Open a Modal Dialog Using Web API

Last modified: May 4, 2026

Introduction

This how-to describes how to open a modal dialog in Studio Pro from an extension. You can use this dialog to display web content.

It also describes how to show a progress dialog that follows a sequence of steps and returns a result when complete.

Prerequisites

If you are using Studio Pro 11.0–11.5 and your extension includes menus, your existing menu code will not work when you upgrade to Studio Pro 11.6. To restore full functionality and support, upgrade to the Extensibility API 11.6 and follow the steps in the Migration Guide.

Before starting this how-to, complete the following prerequisites:

This how-to uses the results of Get Started with the Web Extensibility API. Complete that how-to before starting this one.
Be familiar with creating menus as described in Create a Menu Using Web API.

To open a modal dialog, create a menu item inside the loaded event in the main entry point (src/main/index.ts). For more information, see Create a Menu Using Web API.

In the menuItemActivated listener event, call studioPro.ui.dialogs.showModal(<dialogInfo>, <uiSpec>) to open a new dialog. The parameters are:

<dialogInfo> – An object containing the title of the dialog (shown in the title bar of your dialog in Studio Pro) and the contentSize object, where you can provide height and width dimensions for the dialog.
<uiSpec> – An object containing two required properties and one optional property:
- componentName – The name of the extension prefixed with extension/. For example, extension/myextension.
- uiEntryPoint – The name mapped from the manifest.json file.
- queryParams (optional) – A key-value pair object for passing data to your web content inside the dialog.

When the showModal method is called, it returns a Promise of unknown or null. This return value represents anything the web content determines should be returned when the dialog closes. The API cannot determine the type in advance, since it can be anything.

In the example below, the dialog contains a form where an object is modified and then returned when the dialog closes.

The following example shows the main entry point (src/main/index.ts) that opens a modal dialog:

import { IComponent, getStudioProApi } from "@mendix/extensions-api";

const menuId = "myextension.ShowModalDialog";

export const component: IComponent = {
    async loaded(componentContext) {
        const studioPro = getStudioProApi(componentContext);

        // Add a menu item to the Extensions menu
        await studioPro.ui.extensionsMenu.add({
            menuId: menuId,
            caption: "Show modal dialog",
            action: async () => {
                const result = await studioPro.ui.dialogs.showModal(
                    {
                        title: "Modal Dialog",
                        contentSize: { height: 170, width: 400 }
                    },
                    {
                        componentName: "extension/myextension",
                        uiEntrypoint: "dialog"
                    }
                );

                if (result !== null) await studioPro.ui.messageBoxes.show("info", JSON.stringify(result));
            }
        });
    }
};

Filling the Dialog with Content

In the previous example, the uiEntryPoint property of the <uispec> object has the value dialog. This value must match the one in the manifest. The following example shows the dialog under the ui property:

{
  "mendixComponent": {
    "entryPoints": {
      "main": "main.js",
      "ui": {
        "dialog": "dialog.js"
      }
    }
  }
}

Update build-extension.mjs to match the manifest with an entry for the new dialog entry point. Add the src/ui/dialog.tsx endpoint to your build script and make sure the variable appDir remains unchanged:

 import * as esbuild from 'esbuild'
 import {copyToAppPlugin, copyManifestPlugin, commonConfig} from "./build.helpers.mjs"
 import parseArgs from "minimist"

 const outDir = `dist/myextension`
 const appDir = "<path to your application>"
 const extensionDirectoryName = "extensions"

 const entryPoints = [
     {
         in: 'src/main/index.ts',
         out: 'main'
     }   
 ]

 entryPoints.push({
     in: 'src/ui/dialog.tsx',
     out: 'dialog'
 })

 const args = parseArgs(process.argv.slice(2))
 const buildContext = await esbuild.context({
   ...commonConfig,
   outdir: outDir,
   plugins: [copyManifestPlugin(outDir), copyToAppPlugin(appDir, outDir, extensionDirectoryName)],
   entryPoints
 })

 if('watch' in args) {
     await buildContext.watch();
 } 
 else {
     await buildContext.rebuild();
     await buildContext.dispose();
 }

Add the dialog.tsx file for the web content inside the src/ui directory:

  import { getStudioProApi, IComponent } from "@mendix/extensions-api";
  import React, { FormEvent, StrictMode } from "react";
  import { createRoot } from "react-dom/client";

  const dialogId = new URLSearchParams(location.search).get("dialogId")!;
  const person: { firstName?: string; lastName?: string } = {
      firstName: undefined,
      lastName: undefined,
  };

  export const component: IComponent = {
      async loaded(componentContext) {
          const studioPro = getStudioProApi(componentContext);

          const handleSubmit = (e: FormEvent<HTMLFormElement>) => {
              e.preventDefault();
              studioPro.ui.dialogs.closeWithResult(
                  dialogId,
                  JSON.stringify(person)
              );
          };

          createRoot(document.getElementById("root")!).render(
              <StrictMode>
                  <form onSubmit={handleSubmit}>
                      <p>
                          {" "}
                          <input
                              placeholder="First Name"
                              value={person.firstName}
                              onChange={(e) =>
                                  (person.firstName = e.target.value)
                              }
                          />
                      </p>
                      <p>
                          {" "}
                          <input
                              placeholder="Surname"
                              value={person.lastName}
                              onChange={(e) => (person.lastName = e.target.value)}
                          />
                      </p>
                      <p>
                          <button type="submit">Submit</button>
                          <button
                              type="button"
                              onClick={(_) =>
                                  studioPro.ui.dialogs.close(dialogId)
                              }
                          >
                              Cancel
                          </button>
                      </p>
                  </form>
              </StrictMode>
          );
      },
  };

The dialogId property is retrieved from the query parameters of the web page. This value is generated when the dialog API is first called. It is then passed back to the web content so the close or closeWithResult methods can be called successfully. The dialog API needs this ID to close the correct dialog.

