Tag Archives: HTML

Adding a New Screen to the React Template Project

In this post I started looking into ReactJS. Following getting the sample project running, I decided that I’ve try adding a new screen. Since it didn’t go as smoothly as I expected, I’ve documented my adventures.

The target of this post is to create a new screen, using the sample project inside Visual Studio.

Step 1

Create a brand new project for React:

If you run this out of the box (if you can’t because of missing packages then see this article), you’ll get a screen that looks like this:

Step 2

Add a new tsx file to the components:

Here’s some code to add into this new file:

import * as React from 'react';
import { RouteComponentProps } from 'react-router';
 
 
export class NewScreen extends React.Component<RouteComponentProps<{}>, {}> {
    public render() {
        return <div>
            <h1>New Screen Test</h1>
        </div>;
    }
}
 

The Javascript as HTML above is one of the things that makes ReactJS an appealing framework. Combine that with Typescript, and you get a very XAML feel to the whole web application.

Step 3

Add a link to the Navigation Screen (NavMenu.tsx):

<div className='navbar-collapse collapse'>
    <ul className='nav navbar-nav'>
        <li>
            <NavLink to={ '/' } exact activeClassName='active'>
                <span className='glyphicon glyphicon-home'></span> Home
            </NavLink>
        </li>
        <li>
            <NavLink to={ '/counter' } activeClassName='active'>
                <span className='glyphicon glyphicon-education'></span> Counter
            </NavLink>
        </li>
        <li>
            <NavLink to={ '/fetchdata' } activeClassName='active'>
                <span className='glyphicon glyphicon-th-list'></span> Fetch data
            </NavLink>
        </li>
        <li>
            <NavLink to={'/newscreen'} activeClassName='active'>
                <span className='glyphicon glyphicon-th-list'></span> New screen
            </NavLink>
        </li>
 
    </ul>
</div>

If you run this now, you’ll see the navigation entry, but clicking on it will give you a blank screen. It is just that scenario that motivated this post!

Step 4

Finally, the routes.tsx file needs updating so that it knows which screen to load when:

import * as React from 'react';
import { Route } from 'react-router-dom';
import { Layout } from './components/Layout';
import { Home } from './components/Home';
import { FetchData } from './components/FetchData';
import { Counter } from './components/Counter';
import { NewScreen } from './components/NewScreen';
 
export const routes = <Layout>
    <Route exact path='/' component={ Home } />
    <Route path='/counter' component={ Counter } />
    <Route path='/fetchdata' component={FetchData} />
    <Route path='/newscreen' component={NewScreen} />
</Layout>;

Create CSS effect to “Shine” a button border

Imagine that you have an HTML button or element on a page and you would like an effect where the border shines all around the perimeter. this provides an excellent example of an effect of the entire element shining, and this post will largely be based on that code.

Animations

CSS has the concept of an animation, to define it, use the following syntax:

.growOnHover:hover:after {
    animation: growAnimation 1s;
}

Here is the HTML referencing this:

<a href="#" class="growOnHover">Grow</a>

Tge “growAnimation” refers to a KeyFrame:

@keyframes growAnimation {
    from {width: 100px; height: 100px;}
    to {width: 110px; height: 110px;}
}

The effect

The effect that I want is for a light to run around the circumference of the button when it’s hovered over. In this case, instead of animating from .. to, we can specify at which stage a particular section of the animation kicks in.


.borderShine:after {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  width: 5;
  height: 5;
  opacity: 0;  

  border-radius: 1;

  background: rgba(255, 255, 255, 10);
}

.borderShine:hover:after {
  animation: shineAnimation 2s 1;  
}

@keyframes shineAnimation {
  0%   {left: 0; top: 0; width: 2; height: 2; opacity: 0}
  10%  {width: 100; height: 2}  
  20%  {left: 98; top: 0; width: 2; height: 2}
  25%  {opacity: 1;}
  30%  {height: 100}
  40%  {left: 98; top: 98; height: 2}
  50%  {left: 0; top: 98; width: 100}
  55%  {opacity: 1;}
  60%  {left: 0; top: 98; width: 2; height: 2}
  70%  {left: 0; top: 0; width: 2; height: 100}
  80%  {left: 0; top: 0; width: 2; height: 2}
  100% {opacity: 0;}
}

There are a few useful things to remember here:

  • The animation is a transition between the state that the screen is currently in, and the state that you want it to be in; so, for example, the opacity set to 1 at 25% will cause the white bar to gradually appear over the steps between the two. The reason that I’ve set opacity twice here is to prevent it from transitioning back too soon.
  • All the figures above are absolute (as my buttons are 100 x 100).

