Example 100 Key Override

Table of Contents

• Live Demo
• Whole Code

Did you know that you can assign functionality to specific key combinations? Imagine, with the up, down, left, and right arrows, you could even control servos! That’s right, you have the freedom to decide what custom action the Ctrl-C combination (or any other) should trigger, if you need it.

In the demo below, you should see that when you press the arrow keys, the banner text changes to the name of the arrow you just pressed.

If you want to reset the arrow key behavior back to normal, just press CTRL + R.

⚠️ Important note: After pressing CTRL + R, this shortcut will also return to its default function, which is reverse-i-search. The only way to fully reset the demo is to reload the page.

Live Demo

All you need to do is call the corresponding key override function. The table includes all the key combinations you can override.

Function Name	Key Combo
overrideUpArrow()	Up Key
overrideDownArrow()	Down Key
overrideLeftArrow()	Left Key
overrideRightArrow()	Right Key
overrideAbortKey()	Ctrl-C Combo
overridePageUpKey()	Page Up Key
overridePageDownKey()	Page Down Key
overrideHomeKey()	Home Key
overrideEndKey()	End Key
overrideLogoutKey()	Ctrl-D Combo
overrideSearchKey()	Ctrl-R Combo

Key override functions work by redirecting control from the default functionality to a callback written by the user (essentially hooks). Because of this, every key override function requires a function that will be called when the specific key is pressed. For example create a callback:

void upArrowCallback( Shellminator* caller ){
    // This will be called when the Up Arrow Key is pressed.
}

And override the up arrow key behavior:

shell.overrideUpArrow( upArrowCallback );

Similar to key override functions, there are key free functions that restore the default behavior.

Function Name	Key Combo
freeUpArrow()	Up Key
freeDownArrow()	Down Key
freeLeftArrow()	Left Key
freeRightArrow()	Right Key
freeAbortKey()	Ctrl-C Combo
freePageUpKey()	Page Up Key
freePageDownKey()	Page Down Key
freeHomeKey()	Home Key
freeEndKey()	End Key
freeLogoutKey()	Ctrl-D Combo
freeSearchKey()	Ctrl-R Combo

Both the key override and key free functions should have the following structure: they should return void and take one argument, which is Shellminator* caller. The function name is up to the user, but the return type and argument are fixed.

Whole Code

/*
 * Created on Aug 10 2020
 *
 * Copyright (c) 2023 - Daniel Hajnal
 * hajnal.daniel96@gmail.com
 * This file is part of the Shellminator project.
 * Modified 2023.05.13
*/
 
#include "Shellminator.hpp"
 
 
// Create a Shellminator object, and initialize it to use Serial
Shellminator shell( &Serial );
 
void upArrowCallback( Shellminator* caller ){
    caller -> setBannerText( "up" );
}
 
void downArrowCallback( Shellminator* caller ){
    caller -> setBannerText( "down" );
}
 
void leftArrowCallback( Shellminator* caller ){
    caller -> setBannerText( "left" );
}
 
void rightArrowCallback( Shellminator* caller ){
    caller -> setBannerText( "right" );
}
 
void searchKeyCallback( Shellminator* caller ){
    caller -> freeSearchKey();
    caller -> freeUpArrow();
    caller -> freeDownArrow();
    caller -> freeLeftArrow();
    caller -> freeRightArrow();
    caller -> setBannerText( "default" );
}
 
// System init section.
void setup(){
 
    Serial.begin(115200);
 
    // Clear the terminal
    shell.clear();
 
    Serial.println( "Use the arrow keys to change the banner text." );
    Serial.print( "To reset the functionality, press" );
    shell.format( &Serial, Shellminator::BOLD, Shellminator::BG_WHITE, Shellminator::BLACK );
    Serial.print( " Ctrl-R ");
    shell.format( &Serial, Shellminator::REGULAR, Shellminator::WHITE );
    Serial.println( "key." );
    Serial.println();
 
    shell.overrideUpArrow( upArrowCallback );
    shell.overrideDownArrow( downArrowCallback );
    shell.overrideLeftArrow( leftArrowCallback );
    shell.overrideRightArrow( rightArrowCallback );
    shell.overrideSearchKey( searchKeyCallback );
 
    // Initialize shell object.
    shell.begin( "arnold" );
 
}
 
// Infinite loop.
void loop(){
 
    // Process the new data.
    shell.update();
 
}

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Banner Text Example	QR Code Example