Responsive Image Overlay

Image overlay is a very common concept in front-end development. It is easy to implement but difficult when we deal it with different screen sizes, where we need to cover the image with the overlay each time the screen size is changed. I have gone through various blog posts when I need to implement the same for Open-event webapp and researched a solution that works for all screen sizes without any media query.

1234

How to add an overlay to an image ?

If we need four images in a single row nearly 300*300px.  The code below shows the markup.

image-holder : The parent class to take the image and overlay inside it.

background-image: This class takes image source.

responsive-overlay: This is the key point to make it responsive. Responsive-overlay contains a class hover-state to add overlay absolutely and a class social-links.

social-links: It adds content to hover-state.

 

<div class="image-holder">
  <img class="background-image" alt="" src="">
   <div class="responsive-overlay">
     <div class="hover-state text-center preserve3d">
       <div class="social-links vertical-align">

       </div>
     </div>
   </div>
 </div>

The styling is written with SASS in .scss file as shown below.

//overlayimage and backgroundshade can be set in config.scss

 .image-holder {
   position: relative;
   overflow: hidden;
   margin-bottom: 12px;

   .background-image {
     height: 300px;
     width: 300px;
     display: block;
     margin: 0 auto;
     background-color: $background-shade;
    }
 
   .responsive-overlay {
     @include responsiveoverlay;

    .preserve3d {
       height: 300px;
      }

    .hover-state {
     @include hoverstate;
     height: 300px;
     width: 300px;
    }

  @mixin responsiveoverlay {
     height: 100%;
     position: absolute;
     top: 0;
     width: 100%;
}

   @mixin hoverstate {
     background: $overlayimage;
     display: block;
     height: 300px;
     left: 0;
     margin: 0 auto;
     opacity: 0;
     position: relative;
     top: 0;
     -moz-transition: all 0.3s ease-out;
     -webkit-transition: all 0.3s ease-out;
     transition: all 0.3s ease-out;
     width: 300px;
     z-index: 2;
   }

This code will work for responsiveness as well. The main catch here is the responsive-overlay class which is made 100% in width but set to position absolute. The images which are 300 * 300 px in size will take an overlay of the same size because of hover-state class. Instead, if we adjust sizes of images in small screens the above code will adjust overlay on the image automatically.

Like, on tablets we can have an overlay like this.

345

And on mobile screen output is like that :

23

Conclusion

Responsiveness is easy if we follow correct concepts. Here, the concepts of absolute and relative positioning in CSS have done the magic. Now we can play by adding different contents and effect on hover following the same basics.

Optimization with SASS

The problem with using CSS is that it can become repetitive when used in large projects. Like using same values of margins, paddings, radius. SASS provides a way to store these values in ONE variable and to use that variable instead.

SASS provides various concepts that optimize CSS. Like discussed above using variables for all the color names and fonts will remove the repetition. A piece of code from Open-Event-Webapp is shown below for declaring variable names.

//config.scss

@charset "UTF-8";
 
// Colors
$black: #000;
$white: #fff;
$red: #e2061c;
$gray-light: #c9c8c8;
$gray: #838282;
$gray-dark: #777;
$gray-extra-dark: #757575;
$gray-extra-light:#e7e7e7 !default;
$gray-perfect :#ddd;
$blue: #253652;
$orange: #e12b00;
$vivid-blue: #2196F3;
$pure-orange: #ff8700;
$light-purple: #ebccd1;
$red-dark: #e52d27;
$light-black: #333333;
$light-skyblue : #b7cdff !default;
$gray-trackshade: #999;
$blue-shade: #2482d3;
$dark-black: rgba(22, 22, 22, 0.99) !default;
$black-main:#232323 !default;
$timeroom-color:rgba(0,0,0,.10) !default;
$session-color: $gray-trackshade !default;
$header-color: #f8f8f8 !default;
$main-background: #fff !default;

// Corp-Colors
$corp-color: $white !default;
$corp-color-dark: darken($corp-color, 15%) !default;
$corp-color-second: $red !default;
$corp-color-second-dark: darken($corp-color-second, 15%) !default;

Nesting

SASS supports nesting concept. The nested SCSS changes to CSS when compiled. A good approach follows nesting elements to three-degree maximum.

// Nesting in application.scss session-list (Open-Event-Webapp)

.session{

  &-list {

    li{
     cursor: pointer;
      }
   .label {
     background: #ff8700;
     border-color: $light-purple;
     color: #FFFFFF;
     font-weight: 500;
     font-size: 80%;
     margin-left: -8px;
    }
   .session-title {
      margin-top: 0.1em;
       .session-link {
         font-size: 12px;
        }
    }
 }
 &-location{
 text-align: left;
 }

}

The output generated after compilation will be

//Code from schedule.css in Open-event-webapp

.session-list li {
 cursor: pointer; 
}

.session-list .label {
 background: #ff8700;
 border-color: #ebccd1;
 color: #FFFFFF;
 font-weight: 500;
 font-size: 80%;
 margin-left: -8px; 
}

.session-list .session-title {
 margin-top: 0.1em; 
}

 .session-list .session-title .session-link {
 font-size: 12px;
 }

.session-location {
 text-align: left; 
}

Mixins

Mixins are another way to optimize the SASS code. Mixins are just like functions that let us pass the values as parameters to make the code more flexible.

