// Copyright 2020 The Ebiten Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package ebiten_test

import (
	"fmt"
	"image"
	"image/color"
	"math"
	"testing"

	"github.com/hajimehoshi/ebiten/v2"
)

func TestShaderFill(t *testing.T) {
	const w, h = 16, 16

	dst := ebiten.NewImage(w, h)
	s, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	return vec4(1, 0, 0, 1)
}
`))
	if err != nil {
		t.Fatal(err)
	}

	dst.DrawRectShader(w/2, h/2, s, nil)

	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			got := dst.At(i, j).(color.RGBA)
			var want color.RGBA
			if i < w/2 && j < h/2 {
				want = color.RGBA{R: 0xff, A: 0xff}
			}
			if got != want {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}
}

func TestShaderFillWithDrawImage(t *testing.T) {
	const w, h = 16, 16

	dst := ebiten.NewImage(w, h)
	s, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	return vec4(1, 0, 0, 1)
}
`))
	if err != nil {
		t.Fatal(err)
	}

	src := ebiten.NewImage(w/2, h/2)
	op := &ebiten.DrawRectShaderOptions{}
	op.Images[0] = src
	dst.DrawRectShader(w/2, h/2, s, op)

	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			got := dst.At(i, j).(color.RGBA)
			var want color.RGBA
			if i < w/2 && j < h/2 {
				want = color.RGBA{R: 0xff, A: 0xff}
			}
			if got != want {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}
}

// Issue #2525
func TestShaderWithDrawImageDoesNotWreckTextureUnits(t *testing.T) {
	const w, h = 16, 16
	rect := image.Rectangle{Max: image.Point{X: w, Y: h}}

	dst := ebiten.NewImageWithOptions(rect, &ebiten.NewImageOptions{Unmanaged: true})
	s, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	return imageSrc0At(srcPos)
}
`))
	if err != nil {
		t.Fatal(err)
	}

	src0 := ebiten.NewImageWithOptions(rect, &ebiten.NewImageOptions{Unmanaged: true})
	src0.Fill(color.RGBA{R: 25, G: 0xff, B: 25, A: 0xff})
	src1 := ebiten.NewImageWithOptions(rect, &ebiten.NewImageOptions{Unmanaged: true})
	src1.Fill(color.RGBA{R: 0xff, A: 0xff})
	op := &ebiten.DrawRectShaderOptions{}
	op.CompositeMode = ebiten.CompositeModeCopy
	op.Images[0] = src0
	op.Images[1] = src1
	dst.DrawRectShader(w, h, s, op)
	op.Images[0] = src1
	op.Images[1] = nil
	dst.DrawRectShader(w, h, s, op) // dst should now be identical to src1.

	// With issue #2525, instead, GL_TEXTURE0 is active but with src0 bound
	// while binding src1 gets skipped!
	// This means that src0, not src1, got copied to dst.

	// Demonstrate the bug with a write to src1, which will actually end up on src0.
	// Validated later.
	var buf []byte
	for i := 0; i < w*h; i++ {
		buf = append(buf, 2, 5, 2, 5)
	}
	src1.WritePixels(buf)

	// Verify that src1 was copied to dst.
	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			got := dst.At(i, j).(color.RGBA)
			want := color.RGBA{R: 0xff, A: 0xff}
			if got != want {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}

	// Fix up texture unit assignment by binding a different texture.
	op.Images[0] = src1
	dst.DrawRectShader(w, h, s, op)
	op.Images[0] = src0
	dst.DrawRectShader(w, h, s, op)

	// Verify that src0 was copied to dst and not overwritten above.
	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			got := dst.At(i, j).(color.RGBA)
			want := color.RGBA{R: 25, G: 0xff, B: 25, A: 0xff}
			if got != want {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}
}

func TestShaderFillWithDrawTriangles(t *testing.T) {
	const w, h = 16, 16

	dst := ebiten.NewImage(w, h)
	s, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	return vec4(1, 0, 0, 1)
}
`))
	if err != nil {
		t.Fatal(err)
	}

	src := ebiten.NewImage(w/2, h/2)
	op := &ebiten.DrawTrianglesShaderOptions{}
	op.Images[0] = src

	vs := []ebiten.Vertex{
		{
			DstX:   0,
			DstY:   0,
			SrcX:   0,
			SrcY:   0,
			ColorR: 1,
			ColorG: 1,
			ColorB: 1,
			ColorA: 1,
		},
		{
			DstX:   w,
			DstY:   0,
			SrcX:   w / 2,
			SrcY:   0,
			ColorR: 1,
			ColorG: 1,
			ColorB: 1,
			ColorA: 1,
		},
		{
			DstX:   0,
			DstY:   h,
			SrcX:   0,
			SrcY:   h / 2,
			ColorR: 1,
			ColorG: 1,
			ColorB: 1,
			ColorA: 1,
		},
		{
			DstX:   w,
			DstY:   h,
			SrcX:   w / 2,
			SrcY:   h / 2,
			ColorR: 1,
			ColorG: 1,
			ColorB: 1,
			ColorA: 1,
		},
	}
	is := []uint16{0, 1, 2, 1, 2, 3}

	dst.DrawTrianglesShader(vs, is, s, op)

	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			got := dst.At(i, j).(color.RGBA)
			want := color.RGBA{R: 0xff, A: 0xff}
			if got != want {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}
}

func TestShaderFunction(t *testing.T) {
	const w, h = 16, 16

	dst := ebiten.NewImage(w, h)
	s, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

func clr(red float) (float, float, float, float) {
	return red, 0, 0, 1
}

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	return vec4(clr(1))
}
`))
	if err != nil {
		t.Fatal(err)
	}

	dst.DrawRectShader(w, h, s, nil)

	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			got := dst.At(i, j).(color.RGBA)
			want := color.RGBA{R: 0xff, A: 0xff}
			if got != want {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}
}

func TestShaderUninitializedUniformVariables(t *testing.T) {
	const w, h = 16, 16

	dst := ebiten.NewImage(w, h)
	s, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

var U vec4

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	return U
}
`))
	if err != nil {
		t.Fatal(err)
	}

	dst.DrawRectShader(w, h, s, nil)

	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			got := dst.At(i, j).(color.RGBA)
			var want color.RGBA
			if got != want {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}
}

func TestShaderMatrix(t *testing.T) {
	const w, h = 16, 16

	dst := ebiten.NewImage(w, h)
	s, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	var a, b mat4
	a[0] = vec4(0.125, 0.0625, 0.0625, 0.0625)
	a[1] = vec4(0.25, 0.25, 0.0625, 0.1875)
	a[2] = vec4(0.1875, 0.125, 0.25, 0.25)
	a[3] = vec4(0.0625, 0.1875, 0.125, 0.25)
	b[0] = vec4(0.0625, 0.125, 0.0625, 0.125)
	b[1] = vec4(0.125, 0.1875, 0.25, 0.0625)
	b[2] = vec4(0.125, 0.125, 0.1875, 0.1875)
	b[3] = vec4(0.25, 0.0625, 0.125, 0.0625)
	return vec4((a * b * vec4(1, 1, 1, 1)).xyz, 1)
}
`))
	if err != nil {
		t.Fatal(err)
	}

	src := ebiten.NewImage(w, h)
	op := &ebiten.DrawRectShaderOptions{}
	op.Images[0] = src
	dst.DrawRectShader(w, h, s, op)

	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			got := dst.At(i, j).(color.RGBA)
			want := color.RGBA{R: 87, G: 82, B: 71, A: 255}
			if got != want {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}
}

func TestShaderSubImage(t *testing.T) {
	const w, h = 16, 16

	s, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	r := imageSrc0At(srcPos).r
	g := imageSrc1At(srcPos).g
	return vec4(r, g, 0, 1)
}
`))
	if err != nil {
		t.Fatal(err)
	}

	src0 := ebiten.NewImage(w, h)
	pix0 := make([]byte, 4*w*h)
	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			if 2 <= i && i < 10 && 3 <= j && j < 11 {
				pix0[4*(j*w+i)] = 0xff
				pix0[4*(j*w+i)+1] = 0
				pix0[4*(j*w+i)+2] = 0
				pix0[4*(j*w+i)+3] = 0xff
			}
		}
	}
	src0.WritePixels(pix0)
	src0 = src0.SubImage(image.Rect(2, 3, 10, 11)).(*ebiten.Image)

	src1 := ebiten.NewImage(w, h)
	pix1 := make([]byte, 4*w*h)
	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			if 6 <= i && i < 14 && 8 <= j && j < 16 {
				pix1[4*(j*w+i)] = 0
				pix1[4*(j*w+i)+1] = 0xff
				pix1[4*(j*w+i)+2] = 0
				pix1[4*(j*w+i)+3] = 0xff
			}
		}
	}
	src1.WritePixels(pix1)
	src1 = src1.SubImage(image.Rect(6, 8, 14, 16)).(*ebiten.Image)

