Adding scroll functionality for ili9341 (#121)

* ili9341: Adding scroll functionality

ili9341/ili9341.go

@@ -7,8 +7,6 @@ import (
 	"time"
 )
 
-const _debug = false
-
 type Config struct {
 	Width    int16
 	Height   int16
@@ -229,6 +227,26 @@ func (d *Device) SetRotation(rotation Rotation) {
 	d.rotation = rotation
 }
 
+// SetScrollWindow sets an area to scroll with fixed top and bottom parts of the display
+func (d *Device) SetScrollArea(topFixedArea, bottomFixedArea int16) {
+	d.sendCommand(VSCRDEF, []uint8{
+		uint8(topFixedArea >> 8), uint8(topFixedArea),
+		uint8(d.height - topFixedArea - bottomFixedArea>>8),
+		uint8(d.height - topFixedArea - bottomFixedArea),
+		uint8(bottomFixedArea >> 8), uint8(bottomFixedArea),
+	})
+}
+
+// SetScroll sets the vertical scroll address of the display.
+func (d *Device) SetScroll(line int16) {
+	d.sendCommand(VSCRSADD, []uint8{uint8(line >> 8), uint8(line)})
+}
+
+// SpotScroll returns the display to its normal state
+func (d *Device) StopScroll() {
+	d.sendCommand(NORON, nil)
+}
+
 // setWindow prepares the screen to be modified at a given rectangle
 func (d *Device) setWindow(x, y, w, h int16) {
 	//x += d.columnOffset