Add a simple Game Of Life example

This is mainly meant to show RenderTarget's capabilities and how to use
Canvas.

examples/game-of-life.rs

@@ -0,0 +1,241 @@
+extern crate sdl2;
+
+use sdl2::rect::{Point, Rect};
+use sdl2::pixels::Color;
+use sdl2::event::Event;
+use sdl2::mouse::MouseButton;
+use sdl2::keyboard::Keycode;
+use sdl2::video::{Window, WindowContext};
+use sdl2::render::{Canvas, Texture, TextureCreator};
+use game_of_life::{SQUARE_SIZE, PLAYGROUND_WIDTH, PLAYGROUND_HEIGHT};
+
+mod game_of_life {
+    pub const SQUARE_SIZE: u32 = 16;
+    pub const PLAYGROUND_WIDTH: u32 = 49;
+    pub const PLAYGROUND_HEIGHT: u32 = 40;
+
+    #[derive(Copy, Clone)]
+    pub enum State {
+        Paused,
+        Playing,
+    }
+
+    pub struct GameOfLife {
+        playground: [bool; (PLAYGROUND_WIDTH*PLAYGROUND_HEIGHT) as usize],
+        state: State,
+    }
+
+    impl GameOfLife {
+        pub fn new() -> GameOfLife {
+            let mut playground = [false; (PLAYGROUND_WIDTH * PLAYGROUND_HEIGHT) as usize];
+
+            // let's make a nice default pattern !
+            for i in 1..(PLAYGROUND_HEIGHT-1) {
+                playground[(1 + i* PLAYGROUND_WIDTH) as usize] = true;
+                playground[((PLAYGROUND_WIDTH-2) + i* PLAYGROUND_WIDTH) as usize] = true;
+            }
+            for j in 2..(PLAYGROUND_WIDTH-2) {
+                playground[(1*PLAYGROUND_WIDTH + j) as usize] = true;
+                playground[((PLAYGROUND_HEIGHT-2)*PLAYGROUND_WIDTH + j) as usize] = true;
+            }
+
+            GameOfLife {
+                playground: playground,
+                state: State::Paused,
+            }
+        }
+
+        pub fn get(&self, x: i32, y: i32) -> Option<bool> {
+            if x >= 0 && y >= 0 &&
+               (x as u32) < PLAYGROUND_WIDTH && (y as u32) < PLAYGROUND_HEIGHT {
+                Some(self.playground[(x as u32 + (y as u32)* PLAYGROUND_WIDTH) as usize])
+            } else {
+                None
+            }
+        }
+
+        pub fn get_mut<'a>(&'a mut self, x: i32, y: i32) -> Option<&'a mut bool> {
+            if x >= 0 && y >= 0 &&
+               (x as u32) < PLAYGROUND_WIDTH && (y as u32) < PLAYGROUND_HEIGHT {
+                Some(&mut self.playground[(x as u32 + (y as u32)* PLAYGROUND_WIDTH) as usize])
+            } else {
+                None
+            }
+        }
+
+        pub fn toggle_state(&mut self) {
+            self.state = match self.state {
+                State::Paused => State::Playing,
+                State::Playing => State::Paused,
+            }
+        }
+
+        pub fn state(&self) -> State {
+            self.state
+        }
+
+        pub fn update(&mut self) {
+            let mut new_playground = self.playground;
+            for (u, mut square) in new_playground.iter_mut().enumerate() {
+                let u = u as u32;
+                let x = u % PLAYGROUND_WIDTH;
+                let y = u / PLAYGROUND_WIDTH;
+                let mut count : u32 = 0;
+                for i in -1..2 {
+                    for j in -1..2 {
+                        if !(i == 0 && j == 0) {
+                            let peek_x : i32 = (x as i32) + i;
+                            let peek_y : i32 = (y as i32) + j;
+                            match self.get(peek_x, peek_y) {
+                                Some(true) => {
+                                    count += 1;
+                                },
+                                _ => {},
+                            }
+                        }
+                    }
+                }
+                if count > 3 || count < 2 {
+                    *square = false;
+                } else if count == 3 {
+                    *square = true;
+                } else if count == 2 {
+                    *square = *square;
+                }
+            }
+            self.playground = new_playground;
+        }
+    }
+
+
+
+    impl<'a> IntoIterator for &'a GameOfLife {
+        type Item = &'a bool;
+        type IntoIter = ::std::slice::Iter<'a, bool>;
+        fn into_iter(self) -> ::std::slice::Iter<'a, bool> {
+            self.playground.iter()
+        }
+    }
+}
+
+fn dummy_texture<'a>(canvas: &mut Canvas<Window>, texture_creator: &'a TextureCreator<WindowContext>) -> Texture<'a>{
+    let mut square_texture : Texture =
+        texture_creator.create_texture_target(None, SQUARE_SIZE, SQUARE_SIZE).unwrap();
+    {
+        // let's change the texture we just created
+        let mut texture_canvas = canvas.with_target(&mut square_texture).unwrap();
+        texture_canvas.set_draw_color(Color::RGB(0, 0, 0));
+        texture_canvas.clear();
+        for i in 0..SQUARE_SIZE {
+            for j in 0..SQUARE_SIZE {
