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display: Create Interfaces for text displays (#42)
* Create Interfaces for text displays * Print errors in interactive mode.
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‎display/displaytest/text.go‎

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// Copyright 2024 The Periph Authors. All rights reserved.
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// Use of this source code is governed under the Apache License, Version 2.0
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// that can be found in the LICENSE file.
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package displaytest
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import (
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"errors"
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"fmt"
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"time"
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"periph.io/x/conn/v3/display"
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)
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// TestTextDisplay exercises the methods provided by the interface. It can be
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// used interactively as a quick smoke test of an implementation, and from test
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// routines. This doesn't test brightness or contrast to avoid EEPROM wear
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// issues.
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func TestTextDisplay(dev display.TextDisplay, interactive bool) []error {
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var result []error
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var err error
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pauseTime := time.Duration(0)
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if interactive {
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pauseTime = 3 * time.Second
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}
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// Turn the dev on and write the String() value.
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if err = dev.Display(true); err != nil {
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result = append(result, err)
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}
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if err = dev.Clear(); err != nil {
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result = append(result, err)
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}
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if _, err = dev.WriteString(dev.String()); err != nil {
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result = append(result, err)
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}
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time.Sleep(pauseTime)
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if err = dev.Clear(); err != nil {
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result = append(result, err)
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}
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_, err = dev.WriteString("Auto Scroll Test")
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if err != nil {
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result = append(result, err)
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}
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time.Sleep(pauseTime)
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err = dev.AutoScroll(true)
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if err != nil {
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result = append(result, err)
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}
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// Test Display fill
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for line := range dev.Rows() {
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c := rune('A')
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if err = dev.MoveTo(dev.MinRow()+line, dev.MinCol()); err != nil {
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result = append(result, err)
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}
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for col := range dev.Cols() {
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if col%5 == 0 && col > 0 {
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_, err = dev.Write([]byte{byte(' ')})
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} else {
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_, err = dev.Write([]byte{byte(c)})
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}
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if err != nil {
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result = append(result, err)
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}
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c = c + 1
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}
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}
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// Test AutoScroll working
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time.Sleep(pauseTime)
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nWritten, err := dev.WriteString("auto scroll happen")
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if err != nil {
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result = append(result, err)
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}
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if nWritten != 18 {
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result = append(result, fmt.Errorf("dev.WriteString() expected %d chars written, received %d", 18, nWritten))
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}
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time.Sleep(pauseTime)
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if err = dev.AutoScroll(false); err != nil {
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result = append(result, err)
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}
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time.Sleep(pauseTime)
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// Test Absolute Positioning
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if err = dev.Clear(); err != nil {
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result = append(result, err)
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}
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if _, err = dev.WriteString("Absolute Positioning"); err != nil {
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result = append(result, err)
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}
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time.Sleep(pauseTime)
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if err = dev.Clear(); err != nil {
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result = append(result, err)
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}
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for ix := range dev.Rows() {
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if err = dev.MoveTo(dev.MinRow()+ix, dev.MinCol()+ix); err != nil {
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result = append(result, err)
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}
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if _, err = dev.WriteString(fmt.Sprintf("(%d,%d)", dev.MinRow()+ix, dev.MinCol()+ix)); err != nil {
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result = append(result, err)
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}
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}
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time.Sleep(pauseTime)
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// Test that MoveTo returns error for invalid coordinates
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moveCases := []struct {
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row int
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col int
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}{
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{row: dev.MinRow() - 1, col: dev.MinCol()},
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{row: dev.MinRow(), col: dev.MinCol() - 1},
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{row: dev.Rows() + 1, col: dev.Cols()},
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{row: dev.Rows(), col: dev.Cols() + 1},
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}
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for _, tc := range moveCases {
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if err = dev.MoveTo(tc.row, tc.col); err == nil {
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result = append(result, fmt.Errorf("did not receive expected error on MoveTo(%d,%d)", tc.row, tc.col))
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}
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}
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// Test Cursor Modes
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if err = dev.Clear(); err != nil {
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result = append(result, err)
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}
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modes := []string{"Off", "Underline", "Block", "Blink"}
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for ix := display.CursorOff; ix <= display.CursorBlink; ix++ {
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if err = dev.MoveTo(dev.MinRow()/2+1, dev.MinCol()); err != nil {
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result = append(result, err)
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}
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if _, err = dev.WriteString("Cursor: " + modes[ix]); err != nil {
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result = append(result, err)
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}
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if err = dev.Cursor(ix); err != nil {
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result = append(result, err)
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}
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time.Sleep(pauseTime)
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if err = dev.Cursor(display.CursorOff); err != nil {
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result = append(result, err)
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}
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if err = dev.Clear(); err != nil {
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result = append(result, err)
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}
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}
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if err = dev.Cursor(display.CursorBlink + 1); err == nil {
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result = append(result, errors.New("did not receive expected error on Cursor() with invalid value"))
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}
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// Test Move Forward and Backward. 2 Should overwrite the 1
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if err = dev.Clear(); err != nil {
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result = append(result, err)
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}
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if _, err = dev.WriteString("Testing >"); err != nil {
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result = append(result, err)
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}
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if err = dev.Move(display.Forward); err != nil {
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result = append(result, err)
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}
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if err = dev.Move(display.Forward); err != nil {
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result = append(result, err)
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}
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for ix := range 10 {
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if _, err = dev.WriteString(fmt.Sprintf("%d", ix)); err != nil {
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result = append(result, err)
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}
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time.Sleep(pauseTime)
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if err = dev.Move(display.Backward); err != nil {
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result = append(result, err)
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}
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}
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if err = dev.Move(display.Down + 1); err == nil {
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result = append(result, errors.New("did not receive expected error on Move() with invalid value"))
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}
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// Test Display on/off
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if err = dev.Clear(); err != nil {
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result = append(result, err)
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}
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if _, err = dev.WriteString("Set dev off"); err != nil {
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result = append(result, err)
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}
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time.Sleep(pauseTime)
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if err = dev.Display(false); err != nil {
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result = append(result, err)
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}
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time.Sleep(pauseTime)
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if err = dev.Display(true); err != nil {
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result = append(result, err)
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}
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if err = dev.Clear(); err != nil {
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result = append(result, err)
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}
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if _, err = dev.WriteString("Set dev on"); err != nil {
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result = append(result, err)
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}
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time.Sleep(pauseTime)
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if interactive {
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for _, e := range result {
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if !errors.Is(err, display.ErrNotImplemented) {
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fmt.Println(e)
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}
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}
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}
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return result
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}

