Implementing the PDF download of Schedule in Open Event Web app

Open Event Web app now provides an option to its users to download the PDF of event schedule. Earlier it supported the download of list-view only, now it provides the support to download calendar-view as well. The problem incurred while downloading the calendar-view was that the view gets cropped due to limitations with the library used for PDF generation, thus only some parts of the calendar remained in the PDF. The problem is resolved by creating an image for every date in the schedule and adding the generated image to the PDF.

Selecting and adding the data for PDF generation

The data to be added to PDF depending on the filters and date-selectors applied is chosen from the DOM. Selection of data is done by looping through all the dates and adding only the ones which do not have ‘hide’ class added to them. The selected dates are first expanded such that their complete view is available while generating the image. The complete data is stored in a variable depending on if the complete schedule is requested for download or some filter is applied, which is later used for generating the image.

let fullScheduler = true;
let mapValue = '';

pdf = new jsPDF('l', 'pt', 'a1');
$('.calendar').each(function() {
 let hidePresent = $(this).attr('class').split(' ').indexOf('hide') <= 0;

 if (hidePresent) {
   $timeline = $(this);

  // Expanding the schedule for current date
 fullScheduler = hidePresent && fullScheduler;

if(fullScheduler) {
 $timeline = $('.calendar').parent();
 mapValue = $timeline.children();

Adding the notification while generating the PDF

A loader with the notification is added to provide better user experience, as the PDF generation takes place at the time of request itself it may take some time depending on the size of the schedule. The notifications are added using ‘sweetalert’ library already added for Add to calendar notifications.

swal("Generating the PDF",{
 icon: "./images/loader.gif",
 buttons: false

Downloading the PDF

The selected dates are stored in an array named ‘schedArr’ whose data sequentially is passed for canvas generation. A new page is added to the PDF of size equal to canvas and the generated canvas is added to that page. With every new page added to the calendar a count is increased to keep a track if all the selected dates are added to PDF.

async.eachSeries(schedArr, function (child, callback) {
 html2canvas(child, {
   onrendered: function (canvas) {
     pdf.addPage(canvas.width, canvas.height); = initialWidth[count] + 'px';
     pdf.addImage(canvas, 'png', 0, 0, canvas.width, canvas.height);
     if(currDate === schedArr.length){
       swal.close(); + '.pdf');

When the last page is added, the notification is closed and user is prompted to download pop-box.


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Implementing Scheduler Actions on Open Event Frontend

After the functionality to display scheduled sessions was added to Open Event Frontend, the read-only implementation of the scheduler had been completed. What was remaining now in the scheduler were the write actions, i.e., the sessions’ scheduling which event organizers do by deciding its timings, duration and venue.

First of all, these actions required the editable flag to be true for the fullcalendar plugin. This allowed the sessions displayed to be dragged and dropped. Once this was enabled, the next task was to embed data in each of the unscheduled sessions so that when they get dropped on the fullcalendar space, they get recognized by the calendar, which can place it at the appropriate location. For this functionality, they had to be jQuery UI draggables and contain an “event” data within them. This was accomplished by the following code:

  zIndex         : 999,
  revert         : true,      // will cause the event to go back to its
  revertDuration : 0  //  original position after the drag

this.$().data('event', {
  title    : this.$().text().replace(/\s\s+/g, ' '), // use the element's text as the event title
  id       : this.$().attr('id'),
  serverId : this.get(''),
  stick    : true, // maintain when user navigates (see docs on the renderEvent method)
  color    : this.get('session.track.color')

Here, “this” refers to each unscheduled session. Note that the session color is fetched via the corresponding session track. Once the unscheduled sessions contain enough relevant data and are of the right type (i.e, jQuery UI draggable type), they’re ready to be dropped on the fullcalendar space.

Now, when an unscheduled session is dropped on the fullcalendar space, fullcalendar’s eventReceive callback is triggered after its drop callback. In this callback, the code removes the session data from the unscheduled sessions’ list, so it disappears from there and gets stuck to the fullcalendar space. Then the code in the drop callback makes a PATCH request to Open Event Server with the relevant data, i.e, start and end times as well as microlocation. This updates the corresponding session on the server.

Similarly, another callback is generated when an event is resized, which means when its duration is changed. This again sends a corresponding session PATCH request to the server. Furthermore, the functionality to pop a scheduled event out of the calendar and add it back to the unscheduled sessions’ list is also implemented, just like in Eventyay version 1. For this, a cross button is implemented, which is embedded in each scheduled session. Clicking this pops the session out of the calendar and adds it back to the unscheduled sessions list. Again, a corresponding PATCH request is sent to the server.

After getting the response of such requests, a notification is displayed on the screen, which informs the users whether the action was successful or not. The main PATCH functionality is in a separate function which is called by different callbacks accordingly, so code reusability is increased:

updateSession(start, end, microlocationId, sessionId) {
    let payload = {
      data: {
        attributes: {
          'starts-at' : start ? start.toISOString() : null,
          'ends-at'   : end ? end.toISOString() : null
        relationships: {
          microlocation: {
            data: {
              type : 'microlocation',
              id   : microlocationId
        type : 'session',
        id   : sessionId

    let config = {
      skipDataTransform: true
    return this.get('loader')
      .patch(`sessions/${sessionId}`, JSON.stringify(payload), config)
      .then(() => {
        this.get('notify').success('Changes have been made successfully');
      .catch(reason => {
        this.set('error', reason);
        this.get('notify').error(`Error: ${reason}`);

This completes the scheduler implementation on Open Event Frontend. Here is how it looks in action:

scheduler actions.gif


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Using TabLayouts in your Android app

So while making a sessions schedule for the open event app, I wanted to separate the sessions on the basis of the days they are scheduled for to improve the visual clarity. So to do this I had various approaches like add a filter to separate by date or add checkboxes to show only checked dates but I though they’d look ugly. Instead the best option was to add tabs in a fragment with a viewpager to scroll within them : It looks appealing, has simple and clean UI, easier to implement with the new design library. So, naturally I opted for using the Tablayout from the design Library.

