Experimental Chromium Web Platform Features

This is not a web-exposed change. The implementation of CanvasRenderingContext2D's measureText(), fillText(), and strokeText() has a drastic change. This might affect performance, so we'd like to run an origin trial so canvas-heavy applications can try out the new implementation.

A system for creating structured headings within a document. The `headingoffset=` attribute can be added to elements that influences the child `h1`-`h6` elements' heading levels, for example a `headingoffset=1` will mean all `h1` elements will have an effective heading level of 2, and so on. In addition the `:heading` pseudo class will select all headings (tags of `h1` to `h6`) and the `:heading(N)` pseudo class will select headings with an _effective_ level of `N`. This allows for documents with different heading structures (for example user generated content) to be combined to create a well defined heading structure without significantly altering the underlying documents.

Dialog elements can be closed through a variety of mechanisms, sometimes developers want to have the ability to prevent closure. To achieve this dialogs fire a cancel event. Originally this was only fired via a close request (e.g. ESC key press), recently a `requestClose()` JS function was added which also fires the cancel event. The 'request-close' command brings that new ability to the declarative invoker commands API.

Add support for the `column-wrap` and `column-height` CSS properties, from multicol Level 2. https://drafts.csswg.org/css-multicol-2/#cwr https://drafts.csswg.org/css-multicol-2/#ch This allows for vertical column layout, or even 2D column layout. Columns can have an explicit constrained height, apart from being derived from the content-box height of the multicol container, and wrap to a new row of columns when all columns have been filled for one row, rather than creating overflowing columns in the inline direction.

This feature adds setDefaultSinkId() to MediaDevices, which enables the top-level frame to change the default audio output device used by its subframes.

There are a range of error conditions that can be hit when using the Private Aggregation API. For example, the privacy budget could run out, preventing any further histogram contributions. This feature allows developers to register histogram contributions that should only be sent if a particular type of error occurs. This feature supports measuring the frequency of the error conditions and to split these measurements on relevant developer-specified dimensions (e.g. version of deployed code). As the errors themselves may be cross-site information, we cannot simply expose them to the page for users without third-party cookies. Instead, this feature reuses the existing aggregate, noised reporting pipelines through the Aggregation Service.

Exposes find-in-page search results to authors as a highlight pseudo-element, like selections and spelling errors. This allows authors to change the foreground and background colors or add text decorations, which can be especially useful if the UA defaults have insufficient contrast with the page colors or are otherwise unsuitable.

Correct the error type thrown during WebAuthn credential creation for 'payment' credentials. Due to a historic specification mismatch, creating a 'payment' credential in a cross-origin iframe without a user activation would throw a SecurityError instead of a NotAllowedError, which is what is thrown for non-payment credentials. This is a breaking change, albeit a niche one. Code that previously detected the type of error thrown (e.g., `e instanceof SecurityError`) would be affected. Code that just generally handles errors during credential creation (e.g. `catch (e)`) will continue to function correctly.

The <canvas> DOM element, like all DOM elements, accepts a `lang` attribute that is used to define language specific treatment for font selection (when fonts have locale specific glyphs). Browsers respect this attribute. However, when an OffscreenCanvas is created there is no way to set locale information, possibly resulting in a state where an offscreen canvas produces rendered results that differ from the canvas in which it's output is used. This feature adds a `lang` IDL attribute to CanvasTextDrawingStyles to give developers direct control over the language for the text drawing and metrics.

The Container Timing API enables monitoring when annotated sections of the DOM are displayed on screen and have finished their initial paint. A developer will have the ability to mark subsections of the DOM with the containertiming attribute (similar to elementtiming for the Element Timing API) and receive performance entries when that section has been painted for the first time. This API will allow developers to measure the timing of various components in their pages.

Enable fine-tuning corners, on top of the existing border-radius, by specifying the shape/curvature of the corner. This allows shapes like squircles, notches, scoops etc., and animating between them.

Custom Functions are similar to custom properties, but instead of returning a single, fixed value, it returns a value based on other custom properties, parameters, and conditionals.