	testPixels := func(testname string, dst *ebiten.Image) {
		for j := 0; j < h; j++ {
			for i := 0; i < w; i++ {
				got := dst.At(i, j).(color.RGBA)
				var want color.RGBA
				if i < w/2 && j < h/2 {
					want = color.RGBA{R: 0xff, G: 0xff, A: 0xff}
				}
				if got != want {
					t.Errorf("%s dst.At(%d, %d): got: %v, want: %v", testname, i, j, got, want)
				}
			}
		}
	}

	t.Run("DrawRectShader", func(t *testing.T) {
		dst := ebiten.NewImage(w, h)
		op := &ebiten.DrawRectShaderOptions{}
		op.Images[0] = src0
		op.Images[1] = src1
		dst.DrawRectShader(w/2, h/2, s, op)
		testPixels("DrawRectShader", dst)
	})

	t.Run("DrawTrianglesShader", func(t *testing.T) {
		dst := ebiten.NewImage(w, h)
		vs := []ebiten.Vertex{
			{
				DstX:   0,
				DstY:   0,
				SrcX:   2,
				SrcY:   3,
				ColorR: 1,
				ColorG: 1,
				ColorB: 1,
				ColorA: 1,
			},
			{
				DstX:   w / 2,
				DstY:   0,
				SrcX:   10,
				SrcY:   3,
				ColorR: 1,
				ColorG: 1,
				ColorB: 1,
				ColorA: 1,
			},
			{
				DstX:   0,
				DstY:   h / 2,
				SrcX:   2,
				SrcY:   11,
				ColorR: 1,
				ColorG: 1,
				ColorB: 1,
				ColorA: 1,
			},
			{
				DstX:   w / 2,
				DstY:   h / 2,
				SrcX:   10,
				SrcY:   11,
				ColorR: 1,
				ColorG: 1,
				ColorB: 1,
				ColorA: 1,
			},
		}
		is := []uint16{0, 1, 2, 1, 2, 3}

		op := &ebiten.DrawTrianglesShaderOptions{}
		op.Images[0] = src0
		op.Images[1] = src1
		dst.DrawTrianglesShader(vs, is, s, op)
		testPixels("DrawTrianglesShader", dst)
	})
}

// Issue #1404
func TestShaderDerivatives(t *testing.T) {
	t.Skip("the results of dfdx, dfdy, and fwidth are indeterministic (#2583)")

	const w, h = 16, 16

	s, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	p := imageSrc0At(srcPos)
	return vec4(abs(dfdx(p.r)), abs(dfdy(p.g)), 0, 1)
}
`))
	if err != nil {
		t.Fatal(err)
	}

	dst := ebiten.NewImage(w, h)
	src := ebiten.NewImage(w, h)
	pix := make([]byte, 4*w*h)
	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			if i < w/2 {
				pix[4*(j*w+i)] = 0xff
			}
			if j < h/2 {
				pix[4*(j*w+i)+1] = 0xff
			}
			pix[4*(j*w+i)+3] = 0xff
		}
	}
	src.WritePixels(pix)

	op := &ebiten.DrawRectShaderOptions{}
	op.Images[0] = src
	dst.DrawRectShader(w, h, s, op)

	// The results of the edges might be unreliable. Skip the edges.
	for j := 1; j < h-1; j++ {
		for i := 1; i < w-1; i++ {
			got := dst.At(i, j).(color.RGBA)
			want := color.RGBA{A: 0xff}
			if i == w/2-1 || i == w/2 {
				want.R = 0xff
			}
			if j == h/2-1 || j == h/2 {
				want.G = 0xff
			}
			if got != want {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}
}

// Issue #1701
func TestShaderDerivatives2(t *testing.T) {
	t.Skip("the results of dfdx, dfdy, and fwidth are indeterministic (#2583)")

	const w, h = 16, 16

	s, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

// This function uses dfdx and then should not be in GLSL's vertex shader (#1701).
func Foo(p vec4) vec4 {
	return vec4(abs(dfdx(p.r)), abs(dfdy(p.g)), 0, 1)
}

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	p := imageSrc0At(srcPos)
	return Foo(p)
}
`))
	if err != nil {
		t.Fatal(err)
	}

	dst := ebiten.NewImage(w, h)
	src := ebiten.NewImage(w, h)
	pix := make([]byte, 4*w*h)
	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			if i < w/2 {
				pix[4*(j*w+i)] = 0xff
			}
			if j < h/2 {
				pix[4*(j*w+i)+1] = 0xff
			}
			pix[4*(j*w+i)+3] = 0xff
		}
	}
	src.WritePixels(pix)

	op := &ebiten.DrawRectShaderOptions{}
	op.Images[0] = src
	dst.DrawRectShader(w, h, s, op)

	// The results of the edges might be unreliable. Skip the edges.
	for j := 1; j < h-1; j++ {
		for i := 1; i < w-1; i++ {
			got := dst.At(i, j).(color.RGBA)
			want := color.RGBA{A: 0xff}
			if i == w/2-1 || i == w/2 {
				want.R = 0xff
			}
			if j == h/2-1 || j == h/2 {
				want.G = 0xff
			}
			if got != want {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}
}

// Issue #1754
func TestShaderUniformFirstElement(t *testing.T) {
	shaders := []struct {
		Name     string
		Shader   string
		Uniforms map[string]any
	}{
		{
			Name: "float array",
			Shader: `//kage:unit pixels

package main

var C [2]float

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	return vec4(C[0], 1, 1, 1)
}`,
			Uniforms: map[string]any{
				"C": []float32{1, 1},
			},
		},
		{
			Name: "float one-element array",
			Shader: `//kage:unit pixels

package main

var C [1]float

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	return vec4(C[0], 1, 1, 1)
}`,
			Uniforms: map[string]any{
				"C": []float32{1},
			},
		},
		{
			Name: "matrix array",
			Shader: `//kage:unit pixels

package main

var C [2]mat2

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	return vec4(C[0][0][0], 1, 1, 1)
}`,
			Uniforms: map[string]any{
				"C": []float32{1, 0, 0, 0, 0, 0, 0, 0},
			},
		},
	}

	for _, shader := range shaders {
		shader := shader
		t.Run(shader.Name, func(t *testing.T) {
			const w, h = 1, 1

			dst := ebiten.NewImage(w, h)
			defer dst.Deallocate()

			s, err := ebiten.NewShader([]byte(shader.Shader))
			if err != nil {
				t.Fatal(err)
			}
			defer s.Deallocate()

			op := &ebiten.DrawRectShaderOptions{}
			op.Uniforms = shader.Uniforms
			dst.DrawRectShader(w, h, s, op)
			if got, want := dst.At(0, 0), (color.RGBA{R: 0xff, G: 0xff, B: 0xff, A: 0xff}); got != want {
				t.Errorf("got: %v, want: %v", got, want)
			}
		})
	}
}

// Issue #2006
func TestShaderFuncMod(t *testing.T) {
	const w, h = 16, 16

	dst := ebiten.NewImage(w, h)
	s, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	r := mod(-0.25, 1.0)
	return vec4(r, 0, 0, 1)
}
`))
	if err != nil {
		t.Fatal(err)
	}

	dst.DrawRectShader(w/2, h/2, s, nil)

	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			got := dst.At(i, j).(color.RGBA)
			var want color.RGBA
			if i < w/2 && j < h/2 {
				want = color.RGBA{R: 0xc0, A: 0xff}
			}
			if !sameColors(got, want, 2) {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}
}

func TestShaderMatrixInitialize(t *testing.T) {
	const w, h = 16, 16

	src := ebiten.NewImage(w, h)
	src.Fill(color.RGBA{R: 0x10, G: 0x20, B: 0x30, A: 0xff})

	dst := ebiten.NewImage(w, h)
	s, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	return mat4(2) * imageSrc0At(srcPos);
}
`))
	if err != nil {
		t.Fatal(err)
	}

	op := &ebiten.DrawRectShaderOptions{}
	op.Images[0] = src
	dst.DrawRectShader(w, h, s, op)

	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			got := dst.At(i, j).(color.RGBA)
			want := color.RGBA{R: 0x20, G: 0x40, B: 0x60, A: 0xff}
			if !sameColors(got, want, 2) {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}
}

// Issue #2029
func TestShaderModVectorAndFloat(t *testing.T) {
	const w, h = 16, 16

	dst := ebiten.NewImage(w, h)
	s, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	r := mod(vec3(0.25, 0.5, 0.75), 0.5)
	return vec4(r, 1)
}
`))
	if err != nil {
		t.Fatal(err)
	}

	dst.DrawRectShader(w, h, s, nil)