Earlier, when the Support design library was not introduce, it was really a tedious job to add it to our app since we had to extend Listeners to check for tab changes and we had to manually open fragments when a tab was selected or unselected or even when it was reselected. Essentially this meant a lot of errors and memory leaks. In the design library we essentially need to add tablayout and a viewpager to our layout like this :

< xmlns:android=""

        app:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar" />

        android:background="@android:color/white" />


Next in our activity/ fragment, we can just inflate this view and create an adapter for the viewpager extending a FragmentPagerAdapter:

public class OurAdapter extends FragmentPagerAdapter {
    private final List<Fragment> mFragmentList = new ArrayList<>();
    private final List<String> mFragmentTitleList = new ArrayList<>();

    public ScheduleViewPagerAdapter(FragmentManager manager) {

    public Fragment getItem(int position) {
        return mFragmentList.get(position);

    public int getCount() {
        return mFragmentList.size();

    public void addFragment(Fragment fragment, String title, int day) {


    public CharSequence getPageTitle(int position) {
        return mFragmentTitleList.get(position);

Now I had to make dynamic number of tabs, since I wanted the app to customisable on the number of days listed in the json downloaded from the server. So, I made some changes in the traditional code. This is what we do in our activity/fragment’s onCreate/OnCreatView :

viewPager = (ViewPager) view.findViewById(;

for (int i = 0; i < daysofEvent; i++) {
    adapter.addFragment(new DayScheduleFragment(),title, dayNo);

scheduleTabLayout = (TabLayout) view.findViewById(;

This is it. Now we have a basic working tablayout in a viewpager. This also has the capability to change according to the number of days specified in the json we have written.

Earlier without the design library, we would have to even add switch cases in the FragmentPagerAdapter like this :

public class OurAdapter extends FragmentPagerAdapter {
 public TabsPagerAdapter(FragmentManager fm) {
 public Fragment getItem(int index) {
 switch (index) {
 case 0:
    return new FirstFragment();
 case 1:
    return new SecondFragment();
 case 2:
    return new ThirdFragment();
 return null;

Then we would have to override methods to listen to activities in tabs :

public void onTabReselected(Tab tab, FragmentTransaction ft) {

public void onTabSelected(Tab tab, FragmentTransaction ft) {
// on tab selected
// show respected fragment view

public void onTabUnselected(Tab tab, FragmentTransaction ft) {

And more code to listen for swiping within tabs in a viewpager:

* on swiping the viewpager make respective tab selected
viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {

public void onPageSelected(int position) {

// on changing the page
// make respected tab selected

public void onPageScrolled(int arg0, float arg1, int arg2) {

public void onPageScrollStateChanged(int arg0) {

You see how easy this got with the inclusion of TabLayout.

Now for the final product I made after inflating the fragments and adding recyclerviews for the schedule, I got this :

Swipable tabs

I urge you to try swipable tabs in your app as well. Adios till next time.

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Webapp: The generator for making schedule pages

Why a static HTML generator


Before we start working on more advanced features like push notifications and iCal exports etc, we have been working on getting a generator (a simple node.js script) up, that can take data for an event either in form of json files, or from a given API in open-event data format, and generate a schedule page.

It has been used to generate the programm page of OpenTechSummit 2016 (

It is based on the open-event-scraper   project of FOSSASIA, and some more features had been added when developing it for OTS16. Some of the new features include –

  • Ability to define copyright and license in the API/Json, and generator adds it in the footer
  • Ability to define sponsors (support for upto 3 levels are there), and the generator adds sponsor logos with links at the bottom of the page.
  • Ability to embed audio, slides and videos into the session cards.

How the process works

Right now if you take a look at the open-event-scraper project under opentechsummit (which is a fork from the FOSSASIA repo, and being used to develop the new features) , you’ll see the process goes like this –

  1. The file scrapes data about sessions and speakers from an internal Google Sheet we have. Then the file gets data about the event itself (copyright, links to social channels).

    This step is not needed if we are using a JSON API endpoint. This is needed only if the data source is a Google Sheet, then local JSON files are created.

  2. Once we have an endpoint or JSON files locally downloaded, there a node.js script – generator.js   which generates a static HTML page.
  3. The generated HTML page is based on a handelbars template – schedule.tpl where all the required markup is there.
  4. And finally there is our own stylesheet which is called schedule.css  and is a very lightweight styling addition, on top of what is majorly a vanilla bootstrap layout.

The road ahead

Going forward we will pull back in this source code to our main repo .

Then we’ll add some parameters that can be fed to generator.js when calling it, like  –

  • Name of event
  • Color scheme
  • URL of endpoints

This will have a minimal form-like frontend

We can host this on heroku then, where filling the form, will run the generator.js and the generated HTML and associated CSS files will be available as a zip.

Continue ReadingWebapp: The generator for making schedule pages