Add drill-down support

When a visual has a hierarchy, you can allow users to use the Power BI drill-down feature to reveal more details.

Read more about the Power BI drill-down feature at Drill mode in the Power BI service. To allows the visual to enable or disable the drill feature dynamically, see Dynamic drill-down control.

Enable drill-down support in the visual

To support drill-down actions in your visual, add a new field to capabilities.json named drill-down. This field has one property called roles that contains the name of the dataRole you want to enable drill-down actions on.

    "drilldown": {
        "roles": [
            "category"
        ]
    }

Note

The drill-down dataRole must be of Grouping type. max property in the dataRole conditions must be set to 1.

Once you add the role to the drill-down field, users can drag multiple fields into the data role.

For example:

{
    "dataRoles": [
        {
            "displayName": "Category",
            "name": "category",
            "kind": "Grouping"
        },
        {
            "displayName": "Value",
            "name": "value",
            "kind": "Measure"
        }
    ],
    "drilldown": {
        "roles": [
            "category"
        ]
    },
    "dataViewMappings": [
        {
            "categorical": {
                "categories": {
                    "for": {
                        "in": "category"
                    }
                },
                "values": {
                    "select": [
                        {
                            "bind": {
                                "to": "value"
                            }
                        }
                    ]
                }
            }
        }
    ]
}

Create a visual with drill-down support

To create a visual with drill-down support, run the following command:

pbiviz new testDrillDown -t default

To create a default sample visual, apply the above sample of capabilities.json to the newly created visual.

Create the property for div container to hold HTML elements of the visual:

"use strict";

import "core-js/stable";
import "./../style/visual.less";
// imports

export class Visual implements IVisual {
    // visual properties
    // ...
    private div: HTMLDivElement; // <== NEW PROPERTY

    constructor(options: VisualConstructorOptions) {
        // constructor body
        // ...
    }

    public update(options: VisualUpdateOptions) {
        // update method body
        // ...
    }

    /**
     * Returns properties pane formatting model content hierarchies, properties and latest formatting values, Then populate properties pane.
     * This method is called once each time we open the properties pane or when the user edits any format property. 
     */
    public getFormattingModel(): powerbi.visuals.FormattingModel {
        return this.formattingSettingsService.buildFormattingModel(this.formattingSettings);
    }
}

Update the constructor of the visual:

export class Visual implements IVisual {
    // visual properties
    // ...
    private div: HTMLDivElement;

    constructor(options: VisualConstructorOptions) {
        console.log('Visual constructor', options);
        this.formattingSettingsService = new FormattingSettingsService();
        this.target = options.element;
        this.updateCount = 0;

        if (document) {
            const new_p: HTMLElement = document.createElement("p");
            new_p.appendChild(document.createTextNode("Update count:"));
            const new_em: HTMLElement = document.createElement("em");
            this.textNode = document.createTextNode(this.updateCount.toString());
            new_em.appendChild(this.textNode);
            new_p.appendChild(new_em);
            this.div = document.createElement("div"); // <== CREATE DIV ELEMENT
            this.target.appendChild(new_p);
        }
    }
}

To create buttons, update the update visual's method:

export class Visual implements IVisual {
    // ...

    public update(options: VisualUpdateOptions) {
        this.formattingSettings = this.formattingSettingsService.populateFormattingSettingsModel(VisualFormattingSettingsModel, options.dataViews);
        console.log('Visual update', options);

        const dataView: DataView = options.dataViews[0];
        const categoricalDataView: DataViewCategorical = dataView.categorical;

        // don't create elements if no data
        if (!options.dataViews[0].categorical ||
            !options.dataViews[0].categorical.categories) {
            return
        }

        // to display current level of hierarchy
        if (typeof this.textNode !== undefined) {
            this.textNode.textContent = categoricalDataView.categories[categoricalDataView.categories.length - 1].source.displayName.toString();
        }

        // remove old elements
        // for better performance use D3js pattern:
        // https://d3js.org/#enter-exit
        while (this.div.firstChild) {
            this.div.removeChild(this.div.firstChild);
        }

        // create buttons for each category value
        categoricalDataView.categories[categoricalDataView.categories.length - 1].values.forEach( (category: powerbi.PrimitiveValue, index: number) => {
            let button = document.createElement("button");
            button.innerText = category.toString();

            this.div.appendChild(button);
        })

    }
    // ...