	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			got := dst.At(i, j).(color.RGBA)
			want := color.RGBA{R: 0x40, B: 0x40, A: 0xff}
			if !sameColors(got, want, 2) {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}
}

func TestShaderTextureAt(t *testing.T) {
	const w, h = 16, 16

	src := ebiten.NewImage(w, h)
	src.Fill(color.RGBA{R: 0x10, G: 0x20, B: 0x30, A: 0xff})

	dst := ebiten.NewImage(w, h)
	s, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

func textureAt(uv vec2) vec4 {
	return imageSrc0UnsafeAt(uv)
}

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	return textureAt(srcPos)
}
`))
	if err != nil {
		t.Fatal(err)
	}

	op := &ebiten.DrawRectShaderOptions{}
	op.Images[0] = src
	dst.DrawRectShader(w, h, s, op)

	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			got := dst.At(i, j).(color.RGBA)
			want := color.RGBA{R: 0x10, G: 0x20, B: 0x30, A: 0xff}
			if !sameColors(got, want, 2) {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}
}

func TestShaderAtan2(t *testing.T) {
	const w, h = 16, 16

	src := ebiten.NewImage(w, h)
	src.Fill(color.RGBA{R: 0x10, G: 0x20, B: 0x30, A: 0xff})

	dst := ebiten.NewImage(w, h)
	s, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	y := vec4(1, 1, 1, 1)
	x := vec4(1, 1, 1, 1)
	return atan2(y, x)
}
`))
	if err != nil {
		t.Fatal(err)
	}

	op := &ebiten.DrawRectShaderOptions{}
	op.Images[0] = src
	dst.DrawRectShader(w, h, s, op)

	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			got := dst.At(i, j).(color.RGBA)
			v := byte(math.Floor(0xff * math.Pi / 4))
			want := color.RGBA{R: v, G: v, B: v, A: v}
			if !sameColors(got, want, 2) {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}
}

func TestShaderUniformMatrix2(t *testing.T) {
	const w, h = 16, 16

	dst := ebiten.NewImage(w, h)
	s, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

var Mat2 mat2
var F float

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	return vec4(F * Mat2 * vec2(1), 1, 1)
}
`))
	if err != nil {
		t.Fatal(err)
	}

	op := &ebiten.DrawRectShaderOptions{}
	op.Uniforms = map[string]any{
		"Mat2": []float32{
			1.0 / 256.0, 2.0 / 256.0,
			3.0 / 256.0, 4.0 / 256.0,
		},
		"F": float32(2),
	}
	dst.DrawRectShader(w, h, s, op)

	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			got := dst.At(i, j).(color.RGBA)
			want := color.RGBA{R: 8, G: 12, B: 0xff, A: 0xff}
			if !sameColors(got, want, 2) {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}
}

func TestShaderUniformMatrix2Array(t *testing.T) {
	const w, h = 16, 16

	dst := ebiten.NewImage(w, h)
	s, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

var Mat2 [2]mat2
var F float

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	return vec4(F * Mat2[0] * Mat2[1] * vec2(1), 1, 1)
}
`))
	if err != nil {
		t.Fatal(err)
	}

	op := &ebiten.DrawRectShaderOptions{}
	op.Uniforms = map[string]any{
		"Mat2": []float32{
			1.0 / 256.0, 2.0 / 256.0,
			3.0 / 256.0, 4.0 / 256.0,
			5.0 / 256.0, 6.0 / 256.0,
			7.0 / 256.0, 8.0 / 256.0,
		},
		"F": float32(256),
	}
	dst.DrawRectShader(w, h, s, op)

	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			got := dst.At(i, j).(color.RGBA)
			want := color.RGBA{R: 54, G: 80, B: 0xff, A: 0xff}
			if !sameColors(got, want, 2) {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}
}

func TestShaderUniformMatrix3(t *testing.T) {
	const w, h = 16, 16

	dst := ebiten.NewImage(w, h)
	s, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

var Mat3 mat3
var F float

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	return vec4(F * Mat3 * vec3(1), 1)
}
`))
	if err != nil {
		t.Fatal(err)
	}

	op := &ebiten.DrawRectShaderOptions{}
	op.Uniforms = map[string]any{
		"Mat3": []float32{
			1.0 / 256.0, 2.0 / 256.0, 3.0 / 256.0,
			4.0 / 256.0, 5.0 / 256.0, 6.0 / 256.0,
			7.0 / 256.0, 8.0 / 256.0, 9.0 / 256.0,
		},
		"F": float32(2),
	}
	dst.DrawRectShader(w, h, s, op)

	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			got := dst.At(i, j).(color.RGBA)
			want := color.RGBA{R: 24, G: 30, B: 36, A: 0xff}
			if !sameColors(got, want, 2) {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}
}

func TestShaderUniformMatrix3Array(t *testing.T) {
	const w, h = 16, 16

	dst := ebiten.NewImage(w, h)
	s, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

var Mat3 [2]mat3
var F float

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	return vec4(F * Mat3[0] * Mat3[1] * vec3(1), 1)
}
`))
	if err != nil {
		t.Fatal(err)
	}

	op := &ebiten.DrawRectShaderOptions{}
	op.Uniforms = map[string]any{
		"Mat3": []float32{
			1.0 / 256.0, 2.0 / 256.0, 3.0 / 256.0,
			4.0 / 256.0, 5.0 / 256.0, 6.0 / 256.0,
			7.0 / 256.0, 8.0 / 256.0, 9.0 / 256.0,
			10.0 / 256.0, 11.0 / 256.0, 12.0 / 256.0,
			13.0 / 256.0, 14.0 / 256.0, 15.0 / 256.0,
			16.0 / 256.0, 17.0 / 256.0, 18.0 / 256.0,
		},
		"F": float32(3),
	}
	dst.DrawRectShader(w, h, s, op)

	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			got := dst.At(i, j).(color.RGBA)
			want := color.RGBA{R: 6, G: 8, B: 9, A: 0xff}
			if !sameColors(got, want, 2) {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}
}

func TestShaderUniformMatrix4(t *testing.T) {
	const w, h = 16, 16

	dst := ebiten.NewImage(w, h)
	s, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

var Mat4 mat4
var F float

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	return F * Mat4 * vec4(1)
}
`))
	if err != nil {
		t.Fatal(err)
	}

	op := &ebiten.DrawRectShaderOptions{}
	op.Uniforms = map[string]any{
		"Mat4": []float32{
			1.0 / 256.0, 2.0 / 256.0, 3.0 / 256.0, 4.0 / 256.0,
			5.0 / 256.0, 6.0 / 256.0, 7.0 / 256.0, 8.0 / 256.0,
			9.0 / 256.0, 10.0 / 256.0, 11.0 / 256.0, 12.0 / 256.0,
			13.0 / 256.0, 14.0 / 256.0, 15.0 / 256.0, 16.0 / 256.0,
		},
		"F": float32(4),
	}
	dst.DrawRectShader(w, h, s, op)

	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			got := dst.At(i, j).(color.RGBA)
			want := color.RGBA{R: 112, G: 128, B: 143, A: 159}
			if !sameColors(got, want, 2) {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}
}

func TestShaderUniformMatrix4Array(t *testing.T) {
	const w, h = 16, 16

	dst := ebiten.NewImage(w, h)
	s, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

var Mat4 [2]mat4
var F float

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	return F * Mat4[0] * Mat4[1] * vec4(1)
}
`))
	if err != nil {
		t.Fatal(err)
	}

	op := &ebiten.DrawRectShaderOptions{}
	op.Uniforms = map[string]any{
		"Mat4": []float32{
			1.0 / 256.0, 2.0 / 256.0, 3.0 / 256.0, 4.0 / 256.0,
			5.0 / 256.0, 6.0 / 256.0, 7.0 / 256.0, 8.0 / 256.0,
			9.0 / 256.0, 10.0 / 256.0, 11.0 / 256.0, 12.0 / 256.0,
			13.0 / 256.0, 14.0 / 256.0, 15.0 / 256.0, 16.0 / 256.0,
			17.0 / 256.0, 18.0 / 256.0, 19.0 / 256.0, 20.0 / 256.0,
			21.0 / 256.0, 22.0 / 256.0, 23.0 / 256.0, 24.0 / 256.0,
			25.0 / 256.0, 26.0 / 256.0, 27.0 / 256.0, 28.0 / 256.0,
			29.0 / 256.0, 30.0 / 256.0, 31.0 / 256.0, 32.0 / 256.0,
		},
		"F": float32(4),
	}
	dst.DrawRectShader(w, h, s, op)

