Reimplement checkered background rendering (#4034)

* Reimplement background checkerboard rendering

node-graph/libraries/wgpu-executor/src/texture_cache.rs

@@ -0,0 +1,95 @@
+use glam::UVec2;
+use std::collections::VecDeque;
+use std::sync::Arc;
+
+pub(crate) struct TextureCache {
+	/// Always sorted oldest-first by insertion/last-use order.
+	textures: VecDeque<Arc<wgpu::Texture>>,
+	max_free_bytes: u64,
+}
+
+impl TextureCache {
+	pub fn new(max_free_bytes: u64) -> Self {
+		Self {
+			textures: VecDeque::new(),
+			max_free_bytes,
+		}
+	}
+
+	pub fn request_texture(&mut self, device: &wgpu::Device, size: UVec2) -> Arc<wgpu::Texture> {
+		let size = size.max(UVec2::ONE);
+
+		if let Some(pos) = self
+			.textures
+			.iter()
+			.position(|texture| UVec2::new(texture.width(), texture.height()) == size && Arc::strong_count(texture) == 1)
+		{
+			let entry = self.textures.remove(pos).unwrap();
+			let texture = entry.clone();
+			self.textures.push_back(entry);
+			return texture;
+		}
+
+		let incoming_bytes = size.x as u64 * size.y as u64 * 4;
+		self.evict_until_fits(incoming_bytes);
+
+		let texture = Arc::new(device.create_texture(&wgpu::TextureDescriptor {
+			label: Some(&format!("cached_texture_{}x{}", size.x, size.y)),
+			size: wgpu::Extent3d {
+				width: size.x,
+				height: size.y,
+				depth_or_array_layers: 1,
+			},
+			mip_level_count: 1,
+			sample_count: 1,
+			dimension: wgpu::TextureDimension::D2,
+			format: wgpu::TextureFormat::Rgba8Unorm,
+			usage: wgpu::TextureUsages::COPY_SRC | wgpu::TextureUsages::COPY_DST | wgpu::TextureUsages::TEXTURE_BINDING | wgpu::TextureUsages::STORAGE_BINDING | wgpu::TextureUsages::RENDER_ATTACHMENT,
+			view_formats: &[],
+		}));
+
+		self.textures.push_back(texture.clone());
+
+		texture
+	}
+
+	fn total_free_bytes(&self) -> u64 {
+		self.textures
+			.iter()
+			.filter(|texture| Arc::strong_count(texture) == 1)
+			.map(|texture| texture.memory_size_estimate())
+			.sum()
+	}
+
+	fn evict_until_fits(&mut self, incoming_bytes: u64) {
+		let mut free_bytes = self.total_free_bytes();
+		let max_free_bytes = self.max_free_bytes;
+
+		if free_bytes + incoming_bytes <= max_free_bytes {
+			return;
+		}
+
+		self.textures.retain(|texture| {
+			if free_bytes + incoming_bytes <= max_free_bytes {
+				return true;
+			}
+			if Arc::strong_count(texture) == 1 {
+				free_bytes -= texture.memory_size_estimate();
+				texture.destroy();
+				false
+			} else {
+				true
+			}
+		});
+	}
+}
+
+trait TextureMemoryCostEstimateExt {
+	fn memory_size_estimate(&self) -> u64;
+}
+
+impl TextureMemoryCostEstimateExt for wgpu::Texture {
+	fn memory_size_estimate(&self) -> u64 {
+		self.width() as u64 * self.height() as u64 * 4
+	}
+}