ScreenUi is a simple user interface library for character based LCDs like those commonly used with Arduinos
C++
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README.md
ScreenUi.cpp
ScreenUi.h
library.properties

README.md

ScreenUi makes it easy to build simple or complex character based user interfaces on small LCD displays like those commonly used with Arduinos. It offers a suite of widgets that you can use to build a screen and a set of simple ways to get data to and from the widgets. ScreenUi incorporates focus management, scrolling, text editing, input and output all in one easy to use library.

Demonstration video: https://www.youtube.com/watch?v=fMjPy8N6kG0

Here is a short Arduino sketch showing an example of how to use the library. Comments in the code explain how each piece works.

// A Sketch demonstrating ScreenUi using a 20x4 character LCD for output and
// a rotary encoder with pushbutton for input. 

#include <pin.h>
#include <encoder.h>
#include <LiquidCrystalFP.h>
// This is the only required include for ScreenUi. 
// The others above are for a specific set of hardware input
// and output.
#include <ScreenUi.h>

// Set up the rotary encoder and LCD.
#define ENCODER_TYPE ALPS

#define ENCA_PIN 3
#define ENCB_PIN 2
#define ENTER_PIN 1
  
#define LCD_RS_PIN 4
#define LCD_ENABLE_PIN 23
#define LCD_DATA4_PIN 28
#define LCD_DATA5_PIN 29
#define LCD_DATA6_PIN 30
#define LCD_DATA7_PIN 31

#define LCD_BRIGHT_PIN 13
#define LCD_CONTRAST_PIN 14

LiquidCrystal lcd(LCD_RS_PIN, LCD_ENABLE_PIN, LCD_DATA4_PIN, LCD_DATA5_PIN, LCD_DATA6_PIN, LCD_DATA7_PIN);

void setup() {
  // Everything here is for setting up the hardware. Nothing ScreenUi specific here.
  lcd.begin(20, 4);
  TCCR2B = 0x01;
  pinMode(LCD_BRIGHT_PIN, OUTPUT);
  pinMode(LCD_CONTRAST_PIN, OUTPUT);
  setBright(128);
  setContrast(98);
  Encoder.begin(ENCODER_TYPE, ENTER_PIN, ENCA_PIN, ENCB_PIN);
  Encoder.setWrap(true);
  Encoder.setMin(-10000);
  Encoder.setMax(10000);
  Encoder.setCount(0);
  Serial.begin(9600);
  Serial.println();
  Serial.println();
  Serial.println();
}

// The loop() function is where all the ScreenUi magic happens. We'll create a
// Screen, display it to the user, allow the user to interact and we'll take
// input from the Components.
void loop() {
  // Create a new Screen with width 20, height 4.
  Screen screen(20, 4);
  
  // Some static text that will be at the top of the screen.
  Label titleLabel("RGB Settings");
  
  // An Input field and a Label to describe it. We pass in the text "0xffee" and
  // any changes the user makes to that text will be reflected in the address 
  // variable.
  Label addressLabel("Address:");
  char *address = "0xffee";
  Input addressInput(address);

  // A List field and a Label to describe it. We add three items to the List for
  // the user to select from.
  Label colorLabel("Color:");
  List colorList(7);
  colorList.addItem("Red");
  colorList.addItem("Orange");
  colorList.addItem("Yellow");

  // A Checkbox field and a Label to describe it.
  Label rgbEnabledLabel("RGB Enabled:");
  Checkbox rgbEnabledCheckbox;
  
  Label brightnessLabel("Brightness:");
  Spinner brightnessSpinner(128, 0, 255, 1, true);
  
  Label contrastLabel("Contrast:");
  Spinner contrastSpinner(128, 0, 255, 1, true);
  
