            x = cmp::min(x, WIDTH - 1);
-            y = cmp::min(y, HEIGHT - 1);
+            let (x, y) = input.mouse_pos;
+            let x = x.min(WIDTH as f64 - 0.0001).max(0.0).floor() as usize;
+            let y = y.min(HEIGHT as f64 - 0.0001).max(0.0).floor() as usize;
             cells[y * WIDTH + x] = true;
             fb.update_buffer(&cells);
             // Give the user extra time to make something pretty each time they click

src/breakout.rs

@@ -18,8 +18,13 @@ pub struct GlutinBreakout {
 pub struct BasicInput {
     /// The mouse position in buffer coordinates.
     ///
-    /// The bottom left of the window is (0, 0).
-    pub mouse_pos: (usize, usize),
+    /// The bottom left of the window is (0, 0). Pixel centers are at multiples of (0.5, 0.5). If
+    /// you want to use this to index into your buffer, in general the following is sufficient:
+    ///
+    /// - clamp each coordinate to the half-open range [0.0, buffer_size)
+    /// - take the floor of each component
+    /// - cast to usize and compute an index: `let index = y * WIDTH + x`
+    pub mouse_pos: (f64, f64),
     /// Stores whether a mouse button was down and is down, in that order.
     ///
     /// If a button has not been pressed yet it will not be in the map.

src/core.rs

@@ -250,7 +250,7 @@ impl Internal {
         let mut running = true;
         let mut input = BasicInput {
             // Not sure how to set mouse pos at start
-            mouse_pos: (0, 0),
+            mouse_pos: (0.0, 0.0),
             mouse: HashMap::new(),
             keys: HashMap::new(),
             modifiers: Default::default(),
@@ -307,10 +307,10 @@ impl Internal {
                 let (x, y): (f64, f64) = pos.to_physical(dpi_factor).into();
                 let x_scale = self.fb.buffer_width as f64 / (self.fb.vp_width as f64);
                 let y_scale = self.fb.buffer_height as f64 / (self.fb.vp_height as f64);
-                let mut mouse_pos = (
-                    (x * x_scale).floor() as usize,
+                let mouse_pos = (
+                    x * x_scale,
                     // use the OpenGL texture coordinate system instead of window coordinates
-                    (self.fb.buffer_height as f64 - y * y_scale).floor() as usize
+                    self.fb.buffer_height as f64 - y * y_scale
                 );
                 input.mouse_pos = mouse_pos;
             }