Add Drill-Down support

Power BI visuals can use Power BI's drill-down.

Read more about Power BI drill-down here

Enable drill-down support in the visual

To support drill down in your visual, add a new field to capabilities.json named "drill-down", which has one property:

*roles - the name of the dataRole you want to enable drill-down on.

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 drill-down, users can drag multiple fields into the data role.

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 the visual with drill-down support

Run

pbiviz new testDrillDown -t default

to create a default sample visual. And 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
        // ...
    }

    private static parseSettings(dataView: DataView): VisualSettings {
        return <VisualSettings>VisualSettings.parse(dataView);
    }

    public enumerateObjectInstances(options: EnumerateVisualObjectInstancesOptions): VisualObjectInstance[] | VisualObjectInstanceEnumerationObject {
        return VisualSettings.enumerateObjectInstances(this.settings || VisualSettings.getDefault(), options);
    }
}

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.target = options.element;
        this.updateCount = 0;

        const new_p: HTMLElement = document.createElement("p");
        new_p.appendChild(document.createTextNode("Hierarchy level:"));
        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.target.appendChild(new_p);

        this.div = document.createElement("div"); // <== CREATE DIV ELEMENT
        this.target.appendChild(this.div);
    }
}

Update the update method of the visual to create buttons:

export class Visual implements IVisual {
    // ...

    public update(options: VisualUpdateOptions) {
        this.settings = Visual.parseSettings(options && options.dataViews && options.dataViews[0]);
        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 to test 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:

Screenshot shows the Power B I Desktop with New hierarchy selected in a contextual menu.

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

Screenshot shows category columns you can add to the new hierarchy.

After those steps you should get following visual:

Dev visual with buttons

Add context menu to visual elements

In this step you'll add context menu to the button's on the visual:

Context menu in the visual

To create context menu, 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";
// imports

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:

Screenshot shows the hierarchy with H2 called out.

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

Animation shows selecting Drill down and Drill up from the visual context menu.

Add drill-down support for matrix data view mapping

Prepare sample data to test the visual with matrix data view mappings:

Row1 Row2 Row3 Column1 Column2 Column3 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

Apply following dataview mapping for 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:

Screenshot shows the MatrixHierarchy with the columns and rows hierarchy and their members selected.

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.settings = Visual.parseSettings(options && options.dataViews && options.dataViews[0]);
        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));
}

At the final step you should get visual with context menu:

Animation shows a context menu for the visual with options to drill down or drill up.

Next steps

For more information, see Understand data view mapping in Power BI visuals.