References

http://jsfiddle.net/AntonTrollback/nqQc7/

https://css-tricks.com/useful-nth-child-recipies/

https://css-tricks.com/using-multi-step-animations-transitions/

Basic Game Using HTML5 and Javascript

This article discusses how to go about creating a basic game loop in HTML5 / JS and to implement control over a sprite.

Introduction

A few years ago, when Microsoft released the idea of WinJS, I wrote a game in HTML5/JS (or WinJS – they are not exactly the same).

I recently decided to see if I could write a web game, using just HTML5 and Javascript. This article covers the initial POC and results in a small red square navigating around the screen:

Game Loop

Looking at established game frameworks, they all basically give you the same things:
– A game loop, consisting of an update and draw phase
– Some helper methods for manipulating graphics, or rendering them to the screen

My attempt will be different, I’ll just provide a game loop; here it is:

(function MainGame() {    

    setInterval(function() {
        Update();
        Draw();
    }, 20);
})();

The loop executes every 20ms, meaning that there are 50 frames per second.

HTML

Basically, what the HTML gives us here is a canvas; so the page is very simple:

<head>    
    <script type="text/javascript" src="./gamelogic.js" ></script>
</head>
<body onresize="onResizeGameWindow()">    
    <canvas id="mainCanvas" style="width: 100%; height: 100%"
        onkeydown="onKeyDown()" tabindex="0">
    </canvas>
</body>

There are two events handled here, because there are two things that the player can do: they can interact with the game (i.e. press a key), and they can resize the browser window. We need to react to both.

Draw

Let’s have a look at the draw function next. All this is, is a way of displaying all the objects on the screen in a controlled fashion:


    function Draw() {
        var canvas = document.getElementById("mainCanvas");
        var ctx = canvas.getContext("2d");
        ctx.clearRect(0, 0, windowWidth, windowHeight);

        ctx.fillStyle = "#FF0000";
        ctx.fillRect(x, y, iconWidth, iconHeight);
    }

As you can see, there are effectively two parts to this function: firstly, the canvas is cleared, and then the items (in this case, a single item) are drawn to the screen. The important variables here are x and y, because that dictates where the square is drawn; the rest could be hard-coded values.

Update


    function Update() {        
        if (initialised == 0) {
            initialise();
        }

        // Bounce
        if (x >= (windowWidth - iconWidth) 
            && directionX > 0)
            directionX = -1;
        else if (x <= 0 && directionX < 0)
            directionX = 1;

        if (y >= (windowHeight - iconHeight)
            && directionY > 0)
            directionY = -1;
        else if (y <= 0 && directionY < 0)
            directionY = 1;

        // Move
        x += directionX * speed;
        y += directionY * speed;
    }

There are three parts to the Update. The first is to perform any initialisation: in my case, I focus on the canvas and call the resize event here. This potentially could be done on an event, but you would still have to check inside this loop if it had been done. The second is to stop the player leaving the screen; and finally, we adjust the player position.

Events

As you saw earlier, there are two events that are handled; the first is the user resizing the screen:

function onResizeGameWindow() {
    var canvas = document.getElementById("mainCanvas");
    
    windowWidth = canvas.width;
    windowHeight = canvas.height;
}

This basically ensures that the game adjusts to the browser dimensions. This might also be where you would determine if the window was made so small that the game could no longer be played.

The second event was the keydown event. This effectively provides the control for the player:


function onKeyDown(e) {
    if (!e) e = window.event;     

    if (e.keyCode == 39) {
        directionX++;
    }
    else if (e.keyCode == 37) {
        directionX--;
    }

    if (e.keyCode == 38) {        
        directionY--;
    }
    else if (e.keyCode == 40) {        
        directionY++;
    }
}

The top line is because the parameter comes through as null.

Conclusion

If you run this game, you’ll see that you can move the square around the screen, increase and decrease its speed, and stop. Not exactly the next Call Of Duty, I’ll grant you, but the foundation of a game, certainly.

TypeScript

Javascript is a dynamic, interpreted language. What that means is that, if you mis-type or mis-spell a variable, or even if you don’t bother to declare it, you won’t get notified at compile time (because, for a start, there is no compile time).

