queue drawing

Movement and sprite flipping

engine/app.odin

@@ -1,6 +1,7 @@
 package engine
 
 import "core:fmt"
+import "core:mem"
 import "core:path/filepath"
 import sdl "vendor:sdl3"
 
@@ -10,7 +11,14 @@ Vertex :: struct {
 }
 
 SPRITE_VERT_COUNT :: 6
-VERTEX_BUFFER_SIZE :: SPRITE_VERT_COUNT * size_of(Vertex)
+MAX_SPRITES :: 128
+SPRITE_VERTS_SIZE :: SPRITE_VERT_COUNT * size_of(Vertex)
+VERTEX_BUFFER_SIZE :: MAX_SPRITES * SPRITE_VERTS_SIZE
+
+Queued_Sprite :: struct {
+	texture: ^sdl.GPUTexture,
+	verts:   [SPRITE_VERT_COUNT]Vertex,
+}
 
 App :: struct {
 	window:            ^sdl.Window,
@@ -25,6 +33,8 @@ App :: struct {
 	swapchain_h:       u32,
 	vertex_buffer:     ^sdl.GPUBuffer,
 	transfer_buffer:   ^sdl.GPUTransferBuffer,
+	draw_list:         [dynamic]Queued_Sprite,
+	clear_color:       sdl.FColor,
 }
 
 Shader_Backend :: enum {
@@ -112,10 +122,14 @@ init :: proc(app: ^App, title: cstring, width, height: i32) -> bool {
 		return false
 	}
 
+	app.draw_list = make([dynamic]Queued_Sprite)
+
 	return true
 }
 
 shutdown :: proc(app: ^App) {
+	delete(app.draw_list)
+
 	if app.device != nil {
 		ok := sdl.WaitForGPUIdle(app.device)
 		if !ok {
@@ -164,9 +178,13 @@ events :: proc() -> bool {
 	return true
 }
 
-begin_frame :: proc(app: ^App, clear: sdl.FColor = {0.12, 0.12, 0.16, 1}) {
-	app.cmd = sdl.AcquireGPUCommandBuffer(app.device)
+begin_frame :: proc(app: ^App, clear_color: sdl.FColor = {0.12, 0.12, 0.16, 1}) {
+	clear(&app.draw_list)
+	app.clear_color = clear_color
+	app.render_pass = nil
+	app.swapchain_texture = nil
 
+	app.cmd = sdl.AcquireGPUCommandBuffer(app.device)
 	if app.cmd == nil {
 		fmt.eprintfln("AcquireGPUCommandBuffer failed: %s", sdl.GetError())
 		return
@@ -181,36 +199,98 @@ begin_frame :: proc(app: ^App, clear: sdl.FColor = {0.12, 0.12, 0.16, 1}) {
 	)
 
 	if !ok || app.swapchain_texture == nil {
+		app.swapchain_texture = nil
 		return
 	}
+}
+
+end_frame :: proc(app: ^App) {
+	if app.cmd == nil {
+		clear(&app.draw_list)
+		return
+	}
+
+	cmd := app.cmd
+	defer {
+		app.render_pass = nil
+		app.swapchain_texture = nil
+		app.cmd = nil
+		clear(&app.draw_list)
+	}
+
+	if app.swapchain_texture == nil {
+		if !sdl.SubmitGPUCommandBuffer(cmd) {
+			fmt.eprintfln("SubmitGPUCommandBuffer failed")
+		}
+		return
+	}
+
+	n := len(app.draw_list)
+	if n > 0 {
+		map_ptr := sdl.MapGPUTransferBuffer(app.device, app.transfer_buffer, false)
+		if map_ptr == nil {
+			fmt.eprintfln("MapGPUTransferBuffer failed: %s", sdl.GetError())
+			if !sdl.SubmitGPUCommandBuffer(cmd) {
+				fmt.eprintfln("SubmitGPUCommandBuffer failed")
+			}
+			return
+		}
+
+		for i in 0 ..< n {
+			q := &app.draw_list[i]
+			offset := i * SPRITE_VERTS_SIZE
+			mem.copy(
+				rawptr(uintptr(map_ptr) + uintptr(offset)),
+				raw_data(q.verts[:]),
+				SPRITE_VERTS_SIZE,
+			)
+		}
+		sdl.UnmapGPUTransferBuffer(app.device, app.transfer_buffer)
+
+		copy_pass := sdl.BeginGPUCopyPass(cmd)
+		src := sdl.GPUTransferBufferLocation {
+			transfer_buffer = app.transfer_buffer,
+			offset          = 0,
+		}
+		dst := sdl.GPUBufferRegion {
+			buffer = app.vertex_buffer,
+			offset = 0,
+			size   = u32(n * SPRITE_VERTS_SIZE),
+		}
+		sdl.UploadToGPUBuffer(copy_pass, src, dst, false)
+		sdl.EndGPUCopyPass(copy_pass)
+	}
 
 	color_info := sdl.GPUColorTargetInfo {
 		texture     = app.swapchain_texture,
-		clear_color = clear,
+		clear_color = app.clear_color,
 		load_op     = .CLEAR,
 		store_op    = .STORE,
 	}
-
-	app.render_pass = sdl.BeginGPURenderPass(app.cmd, &color_info, 1, nil)
-
+	app.render_pass = sdl.BeginGPURenderPass(cmd, &color_info, 1, nil)
 	sdl.BindGPUGraphicsPipeline(app.render_pass, app.pipeline)
-}
 
