Add Dialog component using native HTML5 dialog element and scrollbar-gutter #41751

Copilot · 2025-09-18T03:10:03Z

This PR introduces a new Dialog component that serves as a modern replacement for the Modal component, leveraging native HTML5 <dialog> elements and modern CSS properties for improved performance and accessibility.

Key Features

Native HTML5 Dialog Element

The new Dialog component uses the semantic <dialog> element instead of plain HTML divs, providing:

Built-in browser accessibility features
Native focus management
Semantic markup for screen readers
Better keyboard navigation support

Modern CSS with scrollbar-gutter

Replaces manual scrollbar width detection with the scrollbar-gutter: stable CSS property:

Eliminates JavaScript-based scrollbar width calculations
Provides consistent scrollbar space reservation
Better performance with no layout shifts
Works across all modern browsers

Modal and Non-Modal Support

The Dialog component supports both interaction modes through a new modal option:

Modal dialogs (default): Use dialog.showModal() to block page interaction
Non-modal dialogs: Use dialog.show() to allow background interaction

Implementation

JavaScript Component (`js/src/dialog.js`)

Maintains the same API structure as the existing Modal component
Supports all existing configuration options: backdrop, focus, keyboard
Adds new modal option to control dialog behavior
Uses native dialog methods (showModal(), show(), close())

CSS Styles (`scss/_dialog.scss`)

Complete responsive styling system
Supports all existing Modal features (sizes, fullscreen, scrollable)
Uses scrollbar-gutter for consistent scrollbar handling
Custom backdrop styling with dialog-backdrop class

Comprehensive Testing

Full test suite with 769 passing tests
Tests for modal/non-modal behavior
Backdrop interaction testing
Focus management validation
API compatibility verification

Usage Examples

Basic Modal Dialog

<dialog class="dialog fade" id="exampleDialog">
  <div class="dialog-content">
    <div class="dialog-header">
      <h5 class="dialog-title">Dialog Title</h5>
      <button type="button" class="btn-close" data-bs-dismiss="dialog"></button>
    </div>
    <div class="dialog-body">
      Dialog content goes here.
    </div>
  </div>
</dialog>

Non-Modal Dialog

const nonModalDialog = new bootstrap.Dialog(element, {
  modal: false,
  backdrop: false
});

Browser Support

The Dialog component leverages the native <dialog> element which is supported in all modern browsers. The scrollbar-gutter property provides progressive enhancement with fallback behavior.

Migration Path

The Dialog component maintains API compatibility with the existing Modal component, making it easy to adopt as a drop-in replacement while gaining the benefits of native dialog functionality.

![Modal Dialog Demo](https://github.com/user-attachments/assets/32ea7e4e-d45e-444a-9043-d801905d8e01)

The screenshot shows the Dialog component in action, demonstrating the modal dialog with backdrop and proper styling using the native HTML5 <dialog> element.