‎display/text_display.go‎

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// Copyright 2024 The Periph Authors. All rights reserved.
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// Use of this source code is governed under the Apache License, Version 2.0
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// that can be found in the LICENSE file.
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package display
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import (
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"errors"
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)
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type CursorDirection int
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const (
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// Constants for moving the cursor relative to it's current position.
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//
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// Move the cursor one unit back.
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Backward CursorDirection = iota
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// Move the cursor one unit forward.
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Forward
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Up
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Down
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)
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type CursorMode int
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const (
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// Turn the cursor Off
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CursorOff CursorMode = iota
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// Enable Underline Cursor
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CursorUnderline
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// Enable Block Cursor
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CursorBlock
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// Blinking
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CursorBlink
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)
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// TextDisplay represents an interface to a basic character device. It provides
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// standard methods implemented by a majority of character LCD devices. Pixel
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// type displays can implement this interface if desired.
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type TextDisplay interface {
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// Enable/Disable auto scroll
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AutoScroll(enabled bool) (err error)
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// Return the number of columns the display supports
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Cols() int
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// Clear the display and move the cursor home.
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Clear() (err error)
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// Set the cursor mode. You can pass multiple arguments.
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// Cursor(CursorOff, CursorUnderline)
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//
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// Implementations should return an error if the value of mode is not
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// mode>= CursorOff && mode <= CursorBlink
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Cursor(mode ...CursorMode) (err error)
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// Move the cursor home (MinRow(),MinCol())
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Home() (err error)
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// Return the min column position.
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MinCol() int
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// Return the min row position.
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MinRow() int
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// Move the cursor forward or backward.
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Move(dir CursorDirection) (err error)
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// Move the cursor to arbitrary position. Implementations should return an
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// error if row < MinRow() || row > (Rows()-MinRow()), or col < MinCol()
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// || col > (Cols()-MinCol())
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MoveTo(row, col int) (err error)
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// Return the number of rows the display supports.
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Rows() int
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// Turn the display on / off
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Display(on bool) (err error)
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// return info about the display.
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String() string
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// Write a set of bytes to the display.
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Write(p []byte) (n int, err error)
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// Write a string output to the display.
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WriteString(text string) (n int, err error)
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}
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type Intensity int
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// Interface for displays that support a monochrome backlight. Displays that
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// support RGB Backlights should implement this as well for maximum
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// compatibility.
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//
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// Many units that support this command write the value to EEPROM, which has a
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// finite number of writes. To turn the unit on/off, use TextDisplay.Display()
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type DisplayBacklight interface {
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Backlight(intensity Intensity) error
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}
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// Interface for displays that support a RGB Backlight. E.G. the Sparkfun SerLCD
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type DisplayRGBBacklight interface {
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RGBBacklight(red, green, blue Intensity) error
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}
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type Contrast int
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// Interface for displays that support a programmable contrast adjustment.
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// As with SetBacklight(), many devices serialize the value to EEPROM,
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// which support only a finite number of writes, so this should be used
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// sparingly.
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type DisplayContrast interface {
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Contrast(contrast Contrast) error
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}
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var ErrNotImplemented = errors.New("not implemented")
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var ErrInvalidCommand = errors.New("invalid command")

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