feat: only present/render canvas when renderables change

src/game/mod.rs

@@ -100,7 +100,7 @@ impl Game {
         // Render map to texture
         canvas
             .with_texture_canvas(&mut map_texture, |map_canvas| {
-                MapRenderer::render_map(map_canvas, &mut atlas, &mut map_tiles);
+                MapRenderer::render_map(map_canvas, &mut atlas, &map_tiles);
             })
             .map_err(|e| GameError::Sdl(e.to_string()))?;
 
@@ -196,10 +196,10 @@ impl Game {
                 profile("collision", collision_system),
                 profile("blinking", blinking_system),
                 profile("directional_render", directional_render_system),
-                profile("render", render_system),
             )
                 .chain(),
         );
+        schedule.add_systems(profile("render", render_system));
 
         // Spawn player
         world.spawn(player);

src/map/render.rs

@@ -19,7 +19,7 @@ impl MapRenderer {
     ///
     /// This function draws the static map texture to the screen at the correct
     /// position and scale.
-    pub fn render_map<T: RenderTarget>(canvas: &mut Canvas<T>, atlas: &mut SpriteAtlas, map_tiles: &mut [AtlasTile]) {
+    pub fn render_map<T: RenderTarget>(canvas: &mut Canvas<T>, atlas: &mut SpriteAtlas, map_tiles: &[AtlasTile]) {
         for (y, row) in TILE_MAP.iter().enumerate() {
             for (x, &tile_index) in row.iter().enumerate() {
                 let mut tile = map_tiles[tile_index];

src/systems/render.rs

@@ -5,6 +5,7 @@ use crate::systems::movement::{Movable, MovementState, Position};
 use crate::texture::sprite::SpriteAtlas;
 use bevy_ecs::entity::Entity;
 use bevy_ecs::event::EventWriter;
+use bevy_ecs::prelude::{Changed, Or, RemovedComponents};
 use bevy_ecs::system::{NonSendMut, Query, Res};
 use sdl2::render::{Canvas, Texture};
 use sdl2::video::Window;
@@ -31,7 +32,10 @@ pub fn directional_render_system(
             if !stopped {
                 texture.tick(dt.0);
             }
-            renderable.sprite = *texture.current_tile();
+            let new_tile = *texture.current_tile();
+            if renderable.sprite != new_tile {
+                renderable.sprite = new_tile;
+            }
         } else {
             errors.write(TextureError::RenderFailed(format!("Entity has no texture")).into());
             continue;
@@ -51,9 +55,14 @@ pub fn render_system(
     mut backbuffer: NonSendMut<BackbufferResource>,
     mut atlas: NonSendMut<SpriteAtlas>,
     map: Res<Map>,
-    renderables: Query<(Entity, &mut Renderable, &Position)>,
+    renderables: Query<(Entity, &Renderable, &Position)>,
+    changed_renderables: Query<(), Or<(Changed<Renderable>, Changed<Position>)>>,
+    removed_renderables: RemovedComponents<Renderable>,
     mut errors: EventWriter<GameError>,
 ) {
+    if changed_renderables.is_empty() && removed_renderables.is_empty() {
+        return;
+    }
     // Clear the main canvas first
     canvas.set_draw_color(sdl2::pixels::Color::BLACK);
     canvas.clear();
@@ -66,17 +75,12 @@ pub fn render_system(
             backbuffer_canvas.clear();
 
             // Copy the pre-rendered map texture to the backbuffer
-            backbuffer_canvas
-                .copy(&map_texture.0, None, None)
-                .err()
-                .map(|e| errors.write(TextureError::RenderFailed(e.to_string()).into()));
+            if let Err(e) = backbuffer_canvas.copy(&map_texture.0, None, None) {
+                errors.write(TextureError::RenderFailed(e.to_string()).into());
+            }
 
             // Render all entities to the backbuffer
-            for (_, mut renderable, position) in renderables
-            // .iter_mut()
-            // .sort_by_key::<&mut Renderable, _, _>(|(renderable, renderable, renderable)| renderable.layer)
-            // .collect()
-            {
+            for (_, renderable, position) in renderables.iter() {
                 let pos = position.get_pixel_pos(&map.graph);
                 match pos {
                     Ok(pos) => {

src/texture/sprite.rs

@@ -21,7 +21,7 @@ pub struct MapperFrame {
     pub height: u16,
 }
 
-#[derive(Copy, Clone, Debug)]
+#[derive(Copy, Clone, Debug, PartialEq)]
 pub struct AtlasTile {
     pub pos: U16Vec2,
     pub size: U16Vec2,
@@ -30,7 +30,7 @@ pub struct AtlasTile {
 
 impl AtlasTile {
     pub fn render<C: RenderTarget>(
-        &mut self,
+        &self,
         canvas: &mut Canvas<C>,
         atlas: &mut SpriteAtlas,
         dest: Rect,
@@ -41,7 +41,7 @@ impl AtlasTile {
     }
 
     pub fn render_with_color<C: RenderTarget>(
-        &mut self,
+        &self,
         canvas: &mut Canvas<C>,
         atlas: &mut SpriteAtlas,
         dest: Rect,

src/texture/text.rs

@@ -103,9 +103,9 @@ impl TextTexture {
         &self.char_map
     }
 
-    pub fn get_tile(&mut self, c: char, atlas: &mut SpriteAtlas) -> Result<Option<&mut AtlasTile>> {
+    pub fn get_tile(&mut self, c: char, atlas: &mut SpriteAtlas) -> Result<Option<&AtlasTile>> {
         if self.char_map.contains_key(&c) {
-            return Ok(self.char_map.get_mut(&c));
+            return Ok(self.char_map.get(&c));
         }
 
         if let Some(tile_name) = char_to_tile_name(c) {
@@ -113,7 +113,7 @@ impl TextTexture {
                 .get_tile(&tile_name)
                 .ok_or(GameError::Texture(TextureError::AtlasTileNotFound(tile_name)))?;
             self.char_map.insert(c, tile);
-            Ok(self.char_map.get_mut(&c))
+            Ok(self.char_map.get(&c))
         } else {
             Ok(None)
         }