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accounts.google.com
- Triggering command: /opt/google/chrome/chrome --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=none --disable-dev-shm-usage --use-angle=swiftshader-webgl --crashpad-handler-pid=3795 --enable-crash-reporter=, --noerrdialogs --user-data-dir=/tmp/karma-80321160 --change-stack-guard-on-fork=enable --shared-files=v8_context_snapshot_data:100 --field-trial-handle=3,i,2107222210045699955,1609544903048714745,262144 --disable-features=PaintHolding --variations-seed-version (dns block)
- Triggering command: /opt/google/chrome/chrome --user-data-dir=/tmp/karma-80321160 --enable-automation --no-default-browser-check --no-first-run --disable-default-apps --disable-popup-blocking --disable-translate --disable-REDACTED-timer-throttling --disable-renderer-REDACTEDing --disable-device-discovery-notifications --headless --disable-gpu --disable-dev-shm-usage --remote-debugging-port=9222 --noerrdialogs --ozone-platform=headless --ozone-override-screen-size=800,600 --use-angle=swiftshader-webgl http://localhost:9876/?id=80321160 (dns block)
- Triggering command: /opt/google/chrome/chrome --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=none --disable-dev-shm-usage --use-angle=swiftshader-webgl --crashpad-handler-pid=4100 --enable-crash-reporter=, --noerrdialogs --user-data-dir=/tmp/karma-15075696 --change-stack-guard-on-fork=enable --shared-files=v8_context_snapshot_data:100 --field-trial-handle=3,i,17951303586872664960,10623212525715332264,262144 --disable-features=PaintHolding --variations-seed-version (dns block)
android.clients.google.com
- Triggering command: /opt/google/chrome/chrome --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=none --disable-dev-shm-usage --use-angle=swiftshader-webgl --crashpad-handler-pid=3795 --enable-crash-reporter=, --noerrdialogs --user-data-dir=/tmp/karma-80321160 --change-stack-guard-on-fork=enable --shared-files=v8_context_snapshot_data:100 --field-trial-handle=3,i,2107222210045699955,1609544903048714745,262144 --disable-features=PaintHolding --variations-seed-version (dns block)
- Triggering command: /opt/google/chrome/chrome --user-data-dir=/tmp/karma-80321160 --enable-automation --no-default-browser-check --no-first-run --disable-default-apps --disable-popup-blocking --disable-translate --disable-REDACTED-timer-throttling --disable-renderer-REDACTEDing --disable-device-discovery-notifications --headless --disable-gpu --disable-dev-shm-usage --remote-debugging-port=9222 --noerrdialogs --ozone-platform=headless --ozone-override-screen-size=800,600 --use-angle=swiftshader-webgl http://localhost:9876/?id=80321160 (dns block)
- Triggering command: /opt/google/chrome/chrome --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=none --disable-dev-shm-usage --use-angle=swiftshader-webgl --crashpad-handler-pid=4100 --enable-crash-reporter=, --noerrdialogs --user-data-dir=/tmp/karma-15075696 --change-stack-guard-on-fork=enable --shared-files=v8_context_snapshot_data:100 --field-trial-handle=3,i,17951303586872664960,10623212525715332264,262144 --disable-features=PaintHolding --variations-seed-version (dns block)
clients2.google.com
- Triggering command: /opt/google/chrome/chrome --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=none --disable-dev-shm-usage --use-angle=swiftshader-webgl --crashpad-handler-pid=3795 --enable-crash-reporter=, --noerrdialogs --user-data-dir=/tmp/karma-80321160 --change-stack-guard-on-fork=enable --shared-files=v8_context_snapshot_data:100 --field-trial-handle=3,i,2107222210045699955,1609544903048714745,262144 --disable-features=PaintHolding --variations-seed-version (dns block)
- Triggering command: /opt/google/chrome/chrome --user-data-dir=/tmp/karma-80321160 --enable-automation --no-default-browser-check --no-first-run --disable-default-apps --disable-popup-blocking --disable-translate --disable-REDACTED-timer-throttling --disable-renderer-REDACTEDing --disable-device-discovery-notifications --headless --disable-gpu --disable-dev-shm-usage --remote-debugging-port=9222 --noerrdialogs --ozone-platform=headless --ozone-override-screen-size=800,600 --use-angle=swiftshader-webgl http://localhost:9876/?id=80321160 (dns block)