	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			got := dst.At(i, j).(color.RGBA)
			want := color.RGBA{R: 44, G: 50, B: 56, A: 62}
			if !sameColors(got, want, 2) {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}
}

func TestShaderOptionsNegativeBounds(t *testing.T) {
	const w, h = 16, 16

	s, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	r := imageSrc0At(srcPos).r
	g := imageSrc1At(srcPos).g
	return vec4(r, g, 0, 1)
}
`))
	if err != nil {
		t.Fatal(err)
	}

	const offset0 = -4
	src0 := ebiten.NewImageWithOptions(image.Rect(offset0, offset0, w+offset0, h+offset0), nil)
	pix0 := make([]byte, 4*w*h)
	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			if 2 <= i && i < 10 && 3 <= j && j < 11 {
				pix0[4*(j*w+i)] = 0xff
				pix0[4*(j*w+i)+1] = 0
				pix0[4*(j*w+i)+2] = 0
				pix0[4*(j*w+i)+3] = 0xff
			}
		}
	}
	src0.WritePixels(pix0)
	src0 = src0.SubImage(image.Rect(2+offset0, 3+offset0, 10+offset0, 11+offset0)).(*ebiten.Image)

	const offset1 = -6
	src1 := ebiten.NewImageWithOptions(image.Rect(offset1, offset1, w+offset1, h+offset1), nil)
	pix1 := make([]byte, 4*w*h)
	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			if 6 <= i && i < 14 && 8 <= j && j < 16 {
				pix1[4*(j*w+i)] = 0
				pix1[4*(j*w+i)+1] = 0xff
				pix1[4*(j*w+i)+2] = 0
				pix1[4*(j*w+i)+3] = 0xff
			}
		}
	}
	src1.WritePixels(pix1)
	src1 = src1.SubImage(image.Rect(6+offset1, 8+offset1, 14+offset1, 16+offset1)).(*ebiten.Image)

	const offset2 = -2
	testPixels := func(testname string, dst *ebiten.Image) {
		for j := offset2; j < h+offset2; j++ {
			for i := offset2; i < w+offset2; i++ {
				got := dst.At(i, j).(color.RGBA)
				var want color.RGBA
				if 0 <= i && i < w/2 && 0 <= j && j < h/2 {
					want = color.RGBA{R: 0xff, G: 0xff, A: 0xff}
				}
				if got != want {
					t.Errorf("%s dst.At(%d, %d): got: %v, want: %v", testname, i, j, got, want)
				}
			}
		}
	}

	t.Run("DrawRectShader", func(t *testing.T) {
		dst := ebiten.NewImageWithOptions(image.Rect(offset2, offset2, w+offset2, h+offset2), nil)
		op := &ebiten.DrawRectShaderOptions{}
		op.Images[0] = src0
		op.Images[1] = src1
		dst.DrawRectShader(w/2, h/2, s, op)
		testPixels("DrawRectShader", dst)
	})

	t.Run("DrawTrianglesShader", func(t *testing.T) {
		dst := ebiten.NewImageWithOptions(image.Rect(offset2, offset2, w+offset2, h+offset2), nil)
		vs := []ebiten.Vertex{
			{
				DstX:   0,
				DstY:   0,
				SrcX:   2 + offset0,
				SrcY:   3 + offset0,
				ColorR: 1,
				ColorG: 1,
				ColorB: 1,
				ColorA: 1,
			},
			{
				DstX:   w / 2,
				DstY:   0,
				SrcX:   10 + offset0,
				SrcY:   3 + offset0,
				ColorR: 1,
				ColorG: 1,
				ColorB: 1,
				ColorA: 1,
			},
			{
				DstX:   0,
				DstY:   h / 2,
				SrcX:   2 + offset0,
				SrcY:   11 + offset0,
				ColorR: 1,
				ColorG: 1,
				ColorB: 1,
				ColorA: 1,
			},
			{
				DstX:   w / 2,
				DstY:   h / 2,
				SrcX:   10 + offset0,
				SrcY:   11 + offset0,
				ColorR: 1,
				ColorG: 1,
				ColorB: 1,
				ColorA: 1,
			},
		}
		is := []uint16{0, 1, 2, 1, 2, 3}

		op := &ebiten.DrawTrianglesShaderOptions{}
		op.Images[0] = src0
		op.Images[1] = src1
		dst.DrawTrianglesShader(vs, is, s, op)
		testPixels("DrawTrianglesShader", dst)
	})
}

// Issue #2186
func TestShaderVectorEqual(t *testing.T) {
	const w, h = 16, 16

	dst := ebiten.NewImage(w, h)
	s, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	a := vec3(1)
	b := vec3(1)
	if a == b {
		return vec4(1, 0, 0, 1)
	} else {
		return vec4(0, 1, 0, 1)
	}
}
`))
	if err != nil {
		t.Fatal(err)
	}

	dst.DrawRectShader(w, h, s, nil)

	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			got := dst.At(i, j).(color.RGBA)
			want := color.RGBA{R: 0xff, A: 0xff}
			if !sameColors(got, want, 2) {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}
}

// Issue #1969
func TestShaderDiscard(t *testing.T) {
	const w, h = 16, 16

	dst := ebiten.NewImage(w, h)
	dst.Fill(color.RGBA{R: 0xff, A: 0xff})

	src := ebiten.NewImage(w, h)
	pix := make([]byte, 4*w*h)
	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			if i >= w/2 || j >= h/2 {
				continue
			}
			pix[4*(j*w+i)+3] = 0xff
		}
	}
	src.WritePixels(pix)

	s, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	p := imageSrc0At(srcPos)
	if p.a == 0 {
		discard()
	} else {
		return vec4(0, 1, 0, 1)
	}
}
`))
	if err != nil {
		t.Fatal(err)
	}

	op := &ebiten.DrawRectShaderOptions{}
	op.Images[0] = src
	dst.DrawRectShader(w, h, s, op)

	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			got := dst.At(i, j).(color.RGBA)
			want := color.RGBA{G: 0xff, A: 0xff}
			if i >= w/2 || j >= h/2 {
				want = color.RGBA{R: 0xff, A: 0xff}
			}
			if !sameColors(got, want, 2) {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}
}

// Issue #2245, #2247
func TestShaderDrawRect(t *testing.T) {
	const (
		dstW = 16
		dstH = 16
		srcW = 8
		srcH = 8
	)

	dst := ebiten.NewImage(dstW, dstH)
	src := ebiten.NewImage(srcW, srcH)

	s, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	// Adjust srcPos into [0, 1].
	srcPos -= imageSrc0Origin()
	srcPos /= imageSrc0Size()
	if srcPos.x >= 0.5 && srcPos.y >= 0.5 {
		return vec4(1, 0, 0, 1)
	}
	return vec4(0, 1, 0, 1)
}
`))
	if err != nil {
		t.Fatal(err)
	}

	const (
		offsetX = (dstW - srcW) / 2
		offsetY = (dstH - srcH) / 2
	)
	op := &ebiten.DrawRectShaderOptions{}
	op.GeoM.Translate(offsetX, offsetY)
	op.Images[0] = src
	dst.DrawRectShader(srcW, srcH, s, op)
	for j := 0; j < dstH; j++ {
		for i := 0; i < dstW; i++ {
			got := dst.At(i, j).(color.RGBA)
			var want color.RGBA
			if offsetX <= i && i < offsetX+srcW && offsetY <= j && j < offsetY+srcH {
				if offsetX+srcW/2 <= i && offsetY+srcH/2 <= j {
					want = color.RGBA{R: 0xff, A: 0xff}
				} else {
					want = color.RGBA{G: 0xff, A: 0xff}
				}
			}
			if got != want {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}
}

func TestShaderDrawRectColorScale(t *testing.T) {
	const w, h = 16, 16

	dst := ebiten.NewImage(w, h)
	s, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	return color
}
`))
	if err != nil {
		t.Fatal(err)
	}

	op := &ebiten.DrawRectShaderOptions{}
	op.ColorScale.SetR(4.0 / 8.0)
	op.ColorScale.SetG(5.0 / 8.0)
	op.ColorScale.SetB(6.0 / 8.0)
	op.ColorScale.SetA(7.0 / 8.0)
	op.ColorScale.ScaleWithColor(color.RGBA{R: 0x40, G: 0x80, B: 0xc0, A: 0xff})
	dst.DrawRectShader(w, h, s, op)