-end_frame :: proc(app: ^App) {
-	if app.render_pass != nil {
+	for q, i in app.draw_list {
+		sampler_binding := sdl.GPUTextureSamplerBinding {
+			texture = q.texture,
+			sampler = app.sampler,
+		}
+		sdl.BindGPUFragmentSamplers(app.render_pass, 0, &sampler_binding, 1)
+
+		vb_binding := sdl.GPUBufferBinding {
+			buffer = app.vertex_buffer,
+			offset = u32(i * SPRITE_VERTS_SIZE),
+		}
+		sdl.BindGPUVertexBuffers(app.render_pass, 0, &vb_binding, 1)
+		sdl.DrawGPUPrimitives(app.render_pass, SPRITE_VERT_COUNT, 1, 0, 0)
+	}
+
 	sdl.EndGPURenderPass(app.render_pass)
 	app.render_pass = nil
-	}
 
-	if app.cmd != nil {
-		ok := sdl.SubmitGPUCommandBuffer(app.cmd)
-		if !ok {
+	if !sdl.SubmitGPUCommandBuffer(cmd) {
 		fmt.eprintfln("SubmitGPUCommandBuffer failed")
 	}
-		app.cmd = nil
-	}
-
-	app.swapchain_texture = nil
 }
 
 load_gpu_shader :: proc(

engine/input.odin

@@ -0,0 +1,28 @@
+package engine
+
+import sdl "vendor:sdl3"
+
+Key :: enum {
+	A,
+	D,
+	Left,
+	Right,
+}
+
+key_down :: proc(key: Key) -> bool {
+	keys := sdl.GetKeyboardState(nil)
+	if keys == nil do return false
+
+	scan_code: sdl.Scancode
+	switch key {
+	case .A:
+		scan_code = .A
+	case .D:
+		scan_code = .D
+	case .Left:
+		scan_code = .LEFT
+	case .Right:
+		scan_code = .RIGHT
+	}
+	return keys[scan_code]
+}

engine/sprite.odin

@@ -1,6 +1,5 @@
 package engine
 
-import "core:mem"
 import sdl "vendor:sdl3"
 
 Vec2 :: [2]f32
@@ -11,6 +10,7 @@ Sprite :: struct {
 	clip:     string,
 	frame:    int,
 	time:     f32,
+	flip_x:   bool,
 }
 
 spawn_sprite :: proc(
@@ -39,7 +39,6 @@ spawn_sprite :: proc(
 	return sprite
 }
 
-// stubbed for later
 update_sprite :: proc(sprite: ^Sprite, dt: f32) {
 	if sprite == nil || sprite.data == nil do return
 	if dt <= 0 do return
@@ -84,12 +83,15 @@ to_clip :: proc(px, py, sw, sh: f32) -> [2]f32 {
 }
 
 draw_sprite :: proc(app: ^App, sprite: ^Sprite) {
-	if app.render_pass == nil || app.cmd == nil || app.swapchain_texture == nil {
+	if app.cmd == nil || app.swapchain_texture == nil {
 		return // begin_frame may have skipped (minimized window, etc.)
 	}
 	if sprite == nil || sprite.data == nil || sprite.data.texture == nil {
 		return
 	}
+	if len(app.draw_list) >= MAX_SPRITES {
+		return
+	}
 
 	rect, ok := character_frame_rect(sprite.data, sprite.clip, sprite.frame)
 	if !ok {
@@ -99,9 +101,10 @@ draw_sprite :: proc(app: ^App, sprite: ^Sprite) {
 	fw := f32(rect[2])
 	fh := f32(rect[3])
 
-	// Feet-centered placement, same as renderer version
-	x0_px := sprite.position.x - fw * 0.5
-	y0_px := sprite.position.y - fh
+	pivot := sprite.data.def.pivot
+	origin := sprite_quad_origin(sprite.position, {fw, fh}, pivot)
+	x0_px := origin.x
+	y0_px := origin.y
 	x1_px := x0_px + fw
 	y1_px := y0_px + fh
 
@@ -118,9 +121,10 @@ draw_sprite :: proc(app: ^App, sprite: ^Sprite) {
 	v0 := f32(rect[1]) / tex_h
 	u1 := f32(rect[0] + rect[2]) / tex_w
 	v1 := f32(rect[1] + rect[3]) / tex_h
+	if sprite.flip_x do u0, u1 = u1, u0
 
