Displaying text letter by letter

Question

I am planing to Write a Text adventure and I don't know how to make the text draw letter by letter in any other way than changing the variable from h to he to hel to hell to hello That would be a terrible amount of work since there are tons of dialogue.

Here is the source code so far

protected override void Update(GameTime gameTime)
{
    //input code removed for clarity

    if (Dialogue == 1)
    {
        Row1 = "Input Text 1 Here.";
        Row2 = "Input Text 2 Here.";
        Row3 = "Input Text 3 Here.";
        Row4 = "Input Text 4 Here.";
    }
    if (Dialogue == 2)
    {
        Row1 = "Text 1";
        Row2 = "Text 2";
        Row3 = "Text 3";
        Row4 = "Text 4";
    }

    base.Update(gameTime);
}

protected override void Draw(GameTime gameTime)
{
    GraphicsDevice.Clear(Color.CornflowerBlue);

    spriteBatch.Begin();
    spriteBatch.Draw(sampleBG, new Rectangle(0, 0, 800, 600), Color.White);
    spriteBatch.Draw(TextBG, new Rectangle(0, 400, 800, 200), Color.White);
    spriteBatch.DrawString(defaultfont, Row1, new Vector2(10, (textheight + (rowspace * 0))), Color.Black);
    spriteBatch.DrawString(defaultfont, Row2, new Vector2(10, (textheight + (rowspace * 1))), Color.Black);
    spriteBatch.DrawString(defaultfont, Row3, new Vector2(10, (textheight + (rowspace * 2))), Color.Black);
    spriteBatch.DrawString(defaultfont, Row4, new Vector2(10, (textheight + (rowspace * 3))), Color.Black);
    spriteBatch.End();
    base.Draw(gameTime);
}

Answer 1

I won't write the code for you, but I can put forth a conceptual path forward.

Assuming your text is displayed in a string, it is possible to iterate through the character array that makes up that string. The goal here is to print each character individually (or however many at a time you want) separated by a delta time.

When you think about it, this isn't really any different than animating a sprite. Instead of moving the index into a spritesheet, you're moving the index into a string and appending that character to the displayed string.

So, for example:

string fullText = "Hello World";
string currentText = "";
int currentTextIndex = 0;
float timeSinceLastIncrement = 0;

update(dt)
{
    timeSinceLastIncrement += dt;

    if(timeSinceLastIncrement >= .5)
    {
         currentText += fullText[currentTextIndex];
         currentTextIndex++;
         timeSinceLastIncrement = 0;
    }
}

draw()
{
    render(currentText);
}

Basically, you're maintaining the full text that will eventually be displayed, the current text that is being rendered, and the current index into the full text. dt is the delta time since the last update and timeSinceLastIncrement is the time that has passed since the last time you moved to the next character in the string. When that time (here in seconds) has gone past half a second, append the character to the current text, increment to the next character, and reset the time.

@ time 0, currentText = "";
@ time .5, currentText = "H";
@ time 1.0, currentText = "He";

And so on...