Apply simple styles in .\style\visual.less:

button {
    margin: 5px;
    min-width: 50px;
    min-height: 50px;
}

Prepare sample data for testing the visual:

H1	H2	H3	VALUES
A	A1	A11	1
A	A1	A12	2
A	A2	A21	3
A	A2	A22	4
A	A3	A31	5
A	A3	A32	6
B	B1	B11	7
B	B1	B12	8
B	B2	B21	9
B	B2	B22	10
B	B3	B31	11
B	B3	B32	12

And create Hierarchy in Power BI Desktop:

Include all category columns (H1, H2, H3) to the new hierarchy:

After those steps you should get following visual:

Add context menu to visual elements

To add a context menu to the buttons on the visual:

Save host object in the properties of the visual and call createSelectionManager method to the create selection manager to display a context menu by using Power BI Visuals API.

"use strict";

import "core-js/stable";
import "./../style/visual.less";
// default imports

import IVisualHost = powerbi.extensibility.visual.IVisualHost;
import ISelectionManager = powerbi.extensibility.ISelectionManager;
import ISelectionId = powerbi.visuals.ISelectionId;

export class Visual implements IVisual {
    // visual properties
    // ...
    private div: HTMLDivElement;
    private host: IVisualHost; // <== NEW PROPERTY
    private selectionManager: ISelectionManager; // <== NEW PROPERTY

    constructor(options: VisualConstructorOptions) {
        // constructor body
        // save the host in the visuals properties
        this.host = options.host;
        // create selection manager
        this.selectionManager = this.host.createSelectionManager();
        // ...
    }

    public update(options: VisualUpdateOptions) {
        // update method body
        // ...
    }

    // ...
}

Change the body of forEach function callback to:

    categoricalDataView.categories[categoricalDataView.categories.length - 1].values.forEach( (category: powerbi.PrimitiveValue, index: number) => {
        // create selectionID for each category value
        let selectionID: ISelectionId = this.host.createSelectionIdBuilder()
            .withCategory(categoricalDataView.categories[0], index)
            .createSelectionId();

        let button = document.createElement("button");
        button.innerText = category.toString();

        // add event listener to click event
        button.addEventListener("click", (event) => {
            // call select method in the selection manager
            this.selectionManager.select(selectionID);
        });

        button.addEventListener("contextmenu", (event) => {
            // call showContextMenu method to display context menu on the visual
            this.selectionManager.showContextMenu(selectionID, {
                x: event.clientX,
                y: event.clientY
            });
            event.preventDefault();
        });

        this.div.appendChild(button);
    });

Apply data to the visual:

In the final step you should get visual with selections and context menu:

Add drill-down support for matrix data view mapping

To test the visual with matrix data view mappings, first prepare sample data:

Row 1	Row 2	Row 3	Column 1	Column 2	Column 3	Values
R1	R11	R111	C1	C11	C111	1
R1	R11	R112	C1	C11	C112	2
R1	R11	R113	C1	C11	C113	3
R1	R12	R121	C1	C12	C121	4
R1	R12	R122	C1	C12	C122	5
R1	R12	R123	C1	C12	C123	6
R1	R13	R131	C1	C13	C131	7
R1	R13	R132	C1	C13	C132	8
R1	R13	R133	C1	C13	C133	9
R2	R21	R211	C2	C21	C211	10
R2	R21	R212	C2	C21	C212	11
R2	R21	R213	C2	C21	C213	12
R2	R22	R221	C2	C22	C221	13
R2	R22	R222	C2	C22	C222	14
R2	R22	R223	C2	C22	C223	16
R2	R23	R231	C2	C23	C231	17
R2	R23	R232	C2	C23	C232	18
R2	R23	R233	C2	C23	C233	19

