Did some refactoring and improved error handling

src/main.rs

@@ -1,23 +1,24 @@
 use sdl2::event::Event;
 use sdl2::keyboard::Keycode;
-use sdl2::pixels::{Color, PixelFormatEnum};
-use sdl2::render::Texture;
+use sdl2::pixels::PixelFormatEnum;
+use sdl2::render::{Canvas, Texture};
+use sdl2::Sdl;
 use std::time::Duration;
 
 struct OutputImage {
     pixel_data: Vec<u8>,
-    width: usize,
-    height: usize,
-    channels: usize,
+    width: u32,
+    height: u32,
+    channels: u32,
 }
 
 impl OutputImage {
-    fn new(width: usize, height: usize) -> OutputImage {
+    fn new(width: u32, height: u32) -> OutputImage {
         OutputImage {
             width: width,
             height: height,
             channels: 3,
-            pixel_data: vec![0; width * height * 3],
+            pixel_data: vec![0; (width * height * 3) as usize],
         }
     }
 
@@ -28,8 +29,9 @@ impl OutputImage {
         self
     }
 
-    fn set_color(&mut self, row: usize, column: usize, red: u8, green: u8, blue: u8) {
-        let index = (row * self.width + column) * self.channels;
+    fn set_color(&mut self, row: u32, column: u32, red: u8, green: u8, blue: u8) {
+        assert!(row < self.height && column < self.width);
+        let index = ((row * self.width + column) * self.channels) as usize;
         self.pixel_data[index] = red;
         self.pixel_data[index + 1] = green;
         self.pixel_data[index + 2] = blue;
@@ -37,38 +39,48 @@ impl OutputImage {
 
     fn update_texture(&self, texture: &mut Texture) {
         texture
-            .update(None, self.pixel_data.as_slice(), self.width * self.channels)
+            .update(
+                None,
+                self.pixel_data.as_slice(),
+                (self.width * self.channels) as usize,
+            )
             .expect("Couldn't update texture.");
     }
 }
 
-pub fn main() {
-    let image_width = 1200;
-    let image_height = 900;
-
-    let sdl_context = sdl2::init().unwrap();
-    let video_subsystem = sdl_context.video().unwrap();
+fn init_canvas(
+    image_width: u32,
+    image_height: u32,
+) -> Result<(Sdl, Canvas<sdl2::video::Window>), Box<dyn std::error::Error>> {
+    let sdl_context = sdl2::init()?;
+    let video_subsystem = sdl_context.video()?;
 
     let window = video_subsystem
         .window("van Rijn", image_width as u32, image_height as u32)
         .position_centered()
-        .build()
-        .unwrap();
+        .build()?;
 
-    let mut canvas = window.into_canvas().build().unwrap();
+    let canvas = window.into_canvas().build().unwrap();
+
+    Ok((sdl_context, canvas))
+}
+
+pub fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let image_width = 1200;
+    let image_height = 900;
+
+    let (sdl_context, mut canvas) = init_canvas(image_width, image_height)?;
 
     let texture_creator = canvas.texture_creator();
-    let mut rendered_image_texture = texture_creator
-        .create_texture_streaming(
-            PixelFormatEnum::RGB24,
-            image_width as u32,
-            image_height as u32,
-        )
-        .unwrap();
+    let mut rendered_image_texture = texture_creator.create_texture_streaming(
+        PixelFormatEnum::RGB24,
+        image_width as u32,
+        image_height as u32,
+    )?;
     let mut output_image = OutputImage::new(image_width, image_height);
     output_image.clear();
 
-    let mut event_pump = sdl_context.event_pump().unwrap();
+    let mut event_pump = sdl_context.event_pump()?;
     let mut i = 0;
     'running: loop {
         i = (i + 1) % 255;
@@ -90,8 +102,9 @@ pub fn main() {
             }
         }
 
-        canvas.copy(&rendered_image_texture, None, None);
+        canvas.copy(&rendered_image_texture, None, None)?;
         canvas.present();
         ::std::thread::sleep(Duration::new(0, 1_000_000_000u32 / 60));
     }
+    Ok(())
 }