// Simple mixin for button
@mixin btn($color, $width, $height) {
 display: block;
 font: 16px “Open sans”, arial;
 color: $color;
 width: $width;
 height: $height;
}

Using these type of simple approaches make CSS more effective and efficient. It will enhance the workflow and help us to write cleaner code.

Responsive UI: Modifying Designs with Device Width

An important feature of websites these days with the advancement of smartphones is being responsive with device size. We nowadays not only worry about the various width of laptop or desktop, which don’t vary by a huge amount but also need to worry about tablets and phones which have a much lesser width. The website’s UI should not break and should be as easy to use on phones as it is on desktops/laptops. Using frameworks like bootstraps, Semantic-UI solves this problem to a large extent. But what if we need to modify certain parts by our own in case of mobile devices? How do we do that?

Continue reading Responsive UI: Modifying Designs with Device Width

Building interactive elements with HTML and javascript: Resizing

{ Repost from my personal blog @ https://blog.codezero.xyz/building-interactive-elements-with-html-and-javascript-resizing }

Unlike draggable, HTML/js does not provide us with a direct spec for allowing users to graphically resize HTML DOM elements. So, we’ll be using mouse events and pointer locations to achieve the ability of resizing.

We’ll start with a box div.

<div id="box">  
    <div>Resize me !</div>
</div>  

A little bit of CSS magic to make it look a little bit better and square.

#box {
    position: relative;
    width: 130px;
    height: 130px;
    background-color: #2196F3;
    color: white;
    display:flex;
    justify-content:center;
    align-items:center;
    border-radius: 10px;
}

Now, we need a handle element. The user will be using this handle element to drag and resize the box.

<div id="box">  
    <div>Resize me !</div>
    <div id="handle">
    </div>
</div>  

Now, we just have an invisible div. Let’s give it some color, make it square. We also have to position it at one corner of the box.

#handle {
    background-color: #727272;
    width: 10px;
    height: 10px;
    cursor: se-resize;
    position:absolute;
    right: 0;
    bottom: 0;
}

The parent div#box has the CSS property position: relative and by setting div#handle the property position:absolute, we have the ability to position the handle absolutely with respect to its parent.

Also, note the cursor: se-resize property. This instructs the browser to set the cursor to the resize cursor () when the user is over it.

Now, it’s upto to javascript to take over. :wink:

var resizeHandle = document.getElementById('handle');  
var box = document.getElementById('box');  

For resizing, the user would click on the handle and drag it. So, we need to start resizing the moment the user presses and holds on the handle. Let’s setup a function to listen for the mousedown event.

resizeHandle.addEventListener('mousedown', initialiseResize, false);  

the initialiseResize function should do two things:

  1. Resize the box every time the mouse pointer moves.
  2. Listen for mouseup event so that the event listeners can be removed as soon as the user is done resizing.
function initialiseResize(e) {  
    window.addEventListener('mousemove', startResizing, false);
    window.addEventListener('mouseup', stopResizing, false);
}
function startResizing(e) {  
    // Do resize here
}
function stopResizing(e) {  
    window.removeEventListener('mousemove', startResizing, false);
    window.removeEventListener('mouseup', stopResizing, false);
}

To resize the box according to the user’s mouse pointer movements, we’ll be taking the current x and y coordinates of the mouse pointer (in pixels) and change the box’s height and width accordingly.

function startResizing(e) {  
   box.style.width = (e.clientX) + 'px';
   box.style.height = (e.clientY) + 'px';
}

e.clientX gives the mouse pointer’s X coordinate and e.clientY gives the mouse pointer’s Y coordinate

Now, this works. But this would only work as expected if the box is placed in the top-left corner of the page. We’ll have to compensate for the box’s left and top offsets. (position from the left and top edges of the page)

function startResizing(e) {  
   box.style.width = (e.clientX - box.offsetLeft) + 'px';
   box.style.height = (e.clientY - box.offsetTop) + 'px';
}

There you go :smile: We can now resize the box !

https://jsfiddle.net/niranjan94/w8k1ffju/embedded

Working with Absolute Positioning

During the past week, I have done a lot of work for making the feature that allow the users to view the schedule of events according to track and time. The toughest part was to have a headstart to think of the mockup that fulfills this criterion.