Then apply the following data view mapping to the visual:

{
    "dataRoles": [
        {
            "displayName": "Columns",
            "name": "columns",
            "kind": "Grouping"
        },
        {
            "displayName": "Rows",
            "name": "rows",
            "kind": "Grouping"
        },
        {
            "displayName": "Value",
            "name": "value",
            "kind": "Measure"
        }
    ],
    "drilldown": {
        "roles": [
            "columns",
            "rows"
        ]
    },
    "dataViewMappings": [
        {
            "matrix": {
                "columns": {
                    "for": {
                        "in": "columns"
                    }
                },
                "rows": {
                    "for": {
                        "in": "rows"
                    }
                },
                "values": {
                    "for": {
                        "in": "value"
                    }
                }
            }
        }
    ]
}

Apply data to the visual:

Import required interfaces to process matrix data view mappings:

// ...
import DataViewMatrix = powerbi.DataViewMatrix;
import DataViewMatrixNode = powerbi.DataViewMatrixNode;
import DataViewHierarchyLevel = powerbi.DataViewHierarchyLevel;
// ...

Create two properties for two divs of rows and columns elements:

export class Visual implements IVisual {
    // ...
    private rowsDiv: HTMLDivElement;
    private colsDiv: HTMLDivElement;
    // ...
    constructor(options: VisualConstructorOptions) {
        // constructor body
        // ...
        // Create div elements and append to main div of the visual
        this.rowsDiv = document.createElement("div");
        this.target.appendChild(this.rowsDiv);

        this.colsDiv = document.createElement("div");
        this.target.appendChild(this.colsDiv);
    }
    // ...
}

Check the data before rendering elements and display the current level of hierarchy:

export class Visual implements IVisual {
    // ...
    constructor(options: VisualConstructorOptions) {
        // constructor body
    }

    public update(options: VisualUpdateOptions) {
        this.formattingSettings = this.formattingSettingsService.populateFormattingSettingsModel(VisualFormattingSettingsModel, options.dataViews);
        console.log('Visual update', options);

        const dataView: DataView = options.dataViews[0];
        const matrixDataView: DataViewMatrix = dataView.matrix;

        // if the visual doesn't receive the data no reason to continue rendering
        if (!matrixDataView ||
            !matrixDataView.columns ||
            !matrixDataView.rows ) {
            return
        }

        // to display current level of hierarchy
        if (typeof this.textNode !== undefined) {
            this.textNode.textContent = categoricalDataView.categories[categoricalDataView.categories.length - 1].source.displayName.toString();
        }
        // ...
    }
    // ...
}

Create function treeWalker for traverse the hierarchy:

export class Visual implements IVisual {
    // ...
    public update(options: VisualUpdateOptions) {
        // ...

        // if the visual doesn't receive the data no reason to continue rendering
        if (!matrixDataView ||
            !matrixDataView.columns ||
            !matrixDataView.rows ) {
            return
        }

        const treeWalker = (matrixNode: DataViewMatrixNode, index: number, levels: DataViewHierarchyLevel[], div: HTMLDivElement)  => {
            // ...
            if (matrixNode.children) {
                // ...
                // traversing child nodes
                matrixNode.children.forEach((node, index) => treeWalker(node, index, levels, childDiv));
            }
        }

        // traversing rows
        const rowRoot: DataViewMatrixNode = matrixDataView.rows.root;
        rowRoot.children.forEach((node, index) => treeWalker(node, index, matrixDataView.rows.levels, this.rowsDiv));

        // traversing columns
        const colRoot = matrixDataView.columns.root;
        colRoot.children.forEach((node, index) => treeWalker(node, index, matrixDataView.columns.levels, this.colsDiv));
    }
    // ...
}

Generate the selections for datapoints.