	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			got := dst.At(i, j).(color.RGBA)
			want := color.RGBA{R: 0x20, G: 0x50, B: 0x90, A: 0xe0}
			if !sameColors(got, want, 1) {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}
}

func TestShaderUniformInt(t *testing.T) {
	const ints = `//kage:unit pixels

package main

var U0 int
var U1 int
var U2 int
var U3 int

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	return vec4(float(U0)/255.0, float(U1)/255.0, float(U2)/255.0, float(U3)/255.0)
}
`

	const intArray = `//kage:unit pixels

package main

var U [4]int

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	return vec4(float(U[0])/255.0, float(U[1])/255.0, float(U[2])/255.0, float(U[3])/255.0)
}
`

	const intVec = `//kage:unit pixels

package main

var U0 ivec4
var U1 [2]ivec3

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	return vec4(float(U0.x)/255.0, float(U0.y)/255.0, float(U1[0].z)/255.0, float(U1[1].x)/255.0)
}
`

	testCases := []struct {
		Name     string
		Uniforms map[string]any
		Shader   string
		Want     color.RGBA
	}{
		{
			Name: "0xff",
			Uniforms: map[string]any{
				"U0": 0xff,
				"U1": 0xff,
				"U2": 0xff,
				"U3": 0xff,
			},
			Shader: ints,
			Want:   color.RGBA{R: 0xff, G: 0xff, B: 0xff, A: 0xff},
		},
		{
			Name: "int",
			Uniforms: map[string]any{
				"U0": int8(0x24),
				"U1": int16(0x3f),
				"U2": int32(0x6a),
				"U3": int64(0x88),
			},
			Shader: ints,
			Want:   color.RGBA{R: 0x24, G: 0x3f, B: 0x6a, A: 0x88},
		},
		{
			Name: "uint",
			Uniforms: map[string]any{
				"U0": uint8(0x85),
				"U1": uint16(0xa3),
				"U2": uint32(0x08),
				"U3": uint64(0xd3),
			},
			Shader: ints,
			Want:   color.RGBA{R: 0x85, G: 0xa3, B: 0x08, A: 0xd3},
		},
		{
			Name: "0xff,slice",
			Uniforms: map[string]any{
				"U": []int{0xff, 0xff, 0xff, 0xff},
			},
			Shader: intArray,
			Want:   color.RGBA{R: 0xff, G: 0xff, B: 0xff, A: 0xff},
		},
		{
			Name: "int,slice",
			Uniforms: map[string]any{
				"U": []int16{0x24, 0x3f, 0x6a, 0x88},
			},
			Shader: intArray,
			Want:   color.RGBA{R: 0x24, G: 0x3f, B: 0x6a, A: 0x88},
		},
		{
			Name: "uint,slice",
			Uniforms: map[string]any{
				"U": []uint8{0x85, 0xa3, 0x08, 0xd3},
			},
			Shader: intArray,
			Want:   color.RGBA{R: 0x85, G: 0xa3, B: 0x08, A: 0xd3},
		},
		{
			Name: "0xff,array",
			Uniforms: map[string]any{
				"U": [...]int{0xff, 0xff, 0xff, 0xff},
			},
			Shader: intArray,
			Want:   color.RGBA{R: 0xff, G: 0xff, B: 0xff, A: 0xff},
		},
		{
			Name: "int,array",
			Uniforms: map[string]any{
				"U": [...]int16{0x24, 0x3f, 0x6a, 0x88},
			},
			Shader: intArray,
			Want:   color.RGBA{R: 0x24, G: 0x3f, B: 0x6a, A: 0x88},
		},
		{
			Name: "uint,array",
			Uniforms: map[string]any{
				"U": [...]uint8{0x85, 0xa3, 0x08, 0xd3},
			},
			Shader: intArray,
			Want:   color.RGBA{R: 0x85, G: 0xa3, B: 0x08, A: 0xd3},
		},
		{
			Name: "0xff,array",
			Uniforms: map[string]any{
				"U": [...]int{0xff, 0xff, 0xff, 0xff},
			},
			Shader: intArray,
			Want:   color.RGBA{R: 0xff, G: 0xff, B: 0xff, A: 0xff},
		},
		{
			Name: "int,array",
			Uniforms: map[string]any{
				"U": [...]int16{0x24, 0x3f, 0x6a, 0x88},
			},
			Shader: intArray,
			Want:   color.RGBA{R: 0x24, G: 0x3f, B: 0x6a, A: 0x88},
		},
		{
			Name: "uint,array",
			Uniforms: map[string]any{
				"U": [...]uint8{0x85, 0xa3, 0x08, 0xd3},
			},
			Shader: intArray,
			Want:   color.RGBA{R: 0x85, G: 0xa3, B: 0x08, A: 0xd3},
		},
		{
			Name: "0xff,ivec",
			Uniforms: map[string]any{
				"U0": [...]int{0xff, 0xff, 0xff, 0xff},
				"U1": [...]int{0xff, 0xff, 0xff, 0xff, 0xff, 0xff},
			},
			Shader: intVec,
			Want:   color.RGBA{R: 0xff, G: 0xff, B: 0xff, A: 0xff},
		},
		{
			Name: "int,ivec",
			Uniforms: map[string]any{
				"U0": [...]int16{0x24, 0x3f, 0x6a, 0x88},
				"U1": [...]int16{0x85, 0xa3, 0x08, 0xd3, 0x13, 0x19},
			},
			Shader: intVec,
			Want:   color.RGBA{R: 0x24, G: 0x3f, B: 0x08, A: 0xd3},
		},
		{
			Name: "uint,ivec",
			Uniforms: map[string]any{
				"U0": [...]uint8{0x24, 0x3f, 0x6a, 0x88},
				"U1": [...]uint8{0x85, 0xa3, 0x08, 0xd3, 0x13, 0x19},
			},
			Shader: intVec,
			Want:   color.RGBA{R: 0x24, G: 0x3f, B: 0x08, A: 0xd3},
		},
	}
	for _, tc := range testCases {
		tc := tc
		t.Run(tc.Name, func(t *testing.T) {
			const w, h = 1, 1

			dst := ebiten.NewImage(w, h)
			defer dst.Deallocate()

			s, err := ebiten.NewShader([]byte(tc.Shader))
			if err != nil {
				t.Fatal(err)
			}
			defer s.Deallocate()

			op := &ebiten.DrawRectShaderOptions{}
			op.Uniforms = tc.Uniforms
			dst.DrawRectShader(w, h, s, op)
			if got, want := dst.At(0, 0).(color.RGBA), tc.Want; !sameColors(got, want, 1) {
				t.Errorf("got: %v, want: %v", got, want)
			}
		})
	}
}

// Issue #2463
func TestShaderUniformVec3Array(t *testing.T) {
	const shader = `//kage:unit pixels

package main

var U [4]vec3

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	return vec4(U[0].x/255.0, U[1].y/255.0, U[2].z/255.0, U[3].x/255.0)
}
`
	const w, h = 1, 1

	dst := ebiten.NewImage(w, h)
	defer dst.Deallocate()

	s, err := ebiten.NewShader([]byte(shader))
	if err != nil {
		t.Fatal(err)
	}
	defer s.Deallocate()

	op := &ebiten.DrawRectShaderOptions{}
	op.Uniforms = map[string]any{
		"U": []float32{
			0x24, 0x3f, 0x6a,
			0x88, 0x85, 0xa3,
			0x08, 0xd3, 0x13,
			0x19, 0x8a, 0x2e,
		},
	}
	dst.DrawRectShader(w, h, s, op)
	if got, want := dst.At(0, 0).(color.RGBA), (color.RGBA{R: 0x24, G: 0x85, B: 0x13, A: 0x19}); !sameColors(got, want, 1) {
		t.Errorf("got: %v, want: %v", got, want)
	}
}

func TestShaderIVecMod(t *testing.T) {
	cases := []struct {
		source string
		want   color.RGBA
	}{
		{
			source: `a := ivec4(0x24, 0x3f, 0x6a, 0x88)
return vec4(a)/255`,
			want: color.RGBA{R: 0x24, G: 0x3f, B: 0x6a, A: 0x88},
		},
		{
			source: `a := ivec4(0x24, 0x3f, 0x6a, 0x88)
a %= 0x85
return vec4(a)/255`,
			want: color.RGBA{R: 0x24, G: 0x3f, B: 0x6a, A: 0x03},
		},
		{
			source: `a := ivec4(0x24, 0x3f, 0x6a, 0x88)
a %= ivec4(0x85, 0xa3, 0x08, 0xd3)
return vec4(a)/255`,
			want: color.RGBA{R: 0x24, G: 0x3f, B: 0x02, A: 0x88},
		},
		{
			source: `a := ivec4(0x24, 0x3f, 0x6a, 0x88)
b := a % 0x85
return vec4(b)/255`,
			want: color.RGBA{R: 0x24, G: 0x3f, B: 0x6a, A: 0x03},
		},
		{
			source: `a := ivec4(0x24, 0x3f, 0x6a, 0x88)
b := a % ivec4(0x85, 0xa3, 0x08, 0xd3)
return vec4(b)/255`,
			want: color.RGBA{R: 0x24, G: 0x3f, B: 0x02, A: 0x88},
		},
	}

	for _, tc := range cases {
		shader := fmt.Sprintf(`//kage:unit pixels

package main

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	%s
}
`, tc.source)
		const w, h = 1, 1

		dst := ebiten.NewImage(w, h)
		defer dst.Deallocate()

		s, err := ebiten.NewShader([]byte(shader))
		if err != nil {
			t.Fatal(err)
		}
		defer s.Deallocate()

		op := &ebiten.DrawRectShaderOptions{}
		dst.DrawRectShader(w, h, s, op)
		if got, want := dst.At(0, 0).(color.RGBA), tc.want; !sameColors(got, want, 1) {
			t.Errorf("%s: got: %v, want: %v", tc.source, got, want)
		}
	}
}

func TestShaderTexelAndPixel(t *testing.T) {
	const dstW, dstH = 13, 17
	const srcW, srcH = 19, 23
	dstTexel := ebiten.NewImage(dstW, dstH)
	dstPixel := ebiten.NewImage(dstW, dstH)
	src := ebiten.NewImage(srcW, srcH)

