I was stuck with that problem too, it is very difficult because the plugin compose the calendar in an odd way, using some tables and locating the events with dynamically with a position absolute and varying the css top property.
However i found a generic solution that works very good. First i will show you the code, and them i will explain what exactly the code does.
I use the option eventAfterAllRender of the fullCalendar. This is an example working.
I use moment for manage time and i assume the id of the fullCalendar html element is 'Calendar'.
eventAfterAllRender: function() {
// define static values, use this values to vary the event item height
var defaultItemHeight = 25;
var defaultEventItemHeight = 18;
// ...
// find all rows and define a function to select one row with an specific time
var rows = [];
$('div.fc-slats > table > tbody > tr[data-time]').each(function() {
rows.push($(this));
});
var rowIndex = 0;
var getRowElement = function(time) {
while (rowIndex < rows.length && moment(rows[rowIndex].attr('data-time'), ['HH:mm:ss']) <= time) {
rowIndex++;
}
var selectedIndex = rowIndex - 1;
return selectedIndex >= 0 ? rows[selectedIndex] : null;
};
// reorder events items position and increment row height when is necessary
$('div.fc-content-col > div.fc-event-container').each(function() { // for-each week column
var accumulator = 0;
var previousRowElement = null;
$(this).find('> a.fc-time-grid-event.fc-v-event.fc-event.fc-start.fc-end').each(function() { // for-each event on week column
// select the current event time and its row
var currentEventTime = moment($(this).find('> div.fc-content > div.fc-time').attr('data-full'), ['h:mm A']);
var currentEventRowElement = getRowElement(currentEventTime);
// the current row has to more than one item
if (currentEventRowElement === previousRowElement) {
accumulator++;
// move down the event (with margin-top prop. IT HAS TO BE THAT PROPERTY TO AVOID CONFLICTS WITH FullCalendar BEHAVIOR)
$(this).css('margin-top', '+=' + (accumulator * defaultItemHeight).toString() + 'px');
// increse the heigth of current row if it overcome its current max-items
var maxItemsOnRow = currentEventRowElement.attr('data-max-items') || 1;
if (accumulator >= maxItemsOnRow) {
currentEventRowElement.attr('data-max-items', accumulator + 1);
currentEventRowElement.css('height', '+=' + defaultItemHeight.toString() + 'px');
}
} else {
// reset count
rowIndex = 0;
accumulator = 0;
}
// set default styles for event item and update previosRow
$(this).css('left', '0');
$(this).css('right', '7px');
$(this).css('height', defaultEventItemHeight.toString() + 'px');
$(this).css('margin-right', '0');
previousRowElement = currentEventRowElement;
});
});
// this is used for re-paint the calendar
$('#calendar').fullCalendar('option', 'aspectRatio', $('#calendar').fullCalendar('option', 'aspectRatio'));
}
How the code works:
First i found all tr elements that are the rows of my calendar (note that they contains an attribute with its owns time).
Later I iterate for each column and get, for each one, its events items. Each event item is an anchor element with some inner child with the date as an attribute data-full.
From the event i peek what should be its row, and in that row if there are more than one item, then increase the position where the event item should be located. I use for that the margin-top property because this property is not used or readjust by the plugin (don't use top property).
In the row i set a data attribute to take the max amount of events that has any column of that row. With that, i can calculate if the row must be increase its height or not.
Well, this is basically what the codes does. If you have some question please do-it.