waveshare213v2: Use color for clearing

This is an API-breaking change, albeit a simple one: Previously the
Dev.Clear function received a byte named "color". It was sent directly
to the display, thus acting more like a pattern to fill the display
with. In practice only 0 and 255 are likely to be used.

With this change the function is changed to receive a value of type
color.Color which is then converted to image1bit.Bit before filling the
display. The latter is also given a unittest.

Signed-off-by: Michael Hanselmann <public@hansmi.ch>

waveshare2in13v2/drawing.go

@@ -5,6 +5,7 @@
 package waveshare2in13v2
 
 import (
+	"bytes"
 	"image"
 	"image/draw"
 
@@ -128,3 +129,30 @@ func drawImage(ctrl controller, opts *drawOpts) {
 		ctrl.sendData(rowData)
 	}
 }
+
+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

@@ -144,3 +144,58 @@ 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

@@ -5,7 +5,6 @@
 package waveshare2in13v2
 
 import (
-	"bytes"
 	"fmt"
 	"image"
 	"image/color"
@@ -249,23 +248,11 @@ func (d *Dev) Init(partialUpdate PartialUpdate) error {
 }
 
 // Clear clears the display.
-func (d *Dev) Clear(color byte) error {
-	spec := (&drawOpts{
-		devSize: image.Pt(d.opts.Width, d.opts.Height),
-		dstRect: d.Bounds(),
-	}).spec()
-
+func (d *Dev) Clear(color color.Color) error {
 	eh := errorHandler{d: *d}
 
-	setMemoryArea(&eh, spec.MemRect)
-
-	eh.sendCommand(writeRAMBW)
-
-	data := bytes.Repeat([]byte{color}, spec.MemRect.Dx())
-
-	for y := 0; y < spec.MemRect.Max.Y; y++ {
-		eh.sendData(data)
-	}
+	clearDisplay(&eh, image.Pt(d.opts.Width, d.opts.Height),
+		image1bit.BitModel.Convert(color).(image1bit.Bit))
 
 	if eh.err == nil {
 		eh.err = d.turnOnDisplay()
@@ -335,7 +322,7 @@ func (d *Dev) DrawPartial(dstRect image.Rectangle, src image.Image, srcPts image
 
 // Halt clears the display.
 func (d *Dev) Halt() error {
-	return d.Clear(0xFF)
+	return d.Clear(image1bit.On)
 }
 
 // String returns a string containing configuration information.