The CSS if() function provides a concise way to express conditional values. It accepts a series of condition-value pairs, delimited by semicolons. The function evaluates each condition sequentially and returns the value associated with the first true condition. If none of the conditions evaluate to true, the function returns an empty token stream. This allows web authors to express complex conditional logic in a simple and concise way. Example: <style> div { color: var(--color); background-color: if(style(--color: white): black; else: white); } .dark { --color: black; } .light { --color: white; } </style> <div class="dark">dark</div> <div class="light">light</div>

The CSS if() function provides a concise way to express conditional values. It accepts a series of condition-value pairs, delimited by semicolons. The function evaluates each condition sequentially and returns the value associated with the first true condition. If none of the conditions evaluate to true, the function returns an empty token stream. This allows web authors to express complex conditional logic in a simple and concise way. Example: <style> div { color: var(--color); background-color: if(style(--color: white): black; else: white); } .dark { --color: black; } .light { --color: white; } </style> <div class="dark">dark</div> <div class="light">light</div>

The CSS if() function provides a concise way to express conditional values. It accepts a series of condition-value pairs, delimited by semicolons. The function evaluates each condition sequentially and returns the value associated with the first true condition. If none of the conditions evaluate to true, the function returns an empty token stream. This allows web authors to express complex conditional logic in a simple and concise way. Example: <style> div { color: var(--color); background-color: if(style(--color: white): black; else: white); } .dark { --color: black; } .light { --color: white; } </style> <div class="dark">dark</div> <div class="light">light</div>

This feature adds on-device speech recognition support to the Web Speech API, allowing websites to ensure that neither audio nor transcribed speech are sent to a third-party service for processing. Websites can query the availability of on-device speech recognition for specific languages, prompt users to install the necessary resources for on-device speech recognition, and choose between on-device or cloud-based speech recognition as needed.

This feature adds on-device speech recognition support to the Web Speech API, allowing websites to ensure that neither audio nor transcribed speech are sent to a third-party service for processing. Websites can query the availability of on-device speech recognition for specific languages, prompt users to install the necessary resources for on-device speech recognition, and choose between on-device or cloud-based speech recognition as needed.

The SVGAElement interface in SVG 2.0 allows manipulation of <a> elements similar to HTML anchor elements. Supporting the rel and relList attributes enhances security and privacy for developers. This alignment with HTML anchor elements ensures consistency and ease of use across web technologies.

Provide a new HTML element that interacts with the permission flow. The permission prompt is currently triggered directly from JS without the user agent having any strong signal of the user's intent. Having an in-content element that the user uses to trigger the permission flow allows for improved permission prompt UX for users as well as a recovery path from the "denied" permission state for sites. Explainer: https://github.com/WICG/PEPC/blob/main/explainer.md Instructions: https://github.com/WICG/PEPC/blob/main/HOWTO.md Developer facing documentation: https://developer.chrome.com/blog/permission-element-origin-trial

Introduces a new violation type called "Potential Permissions Policy violation", which will only look at Permissions Policy (including report-only policy) and the allow attribute set in iframes to detect the conflict between Permissions Policy enforced vs permissions propagated to iframes.

Chromium supports animation of the caret-color property, but when animated the default blinking behavior of the caret interferes with the animation. For instance, see the example at https://drafts.csswg.org/css-ui/#caret-animation where an animation from blue to red and back is rendered as a blinking cursor that is randomly blue or red. The CSS caret-animation property has two possible values: auto and manual, where auto means browser default (blinking) and manual means the page author is controlling the caret animation. In addition, via a user stylesheet, it allows users who are disturbed by or have adverse reactions to blinking or flashing visuals to disable the blinking.

shape() allows responsive free-form shapes in clip-path. The author can define a series of verbs, roughly equivalent to the verbs in path(), but where the verbs accept responsive units (e.g. % or vw), as well as any CSS values such as custom properties or rather than pixel-values. See https://drafts.csswg.org/css-shapes-2/#shape-function

sibling-index() and sibling-count() can be used as integers in CSS property values to style elements based on their position among its siblings, or the total number of siblings respectively. These functions can be used directly as integer values, but more interestingly inside calc() expressions. Example: li { margin-left: calc(10px * sibling-index()); }

'match-element' generates a unique id based on the element's identity and renames the same for this element. This is used in Single Page App cases where the element is being moved around and the desire is to animate it with a view transition Note this is split off from https://chromestatus.com/feature/6575974796492800 which contains additional discussions

Expose "paintTime" and "presentationTime" in event timing, element timing, LCP, long animation frames, paint timing. "paintTime" means the time when the rendering phase ended and the browser started the paint phase. "presentationTime" means the time when the "pixels reached the screen", which is somewhat implementation-defined

Extends the use of the "opener" rel type to same-window navigations to signal to the browser that the destination page will open a new window and the referring page expects to be able to access it. Some user agents perform browsing context group changes on navigation that aren't strictly necessary for security in order to improve performance. This results in named window reuse not being possible across a back navigation. Annotating an anchor element with "opener" will signal to the user agent that performing a browsing context group change would break a future opener relationship.

This feature adds support for Curve25519 algorithms in the Web Cryptography API, namely the signature algorithm Ed25519