After the mockup, I started coding it and realized that I have to add CSS by using Javascript. The frontend needs to calculate the top of each pop-up that appears when the track is hovered and to append the box just below it.

a

The interesting part was to calculate the top each time the element is hovered and to place the box at the right position by using jQuery.

Position Absolute 

The difficulty becomes maximum when we use “position : absolute “. As, it takes the element out of the layer. The element with absolute positioning is difficult to handle when it comes to responsiveness. Here also the pop-overs showing the speakers are to be made with absolute positioning.

The code snippet shows the calculation for exact position of the pop-up box.

$(document).ready(function(){

 $('.pop-box').hide();
 $('.item').hover(function (event) {

 event.preventDefault();
 event.stopPropagation();
 var track = $(event.target);
 var link = track.children(0);
 var offset =$(link).offset();

 var position= offset.top-link.height()-30;
 if( $(window).width()<600){
 var position= offset.top-link.height()-48; 
 }
 if(offset.top){
 
 $('.pop-box').hide();
 var p=$(this);
 $(p).next().show();
 var posY = event.pageY;
 nextOfpop=$(p).next();
 
 var toptrack = position ;

 $(nextOfpop).css({'top':toptrack
                 });

 $(document).mouseup(function (e)
 {
 var container = $(".pop-box");

  if (!container.is(e.target) 
  && container.has(e.target).length === 0 && (e.target)!=$('html').get(0)) 
   {
   container.hide();
   }
   });
  });
 })

This code sets the value of top of the pop-over in the variable position and copy it to toptrack that is passed to CSS to adjust the top dynamically.

Responsiveness for top

I was struggling a whole day to find out the best possible way for the responsiveness of track page. Obviously, the difficult part was the recalculation of top with the screen-size. Currently I have used $window.width() to check the width of screen and adjust the top on mobile. But, it will include more complexity when it is done for other screen sizes rather than mobile.

 if( $(window).width()<600){
 var position= offset.top-link.height()-48; 
 }

The tracks page is ready now with both light and dark theme.

10.png

That’s how the position absolute is handled with jQuery. To remove the complexity, all the CSS except the calculation of top is written with SASS.

Building interactive elements with HTML and javascript: Drag and Drop

{ Repost from my personal blog @ https://blog.codezero.xyz/building-interactive-elements-with-html-and-javascript-drag-and-drop }

Traditionally, all interactions in a website has been mostly via form inputs or clicking on links/button. The introduction of native Drag-and-drop as a part of the HTML5 spec, opened developers to a new way of Graphical input. So, how could this be implemented ?

Making any HTML element draggable is as simple as adding draggable="true" as an attribute.

<div id="a-draggable-div" draggable=true>  
    <h4>Drag me</h4>
</div>  

This will allow the user to drag div#a-draggable-div. Next, we need to designate a dropzone, into which the user can drop the div.

<div id="dropzone" ondragover="onDragOver(event)">  
</div>  
function onDragOver(e) {  
    // This function is called everytime 
    // an element is dragged over div#dropzone
    var dropzone = ev.target;

}

Now, the user will be able to drag the element. But, nothing will happen when the user drops it into the dropzone. We’ll need to define and handle that event. HTML5 provides ondrop attribute to bind to the drop event.

When the user drops the div into the drop zone, we’ll have to move the div from it’s original position into the drop zone. This has to be done in the drop event.

<div id="dropzone"  
ondrop="onDrop(event)"  
ondragover="onDragOver(event)"> </div>  
function onDrop(e) {  
    e.preventDefault();
    var draggableDiv = document.getElementById("a-draggable-div");
    draggableDiv.setAttribute("draggable", "false");
    e.target.appendChild(draggableDiv);
}

So, when the user drops the div into the drop zone, we’re disabling the draggable property of the div and appending it into the drop zone.

This is a very basic drag and drop implementation. It gets the job done. But, HTML5 provides us with more events to make the user’s experience even better 1.

Event Description
drag Fired when an element or text selection is being dragged.
dragend Fired when a drag operation is being ended (for example, by releasing a mouse button or hitting the escape key).
dragenter Fired when a dragged element or text selection enters a valid drop target.
dragexit Fired when an element is no longer the drag operation’s immediate selection target.
dragleave Fired when a dragged element or text selection leaves a valid drop target.
dragover Fired when an element or text selection is being dragged over a valid drop target
dragstart Fired when the user starts dragging an element or text selection.
drop Fired when an element or text selection is dropped on a valid drop target.

With these events a little bit of css magic a more user friendly experience can be created like highlighting the drop zones when the user starts to drag an element or changing the element’s text based on its state.

Demo:

https://jsfiddle.net/niranjan94/tkbcv3md/16/embedded/

External Resources:

SASS for the theme based concept

Until yesterday, I was exploring all around the internet, to find the best possible way for the theme concept in the web app. The theme concept allows an organizer to choose the theme for the web app from the set of provided themes.