	shaderTexel, err := ebiten.NewShader([]byte(fmt.Sprintf(`//kage:unit texels

package main

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	pos := (srcPos - imageSrc0Origin()) / imageSrc0Size()
	pos *= vec2(%d, %d)
	pos /= 255
	return vec4(pos.x, pos.y, 0, 1)
}
`, srcW, srcH)))
	if err != nil {
		t.Fatal(err)
	}
	shaderPixel, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	pos := srcPos - imageSrc0Origin()
	pos /= 255
	return vec4(pos.x, pos.y, 0, 1)
}
`))
	if err != nil {
		t.Fatal(err)
	}

	op := &ebiten.DrawRectShaderOptions{}
	op.Images[0] = src
	dstTexel.DrawRectShader(src.Bounds().Dx(), src.Bounds().Dy(), shaderTexel, op)
	dstPixel.DrawRectShader(src.Bounds().Dx(), src.Bounds().Dy(), shaderPixel, op)

	for j := 0; j < dstH; j++ {
		for i := 0; i < dstW; i++ {
			c0 := dstTexel.At(i, j).(color.RGBA)
			c1 := dstPixel.At(i, j).(color.RGBA)
			if !sameColors(c0, c1, 1) {
				t.Errorf("dstTexel.At(%d, %d) %v != dstPixel.At(%d, %d) %v", i, j, c0, i, j, c1)
			}
		}
	}
}

func TestShaderDifferentTextureSizes(t *testing.T) {
	src0 := ebiten.NewImageWithOptions(image.Rect(0, 0, 20, 4000), &ebiten.NewImageOptions{
		Unmanaged: true,
	}).SubImage(image.Rect(4, 1025, 6, 1028)).(*ebiten.Image)
	defer src0.Deallocate()

	src1 := ebiten.NewImageWithOptions(image.Rect(0, 0, 4000, 20), &ebiten.NewImageOptions{
		Unmanaged: true,
	}).SubImage(image.Rect(2047, 7, 2049, 10)).(*ebiten.Image)
	defer src1.Deallocate()

	src0.Fill(color.RGBA{0x10, 0x20, 0x30, 0xff})
	src1.Fill(color.RGBA{0x30, 0x20, 0x10, 0xff})

	for _, unit := range []string{"texels", "pixels"} {
		unit := unit
		t.Run(fmt.Sprintf("unit %s", unit), func(t *testing.T) {
			shader, err := ebiten.NewShader([]byte(fmt.Sprintf(`//kage:unit %s

package main

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	return imageSrc0At(srcPos) + imageSrc1At(srcPos)
}
`, unit)))
			if err != nil {
				t.Fatal(err)
			}
			defer shader.Deallocate()

			dst := ebiten.NewImage(2, 3)
			defer dst.Deallocate()

			op := &ebiten.DrawRectShaderOptions{}
			op.Images[0] = src0
			op.Images[1] = src1
			dst.DrawRectShader(2, 3, shader, op)

			for j := 0; j < 3; j++ {
				for i := 0; i < 2; i++ {
					got := dst.At(i, j).(color.RGBA)
					want := color.RGBA{0x40, 0x40, 0x40, 0xff}
					if !sameColors(got, want, 1) {
						t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
					}
				}
			}
		})
	}
}

func TestShaderIVec(t *testing.T) {
	const w, h = 16, 16
	dst := ebiten.NewImage(w, h)
	src := ebiten.NewImage(w, h)

	pix := make([]byte, 4*w*h)
	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			pix[4*(j*w+i)] = byte(i)
			pix[4*(j*w+i)+1] = byte(j)
			pix[4*(j*w+i)+3] = 0xff
		}
	}
	src.WritePixels(pix)

	// Test that ivec2 can take any float values that can be casted to integers.
	// This seems the common behavior in shading languages like GLSL, Metal, and HLSL.
	shader, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	pos := ivec2(3, 4)
	return imageSrc0At(vec2(pos) + imageSrc0Origin())
}
`))
	if err != nil {
		t.Fatal(err)
	}

	op := &ebiten.DrawRectShaderOptions{}
	op.Images[0] = src
	dst.DrawRectShader(w, h, shader, op)

	got := dst.At(0, 0).(color.RGBA)
	want := color.RGBA{3, 4, 0, 0xff}
	if got != want {
		t.Errorf("got: %v, want: %v", got, want)
	}
}

func TestShaderUniformSizes(t *testing.T) {
	const w, h = 16, 16

	dst := ebiten.NewImage(w, h)
	s, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

var U vec4
var V [3]float

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	return vec4(0)
}
`))
	if err != nil {
		t.Fatal(err)
	}

	tests := []struct {
		uniforms map[string]any
		err      bool
	}{
		{
			uniforms: nil,
			err:      false,
		},
		{
			uniforms: map[string]any{
				"U": 1,
			},
			err: true,
		},
		{
			uniforms: map[string]any{
				"U": "1",
			},
			err: true,
		},
		{
			uniforms: map[string]any{
				"U": []int32{1, 2, 3},
			},
			err: true,
		},
		{
			uniforms: map[string]any{
				"U": []int32{1, 2, 3, 4},
			},
			err: false,
		},
		{
			uniforms: map[string]any{
				"U": []int32{1, 2, 3, 4, 5},
			},
			err: true,
		},
		{
			uniforms: map[string]any{
				"V": 1,
			},
			err: true,
		},
		{
			uniforms: map[string]any{
				"V": "1",
			},
			err: true,
		},
		{
			uniforms: map[string]any{
				"V": []int32{1, 2},
			},
			err: true,
		},
		{
			uniforms: map[string]any{
				"V": []int32{1, 2, 3},
			},
			err: false,
		},
		{
			uniforms: map[string]any{
				"V": []int32{1, 2, 3, 4},
			},
			err: true,
		},
	}
	for _, tc := range tests {
		tc := tc
		t.Run(fmt.Sprintf("%v", tc.uniforms), func(t *testing.T) {
			defer func() {
				r := recover()
				if r != nil && !tc.err {
					t.Errorf("DrawRectShader must not panic but did")
				} else if r == nil && tc.err {
					t.Errorf("DrawRectShader must panic but does not")
				}
			}()
			op := &ebiten.DrawRectShaderOptions{}
			op.Uniforms = tc.uniforms
			dst.DrawRectShader(w, h, s, op)
		})
	}
}

// Issue #2709
func TestShaderUniformDefaultValue(t *testing.T) {
	const w, h = 16, 16

	dst := ebiten.NewImage(w, h)
	s, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

var U vec4

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	return U
}
`))
	if err != nil {
		t.Fatal(err)
	}

	// Draw with a uniform variable value.
	op := &ebiten.DrawRectShaderOptions{}
	op.Uniforms = map[string]any{
		"U": [...]float32{1, 1, 1, 1},
	}
	dst.DrawRectShader(w, h, s, op)

	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			got := dst.At(i, j).(color.RGBA)
			want := color.RGBA{0xff, 0xff, 0xff, 0xff}
			if got != want {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}

	// Draw without a uniform variable value. In this case, the uniform variable value should be 0.
	dst.Clear()
	op.Uniforms = nil
	dst.DrawRectShader(w, h, s, op)

	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			got := dst.At(i, j).(color.RGBA)
			want := color.RGBA{0, 0, 0, 0}
			if got != want {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}
}

// Issue #2166
func TestShaderDrawRectWithoutSource(t *testing.T) {
	const (
		dstW = 16
		dstH = 16
		srcW = 8
		srcH = 8
	)

	src := ebiten.NewImage(srcW, srcH)

	for _, unit := range []string{"pixels", "texels"} {
		s, err := ebiten.NewShader([]byte(fmt.Sprintf(`//kage:unit %s

package main

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	t := srcPos

	size := imageSrc0Size()

	// If the unit is texels and no source images are specified, size is always 0.
	if size == vec2(0) {
		// Even in this case, t is in pixels (0, 0) to (8, 8).
		if t.x >= 4 && t.y >= 4 {
			return vec4(1, 0, 1, 1)
		}
		return vec4(0, 1, 1, 1)
	}