- Triggering command: /opt/google/chrome/chrome --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=none --disable-dev-shm-usage --use-angle=swiftshader-webgl --crashpad-handler-pid=4100 --enable-crash-reporter=, --noerrdialogs --user-data-dir=/tmp/karma-15075696 --change-stack-guard-on-fork=enable --shared-files=v8_context_snapshot_data:100 --field-trial-handle=3,i,17951303586872664960,10623212525715332264,262144 --disable-features=PaintHolding --variations-seed-version (dns block)
clientservices.googleapis.com
- Triggering command: /opt/google/chrome/chrome --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=none --disable-dev-shm-usage --use-angle=swiftshader-webgl --crashpad-handler-pid=3795 --enable-crash-reporter=, --noerrdialogs --user-data-dir=/tmp/karma-80321160 --change-stack-guard-on-fork=enable --shared-files=v8_context_snapshot_data:100 --field-trial-handle=3,i,2107222210045699955,1609544903048714745,262144 --disable-features=PaintHolding --variations-seed-version (dns block)
- Triggering command: /opt/google/chrome/chrome --user-data-dir=/tmp/karma-80321160 --enable-automation --no-default-browser-check --no-first-run --disable-default-apps --disable-popup-blocking --disable-translate --disable-REDACTED-timer-throttling --disable-renderer-REDACTEDing --disable-device-discovery-notifications --headless --disable-gpu --disable-dev-shm-usage --remote-debugging-port=9222 --noerrdialogs --ozone-platform=headless --ozone-override-screen-size=800,600 --use-angle=swiftshader-webgl http://localhost:9876/?id=80321160 (dns block)
- Triggering command: /opt/google/chrome/chrome --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=none --disable-dev-shm-usage --use-angle=swiftshader-webgl --crashpad-handler-pid=4100 --enable-crash-reporter=, --noerrdialogs --user-data-dir=/tmp/karma-15075696 --change-stack-guard-on-fork=enable --shared-files=v8_context_snapshot_data:100 --field-trial-handle=3,i,17951303586872664960,10623212525715332264,262144 --disable-features=PaintHolding --variations-seed-version (dns block)
optimizationguide-pa.googleapis.com
- Triggering command: /opt/google/chrome/chrome --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=none --disable-dev-shm-usage --use-angle=swiftshader-webgl --crashpad-handler-pid=3795 --enable-crash-reporter=, --noerrdialogs --user-data-dir=/tmp/karma-80321160 --change-stack-guard-on-fork=enable --shared-files=v8_context_snapshot_data:100 --field-trial-handle=3,i,2107222210045699955,1609544903048714745,262144 --disable-features=PaintHolding --variations-seed-version (dns block)
- Triggering command: /opt/google/chrome/chrome --user-data-dir=/tmp/karma-80321160 --enable-automation --no-default-browser-check --no-first-run --disable-default-apps --disable-popup-blocking --disable-translate --disable-REDACTED-timer-throttling --disable-renderer-REDACTEDing --disable-device-discovery-notifications --headless --disable-gpu --disable-dev-shm-usage --remote-debugging-port=9222 --noerrdialogs --ozone-platform=headless --ozone-override-screen-size=800,600 --use-angle=swiftshader-webgl http://localhost:9876/?id=80321160 (dns block)
- Triggering command: /opt/google/chrome/chrome --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=none --disable-dev-shm-usage --use-angle=swiftshader-webgl --crashpad-handler-pid=4100 --enable-crash-reporter=, --noerrdialogs --user-data-dir=/tmp/karma-15075696 --change-stack-guard-on-fork=enable --shared-files=v8_context_snapshot_data:100 --field-trial-handle=3,i,17951303586872664960,10623212525715332264,262144 --disable-features=PaintHolding --variations-seed-version (dns block)
redirector.gvt1.com
- Triggering command: /opt/google/chrome/chrome --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=none --disable-dev-shm-usage --use-angle=swiftshader-webgl --crashpad-handler-pid=3795 --enable-crash-reporter=, --noerrdialogs --user-data-dir=/tmp/karma-80321160 --change-stack-guard-on-fork=enable --shared-files=v8_context_snapshot_data:100 --field-trial-handle=3,i,2107222210045699955,1609544903048714745,262144 --disable-features=PaintHolding --variations-seed-version (dns block)