After some time, I realised that this awesomeness to the web app can be added by using Syntactically Awesome Stylesheets.

How SASS supports the theme concept?

 

In the web app, a folder name _scss is added which has the directory structure as shown

tree
_scss folder directory structure

There is a file _config.scss inside the _base folder that includes the SASS variables which are used in all the files after importing it.

Each of the SASS variables uses a flag !default at the end, which means it can be overwritten in any other file. This property of SASS leads to the theme concept.

//_.config.scss

@charset "UTF-8";
 
// Colors
$black: #000;
$white: #fff;
$red: #e2061c;
$gray-light: #c9c8c8;
$gray: #838282;
$gray-dark: #333333;
$blue: #253652;
 
// Corp-Colors
$corp-color: $white !default;
$corp-color-dark: darken($corp-color, 15%) !default;
$corp-color-second: $red !default;
$corp-color-second-dark: darken($corp-color-second, 15%) !default;
 
// Fontbasic
$base-font-size: 1.8 !default;
$base-font-family: Helvetica, Arial, Sans-Serif !default;
$base-font-color: $gray-dark !default;
 
// Border
$base-border-radius: 2px !default;
$rounded-border-radius: 50% !default;
$base-border-color: $gray !default;

The main file that includes all the required style is the application.scss. Here, $corp-color takes default value from  _config.scss. It can be overwritten by the themes.

//application.scss

@charset 'UTF-8';

// 1.Base
@import '_base/_config.scss';

/* Offsets for fixed navbar */
body {
 margin-top: 50px;
 background-color:$corp-color !important;
}

Making a light theme 

 

The light theme will overwrite the $corp-color value to $gray-light which is defined in _config.scss. This will change the background-color defined in application.scss to #c9c8c8. So, in this way a light theme is generated. The similar approach can be followed to generate the dark theme.

//_light.scss

@charset 'UTF-8';
@import '../../_base/config';
// 1.Overwrite stuff
$corp-color: $gray-light;

@import '../../application';

Making a dark theme 

 

//_dark.scss

@charset 'UTF-8';
@import '../../_base/config';
// 1.Overwrite stuff
$corp-color: $gray;

@import '../../application';

How to compile the CSS from SASS files ?

 

  1. We can easily compile these SASS files by using command
    sass /path/application.scss /path/schedule.css

    For generating light theme and dark theme:

    sass /path/_light.scss  /path/schedule.css
    sass /path/_dark.scss  /path/schedule.css

Optimization of Code

 

SASS is very powerful for optimizing the code. It allows the concepts such as nesting, mixins which reduce the line of code. I have rewritten schedule.css into application.scss to make it more optimized.

/* Adjustments for smaller screens */

@media (min-width: 450px) {
 body {
 font-size: 14px
 }
 .session {
   &-list{
     .label{
         font-size: 90%;
         padding: .2em .6em .3em;
           }
         }
    &-title {
         float:left;
         width: 75%;
         }
    &-location {
         float: right;
         width: 25%;
         text-align: right;
        }
  }
}

Further Exploration

 

This is one of the ways to deal with the SASS structure, but there are other resources that can be helpful in dealing with SASS projects.

Also, check out, Jeremy Hexon article here.

New Color Schemes in Engelsystem

Engelsystem is a well-built MVC application. It seems to have everything an event manager could want. During the Week 2 of my Summer of Code, I worked on creating new color schemes/themes for the system. Engelsystem initially had 4 color schemes:

  1. Engelsystem cccamp15
    01

  2. Engelsystem 32C3

    02

  3. Engelsystem Dark

    03

  4. Engelsystem Light

    04

Color wields enormous sway over our attitudes and emotions. When our eyes take in a color, they communicate with a region of the brain known as the hypothalamus, which in turn sends a cascade of signals to the pituitary gland, on to the endocrine system, and then to the thyroid glands. The thyroid glands signal the release of hormones, which cause fluctuation in mood, emotion, and resulting behavior.

Research from QuickSprout indicates that 90% of all product assessments have to do with color. “Color,” writes Neil Patel, is “85% of the reason you purchased a specific product.” It’s a no-brainer fact of any website that color affects conversions. Big time.

So, the bottom line is: use the right colors, and you win.

Color schemes lets the user to set the system looks (i.e how the system will appear) which the user likes. During the week 2 of my Summer of Code, I worked on implementing 2 new color schemes for the system:

  1. Engelsystem color scheme-1

    05

  2. Engelsystem color scheme-2

    06

In the later weeks, other developers and I would be working on creating more themes and enhancing them. Anyone who would like to work in the project are welcome. Developers can feel free to take up any issues they would like to work on just like any other open source projects.

Development: https://github.com/fossasia/engelsystem                                           Issues/Bugs:https://github.com/fossasia/engelsystem/issues