	// Adjust srcPos into [0, 1].
	t -= imageSrc0Origin()
	if size != vec2(0) {
		t /= size
	}
	if t.x >= 0.5 && t.y >= 0.5 {
		return vec4(1, 0, 0, 1)
	}
	return vec4(0, 1, 0, 1)
}
`, unit)))
		if err != nil {
			t.Fatal(err)
		}

		for _, withSrc := range []bool{false, true} {
			withSrc := withSrc
			title := "WithSrc,unit=" + unit
			if !withSrc {
				title = "WithoutSrc,unit=" + unit
			}
			t.Run(title, func(t *testing.T) {
				dst := ebiten.NewImage(dstW, dstH)
				const (
					offsetX = (dstW - srcW) / 2
					offsetY = (dstH - srcH) / 2
				)
				op := &ebiten.DrawRectShaderOptions{}
				op.GeoM.Translate(offsetX, offsetY)
				if withSrc {
					op.Images[0] = src
				}
				dst.DrawRectShader(srcW, srcH, s, op)
				for j := 0; j < dstH; j++ {
					for i := 0; i < dstW; i++ {
						got := dst.At(i, j).(color.RGBA)
						var want color.RGBA
						if offsetX <= i && i < offsetX+srcW && offsetY <= j && j < offsetY+srcH {
							var blue byte
							if !withSrc && unit == "texels" {
								blue = 0xff
							}
							if offsetX+srcW/2 <= i && offsetY+srcH/2 <= j {
								want = color.RGBA{0xff, 0, blue, 0xff}
							} else {
								want = color.RGBA{0, 0xff, blue, 0xff}
							}
						}
						if got != want {
							t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
						}
					}
				}
			})
		}
	}
}

// Issue #2719
func TestShaderMatrixDivFloat(t *testing.T) {
	const w, h = 16, 16

	src := ebiten.NewImage(w, h)
	src.Fill(color.RGBA{R: 0x10, G: 0x20, B: 0x30, A: 0xff})

	dst := ebiten.NewImage(w, h)
	s, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	var x = 2.0
	return mat4(3) / x * imageSrc0At(srcPos);
}
`))
	if err != nil {
		t.Fatal(err)
	}

	op := &ebiten.DrawRectShaderOptions{}
	op.Images[0] = src
	dst.DrawRectShader(w, h, s, op)

	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			got := dst.At(i, j).(color.RGBA)
			want := color.RGBA{R: 0x18, G: 0x30, B: 0x48, A: 0xff}
			if !sameColors(got, want, 2) {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}
}

func TestShaderDifferentSourceSizes(t *testing.T) {
	src0 := ebiten.NewImageWithOptions(image.Rect(0, 0, 20, 4000), &ebiten.NewImageOptions{
		Unmanaged: true,
	}).SubImage(image.Rect(4, 1025, 7, 1029)).(*ebiten.Image) // 3x4
	defer src0.Deallocate()

	src1 := ebiten.NewImageWithOptions(image.Rect(0, 0, 4000, 20), &ebiten.NewImageOptions{
		Unmanaged: true,
	}).SubImage(image.Rect(2047, 7, 2049, 10)).(*ebiten.Image) // 2x3
	defer src1.Deallocate()

	src0.Fill(color.RGBA{0x10, 0x20, 0x30, 0xff})
	src1.Fill(color.RGBA{0x30, 0x20, 0x10, 0xff})

	for _, unit := range []string{"texels", "pixels"} {
		unit := unit
		t.Run(fmt.Sprintf("unit %s", unit), func(t *testing.T) {
			if unit == "texels" {
				defer func() {
					if r := recover(); r == nil {
						t.Errorf("DrawTrianglesShader must panic with different sizes but not (unit=%s)", unit)
					}
				}()
			}
			shader, err := ebiten.NewShader([]byte(fmt.Sprintf(`//kage:unit %s

package main

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	return imageSrc0At(srcPos) + imageSrc1At(srcPos)
}
`, unit)))
			if err != nil {
				t.Fatal(err)
			}
			defer shader.Deallocate()

			dst := ebiten.NewImage(3, 4)
			defer dst.Deallocate()

			op := &ebiten.DrawTrianglesShaderOptions{}
			op.Images[0] = src0
			op.Images[1] = src1
			vs := []ebiten.Vertex{
				{
					DstX:   0,
					DstY:   0,
					SrcX:   4,
					SrcY:   1025,
					ColorR: 1,
					ColorG: 1,
					ColorB: 1,
					ColorA: 1,
				},
				{
					DstX:   3,
					DstY:   0,
					SrcX:   7,
					SrcY:   1025,
					ColorR: 1,
					ColorG: 1,
					ColorB: 1,
					ColorA: 1,
				},
				{
					DstX:   0,
					DstY:   4,
					SrcX:   4,
					SrcY:   1029,
					ColorR: 1,
					ColorG: 1,
					ColorB: 1,
					ColorA: 1,
				},
				{
					DstX:   3,
					DstY:   4,
					SrcX:   7,
					SrcY:   1029,
					ColorR: 1,
					ColorG: 1,
					ColorB: 1,
					ColorA: 1,
				},
			}
			is := []uint16{0, 1, 2, 1, 2, 3}
			dst.DrawTrianglesShader(vs, is, shader, op)

			if unit == "texel" {
				t.Fatal("not reached")
			}

			for j := 0; j < 4; j++ {
				for i := 0; i < 3; i++ {
					got := dst.At(i, j).(color.RGBA)
					var want color.RGBA
					if i < 2 && j < 3 {
						want = color.RGBA{0x40, 0x40, 0x40, 0xff}
					} else {
						want = color.RGBA{0x10, 0x20, 0x30, 0xff}
					}
					if !sameColors(got, want, 1) {
						t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
					}
				}
			}
		})
	}
}

// Issue #2752
func TestShaderBitwiseOperator(t *testing.T) {
	const w, h = 16, 16

	src := ebiten.NewImage(w, h)
	src.Fill(color.RGBA{R: 0x24, G: 0x3f, B: 0x6a, A: 0xff})

	for _, assign := range []bool{false, true} {
		assign := assign
		name := "op"
		if assign {
			name = "op+assign"
		}
		t.Run(name, func(t *testing.T) {
			var code string
			if assign {
				code = `	v.rgb &= 0x5a
	v.rgb |= 0x30
	v.rgb ^= 0x8d`
			} else {
				code = `	v.rgb = v.rgb & 0x5a
	v.rgb = v.rgb | 0x30
	v.rgb = v.rgb ^ 0x8d`
			}

			s, err := ebiten.NewShader([]byte(fmt.Sprintf(`//kage:unit pixels

package main

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	v := ivec4(imageSrc0At(srcPos) * 0xff)
%s
	return vec4(v) / 0xff;
}
`, code)))
			if err != nil {
				t.Fatal(err)
			}

			dst := ebiten.NewImage(w, h)
			op := &ebiten.DrawRectShaderOptions{}
			op.Images[0] = src
			dst.DrawRectShader(w, h, s, op)

			for j := 0; j < h; j++ {
				for i := 0; i < w; i++ {
					got := dst.At(i, j).(color.RGBA)
					want := color.RGBA{R: 0xbd, G: 0xb7, B: 0xf7, A: 0xff}
					if !sameColors(got, want, 2) {
						t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
					}
				}
			}
		})
	}
}

func TestShaderDispose(t *testing.T) {
	const w, h = 16, 16

	dst := ebiten.NewImage(w, h)
	s, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	return vec4(1, 0, 0, 1)
}
`))
	if err != nil {
		t.Fatal(err)
	}

	dst.DrawRectShader(w/2, h/2, s, nil)

	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			got := dst.At(i, j).(color.RGBA)
			var want color.RGBA
			if i < w/2 && j < h/2 {
				want = color.RGBA{R: 0xff, A: 0xff}
			}
			if got != want {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}

	s.Dispose()

	dst.Clear()

	defer func() {
		if e := recover(); e == nil {
			panic("DrawRectShader with a disposed shader must panic but not")
		}
	}()

	dst.DrawRectShader(w/2, h/2, s, nil)
}

func TestShaderDeallocate(t *testing.T) {
	const w, h = 16, 16

	dst := ebiten.NewImage(w, h)
	s, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	return vec4(1, 0, 0, 1)
}
`))
	if err != nil {
		t.Fatal(err)
	}

	dst.DrawRectShader(w/2, h/2, s, nil)

	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			got := dst.At(i, j).(color.RGBA)
			var want color.RGBA
			if i < w/2 && j < h/2 {
				want = color.RGBA{R: 0xff, A: 0xff}
			}
			if got != want {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}

	// Even after Deallocate is called, the shader is still available.
	s.Deallocate()

	dst.Clear()
	dst.DrawRectShader(w/2, h/2, s, nil)

	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			got := dst.At(i, j).(color.RGBA)
			var want color.RGBA
			if i < w/2 && j < h/2 {
				want = color.RGBA{R: 0xff, A: 0xff}
			}
			if got != want {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}
}

// Issue #2923
func TestShaderReturnArray(t *testing.T) {
	const w, h = 16, 16

	dst := ebiten.NewImage(w, h)
	s, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

func foo() [4]float {
	return [4]float{0.25, 0.5, 0.75, 1}
}

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	a := foo()
	return vec4(a[0], a[1], a[2], a[3])
}
`))
	if err != nil {
		t.Fatal(err)
	}

	dst.DrawRectShader(w, h, s, nil)

	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			got := dst.At(i, j).(color.RGBA)
			want := color.RGBA{R: 0x40, G: 0x80, B: 0xc0, A: 0xff}
			if !sameColors(got, want, 2) {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}
}

