LGTM3 On Wednesday, June 24, 2026 at 11:12:26 AM UTC-4 Rick Byers wrote:
> Ok thanks Alex, that sounds like an OK compromise to me. LGTM2 > > On Wed, Jun 17, 2026 at 2:41 PM 'Alexander Kyereboah' via blink-dev < > [email protected]> wrote: > >> I agree that carrying three different properties for the same feature >> long-term is not ideal! I also don’t think we should expect that either >> legacy spelling is safely removable at the same time we ship `window-drag`. >> The ChromeStatus cites non-trivial usage for both existing names: >> `-webkit-app-region` at 0.79% of page loads and `app-region` at 0.24% as of >> June 2026. >> >> That being said, with the CSS UI 4 spec now standardizing `window-drag` >> as the canonical property, I think we can work towards deprecating at least >> one of the supported shorthands. I propose we keep the existing aliases >> initially for compatibility, update developer-facing documentation >> (Electron) to prefer `window-drag`, and track usage so we can revisit >> removal later. Based on today’s signals, app-region is the more plausible >> eventual deprecation candidate once window-drag has had time to gain >> adoption; -webkit-app-region looks less plausible to remove near-term >> because usage is higher and it represents older compatibility content (we >> support a lot of -webkit prefixed >> <https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/renderer/core/css/css_properties.json5;l=1913?q=css_properties.json5>legacy >> >> properties in Chromium). I’m happy to explicitly add that follow-up plan to >> the ChromeStatus entry and track it as a CRBug so we’re not treating the >> extra names as permanent. >> >> Thank you, >> Alex >> On Thursday, June 11, 2026 at 2:45:01 PM UTC-7 Alexander Kyereboah wrote: >> >>> *Contact emails* >>> [email protected] >>> >>> *Specification* >>> https://drafts.csswg.org/css-ui-4/#window-drag >>> >>> *Summary* >>> The `window-drag` CSS property allows web content to designate regions >>> of an installed desktop web app’s UI that should behave as draggable window >>> titlebar areas. When applied, user pointer interactions (e.g., >>> click-and-drag) on that region move the top-level application window rather >>> than triggering normal page interaction. This is primarily used by desktop >>> PWAs or apps using features like Window Controls Overlay to implement >>> custom title bars and draggable areas when the browser-provided title bar >>> is hidden. This feature standardizes and renames the existing `app-region` >>> CSS property, changes its value names to `move` and `none`, and adds >>> explicit inheritance behavior. This property is used by installed web apps >>> and Electron-based applications for the same purpose. >>> >>> *Blink component* >>> Blink>CSS >>> <https://issues.chromium.org/issues?q=customfield1222907:%22Blink%3ECSS%22> >>> >>> *Web Feature ID* >>> Missing feature (Feature request >>> <https://github.com/web-platform-dx/web-features/issues/3948>) >>> >>> *Motivation* >>> The CSS Working Group resolved to standardize the property under the >>> name `window-drag` to better reflect its behavior. This feature adds >>> support for the standardized `window-drag `property as a new CSS property >>> in Chromium. Chromium is not deprecating or removing `app-region` or >>> `-webkit-app-region`. Both legacy properties will remain fully supported. >>> Internally, `app-region` is implemented as a surrogate that maps to >>> `window-drag`, making this an additive change with no migration burden on >>> existing content. Supporting the standardized name aligns Chromium with the >>> CSSWG resolution while keeping the cost and risk minimal. >>> >>> *Initial public proposal* >>> Standardizing `app-region` for draggable app windows · Issue #7017 · >>> w3c/csswg-drafts <https://github.com/w3c/csswg-drafts/issues/7017> >>> >>> *Search tags* >>> WCO <https://chromestatus.com/features#tags:WCO>, app-region >>> <https://chromestatus.com/features#tags:app-region>, window-drag >>> <https://chromestatus.com/features#tags:window-drag> >>> >>> *TAG review* >>> *No information provided* >>> >>> *TAG review status* >>> Not applicable >>> >>> *Risks* >>> >>> *Interoperability and Compatibility* >>> Historically, this feature evolved entirely within Chromium prior to >>> standardization. The original prefixed property, `-webkit-app-region`, >>> shipped as part of Window Controls Overlay, and was later unprefixed to >>> `app-region` and shipped broadly before any formal CSS Working Group >>> specification work. Feedback from other browser vendors and CSSWG >>> participants on the naming and generality of the property only emerged >>> after shipping, at which point concerns were raised that `app-region` was >>> unintuitively named. In response, the CSS Working Group resolved to >>> standardize the behavior under the clearer name `window-drag`, while >>> retaining the already-shipped properties for compatibility. Renaming >>> `app-region` to `window-drag` carries some interoperability risk because >>> the feature is currently only implemented in Chromium, and other engines do >>> not yet support either the legacy or renamed property. In the near term, >>> this means the rename will not immediately improve cross-browser >>> compatibility. However, this risk is moderated by the CSSWG resolution to >>> standardize on `window-drag` and the existence of corresponding spec text >>> in CSS UI Level 4, which places the platform on a clearer path toward >>> eventual interoperability while preserving backward compatibility with >>> existing content. >>> >>> *Gecko*: Positive ( >>> https://github.com/mozilla/standards-positions/issues/1409) >>> >>> *WebKit*: No signal ( >>> https://github.com/WebKit/standards-positions/issues/668) >>> >>> *Web developers*: Positive (https://issues.chromium.org/issues/40616128) >>> Attached >>> original tracking bug for WCO with 45+ upvotes from the community. >>> `app-region` and `window-drag` are explicitly tied to WCO functionality in >>> Chromium. >>> >>> *Other signals*: >>> >>> *Ergonomics* >>> The ergonomics