ebiten: revert the changes for DrawRectShader

This reverts these commits:
- 9bd46cb2b5.
- f8c4634017.

This causes test failures on the Steam bot. See #2246.

Updates #2166
Closes #2246

image.go

@@ -701,11 +701,6 @@ func (i *Image) DrawRectShader(width, height int, shader *Shader, options *DrawR
 		b := img.Bounds()
 		sx, sy = img.adjustPosition(b.Min.X, b.Min.Y)
 		sr = img.adjustedRegion()
-	} else {
-		sr = graphicsdriver.Region{
-			Width:  float32(width),
-			Height: float32(height),
-		}
 	}
 
 	if offsetX, offsetY := i.adjustPosition(0, 0); offsetX != 0 || offsetY != 0 {

shader_test.go

@@ -1181,70 +1181,3 @@ func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
 		}
 	}
 }
-
-// Issue #2166
-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(`package main
-
-func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
-	// Adjust texCoord into [0, 1].
-	t := texCoord
-	origin, size := imageSrcRegionOnTexture()
-	t -= origin
-	t /= size
-	if t.x >= 0.5 && t.y >= 0.5 {
-		return vec4(1, 0, 0, 1)
-	}
-	return vec4(0, 1, 0, 1)
-}
-`))
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	for _, withSrc := range []bool{false, true} {
-		withSrc := withSrc
-		title := "WithSrc"
-		if !withSrc {
-			title = "WithoutSrc"
-		}
-		t.Run(title, func(t *testing.T) {
-			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 {
-						if offsetX+srcW/2 <= i && offsetY+srcH/2 <= j {
-							want = color.RGBA{0xff, 0, 0, 0xff}
-						} else {
-							want = color.RGBA{0, 0xff, 0, 0xff}
-						}
-					}
-					if got != want {
-						t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
-					}
-				}
-			}
-		})
-	}
-}