waveshare2in13v2: Use drawing functionality for clearing

With the introduction of the shadow buffer in commit 4f99575 there's
always a sufficiently large memory buffer to keep the bytes to send for
clearing and the dedicated code using a smaller buffer is no longer
needed. This also has the advantage of automatically updating both
on-device buffers.

waveshare2in13v2/drawing.go

@@ -5,7 +5,6 @@
 package waveshare2in13v2
 
 import (
-	"bytes"
 	"image"
 	"image/draw"
 
@@ -130,30 +129,3 @@ func drawImage(ctrl controller, opts *drawOpts) {
 		sendImage(ctrl, cmd, s.MemRect, opts.buffer)
 	}
 }
-
-func clearDisplay(ctrl controller, size image.Point, color image1bit.Bit) {
-	var colorValue byte
-
-	if color == image1bit.On {
-		colorValue = 0xff
-	}
-
-	spec := (&drawOpts{
-		devSize: size,
-		dstRect: image.Rectangle{Max: size},
-	}).spec()
-
-	if spec.MemRect.Empty() {
-		return
-	}
-
-	setMemoryArea(ctrl, spec.MemRect)
-
-	ctrl.sendCommand(writeRAMBW)
-
-	data := bytes.Repeat([]byte{colorValue}, spec.MemRect.Dx())
-
-	for y := 0; y < spec.MemRect.Max.Y; y++ {
-		ctrl.sendData(data)
-	}
-}

waveshare2in13v2/drawing_test.go

@@ -207,58 +207,3 @@ func TestDrawImage(t *testing.T) {
 		})
 	}
 }
-
-func TestClearDisplay(t *testing.T) {
-	for _, tc := range []struct {
-		name  string
-		size  image.Point
-		color image1bit.Bit
-		want  []record
-	}{
-		{
-			name: "empty",
-		},
-		{
-			name:  "off",
-			size:  image.Pt(100, 10),
-			color: image1bit.Off,
-			want: []record{
-				{cmd: dataEntryModeSetting, data: []byte{0x3}},
-				{cmd: setRAMXAddressStartEndPosition, data: []byte{0, (100+7)/8 - 1}},
-				{cmd: setRAMYAddressStartEndPosition, data: []byte{0, 0, 10 - 1, 0}},
-				{cmd: setRAMXAddressCounter, data: []byte{0}},
-				{cmd: setRAMYAddressCounter, data: []byte{0, 0}},
-				{
-					cmd:  writeRAMBW,
-					data: bytes.Repeat([]byte{0}, 13*10),
-				},
-			},
-		},
-		{
-			name:  "on",
-			size:  image.Pt(32, 20),
-			color: image1bit.On,
-			want: []record{
-				{cmd: dataEntryModeSetting, data: []byte{0x3}},
-				{cmd: setRAMXAddressStartEndPosition, data: []byte{0, 32/8 - 1}},
-				{cmd: setRAMYAddressStartEndPosition, data: []byte{0, 0, 20 - 1, 0}},
-				{cmd: setRAMXAddressCounter, data: []byte{0}},
-				{cmd: setRAMYAddressCounter, data: []byte{0, 0}},
-				{
-					cmd:  writeRAMBW,
-					data: bytes.Repeat([]byte{0xff}, 4*20),
-				},
-			},
-		},
-	} {
-		t.Run(tc.name, func(t *testing.T) {
-			var got fakeController
-
-			clearDisplay(&got, tc.size, tc.color)
-
-			if diff := cmp.Diff([]record(got), tc.want, cmpopts.EquateEmpty(), cmp.AllowUnexported(record{})); diff != "" {
-				t.Errorf("clearDisplay() difference (-got +want):\n%s", diff)
-			}
-		})
-	}
-}

waveshare2in13v2/waveshare213v2.go

@@ -229,18 +229,9 @@ func (d *Dev) SetUpdateMode(mode PartialUpdate) error {
 
 // Clear clears the display.
 func (d *Dev) Clear(color color.Color) error {
-	eh := errorHandler{d: *d}
-
-	c := image1bit.BitModel.Convert(color).(image1bit.Bit)
-	draw.Src.Draw(d.buffer, d.buffer.Bounds(), &image.Uniform{c}, image.Point{})
-
-	clearDisplay(&eh, image.Pt(d.opts.Width, d.opts.Height), c)
-
-	if eh.err == nil {
-		updateDisplay(&eh, Full)
-	}
-
-	return eh.err
+	return d.Draw(d.buffer.Bounds(), &image.Uniform{
+		C: image1bit.BitModel.Convert(color).(image1bit.Bit),
+	}, image.Point{})
 }
 
 // ColorModel returns a 1Bit color model.