This form contains two text boxes for firstName and lastName. When you submit the form, it closes the dialog and passes the content of the object modified by the form. The form also contains a Close button, which calls the close method without any extra data, except the required dialogId.

After you build and install the extension in Studio Pro, the dialog opens when you click the menu and displays the web content from the dialog.tsx file.

You can modify the dimensions of a dialog using the update method. To do this, add a button to the form in the dialog.tsx file:

<button
  type="button"
  onClick={(_) => {
    studioPro.ui.dialogs.update(dialogId, {
      height: document.documentElement.scrollHeight + 20,
      width: document.documentElement.scrollWidth + 20,
    });
  }}
>
  Expand by 20 pixels
</button>

You can modify the dialog's dimensions while it is open.

Showing a Progress Dialog

To show a progress dialog, call the method studioPro.ui.dialogs.showProgressDialog(<title>, <steps>). The parameters are:

<title> – A string that is displayed in the title bar of the dialog.
<steps> – An array of ProgressDialogStep objects, which run in the same order provided in the array. A ProgressDialogStep object contains the following properties:
- title – The title of the step, which is highlighted when the step runs.
- description – The description of the step, which shows at the bottom of the dialog next to the progress bar.
- action – The action the step performs that returns Promise<true | string>, where string indicates the reason for failure if the step fails, and true is returned otherwise.

A checkmark icon appears next to the step title when the step completes successfully. If one of the steps fails, the dialog closes and the remaining steps do not run.

The showProgressDialog method returns a Promise<ProgressDialogResult>. ProgressDialogResult is an object that contains the following properties:

result – A string that is either Success, Failure, or UserCancelled:
- Success – Returned when all steps return true.
- Failure – Returned when one step fails, causing the dialog to close.
- UserCancelled – Returned when the user closes the dialog and interrupts the process.
failedStep (optional) – An object of type FailedProgressStepResult that describes the step that failed.

The FailedProgressStepResult object contains the following properties:

stepTitle – The title of the step that failed, causing the whole process to fail.
error – A string that describes the error or exception that occurred during step execution.

The following example creates a menu to show the modal progress dialog and runs three steps inside the loaded event in the main entry point (src/main/index.ts):

import { ComponentContext, IComponent, ProgressDialogStep, getStudioProApi } from "@mendix/extensions-api";

export const component: IComponent = {
    async loaded(componentContext: ComponentContext) {
        const studioPro = getStudioProApi(componentContext);

        const step1: ProgressDialogStep = {
            title: "Step 1",
            description: "Executing Step 1",
            action: async () => {
                // perform action
                return true;
            }
        };

        const step2: ProgressDialogStep = {
            title: "Step 2",
            description: "Executing Step 2",
            action: async () => {
                // perform action
                return true;
            }
        };

        const step3: ProgressDialogStep = {
            title: "Step 3",
            description: "Executing Step 3",
            action: async () => {
                // perform action
                return true;
            }
        };

        // menu to call `showProgressDialog` method
        await studioPro.ui.extensionsMenu.add({
            caption: "Sample Progress Dialog",
            menuId: `myextension.start-progress-menu`,
            action: async () => {
                const steps = [step1, step2, step3];
                const progressDialogResult = await studioPro.ui.dialogs.showProgressDialog("Sample Progress Dialog", steps);

                switch (progressDialogResult.result) {
                    case "Success":
                        await studioPro.ui.messageBoxes.show("info", "Process completed successfully");
                        break;

                    case "UserCancelled":
                        await studioPro.ui.messageBoxes.show("info", "Process was cancelled by the user");
                        break;

                    case "Failure": {
                        const errorMessage = `Step '${progressDialogResult.failedStep?.stepTitle}' has failed'`;
                        const errorDetails = progressDialogResult.failedStep?.error ?? "";

                        await studioPro.ui.messageBoxes.show("error", errorMessage, errorDetails);
                        break;
                    }
                }
            }
        });
    }
};

Mendix recommends wrapping your step action body in a try/catch block so you can control the error that is returned to the user:

const step: ProgressDialogStep = {
            title: "Step X",
            description: "Executing Step X",
            action: async () => {
                try {
                    // perform action
                    return true;
                } catch (error: Error | unknown) {
                    return error instanceof Error ? error.message : "An error occurred while performing Step X";
                }
            }
        };

When running, the progress dialog looks like this:

Sample progress dialog showing three steps

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Open a Modal Dialog Using Web API

Introduction

Prerequisites

Opening a Modal Dialog

Filling the Dialog with Content

Modifying a Modal Dialog

Showing a Progress Dialog

Extensibility Feedback

Feedback