impact of this change is expected to be low. The property >>> is primarily used in installed web app scenarios, often in conjunction with >>> APIs like Window Controls Overlay, where `app-region` and >>> `-webkit-app-region` are already established patterns. Renaming to >>> `window-drag` improves clarity and alignment with CSS naming conventions >>> without changing the underlying usage model. Chromium will continue to >>> support existing `app-region` usage as a legacy alias, ensuring that >>> current content continues to function while developers gradually migrate to >>> the standardized name, reducing the risk of breakage or developer friction. >>> This change also introduces explicit inheritance on the `window-drag`, >>> `app-region`, and `-webkit-app-region` keywords. There would be a potential >>> additive change in behavior for child elements that overflow out of a >>> draggable parent container, now becoming draggable as well. However, >>> Chromium `app-region` has no effect if WCO is not enabled, and WCO is only >>> present in .13% of page loads as of June 2026. A further subset of this >>> would be developers using `app-region` in conjunction with WCO. Taking into >>> account this data and the specificity of the edge case, the actual risk is >>> very low. >>> >>> *Activation* >>> There are no significant activation risks associated with this change. >>> The rename from `app-region` to `window-drag` does not introduce new >>> functionality or require additional permissions, and continues to operate >>> within the same installed web app contexts (alongside Window Controls >>> Overlay). Existing usage patterns remain unchanged. >>> >>> *Security* >>> This change does not introduce new security risks. The `window-drag` >>> property provides the same behavior as `app-region`, which is limited to >>> defining draggable regions in installed web app windows and does not expose >>> new capabilities or access to sensitive data. As the rename is purely a >>> syntactic and standardization change, it does not expand the attack surface. >>> >>> *WebView application risks* >>> >>> Does this intent deprecate or change behavior of existing APIs, such >>> that it has potentially high risk for Android WebView-based applications? >>> No >>> >>> >>> *Debuggability* >>> `window-drag` will be exposed as a CSS property at the same capacity as >>> `app-region`, viewable through DevTools when examining the CSS. >>> >>> *Will this feature be supported on all six Blink platforms (Windows, >>> Mac, Linux, ChromeOS, Android, and Android WebView)?* >>> Yes >>> >>> *Is this feature fully tested by web-platform-tests >>> <https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md>?* >>> Yes >>> Manual WPT: >>> https://github.com/web-platform-tests/wpt/blob/master/appmanifest/display-override-member/display-override-member-window-drag-window-controls-overlay-manual.tentative.html >>> Chromium >>> side, we have an internal web test confirming support for all 3 properties: >>> `-webkit-app-region`, `app-region`, and `window-drag`. This test is not >>> surfaced as a WPT since `window-drag` is the only standardized property, >>> but we support the legacy surrogate in Chromium. Internal web tests: >>> https://chromium-review.googlesource.com/c/chromium/src/+/7858427/5/third_party/blink/web_tests/fast/css/window-drag-app-region-surrogate.html >>> >>> *Flag name on about://flags* >>> *No information provided* >>> >>> *Finch feature name* >>> CSSWindowDrag >>> >>> *Rollout plan* >>> Will ship enabled for all users >>> >>> *Requires code in //chrome?* >>> False >>> >>> *Tracking bug* >>> https://issues.chromium.org/issues/477608113 >>> >>> *Availability expectation* >>> Feature is fully supported in Chromium browsers on launch. With >>> standardization in the css-ui-4 spec, the chances that other vendors will >>> adopt this are higher. >>> >>> *Adoption expectation* >>> Feature is considered a best practice for custom window interactions >>> within 12 months of reaching Web Platform baseline. >>> >>> *Adoption plan* >>> The adoption plan is to update references from `app-region` to >>> `window-drag` across relevant specifications and developer-facing >>> documentation, including the Window Controls Overlay spec and >>> platform-specific guidance such as Electron’s custom window interaction >>> docs. Chromium will continue to support `app-region` as a legacy alias >>> during the transition to enable gradual migration without breaking existing >>> content. MDN Document Request being tracked at >>> https://issuetracker.google.com/issues/514738005 >>> >>> *Non-OSS dependencies* >>> >>> Does the feature depend on any code or APIs outside the Chromium open >>> source repository and its open-source dependencies to function? >>> None. >>> >>> *Estimated milestones* >>> >>> Shipping on desktop >>> 151 >>> >>> *Anticipated spec changes* >>> >>> Open questions about a feature may be a source of future web compat or >>> interop issues. Please list open issues (e.g. links to known github issues >>> in the project for the feature specification) whose resolution may >>> introduce web compat/interop risk (e.g., changing to naming or structure of >>> the API in a non-backward-compatible way). >>> None expected. >>> >>> *Link to entry on the Chrome Platform Status* >>> https://chromestatus.com/feature/5201338641285120?gate=5822390643851264 >>> >>> This intent message was generated by Chrome Platform Status >>> <https://chromestatus.com/>. >>> >> -- >> > You received this message because you are subscribed to the Google Groups >> "blink-dev" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> > To view this discussion visit >> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/4b897395-4611-4299-9ecf-5cb0fa822849n%40chromium.org >> >> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/4b897395-4611-4299-9ecf-5cb0fa822849n%40chromium.org?utm_medium=email&utm_source=footer> >> . >> > -- You received this message because you are subscribed to the Google Groups "blink-dev" group. 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