+                // drawing pixel by pixel isn't very effective, but we only do it once and store
+                // the texture afterwards so it's still alright!
+                if (i+j) % 7 == 0 {
+                    // this doesn't mean anything, there was some trial and serror to find
+                    // something that wasn't too ugly
+                    texture_canvas.set_draw_color(Color::RGB(192, 192, 192));
+                    texture_canvas.draw_point(Point::new(i as i32, j as i32)).unwrap();
+                }
+                if (i+j*2) % 5 == 0 {
+                    texture_canvas.set_draw_color(Color::RGB(64, 64, 64));
+                    texture_canvas.draw_point(Point::new(i as i32, j as i32)).unwrap();
+                }
+            }
+        }
+    }
+    square_texture
+}
+
+pub fn main() {
+    let sdl_context = sdl2::init().unwrap();
+    let video_subsystem = sdl_context.video().unwrap();
+    
+    // the window is the representation of a window in your operating system,
+    // however you can only manipulate properties of that window, like its size, whether it's
+    // fullscreen, ... but you cannot change its content without using a Canvas or using the
+    // `surface()` method.
+    let window = video_subsystem
+        .window("rust-sdl2 demo: Game of Life",
+                SQUARE_SIZE*PLAYGROUND_WIDTH,
+                SQUARE_SIZE*PLAYGROUND_HEIGHT)
+        .position_centered()
+        .build()
+        .unwrap();
+
+    // the canvas allows us to both manipulate the property of the window and to change its content
+    // via hardware or software rendering. See CanvasBuilder for more info.
+    let mut canvas = window.into_canvas()
+        .target_texture()
+        .present_vsync()
+        .build().unwrap();
+
+    println!("Using SDL_Renderer \"{}\"", canvas.info().name);
+    canvas.set_draw_color(Color::RGB(0, 0, 0));
+    // clears the canvas with the color we set in `set_draw_color`.
+    canvas.clear();
+    // However the canvas has not been updated to the window yet, everything has been processed to
+    // an internal buffer, but if we want our buffer to be displayed on the window, we need to call
+    // `present`. We need to call this everytime we want to render a new frame on the window.
+    canvas.present();
+
+    // this struct manages textures. For lifetime reasons, the canvas cannot directly create
+    // textures, you have to create a `TextureCreator` instead.
+    let texture_creator : TextureCreator<_> = canvas.texture_creator();
+
+    // Create a "target" texture so that we can use our Renderer with it later
+    let square_texture = dummy_texture(&mut canvas, &texture_creator);
+    let mut game = game_of_life::GameOfLife::new();
+
+    let mut event_pump = sdl_context.event_pump().unwrap();
+    let mut frame : u32 = 0;
+    'running: loop {
+        // get the inputs here
+        for event in event_pump.poll_iter() {
+            match event {
+                Event::Quit {..} | Event::KeyDown { keycode: Some(Keycode::Escape), .. } => {
+                    break 'running
+                },
+                Event::KeyDown { keycode: Some(Keycode::Space), repeat: false, .. } => {
+                    game.toggle_state();
+                },
+                Event::MouseButtonDown { x, y, mouse_btn: MouseButton::Left, .. } => {
+                    let x = (x as u32) / SQUARE_SIZE;
+                    let y = (y as u32) / SQUARE_SIZE;
+                    match game.get_mut(x as i32, y as i32) {
+                        Some(mut square) => {*square = !(*square);},
+                        None => {panic!()}
+                    };
+                },
+                _ => {}
+            }
+        }
+
+        // update the game loop here
+        if frame >= 29 {
+            game.update();
+            frame = 0;
+        }
+
+        canvas.set_draw_color(Color::RGB(0, 0, 0));
+        canvas.clear();
+        for (i, unit) in (&game).into_iter().enumerate() {
+            let i = i as u32;
+            match *unit {
+                true => {
+                    canvas.copy(&square_texture,
+                                None,
+                                Rect::new(((i % PLAYGROUND_WIDTH) * SQUARE_SIZE) as i32,
+                                          ((i / PLAYGROUND_WIDTH) * SQUARE_SIZE) as i32,
+                                          SQUARE_SIZE,
+                                          SQUARE_SIZE)).unwrap();
+                },
+                false => {},
+            }
+        }
+        canvas.present();
+        match game.state() {
+            game_of_life::State::Playing => { frame += 1; },
+            _ => {}
+        };
+    }
+}