One possible way around this is to use one of the languages that compile down to Javascript. That does seem like a bizarre notion – that you should compile down to a second language; but it does mean (as the name suggests) that you can introduce some static typing into your Javascript.

The following was with VS2017, but you can use VS2015. I believe earlier versions don’t support Typescript out of the box (but I could be wrong).

Javascript

The first thing we’ll do is create a new web project and create some Javascript:

Create new project

Create new project

Create a basic html page:

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8" />
    <title></title>
    
</head>
<body>
    <div>
        <input id="testInput" type="text" />
    </div>
    <div>
        <p id="testOutput">Output</p> 
    </div>
    <div>
        <button onclick="buttonClicked()">Test</button>
    </div>

    <script src="typescript.js"></script>

    
</body>

And the Javascript:

function buttonClicked() {
    var input = getElementById("testInput");
    var ouput = getElementById("testOutput");

    output.value = input.value;

}

This code will run (the web-site will appear), but it will not do what it’s supposed to.

Typescript

Now we have a project, the next thing to do is to add .ts file to project. This gets compiled into a .js file, and can be referenced with a .js extension. Just copy the code:

Code sample

As you can see, the code no-longer “compiles”. The correct Typescript looks more like this:

function buttonClicked() {
    var input = <HTMLInputElement>document.getElementById("testInput");
    var output = document.getElementById("testOutput");

    output.innerText = input.value;

}

The <> brackets are typescript casts. Once you build this typescript file, it will compile down to Javascript:

Project tree

The compiled Javascript now looks like this:

function buttonClicked() {
    var input = document.getElementById("testInput");
    var output = document.getElementById("testOutput");
    output.innerText = input.value;
}
//# sourceMappingURL=typescript.js.map

The typescript.js.map file tells it where your file really is and, from looking at the debugger, we can see that the typescript file is being used:

All works well:

But why

As you can see, above; we had a piece of Javascript code that didn’t work, but it ran. Any statically typed language would have simply failed to compile. Typescript means that you can benefit from this additional check before runtime. There is a cost here, and that is that you lose the dynamic typed capability of Javascript; for example, the following won’t compile:

IMHO, this is a good thing, but I’m aware there are people out there in the world that think otherwise.

References

http://stackoverflow.com/questions/34888434/how-to-reference-a-typescript-file-from-a-web-page

http://stackoverflow.com/questions/12686927/typescript-casting-htmlelement

CSS Overlaying Controls (absolute and relative positioning)

Having looked at CSS in the past, and thought that it’s probably something that people who are better at UI design that me should concern themselves with, I’ve recently been playing with it while looking at the new Dot Net Core web apps.

The problem that I’m looking at in this particular article is how to overlay one control on top of another. I have no doubt that there are dozens of possibilities; but the two specific ones that I’ll be focusing on are positioning absolute and relative.

Target

The idea here is for a web-page that looks like this:

Target Layout

HTML

The HTML is pretty basic for this:

<body>
  <form>
    <div>
      <img src=""  />
    </div>
    <div class="overlay">
      <input type="text" name="destination" />
    </div>
  </form>
</body>

CSS: absolute positioning

We have the basic elements, so now it’s down to CSS to make the screen above. By default, web browsers will render the div’s sequentially, and so the input box will appear below the image.

One possibility is to use “absolute” positioning. This means that I can position an element without regard to where other elements on the page might be; here’s an example:

.overlay {
    position: absolute; 
    top: 30%;         
    text-align: center;
    z-index: 10;
}

img {
  background-color: blue;
  width: 100%;
  height: 500px;
}

I’ve used 30% here because it matters on the size of your viewport – so that’s not ideal. Also, the centre align doesn’t work. This kind of makes sense when you think about it, because you’re using an absolute position – so what do you want to centralise it to?

CSS: relative positioning

Relative positioning took me a while to work out. It sounds like it’s relative to something else – but it’s actually relative to itself. Here’s what I tried for relative positioning:

.overlay {
    position: relative;
    width: 80%;
    height: 35px;
    top: -50px;
    border: none;
    text-align: center;
    z-index: 10;    
}

As you can see, it’s top position is negative, so it moves up from where it would have been. Also, because the positioning is relative, the centre align now works, because it’s back in the flow of the page.

References

https://css-tricks.com/absolute-relative-fixed-positioining-how-do-they-differ/

https://www.w3.org/Style/Examples/007/center.en.html#block