Remove unnecessary backbuffer copy

.vscode/launch.json

@@ -5,7 +5,7 @@
 			"name": "Runner",
 			"type": "gdb",
 			"request": "launch",
-			"target": "${workspaceRoot}/demos/inputs.out",
+			"target": "${workspaceRoot}/demos/effects.out",
 			"cwd": "${workspaceRoot}/demos/",
 			"valuesFormatting": "prettyPrinters",
 			"preLaunchTask": "Build All"

demos/effects.zig

@@ -72,7 +72,7 @@ fn render(commands: gfx.Commands, effects: ona.Write(Effects), app: ona.Read(ona
 	});
 
 	try commands.set_target(.{
-		.texture = .backbuffer,
+		.texture = null,
 		.clear_color = null,
 		.clear_depth = null,
 		.clear_stencil = null,

src/gfx/Resources.zig

@@ -249,7 +249,6 @@ pub const Texture = struct {
 	access: Access,
 
 	pub const Access = union (enum) {
-		empty,
 		render: RenderAccess,
 		static: StaticAccess,
 	};
@@ -275,8 +274,6 @@ pub const Texture = struct {
 			.static => |static| {
 				sokol.gfx.destroyImage(static.image);
 			},
-
-			.empty => {},
 		}
 
 		self.* = undefined;
@@ -290,14 +287,6 @@ pub const Texture = struct {
 
 		switch (desc.access) {
 			.render => |render| {
-				if (render.width == 0 or render.height == 0) {
-					return .{
-						.width = render.width,
-						.height = render.height,
-						.access = .empty,
-					};
-				}
-
 				const color_image = sokol.gfx.makeImage(.{
 					.pixel_format = pixel_format,
 					.width = render.width,
@@ -345,14 +334,6 @@ pub const Texture = struct {
 					return error.OutOfMemory;
 				};
 
-				if (static.width == 0 or height == 0) {
-					return .{
-						.width = static.width,
-						.height = height,
-						.access = .empty,
-					};
-				}
-
 				const image = sokol.gfx.makeImage(image_desc: {
 					var image_desc = sokol.gfx.ImageDesc{
 						.height = height,
@@ -503,16 +484,5 @@ pub fn init() !Self {
 		},
 	}));
 
-	assert.is_handle(gfx.Texture.backbuffer, try pools.create_texture(.{
-		.format = .rgba8,
-
-		.access = .{
-			.render = .{
-				.width = 0,
-				.height = 0,
-			},
-		}
-	}));
-
 	return pools;
 }

src/gfx/gfx.zig

@@ -186,7 +186,7 @@ pub const Commands = struct {
 	};
 
 	pub const SetTargetCommand = struct {
-		texture: Texture,
+		texture: ?Texture = null,
 		clear_color: ?Color,
 		clear_depth: ?f32,
 		clear_stencil: ?u8,
@@ -309,7 +309,6 @@ pub const Rect = struct {
 
 pub const Texture = enum (u32) {
 	default,
-	backbuffer,
 	_,
 
 	pub const Desc = struct {

src/gfx/rendering.zig

@@ -21,8 +21,10 @@ const Frame = struct {
 	drawn_count: usize = 0,
 	flushed_count: usize = 0,
 	current_source_texture: gfx.Texture = .default,
-	current_target_texture: gfx.Texture = .backbuffer,
+	current_target_texture: ?gfx.Texture = null,
 	current_effect: gfx.Effect = .default,
+	width: u16 = 0,
+	height: u16 = 0,
 
 	const DrawTexture = extern struct {
 		transform: gfx.Transform2D,
@@ -103,11 +105,13 @@ const Frame = struct {
 
 	pub fn finish(self: *Frame, resources: *Resources) void {
 		self.flush(resources);
+		sokol.gfx.endPass();
+		sokol.gfx.commit();
 
 		self.drawn_count = 0;
 		self.flushed_count = 0;
 		self.current_source_texture = .default;
-		self.current_target_texture = .backbuffer;
+		self.current_target_texture = null;
 		self.current_effect = .default;
 	}
 
@@ -132,17 +136,14 @@ const Frame = struct {
 				bindings.fs.images[0] = static.image;
 				bindings.fs.samplers[0] = default_sampler;
 			},
-
-			.empty => {
-				@panic("Cannot render empty textures");
-			},
 		}
 
 		const effect = resources.get_effect(self.current_effect).?;
 
 		sokol.gfx.applyPipeline(effect.pipeline);
 
-		const texture = resources.get_texture(self.current_target_texture).?;
+		if (self.current_target_texture) |target_texture| {
+			const texture = resources.get_texture(target_texture).?;
 
 			sokol.gfx.applyUniforms(.VS, 0, sokol.gfx.asRange(&orthographic_projection(-1.0, 1.0, .{
 				.left = 0,
@@ -150,6 +151,14 @@ const Frame = struct {
 				.right = @floatFromInt(texture.width),
 				.bottom = @floatFromInt(texture.height),
 			})));
+		} else {
+			sokol.gfx.applyUniforms(.VS, 0, sokol.gfx.asRange(&orthographic_projection(-1.0, 1.0, .{
+				.left = 0,
+				.top = 0,
+				.right = @floatFromInt(self.width),
+				.bottom = @floatFromInt(self.height),
+			})));
+		}
 
 		if (effect.properties.len != 0) {
 			sokol.gfx.applyUniforms(.FS, 0, sokol.gfx.asRange(effect.properties));
@@ -214,16 +223,53 @@ const Frame = struct {
 			pass.action.depth = .{.load_action = .LOAD};
 		}
 
