Adding Interactivity to our DataTable

Now we will add interactivity to our datatable. We do this using event handlers and event triggers.

The first example implements a handler for the on_cell_clicked event trigger, which is called when the user clicks on a cell of the data editor. The event trigger receives the coordinates of the cell.

The state has a var called clicked_cell that will store a message about which cell was clicked. We define an event handler get_clicked_data that updates the value of the clicked_cell var when it is called. In essence, we have clicked on a cell, called the on_cell_clicked event trigger which calls the get_clicked_data event handler, which updates the clicked_cell var.

The event handler on_cell_context_menu can be used in the same way as on_cell_clicked, except here the event trigger is called when the user right clicks, i.e. when the cell should show a context menu.

Another important type of interactivity we will showcase is how to edit cells. Here we use the on_cell_edited event trigger to update the data based on what the user entered.

The on_cell_edited event trigger is called when the user modifies the content of a cell. It receives the coordinates of the cell and the modified content. We pass these into the get_edited_data event handler and use them to update the data state var at the appropriate position. We then update the edited_cell var value.

We can define group headers which are headers that encompass a group of columns. We define these in the columns using the group property such as "group": "Data". The columns would now be defined as below. Only the Title does not fall under a group header, all the rest fall under the Data group header.

The table now has a header as below.

There are several event triggers we can apply to the group header.

In this example we use the on_group_header_context_menu event trigger which is called when the user right-clicks on a group header. It returns the index and the data of the group header. We can also use the on_group_header_clicked and on_group_header_renamed event triggers which are called when the user left-clicks on a group header and when a user renames a group header respectively.

There are several other event triggers that are worth exploring. The on_item_hovered event trigger is called whenever the user hovers over an item in the datatable. The on_delete event trigger is called when the user deletes a cell from the datatable.

The final event trigger to check out is on_column_resize. on_column_resize allows us to respond to the user dragging the handle between columns. The event trigger returns the col we are adjusting and the new width we have defined. The col that is returned is a dictionary for example: {'title': 'Name', 'type': 'str', 'group': 'Data', 'width': 198, 'pos': 1}. We then index into self.cols defined in our state and change the width of that column using this code: self.cols[col['pos']]['width'] = width.