Custom Lightbox

Ways of creating a custom lightbox

You can create a fully custom lightbox for Gantt and replace the default one with it. There are two possible ways to do it:

1. By redefining the showLightbox() method:

gantt.showLightbox = (id) => {
    // code of the custom form
};

• id - (string/number) - the task ID

There's also the hideLightbox() method that will help in the lightbox implementation.

Let's create an HTML container "my-form" where we'll put a custom lightbox:

<div id="my-form">
    <label for="description">Task text
        <input type="text" name="description" value=""/>
    </label>
    <input type="button" name="save" value="Save"/>
    <input type="button" name="close" value="Close"/>
    <input type="button" name="delete" value="Delete"/>
</div>

Then to make a custom lightbox, you can use the configuration similar to this:

let currentTaskId = null;

gantt.showLightbox = (id) => {
    currentTaskId = id;
    const task = gantt.getTask(id);

    const form = getForm();
    const descriptionInput = form.querySelector("[name='description']");
    descriptionInput.focus();
    descriptionInput.value = task.text;

    form.style.display = "block";

    form.querySelector("[name='save']").onclick = save;
    form.querySelector("[name='close']").onclick = cancel;
    form.querySelector("[name='delete']").onclick = remove;
};

gantt.hideLightbox = () => {
    getForm().style.display = "";
    currentTaskId = null;
};

function getForm() {
    return document.getElementById("my-form");
}

function save() {
    const task = gantt.getTask(currentTaskId);

    task.text = getForm().querySelector("[name='description']").value;

    if (task.$new) {
        delete task.$new;
        gantt.addTask(task, task.parent);
    } else {
        gantt.updateTask(task.id);
    }

    gantt.hideLightbox();
}

function cancel() {
    const task = gantt.getTask(currentTaskId);

    if (task.$new) {
        gantt.deleteTask(task.id);
    }

    gantt.hideLightbox();
}

function remove() {
    gantt.deleteTask(currentTaskId);
    gantt.hideLightbox();
}

2. Use the onBeforeLightbox event. In this case, the algorithm of actions is the following:

• detect when the lightbox is about to be shown
• block the default lightbox
• show a custom form and fill in the task data

gantt.attachEvent("onBeforeLightbox", (id) => {
    const task = gantt.getTask(id);

    if (task.$new) {
        dhtmlx.confirm({
            text: "Create task?",
            callback: (confirmed) => {
                if (confirmed) {
                    //..apply values
                    delete task.$new;
                    gantt.addTask(task);
                } else {
                    gantt.deleteTask(task.id);
                }
            }
        });

        return false;
    }

    return true;
});

Processing actions in the custom form

When the user saves the form, you'll need to manually get form values and update the appropriate task using the public API: addTask(), updateTask(), and deleteTask().

Note that when a lightbox is triggered by a new task, for example by clicking the 'plus' button, and should be deleted if the user clicks 'Cancel' to revert task creation, the task object will have the '$new' property set.

You can process lightbox closing, as shown in the example below. The action type, "save", "cancel", or "delete", is passed as the "action" parameter:

switch (action) {
    case "save":
        task.text = ""; // apply values from form

        // Add a new task or update an existing one.
        if (task.$new) {
            delete task.$new;
            gantt.addTask(task, task.parent);
        } else {
            gantt.updateTask(id);
        }

        break;
    case "cancel":
        // If the user cancels creation of a new task, delete it.
        if (task.$new) {
            gantt.deleteTask(id);
        }

        break;
    case "delete":
        gantt.deleteTask(id);
        break;
}