// Issue #2798
func TestShaderInvalidPremultipliedAlphaColor(t *testing.T) {
	// This test checks the rendering result when the shader returns an invalid premultiplied alpha color.
	// The result values are kept and not clamped.

	const w, h = 16, 16

	dst := ebiten.NewImage(w, h)
	s, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	return vec4(1, 0.75, 0.5, 0.25)
}
`))
	if err != nil {
		t.Fatal(err)
	}

	dst.DrawRectShader(w, h, s, nil)

	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			got := dst.At(i, j).(color.RGBA)
			want := color.RGBA{R: 0xff, G: 0xc0, B: 0x80, A: 0x40}
			if !sameColors(got, want, 2) {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}

	dst.Clear()
	s, err = ebiten.NewShader([]byte(`//kage:unit pixels

package main

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	return vec4(1, 0.75, 0.5, 0)
}
`))
	if err != nil {
		t.Fatal(err)
	}

	dst.DrawRectShader(w, h, s, nil)

	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			got := dst.At(i, j).(color.RGBA)
			want := color.RGBA{R: 0xff, G: 0xc0, B: 0x80, A: 0}
			if !sameColors(got, want, 2) {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}
}

// Issue #2933
func TestShaderIncDecStmt(t *testing.T) {
	const w, h = 16, 16

	dst := ebiten.NewImage(w, h)
	s, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	a := 0
	a++
	b := -0.5
	b++
	c := ivec2(0)
	c++
	d := vec2(-0.25)
	d++
	return vec4(float(a), b, float(c.x), d.y)
}
`))
	if err != nil {
		t.Fatal(err)
	}

	dst.DrawRectShader(w, h, s, nil)

	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			got := dst.At(i, j).(color.RGBA)
			want := color.RGBA{R: 0xff, G: 0x80, B: 0xff, A: 0xc0}
			if !sameColors(got, want, 2) {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}

	dst.Clear()

	s, err = ebiten.NewShader([]byte(`//kage:unit pixels

package main

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	a := 1
	a--
	b := 1.5
	b--
	c := ivec2(1)
	c--
	d := vec2(1.25)
	d--
	return vec4(float(a), b, float(c.x), d.y)
}
`))
	if err != nil {
		t.Fatal(err)
	}

	dst.DrawRectShader(w, h, s, nil)

	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			got := dst.At(i, j).(color.RGBA)
			want := color.RGBA{R: 0x00, G: 0x80, B: 0x00, A: 0x40}
			if !sameColors(got, want, 2) {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}
}

// Issue #2934
func TestShaderAssignConst(t *testing.T) {
	const w, h = 16, 16

	dst := ebiten.NewImage(w, h)
	s, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	a := 0.0
	a = 1
	b, c := 0.0, 0.0
	b, c = 1, 1
	d := 0.0
	d += 1
	return vec4(a, b, c, d)
}
`))
	if err != nil {
		t.Fatal(err)
	}

	dst.DrawRectShader(w, h, s, nil)

	for j := 0; j < h; j++ {
		for i := 0; i < w; i++ {
			got := dst.At(i, j).(color.RGBA)
			want := color.RGBA{R: 0xff, G: 0xff, B: 0xff, A: 0xff}
			if !sameColors(got, want, 2) {
				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}
}

// Issue #2930
func TestShaderMRT(t *testing.T) {
	const w, h = 16, 16

	s, err := ebiten.NewShader([]byte(`//kage:unit pixels

package main

func Fragment(dstPos vec4, srcPos vec2, color vec4) (vec4, vec4, vec4, vec4, vec4, vec4, vec4, vec4) {
	return vec4(1, 0, 0, 1),
		vec4(0, 1, 0, 1),
		vec4(0, 0, 1, 1),
		vec4(1, 0, 1, 1),
		vec4(1, 1, 0, 1),
		vec4(0, 1, 1, 1),
		vec4(1, 1, 1, 1),
		vec4(1, 1, 1, 0)
}
`))
	if err != nil {
		t.Fatal(err)
	}

	bounds := image.Rect(0, 0, w, h)
	opts := &ebiten.NewImageOptions{
		Unmanaged: true,
	}
	vertices := []ebiten.Vertex{
		{
			DstX: 0,
			DstY: 0,
		},
		{
			DstX: w,
			DstY: 0,
		},
		{
			DstX: 0,
			DstY: h,
		},
		{
			DstX: w,
			DstY: h,
		},
	}
	indices := []uint16{0, 1, 2, 1, 2, 3}
	t.Run("8 locations", func(t *testing.T) {
		imgs := [8]*ebiten.Image{
			ebiten.NewImageWithOptions(bounds, opts),
			ebiten.NewImageWithOptions(bounds, opts),
			ebiten.NewImageWithOptions(bounds, opts),
			ebiten.NewImageWithOptions(bounds, opts),
			ebiten.NewImageWithOptions(bounds, opts),
			ebiten.NewImageWithOptions(bounds, opts),
			ebiten.NewImageWithOptions(bounds, opts),
			ebiten.NewImageWithOptions(bounds, opts),
		}
		wantColors := [8]color.RGBA{
			{R: 0xff, G: 0, B: 0, A: 0xff},
			{R: 0, G: 0xff, B: 0, A: 0xff},
			{R: 0, G: 0, B: 0xff, A: 0xff},
			{R: 0xff, G: 0, B: 0xff, A: 0xff},
			{R: 0xff, G: 0xff, B: 0, A: 0xff},
			{R: 0, G: 0xff, B: 0xff, A: 0xff},
			{R: 0xff, G: 0xff, B: 0xff, A: 0xff},
			{R: 0xff, G: 0xff, B: 0xff, A: 0},
		}
		ebiten.DrawTrianglesShaderMRT(imgs, vertices, indices, s, nil)
		for k, dst := range imgs {
			for j := 0; j < h; j++ {
				for i := 0; i < w; i++ {
					got := dst.At(i, j).(color.RGBA)
					want := wantColors[k]
					if !sameColors(got, want, 1) {
						t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
					}
				}
			}
		}
	})

	t.Run("Empty locations", func(t *testing.T) {
		imgs := [8]*ebiten.Image{
			ebiten.NewImageWithOptions(bounds, opts),
			ebiten.NewImageWithOptions(bounds, opts),
			ebiten.NewImageWithOptions(bounds, opts),
			ebiten.NewImageWithOptions(bounds, opts),
			ebiten.NewImageWithOptions(bounds, opts),
			ebiten.NewImageWithOptions(bounds, opts),
			ebiten.NewImageWithOptions(bounds, opts),
			ebiten.NewImageWithOptions(bounds, opts),
		}
		wantColors := [8]color.RGBA{
			{},
			{R: 0, G: 0xff, B: 0, A: 0xff},
			{},
			{R: 0xff, G: 0, B: 0xff, A: 0xff},
			{},
			{R: 0, G: 0xff, B: 0xff, A: 0xff},
			{},
			{R: 0xff, G: 0xff, B: 0xff, A: 0},
		}
		dsts := [8]*ebiten.Image{
			nil, imgs[1], nil, imgs[3], nil, imgs[5], nil, imgs[7],
		}
		ebiten.DrawTrianglesShaderMRT(dsts, vertices, indices, s, nil)
		for k, dst := range imgs {
			for j := 0; j < h; j++ {
				for i := 0; i < w; i++ {
					got := dst.At(i, j).(color.RGBA)
					want := wantColors[k]
					if !sameColors(got, want, 1) {
						t.Errorf("%d dst.At(%d, %d): got: %v, want: %v", k, i, j, got, want)
					}
				}
			}
		}
	})

	t.Run("1 location (first slot)", func(t *testing.T) {
		imgs := [8]*ebiten.Image{
			ebiten.NewImageWithOptions(bounds, opts),
			ebiten.NewImageWithOptions(bounds, opts),
			ebiten.NewImageWithOptions(bounds, opts),
			ebiten.NewImageWithOptions(bounds, opts),
			ebiten.NewImageWithOptions(bounds, opts),
			ebiten.NewImageWithOptions(bounds, opts),
			ebiten.NewImageWithOptions(bounds, opts),
			ebiten.NewImageWithOptions(bounds, opts),
		}
		wantColors := [8]color.RGBA{
			{R: 0xff, G: 0, B: 0, A: 0xff},
			{}, {}, {}, {}, {}, {}, {},
		}
		dsts := [8]*ebiten.Image{
			imgs[0], nil, nil, nil, nil, nil, nil, nil,
		}
		ebiten.DrawTrianglesShaderMRT(dsts, vertices, indices, s, nil)
		for k, dst := range imgs {
			for j := 0; j < h; j++ {
				for i := 0; i < w; i++ {
					got := dst.At(i, j).(color.RGBA)
					want := wantColors[k]
					if !sameColors(got, want, 1) {
						t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
					}
				}
			}
		}
	})
}