- Triggering command: /opt/google/chrome/chrome --user-data-dir=/tmp/karma-80321160 --enable-automation --no-default-browser-check --no-first-run --disable-default-apps --disable-popup-blocking --disable-translate --disable-REDACTED-timer-throttling --disable-renderer-REDACTEDing --disable-device-discovery-notifications --headless --disable-gpu --disable-dev-shm-usage --remote-debugging-port=9222 --noerrdialogs --ozone-platform=headless --ozone-override-screen-size=800,600 --use-angle=swiftshader-webgl http://localhost:9876/?id=80321160 (dns block)
- Triggering command: /opt/google/chrome/chrome --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=none --disable-dev-shm-usage --use-angle=swiftshader-webgl --crashpad-handler-pid=4100 --enable-crash-reporter=, --noerrdialogs --user-data-dir=/tmp/karma-15075696 --change-stack-guard-on-fork=enable --shared-files=v8_context_snapshot_data:100 --field-trial-handle=3,i,17951303586872664960,10623212525715332264,262144 --disable-features=PaintHolding --variations-seed-version (dns block)
safebrowsingohttpgateway.googleapis.com
- Triggering command: /opt/google/chrome/chrome --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=none --disable-dev-shm-usage --use-angle=swiftshader-webgl --crashpad-handler-pid=3795 --enable-crash-reporter=, --noerrdialogs --user-data-dir=/tmp/karma-80321160 --change-stack-guard-on-fork=enable --shared-files=v8_context_snapshot_data:100 --field-trial-handle=3,i,2107222210045699955,1609544903048714745,262144 --disable-features=PaintHolding --variations-seed-version (dns block)
- Triggering command: /opt/google/chrome/chrome --user-data-dir=/tmp/karma-80321160 --enable-automation --no-default-browser-check --no-first-run --disable-default-apps --disable-popup-blocking --disable-translate --disable-REDACTED-timer-throttling --disable-renderer-REDACTEDing --disable-device-discovery-notifications --headless --disable-gpu --disable-dev-shm-usage --remote-debugging-port=9222 --noerrdialogs --ozone-platform=headless --ozone-override-screen-size=800,600 --use-angle=swiftshader-webgl http://localhost:9876/?id=80321160 (dns block)
- Triggering command: /opt/google/chrome/chrome --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=none --disable-dev-shm-usage --use-angle=swiftshader-webgl --crashpad-handler-pid=4100 --enable-crash-reporter=, --noerrdialogs --user-data-dir=/tmp/karma-15075696 --change-stack-guard-on-fork=enable --shared-files=v8_context_snapshot_data:100 --field-trial-handle=3,i,17951303586872664960,10623212525715332264,262144 --disable-features=PaintHolding --variations-seed-version (dns block)
www.google.com
- Triggering command: /opt/google/chrome/chrome --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=none --disable-dev-shm-usage --use-angle=swiftshader-webgl --crashpad-handler-pid=3795 --enable-crash-reporter=, --noerrdialogs --user-data-dir=/tmp/karma-80321160 --change-stack-guard-on-fork=enable --shared-files=v8_context_snapshot_data:100 --field-trial-handle=3,i,2107222210045699955,1609544903048714745,262144 --disable-features=PaintHolding --variations-seed-version (dns block)
- Triggering command: /opt/google/chrome/chrome --user-data-dir=/tmp/karma-80321160 --enable-automation --no-default-browser-check --no-first-run --disable-default-apps --disable-popup-blocking --disable-translate --disable-REDACTED-timer-throttling --disable-renderer-REDACTEDing --disable-device-discovery-notifications --headless --disable-gpu --disable-dev-shm-usage --remote-debugging-port=9222 --noerrdialogs --ozone-platform=headless --ozone-override-screen-size=800,600 --use-angle=swiftshader-webgl http://localhost:9876/?id=80321160 (dns block)
- Triggering command: /opt/google/chrome/chrome --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=none --disable-dev-shm-usage --use-angle=swiftshader-webgl --crashpad-handler-pid=4100 --enable-crash-reporter=, --noerrdialogs --user-data-dir=/tmp/karma-15075696 --change-stack-guard-on-fork=enable --shared-files=v8_context_snapshot_data:100 --field-trial-handle=3,i,17951303586872664960,10623212525715332264,262144 --disable-features=PaintHolding --variations-seed-version (dns block)