  // A ScrollContainer to allow scrolling through multiple Components. Since our
  // screen is only 4 lines high but we want to show 5 lines of Components, we add
  // three of the widgets to the ScrollContainer. The ScrollContainer will appear
  // in the middle two lines of the display and allow the user to scroll through
  // as many Components as we like.
  // This line creates the ScrollContainer, passing the screen it will be attached
  // to and the width and height for the new ScrollContainer.
  ScrollContainer scrollContainer(&screen, screen.width(), 2);
  // Add the Components to the ScrollContainer, setting their position within it.
  scrollContainer.add(&addressLabel, 0, 0);
  scrollContainer.add(&addressInput, 8, 0);
  scrollContainer.add(&colorLabel, 0, 1);
  scrollContainer.add(&colorList, 6, 1);
  scrollContainer.add(&rgbEnabledLabel, 0, 2);
  scrollContainer.add(&rgbEnabledCheckbox, 12, 2);
  scrollContainer.add(&brightnessLabel, 0, 3);
  scrollContainer.add(&brightnessSpinner, 11, 3);
  scrollContainer.add(&contrastLabel, 0, 4);
  scrollContainer.add(&contrastSpinner, 9, 4);

  // A simple Cancel button.
  Button cancelButton("Cancel");

  // A Simple Ok button.
  Button okButton("Ok");
 
  // Add the title Label, the ScrollContainer and the Cancel and Ok buttons to the
  // screen.
  screen.add(&titleLabel, 0, 0);
  screen.add(&scrollContainer, 0, 1);
  screen.add(&cancelButton, 0, 3);
  screen.add(&okButton, 16, 3);

  // Start processing the Screen in a loop. 
  while (1) {
    // screen.update() tells the Screen to display itself, accept input and manage
    // it's resources. 
    screen.update();
    // After calling screen.update(), all of the Components have been updated and drawn
    // to the Screen and their inputs are now available for querying.
    setBright(brightnessSpinner.intValue());
    setContrast(contrastSpinner.intValue());
    if (okButton.pressed()) {
      // Do some work
    }
  }
}

// The next 8 methods are required to be implemented by the user of ScreenUi. These
// methods are what tie ScreenUi to your specific hardware for input and output.
// In general, these will be very similar across platforms and can probably be copied
// from one program to another and slightly modified.

// User defined method that receives input from the input method. ScreenUi calls
// this method during each update to see how the input state has changed since
// the last update. ScreenUi expects the function to fill in the values
// for x, y, selected and cancelled.
// x and y are the number of inputs in either the x or y axis since the last call
// to this method. The values can be positive or negative. A common control scheme
// for a rotary encoder would be negative y for left, positive y for right. For
// an input method consisting of the buttons on a NES control pad, for instance, might
// have the D pad control x and y, the A button control selected and the B button
// control cancelled.
void Screen::getInputDeltas(int *x, int *y, bool *selected, bool *cancelled) {
  *x = 0;
  *y = Encoder.getDelta();
  *selected = Encoder.ok();
  *cancelled = Encoder.cancel();
  Encoder.setCount(0);
}

// User defined method that clears the output device completely.
void Screen::clear() {
  lcd.clear();
}  

// User defined method that creates a custom character in font memory. This is
// currently used by the Checkbox Component to create a nice check mark.
void Screen::createCustomChar(uint8_t slot, uint8_t *data) {
  lcd.createChar(slot, data);
}

// User defined method that draws the given text at the given x and y position.
// The text should be drawn exactly as specified with no interpretation, scrolling
// or wrapping. 
void Screen::draw(uint8_t x, uint8_t y, const char *text) {
  lcd.setCursor(x, y);
  lcd.print(text);
}

// User defined method that draws the given custom character at the given x
// and y position. The custom character will be one specified to the
// Screen::createCustomChar() method.
void Screen::draw(uint8_t x, uint8_t y, uint8_t customChar) {
  lcd.setCursor(x, y);
  lcd.write(customChar);
}

// User defined method that turns the character cursor on or off.
void Screen::setCursorVisible(bool visible) {
  visible ? lcd.cursor() : lcd.noCursor();
}

// User defined method positions the character cursor.
void Screen::moveCursor(uint8_t x, uint8_t y) {
  lcd.setCursor(x, y);
}

// User defined method that turns the blinking character on or off.
void Screen::setBlink(bool blink) {
  blink ? lcd.blink() : lcd.noBlink();
}

// Utility function for setting the brightness of the LCD. Not required for ScreenUi.
void setBright(byte val) {
  analogWrite(LCD_BRIGHT_PIN, 255 - val);
}

// Utility function for setting the contrast of the LCD. Not required for ScreenUi.
void setContrast(byte val) {
  analogWrite(LCD_CONTRAST_PIN, val);
}