-		pass.attachments = switch (resources.get_texture(self.current_target_texture).?.access) {
-			.static => @panic("Cannot render to static textures"),
-			.empty => @panic("Cannot render to empty textures"),
-			.render => |render| render.attachments,
-		};
-
 		self.current_target_texture = command.texture;
 
+		if (self.current_target_texture) |target_texture| {
+			pass.attachments = switch (resources.get_texture(target_texture).?.access) {
+				.static => @panic("Cannot render to static textures"),
+				.render => |render| render.attachments,
+			};
+		} else {
+			pass.swapchain = .{
+				.width = self.width,
+				.height = self.height,
+				.sample_count = 1,
+				.color_format = .RGBA8,
+				.depth_format = .DEPTH_STENCIL,
+				.gl = .{.framebuffer = 0},
+			};
+		}
+
 		sokol.gfx.beginPass(pass);
 	}
+
+	pub fn start(self: *Frame, width: u16, height: u16) void {
+		self.width = width;
+		self.height = height;
+
+		sokol.gfx.beginPass(pass: {
+			var pass = sokol.gfx.Pass{
+				.swapchain = .{
+					.width = width,
+					.height = height,
+					.sample_count = 1,
+					.color_format = .RGBA8,
+					.depth_format = .DEPTH_STENCIL,
+					.gl = .{.framebuffer = 0},
+				},
+
+				.action = .{
+					.stencil = .{.load_action = .CLEAR},
+					.depth = .{.load_action = .CLEAR},
+				},
+			};
+
+			pass.action.colors[0] = .{.load_action = .CLEAR};
+
+			break: pass pass;
+		});
+	}
 };
 
 fn Matrix(comptime n: usize, comptime Element: type) type {
@@ -319,46 +365,7 @@ pub fn process_work(pending_work: *gfx.Assets.WorkQueue, window: *ext.SDL_Window
 			},
 
 			.render_frame => |render_frame| {
-				const backbuffer = resources.get_texture(.backbuffer).?;
+				frame.start(render_frame.width, render_frame.height);
-
-				if (backbuffer.width != render_frame.width or backbuffer.height != render_frame.height) {
-					backbuffer.deinit();
-
-					backbuffer.* = try Resources.Texture.init(.{
-						.format = .rgba8,
-
-						.access = .{
-							.render = .{
-								.width = render_frame.width,
-								.height = render_frame.height,
-							},
-						},
-					});
-				}
-
-				sokol.gfx.beginPass(pass: {
-					var pass = sokol.gfx.Pass{
-						.action = .{
-							.stencil = .{
-								.load_action = .CLEAR,
-							},
-
-							.depth = .{
-								.load_action = .CLEAR,
-								.clear_value = 0,
-							}
-						},
-					};
-
-					pass.action.colors[0] = .{
-						.load_action = .CLEAR,
-						.clear_value = @bitCast(render_frame.clear_color),
-					};
-
-					pass.attachments = resources.get_texture(.backbuffer).?.access.render.attachments;
-
-					break: pass pass;
-				});
 
 				var has_command_params = render_frame.has_command_params;
 
@@ -373,9 +380,8 @@ pub fn process_work(pending_work: *gfx.Assets.WorkQueue, window: *ext.SDL_Window
 
 					frame.flush(&resources);
 
-					if (frame.current_target_texture != .backbuffer) {
+					if (frame.current_target_texture != null) {
 						frame.set_target(&resources, .{
-							.texture = .backbuffer,
 							.clear_color = null,
 							.clear_depth = null,
 							.clear_stencil = null,
@@ -383,43 +389,7 @@ pub fn process_work(pending_work: *gfx.Assets.WorkQueue, window: *ext.SDL_Window
 					}
 				}
 
-				sokol.gfx.endPass();
-
-				sokol.gfx.beginPass(swapchain_pass: {
-					var pass = sokol.gfx.Pass{
-						.swapchain = .{
-							.width = render_frame.width,
-							.height = render_frame.height,
-							.sample_count = 1,
-							.color_format = .RGBA8,
-							.depth_format = .DEPTH_STENCIL,
-							.gl = .{.framebuffer = 0},
-						},
-
-						.action = .{
-							.stencil = .{.load_action = .CLEAR},
-							.depth = .{.load_action = .CLEAR},
-						},
-					};
-
-					pass.action.colors[0] = .{.load_action = .CLEAR};
-
-					break: swapchain_pass pass;
-				});
-
-				try frame.draw_texture(&resources, .{
-					.texture = .backbuffer,
-
-					.transform = .{
-						.origin = .{@as(f32, @floatFromInt(render_frame.width)) / 2, @as(f32, @floatFromInt(render_frame.height)) / 2},
-						.xbasis = .{@floatFromInt(render_frame.width), 0},
-						.ybasis = .{0, @floatFromInt(render_frame.height)},
-					},
-				});
-
 				frame.finish(&resources);
-				sokol.gfx.endPass();
-				sokol.gfx.commit();
 				ext.SDL_GL_SwapWindow(window);
 				render_frame.finished.set();
 			},