graphics: Bug fix: render source might not be initialized

image_test.go

@@ -1095,3 +1095,33 @@ func TestImageSubImageSize(t *testing.T) {
 		t.Errorf("got: %v, want: %v", got, want)
 	}
 }
+
+func TestImageDrawImmediately(t *testing.T) {
+	const w, h = 16, 16
+	img0, _ := NewImage(w, h, FilterDefault)
+	img1, _ := NewImage(w, h, FilterDefault)
+	// Do not manipulate img0 here.
+
+	img0.Fill(color.RGBA{0xff, 0, 0, 0xff})
+	for j := 0; j < h; j++ {
+		for i := 0; i < w; i++ {
+			got := img0.At(i, j).(color.RGBA)
+			want := color.RGBA{0xff, 0, 0, 0xff}
+			if got != want {
+				t.Errorf("img0.At(%d, %d): got %v, want: %v", i, j, got, want)
+			}
+		}
+	}
+
+	img0.DrawImage(img1, nil)
+
+	for j := 0; j < h; j++ {
+		for i := 0; i < w; i++ {
+			got := img0.At(i, j).(color.RGBA)
+			want := color.RGBA{0xff, 0, 0, 0xff}
+			if got != want {
+				t.Errorf("img0.At(%d, %d): got %v, want: %v", i, j, got, want)
+			}
+		}
+	}
+}

internal/graphicscommand/image.go

@@ -143,6 +143,21 @@ func (i *Image) DrawImage(src *Image, vertices []float32, indices []uint16, clr
 	default:
 		panic("not reached")
 	}
+
+	switch src.state {
+	case imageStateInit:
+		src.clearByReplacingPixels()
+	case imageStateReplacePixelsOnly:
+		// Do nothing
+		// TODO: Check the region.
+	case imageStateDrawable:
+		// Do nothing
+	case imageStateScreen:
+		panic("not reached")
+	default:
+		panic("not reached")
+	}
+
 	theCommandQueue.EnqueueDrawImageCommand(i, src, vertices, indices, clr, mode, filter)
 }