[oden] Stop doing passes per draw mode that's silly

src/lib.rs

@@ -277,6 +277,22 @@ impl<T: bytemuck::Pod> VertexBufferPool<T> {
         self.next_free_buffer = 0;
     }
 
+    fn get_a_buffer(&mut self, device: &wgpu::Device) -> (u32, VertexBufferHandle) {
+        if self.next_free_buffer > 0 {
+            let vb = &mut self.buffers[self.next_free_buffer - 1];
+            if vb.vec.len() < vb.capacity {
+                let draw_start = vb.vec.len();
+                let handle = VertexBufferHandle {
+                    index: self.next_free_buffer - 1,
+                    capacity: vb.capacity,
+                };
+                return (draw_start.try_into().unwrap(), handle);
+            }
+        }
+
+        (0, self.new_buffer(device))
+    }
+
     fn new_buffer(&mut self, device: &wgpu::Device) -> VertexBufferHandle {
         if self.next_free_buffer >= self.buffers.len() {
             let max_sprites: usize = 4096;
@@ -694,6 +710,7 @@ enum DrawMode {
 
 trait DrawModeInstance: Sized {
     const MODE: DrawMode;
+
     fn get_vertex_buffer<'a>(
         state: &'a mut State,
         vb: &VertexBufferHandle,
@@ -702,6 +719,7 @@ trait DrawModeInstance: Sized {
 
 impl DrawModeInstance for SpriteInstance {
     const MODE: DrawMode = DrawMode::Sprites;
+
     fn get_vertex_buffer<'a>(
         state: &'a mut State,
         vb: &VertexBufferHandle,
@@ -712,6 +730,7 @@ impl DrawModeInstance for SpriteInstance {
 
 impl DrawModeInstance for CircleInstance {
     const MODE: DrawMode = DrawMode::Circles;
+
     fn get_vertex_buffer<'a>(
         state: &'a mut State,
         vb: &VertexBufferHandle,
@@ -921,31 +940,22 @@ impl<'a> FrameBuilder<'a> {
     fn start_pass(&mut self, color: Option<[f64; 4]>, target: Rc<wgpu::TextureView>) {
         // NOTE: We're not changing drawing modes here which means we can preserve the
         //       buffer tail if we want to.
+        // TODO: Do we need to do this actually?
         let first_call = match self.draw_calls.last() {
-            Some(call) => call.new_at_buffer_tail(),
-            None => DrawCall::new(self.mode, self.new_instance_buffer(), 0),
+            Some(call) => Some(call.new_at_buffer_tail()),
+            None => None,
         };
 
         self.flush();
 
-        self.draw_calls.push(first_call);
+        match first_call {
+            Some(fc) => self.draw_calls.push(fc),
+            None => {}
+        }
         self.color = color;
         self.target = target;
     }
 
-    fn new_instance_buffer(&mut self) -> VertexBufferHandle {
-        match self.mode {
-            DrawMode::Sprites => self
-                .state
-                .sprite_instance_buffers
-                .new_buffer(&self.state.device),
-            DrawMode::Circles => self
-                .state
-                .circle_instance_buffers
-                .new_buffer(&self.state.device),
-        }
-    }
-
     fn use_texture(&mut self, texture_id: u32) {
         match self.draw_calls.last_mut() {
             Some(call) => match call.texture_id {
@@ -965,28 +975,47 @@ impl<'a> FrameBuilder<'a> {
                 }
             },
             None => {
-                let mut call = DrawCall::new(self.mode, self.new_instance_buffer(), 0);
+                let (draw_start, buffer) = self.new_instance_buffer();
+                let mut call = DrawCall::new(self.mode, buffer, draw_start);
                 call.texture_id = Some(texture_id);
                 self.draw_calls.push(call);
             }
         }
     }
 
-    fn get_instance_buffer<T: DrawModeInstance>(&mut self) -> &mut VertexBuffer<T> {
-        if self.mode != T::MODE {
-            self.flush();
-            self.mode = T::MODE;
-        }
+    fn new_instance_buffer(&mut self) -> (u32, VertexBufferHandle) {
+        match self.mode {
+            DrawMode::Sprites => self
+                .state
+                .sprite_instance_buffers
+                .get_a_buffer(&self.state.device),
 
+            DrawMode::Circles => self
+                .state
+                .circle_instance_buffers
+                .get_a_buffer(&self.state.device),
+        }
+    }
+
+    fn get_instance_buffer<T: DrawModeInstance>(&mut self) -> &mut VertexBuffer<T> {
+        // TODO: Re-work the mode shuffle. Keep the most recent vertex buffer
+        // around from the
+
+        self.mode = T::MODE;
         match self.draw_calls.last_mut() {
-            Some(call) => match call.allocate_capacity(1) {
-                Some(vb) => return T::get_vertex_buffer(self.state, &vb),
-                None => {}
-            },
+            Some(call) => {
+                if call.mode == T::MODE {
+                    match call.allocate_capacity(1) {
+                        Some(vb) => return T::get_vertex_buffer(self.state, &vb),
+                        None => {}
+                    }
+                }
+            }
             None => {}
         };
 
-        let mut call = DrawCall::new(self.mode, self.new_instance_buffer(), 0);
+        let (draw_start, buffer) = self.new_instance_buffer();
+        let mut call = DrawCall::new(self.mode, buffer, draw_start);
         let vb = call.allocate_capacity(1).unwrap();
         self.draw_calls.push(call);
         T::get_vertex_buffer(self.state, &vb)
@@ -1035,12 +1064,19 @@ impl<'a> FrameBuilder<'a> {
                 depth_stencil_attachment: None,
             });
 
-            match self.mode {
-                DrawMode::Sprites => pass.set_pipeline(&self.state.sprite_pipeline),
-                DrawMode::Circles => pass.set_pipeline(&self.state.circle_pipeline),
-            }
-
+            let mut last_mode = None;
             for call in &self.draw_calls {
+                let need_set_pipeline = match last_mode {
+                    None => true,
+                    Some(m) => call.mode != m,
+                };
+                if need_set_pipeline {
+                    match call.mode {
+                        DrawMode::Sprites => pass.set_pipeline(&self.state.sprite_pipeline),
+                        DrawMode::Circles => pass.set_pipeline(&self.state.circle_pipeline),
+                    }
+                    last_mode = Some(call.mode);
+                }
                 call.draw(&self.state, &mut pass);
             }
         }