entities: rendering hud with semi transparent background

src/entities/diag_hud.rs

@@ -0,0 +1,31 @@
+use sdl2::pixels::Color;
+use sdl2::rect::{Point, Rect};
+use sdl2::render::WindowCanvas;
+
+pub struct DiagHud {
+    position: Point,
+    background_color: Color,
+    height: u32,
+}
+
+impl DiagHud {
+    pub fn new(position: Point) -> DiagHud {
+        let background_color = Color::RGBA(0, 0, 0, 0xaa);
+        let height = 40;
+        DiagHud {
+            position,
+            background_color,
+            height,
+        }
+    }
+
+    pub fn render(&self, canvas: &mut WindowCanvas) -> Result<(), String> {
+        let (width, _) = canvas.window().size();
+        let rect = Rect::new(self.position.x, self.position.y, width, self.height);
+
+        canvas.set_draw_color(self.background_color);
+        canvas.fill_rect(rect)?;
+
+        Ok(())
+    }
+}

src/entities/mod.rs

@@ -1,3 +1,4 @@
+pub mod diag_hud;
 pub mod floor;
 pub mod grid;
 pub mod text;

src/game.rs

@@ -2,6 +2,7 @@ use crate::engine::assets::image_asset::ImageAsset;
 use sdl2::render::WindowCanvas;
 
 use crate::arena::arena::Arena;
+use crate::entities::diag_hud::DiagHud;
 use crate::entities::floor::Floor;
 use crate::entities::grid::Grid;
 use crate::entities::text::{FontBlend, Text};
@@ -17,6 +18,7 @@ pub struct Game<'a> {
     floor: Floor<'a>,
     grid: Grid,
     walls: Walls<'a>,
+    diag_hud: DiagHud,
     diag_text: Text<'a>,
 
     camera_platform: Point,
@@ -32,13 +34,15 @@ impl<'a> Game<'a> {
         let floor = Floor::from_arena(&arena, floor_asset, TILE_SIZE);
         let grid = Grid::new(arena.ncols, arena.nrows, TILE_SIZE);
         let walls = Walls::new(&arena.walls, wall_asset, TILE_SIZE);
+        let diag_hud = DiagHud::new(Point::new(0, 0));
 
         let camera_platform = Point::new(0, 0);
         Ok(Game {
             floor,
             walls,
             arena,
             grid,
+            diag_hud,
             diag_text,
             camera_platform,
         })
@@ -69,6 +73,7 @@ impl<'a> Game<'a> {
         }
         self.floor.render(canvas, &self.camera_platform)?;
         self.walls.render(canvas, &self.camera_platform)?;
+        self.diag_hud.render(canvas)?;
         self.diag_text.render(
             canvas,
             Point::new(10, 10),

src/lib.rs

@@ -7,7 +7,7 @@ use std::fmt;
 
 use sdl2::event::Event;
 use sdl2::keyboard::Keycode;
-use sdl2::render::WindowCanvas;
+use sdl2::render::{BlendMode, WindowCanvas};
 use sdl2::video::{Window, WindowBuildError, WindowBuilder};
 use sdl2::{IntegerOrSdlError, Sdl, VideoSubsystem};
 
@@ -51,6 +51,8 @@ pub fn start(config: &Config) -> Result<(), Box<dyn Error>> {
     let window: Window = build_window(&video_subsystem, &config.window_settings)?;
 
     let mut canvas = build_canvas(window)?;
+    canvas.set_blend_mode(BlendMode::Blend);
+
     let texture_creator = canvas.texture_creator();
 
     let image_assets = ImageAssets::new(&texture_creator)?;