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GameMaker Tutorial: Password systems 3: on-screen keyboard

Yeah, I know. Last article, I said in this article we’d cover parsing and validation and converting the password into gamestate data. We’ll get there eventually. But I want to take a detour and show you how to build an on-screen keyboard.

In the first article in this series, I handled the user input simply, by using the get_string_async() function. This is good enough to be functional, but has two main problems:

First, because we’re allowing input directly from the keyboard, the player can enter any characters at all, which means that we’d need to handle characters that are not part of our password’s alphabet. This means extra programming. Not necessarily a bad thing, if that’s what’s right for the user, but it is more work to write up validation scripts that properly handle our Base64 password alphabet.

Second, the user experience of typing a password into a textbox is fine, as far as it goes, but it isn’t at all like an authentic old school keyboard system. This is a somewhat debatable point — old school consoles used on-screen keyboards not because they were better than keyboard entry, but because there was no keyboard. Entering passwords this way is slower and more tedious. But, if we are going to re-create the experience authentically, we need to heed the conventions of the time.

Every onscreen keyboard in the old days was a custom implementation. No two were exactly the same, although there were a lot of commonalities, and most of the differences were cosmetic. The most common implementation was a grid of characters, which the player selected one at a time using the D-pad, pressing a button to enter the character, and another button to go back. When the entire password was entered, typically the player submitted it by pressing the Start button, or sometimes there was an on-screen button that the player would select with the D-pad. We’ll build something like that in this tutorial, although we’ll use the keyboard rather than a gamepad control. Implementing the gamepad controller input capability isn’t too difficult, though, so I’ll probably come back and add that eventually.

The Alphabet and the Font

One of the problems people have with writing down (and later reading) passwords is that certain characters look very similar (such as 0, o O, l, l, 5, S, 9, g, etc.) You can’t help the player’s handwriting, but at least when the game is displaying the characters on the screen, you should be sure to pick a font that makes these characters unambiguous. These symbols are merely labels which stand for a number value, so it doesn’t really matter what they are.

It’s not a bad idea to omit the similar looking characters, although for this tutorial I’m going to stick with the full alphabet. We’ll at least want a font that has very distinct characters to aid the player in recognizing them correctly. Google for “programmer” or “console” fonts, for suggestions on good ones to use, and pick something out that looks right for the style of game that you’re making. Make sure the capital “I” has serifs and the zero has a slash or dot in it, and so on.

The Onscreen Keyboard Object

oOnScreenKeyboard

Create

alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789!?";
font = fConsole;
var k = 1;
for (var i = 0; i < 8; i++){
 for (var j = 0; j < 8; j++){
 keyboard[i,j] = string_copy(alphabet,k,1);
 k++;
 }
}
row_selected = 0;
column_selected = 0;
instructions_text = "Press A to select letter. Press B to erase letter. Press Enter to submit password.";

input_string = "";
max_input_string_length = 4;

Draw

draw_set_font(font);
draw_set_halign(fa_left);
draw_set_valign(fa_top);
draw_text(10,10, "PASSWORD: " + input_string);

draw_set_halign(fa_center);
draw_set_valign(fa_middle);

for (var i = 0; i < 8; i++){
 for (var j = 0; j < 8; j++){
 draw_text(x+(32*i), y+(32*j), keyboard[j,i]);
 }
}
draw_rectangle((column_selected * 32) - 16 + x,
 (row_selected * 32) - 16 + y, 
 (column_selected * 32) + 16 + x, 
 (row_selected * 32) + 16 + y, 
 true);

Press Button1

(Pick whatever keyboard key you want for this.)

if string_length(input_string) < max_input_string_length {
 input_string += string_copy(alphabet, (row_selected*8) + column_selected + 1, 1);
}else{
 audio_play_sound(snBadPassword,1,false); 
}

Press Button2

(Again pick whatever keyboard key you want for this.)

input_string = string_copy(input_string,1,string_length(input_string)-1);

Press Enter

if validate_password(input_string){
 apply_password(input_string);
 room_goto(rmGameStart);
} else {
 bad_password();
}

Press Up

row_selected = (row_selected + 7) mod 8;

Press Down

row_selected = (row_selected + 1) mod 8;

Press Left

column_selected = (column_selected + 7) mod 8;

Press Right

column_selected = (column_selected + 1) mod 8;

That's it for the Events, but we need to write three scripts for the Press Enter event. These passwords are where most of the implementation-specific code is going to go.

The details of these scripts will vary from project to project, but this is where we'll handle the validation, parsing, and conversion to gamestate data -- what I thought we'd be covering in this article. We'll cover our example versions of them in the next article.

2 Comments

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  1. wheres the next part!!! :((

      

    1. Well, I never did get around to completing it… I guess it's an exercise for the reader, sorry! :S

        

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