 	// Two triangles: (0,1,2) and (0,2,3)
-	verts := [6]Vertex {
+	verts := [SPRITE_VERT_COUNT]Vertex {
 		{pos = p0, uv = {u0, v0}},
 		{pos = p1, uv = {u1, v0}},
 		{pos = p2, uv = {u1, v1}},
@@ -129,54 +133,10 @@ draw_sprite :: proc(app: ^App, sprite: ^Sprite) {
 		{pos = p3, uv = {u0, v1}},
 	}
 
-	map_ptr := sdl.MapGPUTransferBuffer(app.device, app.transfer_buffer, false)
-	if map_ptr == nil {
-		return
-	}
-	mem.copy(map_ptr, raw_data(verts[:]), size_of(verts))
-	sdl.UnmapGPUTransferBuffer(app.device, app.transfer_buffer)
-
-	// IMPORTANT: SDL does not allow beginning a copy pass while a render pass
-	// is active on the same command buffer. Upload on a separate command buffer.
-	copy_cmd := sdl.AcquireGPUCommandBuffer(app.device)
-	if copy_cmd == nil {
-		return
-	}
-	copy_pass := sdl.BeginGPUCopyPass(copy_cmd)
-
-	src := sdl.GPUTransferBufferLocation {
-		transfer_buffer = app.transfer_buffer,
-		offset          = 0,
-	}
-	dst := sdl.GPUBufferRegion {
-		buffer = app.vertex_buffer,
-		offset = 0,
-		size   = u32(size_of(verts)),
-	}
-	sdl.UploadToGPUBuffer(copy_pass, src, dst, false)
-	sdl.EndGPUCopyPass(copy_pass)
-	fence := sdl.SubmitGPUCommandBufferAndAcquireFence(copy_cmd)
-	if fence == nil {
-		return
-	}
-	defer sdl.ReleaseGPUFence(app.device, fence)
-	if !sdl.WaitForGPUFences(app.device, true, &fence, 1) {
-		return
-	}
-
-	sampler_binding := sdl.GPUTextureSamplerBinding {
-		texture = sprite.data.texture,
-		sampler = app.sampler,
-	}
-	sdl.BindGPUFragmentSamplers(app.render_pass, 0, &sampler_binding, 1)
-
-	vb_binding := sdl.GPUBufferBinding {
-		buffer = app.vertex_buffer,
-		offset = 0,
-	}
-	sdl.BindGPUVertexBuffers(app.render_pass, 0, &vb_binding, 1)
-
-	sdl.DrawGPUPrimitives(app.render_pass, 6, 1, 0, 0)
+	append(
+		&app.draw_list,
+		Queued_Sprite{texture = sprite.data.texture, verts = verts},
+	)
 }
 
 set_sprite_clip :: proc(sprite: ^Sprite, clip: string) {
@@ -191,3 +151,12 @@ set_sprite_clip :: proc(sprite: ^Sprite, clip: string) {
 	sprite.frame = 0
 	sprite.time = 0
 }
+
+sprite_quad_origin :: proc(position: Vec2, size: Vec2, pivot: [2]f32) -> Vec2 {
+	return {position.x - size.x * pivot[0], position.y - size.y * pivot[1]}
+}
+
+set_sprite_flip_x :: proc(sprite: ^Sprite, flip: bool) {
+	if sprite == nil do return
+	sprite.flip_x = flip
+}

engine/sprite_test.odin

@@ -19,3 +19,17 @@ to_clip_corners :: proc(t: ^testing.T) {
 	testing.expect_value(t, p[0], f32(0))
 	testing.expect_value(t, p[1], f32(0))
 }
+
+@(test)
+sprite_quad_origin_feet :: proc(t: ^testing.T) {
+	o := sprite_quad_origin({400, 500}, {100, 200}, {0.5, 1.0})
+	testing.expect_value(t, o.x, f32(350))
+	testing.expect_value(t, o.y, f32(300))
+}
+
+@(test)
+sprite_quad_origin_center :: proc(t: ^testing.T) {
+	o := sprite_quad_origin({400, 500}, {100, 200}, {0.5, 0.5})
+	testing.expect_value(t, o.x, f32(350))
+	testing.expect_value(t, o.y, f32(400))
+}

examples/toad/main.odin

@@ -15,12 +15,30 @@ main :: proc() {
 	toad := eng.spawn_sprite(&data, {400, 500}, "idle", 0)
 
 	last := eng.now_seconds()
+	SPEED :: f32(200)
 
 	for eng.events() {
 		now := eng.now_seconds()
 		dt := f32(now - last)
 		last = now
 
+		left := eng.key_down(.A) || eng.key_down(.Left)
+		right := eng.key_down(.D) || eng.key_down(.Right)
+
+		if left || right {
+			eng.set_sprite_clip(&toad, "walk")
+			if left {
+				toad.position.x -= SPEED * dt
+				toad.flip_x = true
+			}
+
+			if right {
+				toad.position.x += SPEED * dt
+				toad.flip_x = false
+			}
+		} else {
+			eng.set_sprite_clip(&toad, "idle")
+		}
 		eng.update_sprite(&toad, dt)
 
 		eng.begin_frame(&app)