snowfall

src/main.rs

@@ -7,10 +7,14 @@ use std::path::PathBuf;
 use std::pin::Pin;
 use std::rc::Rc;
 
-use sdl2::render::{WindowCanvas, Texture, TextureCreator};
+use sdl2::render::{WindowCanvas, BlendMode};
 use sdl2::image::ImageRWops;
 use sdl2::surface::Surface;
-use sdl2::video::WindowContext;
+use sdl2::pixels::{Color, PixelFormatEnum};
+use sdl2::rect::Rect;
+
+use rand::{SeedableRng, Rng};
+use rand_xoshiro::Xoshiro128Plus;
 
 use structopt::StructOpt;
 
@@ -40,6 +44,9 @@ struct Zretro {
     emu: Pin<Box<RetroComponentBase>>,
     canvas: WindowCanvas,
     font: Surface<'static>,
+    rng: Xoshiro128Plus,
+    ui_bg: Option<Surface<'static>>,
+    snowflakes: Vec<Rect>,
     sdl2surf_comp: Rc<RefCell<Sdl2SurfaceComponent>>,
 }
 
@@ -63,7 +70,7 @@ impl Zretro {
             .window(title.as_str(), geometry.base_width, geometry.base_height)
             .borderless()
             .build()?;
-        let mut canvas = window.into_canvas().build()?;
+        let canvas = window.into_canvas().build()?;
 
         let sdl2surf_comp = Rc::new(RefCell::new(
             Sdl2SurfaceComponent::new(emu.libretro_core())?
@@ -95,27 +102,64 @@ impl Zretro {
             Surface::from_ll(ptr)
         };
 
+        let mut rng = rand_xoshiro::Xoshiro128Plus::from_entropy();
+        let mut ui_bg = Surface::new(geometry.base_width, geometry.base_height, PixelFormatEnum::ABGR8888)?;
+        ui_bg.fill_rect(None, Color::RGBA(0, 0, 128, 128))?;
+        let snowflakes = (0..100).into_iter()
+            .map(|_| Rect::new(
+                rng.gen_range(0..ui_bg.width() as i32),
+                rng.gen_range(0..ui_bg.height() as i32),
+                2, 2))
+            .collect();
+
         Ok(Zretro {
             emu,
             canvas,
             font,
+            rng,
+            ui_bg: Some(ui_bg),
+            snowflakes,
             sdl2surf_comp,
         })
     }
 
+    fn update_snow(&mut self) -> Result<()> {
+        let mut ui_bg = self.ui_bg.take().ok_or("no ui_bg?")?;
+        ui_bg.fill_rect(None, Color::RGBA(0, 0, 128, 128))?;
+        let w = ui_bg.width() as i32;
+        let h = ui_bg.height() as i32;
+        for flake in &mut self.snowflakes {
+            let x = flake.x() + self.rng.gen_range(-1..=1);
+            let y = flake.y() + 1;
+            flake.set_x(x % w);
+            flake.set_y(y % h);
+        }
+        let mut ui_canvas = ui_bg.into_canvas()?;
+        ui_canvas.set_draw_color(Color::RGBA(255, 255, 255, 160));
+        ui_canvas.draw_rects(&self.snowflakes[..])?;
+        self.ui_bg = Some(ui_canvas.into_surface());
+        Ok(())
+    }
+
     fn run(&mut self) -> Result<()> {
         let tc = self.canvas.texture_creator();
         let font_tx = tc.create_texture_from_surface(&self.font)?;
         let mut font_rect = self.font.rect();
         font_rect.set_height(64);
         while let ControlFlow::Continue = self.emu.run() {
+            self.update_snow()?;
             let ref_mut = RefCell::try_borrow_mut(&self.sdl2surf_comp)?;
-            let mut surface = ref_mut.surface();
+            let surface = ref_mut.surface();
 
-            let texture = tc.create_texture_from_surface(surface)?;
+            let emu_tx = tc.create_texture_from_surface(surface)?;
+
+            let ui_bg_surf_ref = self.ui_bg.as_ref().ok_or("no bg?")?;
+            let mut ui_tx = tc.create_texture_from_surface(ui_bg_surf_ref)?;
+            ui_tx.set_blend_mode(BlendMode::Blend);
 
             self.canvas.clear();
-            self.canvas.copy(&texture, None, None)?;
+            self.canvas.copy(&emu_tx, None, None)?;
+            self.canvas.copy(&ui_tx, None, None)?;
             self.canvas.copy(&font_tx, font_rect, font_rect)?;
             self.canvas.present();
         }