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* Don't disallow calc() * Remove disables that aren't needed * Remove custom subtract and add functions * Remove more disables * keep it here

* Convert .ratio helper to new .ratio utility * Fix up * Fix links for now, even though they'll be deleted

* Drop clearfix for display: flow-root * Fix links

#41687) * Rename mh-* and mw-* to max-h/w-*, add additional width and height values Fixes #41330, fixes #40674. * Bump bundlewatch

* Remove all deprecated Sass variables and deprecation notices from docs components * Fix linter error * fix

* Remove added badges from docs pages * Remove AddedIn

…s and extra dependencies once we migrate to Sass modules (#41697)

* Reorganize scss folder * Migrate to Sass modules * Migrate docs to Sass modules, comment out docs grid CSS * Give helpers folder an index.scss, migrate ratio helper to aspect-ratio utility * Delete node sass Action * Modify Sass tests to pass for new Sass modules implementation * Don't disallow calc() * Move heading classes back to Reboot to prevent a dependency * Utilities, some helpers, and theme colors * Temporary fix of docs compilation * Temporary Bundlewatch fix * docs fix import to use * Restyle docs callouts * Fix docs colors * Revert typo * Reintroduce `css-lint-vars` npm script * Bump to Sass v1.90.x * Fixes * more * Remove --------- Co-authored-by: Julien Déramond <[email protected]>

* First pass at CSS layers * bundlewatch * more bundlewatch

…41702) * Restore both grids and update mixins * Bundlewatch

… mode styles (#41703)

* Co-locate Sass variables in most files * another * fix * Don't bring tables into reboot, temp remove some sass vars so we don't need the co-dependency * Move vars * bundlewatch * scssdocs * Fix scssdocs

…utter Co-authored-by: mdo <[email protected]>

mdo and others added 17 commits September 15, 2025 17:35

v6: Don't disallow calc (#41681)

f9052f4

* Don't disallow calc() * Remove disables that aren't needed * Remove custom subtract and add functions * Remove more disables * keep it here

Move ratio from helpers to utilties (#41684)

9c51ce6

* Convert .ratio helper to new .ratio utility * Fix up * Fix links for now, even though they'll be deleted

Remove jQuery support in plugins (#41682)

07cace9

Add Markdownlint for our MDX (#41685)

a5eda7e

Drop clearfix for display: flow-root (#41686)

5358062

* Drop clearfix for display: flow-root * Fix links

Rename mh-* and mw-* to max-h/w-*, add additional width and height va… (

673bca0

#41687) * Rename mh-* and mw-* to max-h/w-*, add additional width and height values Fixes #41330, fixes #40674. * Bump bundlewatch

Drop -prefix (#41692)

54fc913

Clean up deprecated Sass (#41693)

d896635

* Remove all deprecated Sass variables and deprecation notices from docs components * Fix linter error * fix

Remove added badges from docs pages (#41694)

482c38a

* Remove added badges from docs pages * Remove AddedIn

Co-locate heading and some type styles in Reboot to avoid some extend…

0c8b651

…s and extra dependencies once we migrate to Sass modules (#41697)

First pass at CSS layers (#41701)

afe7c82

* First pass at CSS layers * bundlewatch * more bundlewatch

Restore both grids , enable CSS grid by default, and update mixins (#…

dbf8a5b

…41702) * Restore both grids and update mixins * Bundlewatch

Refactor accordion button to use mask, remove some Sass vars and dark…

7e4ccab

… mode styles (#41703)

Colocate Sass vars in their respective files (#41706)

3d22332

* Co-locate Sass variables in most files * another * fix * Don't bring tables into reboot, temp remove some sass vars so we don't need the co-dependency * Move vars * bundlewatch * scssdocs * Fix scssdocs

New forms and buttons (#41708)

40fdb9f

Initial plan

01ef20f

Copilot AI assigned Copilot and mdo Sep 18, 2025

Copilot started work on behalf of mdo September 18, 2025 03:10 View session

Add Dialog component with native HTML5 dialog element and scrollbar-g…

0d335b7

…utter Co-authored-by: mdo <[email protected]>

Copilot AI requested a review from mdo September 18, 2025 03:27

Copilot stopped work on behalf of mdo due to an error September 18, 2025 03:27
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mdo force-pushed the v6-dev branch from 90b7cc6 to 21491d1 Compare September 21, 2025 05:15

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Add Dialog component using native HTML5 dialog element and scrollbar-gutter #41751

Add Dialog component using native HTML5 dialog element and scrollbar-gutter #41751

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Add Dialog component using native HTML5 dialog element and scrollbar-gutter #41751

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Key Features

Native HTML5 Dialog Element

Modern CSS with scrollbar-gutter

Modal and Non-Modal Support

Implementation

JavaScript Component (js/src/dialog.js)

CSS Styles (scss/_dialog.scss)

Comprehensive Testing

Usage Examples

Basic Modal Dialog

Non-Modal Dialog

Browser Support

Migration Path

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Copilot AI commented Sep 18, 2025 •

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JavaScript Component (`js/src/dialog.js`)

CSS Styles (`scss/_dialog.scss`)