const treeWalker = (matrixNode: DataViewMatrixNode, index: number, levels: DataViewHierarchyLevel[], div: HTMLDivElement)  => {
    // generate selectionID for each node of matrix
    const selectionID: ISelectionID = this.host.createSelectionIdBuilder()
        .withMatrixNode(matrixNode, levels)
        .createSelectionId();
    // ...
    if (matrixNode.children) {
        // ...
        // traversing child nodes
        matrixNode.children.forEach((node, index) => treeWalker(node, index, levels, childDiv));
    }
}

Create div for each level of hierarchy:

const treeWalker = (matrixNode: DataViewMatrixNode, index: number, levels: DataViewHierarchyLevel[], div: HTMLDivElement)  => {
    // generate selectionID for each node of matrix
    const selectionID: ISelectionID = this.host.createSelectionIdBuilder()
        .withMatrixNode(matrixNode, levels)
        .createSelectionId();
    // ...
    if (matrixNode.children) {
        // create div element for level
        const childDiv = document.createElement("div");
        // add to current div
        div.appendChild(childDiv);
        // create paragraph element to display next
        const p = document.createElement("p");
        // display level name on paragraph element
        const level = levels[matrixNode.level];
        p.innerText = level.sources[level.sources.length - 1].displayName;
        // add paragraph element to created child div
        childDiv.appendChild(p);
        // traversing child nodes
        matrixNode.children.forEach((node, index) => treeWalker(node, index, levels, childDiv));
    }
}

Create buttons to interact with visual and display context menu for matrix datapoints:

const treeWalker = (matrixNode: DataViewMatrixNode, index: number, levels: DataViewHierarchyLevel[], div: HTMLDivElement)  => {
    // generate selectionID for each node of matrix
    const selectionID: ISelectionID = this.host.createSelectionIdBuilder()
        .withMatrixNode(matrixNode, levels)
        .createSelectionId();

    // create button element
    let button = document.createElement("button");
    // display node value/name of the button's text
    button.innerText = matrixNode.value.toString();

    // add event listener on click
    button.addEventListener("click", (event) => {
        // call select method in the selection manager
        this.selectionManager.select(selectionID);
    });

    // display context menu on click
    button.addEventListener("contextmenu", (event) => {
        // call showContextMenu method to display context menu on the visual
        this.selectionManager.showContextMenu(selectionID, {
            x: event.clientX,
            y: event.clientY
        });
        event.preventDefault();
    });

    div.appendChild(button);

    if (matrixNode.children) {
        // ...
    }
}

Clear div elements before render elements again:

public update(options: VisualUpdateOptions) {
    // ...
    const treeWalker = (matrixNode: DataViewMatrixNode, index: number, levels: DataViewHierarchyLevel[], div: HTMLDivElement)  => {
        // ...
    }

    // remove old elements
    // to better performance use D3js pattern:
    // https://d3js.org/#enter-exit
    while (this.rowsDiv.firstChild) {
        this.rowsDiv.removeChild(this.rowsDiv.firstChild);
    }
    // create label for row elements
    const prow = document.createElement("p");
    prow.innerText = "Rows";
    this.rowsDiv.appendChild(prow);

    while (this.colsDiv.firstChild) {
        this.colsDiv.removeChild(this.colsDiv.firstChild);
    }
    // create label for columns elements
    const pcol = document.createElement("p");
    pcol.innerText = "Columns";
    this.colsDiv.appendChild(pcol);

    // render elements for rows
    const rowRoot: DataViewMatrixNode = matrixDataView.rows.root;
    rowRoot.children.forEach((node, index) => treeWalker(node, index, matrixDataView.rows.levels, this.rowsDiv));

    // render elements for columns
    const colRoot = matrixDataView.columns.root;
    colRoot.children.forEach((node, index) => treeWalker(node, index, matrixDataView.columns.levels, this.colsDiv));
}

Finally, you should get a visual with context menu:

Related content

• How to use the drill down support API
• Dynamic drill-down control