From 2ae971941de5b159bc62cb7d6fd2591e6b9c4923 Mon Sep 17 00:00:00 2001 From: dgash Date: Fri, 5 Feb 2016 11:15:17 -0800 Subject: [PATCH] Copy edit Spelling, grammar, punctuation, markdown formatting; no significant content changes. --- extensions/amp-iframe/amp-iframe.md | 78 ++++++++++++++--------------- 1 file changed, 37 insertions(+), 41 deletions(-) diff --git a/extensions/amp-iframe/amp-iframe.md b/extensions/amp-iframe/amp-iframe.md index dc99373c833c..bd25bbfc8e48 100644 --- a/extensions/amp-iframe/amp-iframe.md +++ b/extensions/amp-iframe/amp-iframe.md @@ -14,16 +14,16 @@ See the License for the specific language governing permissions and limitations under the License. --> -### `amp-iframe` +## `amp-iframe` Displays an iframe. -`amp-iframe` has several important differences from vanilla iframes that are designed to make it more secure and avoid AMP files that are dominated by a single iframe: +The `amp-iframe` extension has several important differences from standard iframes, designed to make it more secure and avoid AMP files that are dominated by a single iframe: -- `amp-iframe` may not appear close to the top of the document (except for iframes that use `placeholder` as described below). They must be either 600px away from the top or not within the first 75% of the viewport when scrolled to the top – whichever is smaller. NOTE: We are currently looking for feedback as to how well this restriction works in practice. -- They are sandboxed by default. [Details](#sandbox) -- They must only request resources via HTTPS or from a data-URI or via the srcdoc attribute. -- They must not be in the same origin as the container unless they do not allow `allow-same-origin` in the sandbox attribute. See the doc ["Iframe origin policy"](../../spec/amp-iframe-origin-policy.md) for further details on allowed origins for iframes. + - `amp-iframe` may not appear close to the top of the document (except for iframes that use `placeholder`, described below). They must be either 600px away from the top or not within the first 75% of the viewport when scrolled to the top, whichever is smaller. **Note:** We are currently looking for feedback as to how well this restriction works in practice. + - They are sandboxed by default (see below). + - They must only request resources via HTTPS, from a data-URI, or via the `srcdoc` attribute. + - They must not be in the same origin as the container unless they do not use `allow-same-origin` in the sandbox attribute. See the [iframe origin policy](../../spec/amp-iframe-origin-policy.md) document for further details on allowed origins for iframes. Example: ```html @@ -35,32 +35,31 @@ Example: ``` -#### Attributes +### Attributes -##### src, srcdoc, frameborder, allowfullscreen, allowtransparency +**src, srcdoc, frameborder, allowfullscreen, allowtransparency** -The attributes above should all behave like they do on standard iframes. +These attributes should behave like they do on standard iframes. -##### sandbox +**sandbox** -Iframes created by `amp-iframe` always have the `sandbox` attribute defined on them. By default the value is empty. That means that they are "maximum sandboxed" by default. By setting sandbox values, one can opt the iframe into being less sandboxed. All values supported by browsers are allowed. E.g. setting `sandbox="allow-scripts"` allows the iframe to run JavaScript, or `sandbox="allow-scripts allow-same-origin"` allows the iframe to run JavaScript, make non-CORS XHRs, and read/write cookies. +Iframes created by `amp-iframe` always have the `sandbox` attribute defined on them. By default the value is empty, meaning that they are "maximum sandboxed". By using other sandbox values, you can set the iframe to be less sandboxed. All values supported by browsers are allowed. For example, setting `sandbox="allow-scripts"` allows the iframe to run JavaScript, while `sandbox="allow-scripts allow-same-origin"` allows the iframe to run JavaScript, make non-CORS XHRs, and read/write cookies. -If you are iframing a document that was not specifically created with sandboxing in mind, you will most likely need to add `allow-scripts allow-same-origin` to the `sandbox` attribute and you mights need to allow additional capabilities. +If you are iframing a document that was not specifically created with sandboxing in mind, you will most likely need to add `allow-scripts allow-same-origin` to the `sandbox` attribute. -Note also, that the sandbox applies to all windows opened from a sandboxed iframe. This includes new windows created by a link with `target=_blank` (Add `allow-popups` to allow this to happen). Adding `allow-popups-to-escape-sandbox` to the `sandbox` attribute, makes those new windows behave like non-sandboxed new windows. This is likely most of the time what you want and expect. Unfortunately, as of this writing, `allow-popups-to-escape-sandbox` is only supported by Chrome. +Note also that the sandbox applies to all windows opened from a sandboxed iframe. This includes new windows created by a link with `target=_blank` (add `allow-popups` to allow this to happen). Adding `allow-popups-to-escape-sandbox` to the `sandbox` attribute makes the new windows behave like non-sandboxed new windows. This is what you want and expect most of the time. However, as of this writing, `allow-popups-to-escape-sandbox` is only supported by Chrome. -See the [the docs on MDN](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/iframe#attr-sandbox) for further details on the sandbox attribute. +See the [sandbox docs on MDN](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/iframe#attr-sandbox) for further details on the sandbox attribute. -#### Iframe Resizing +### Iframe Resizing -An `amp-iframe` must have static layout defined as is the case with any other AMP element. However, -it's possible to resize an `amp-iframe` in runtime. To do so: +An `amp-iframe` must have static layout defined as any other AMP element. However, it is possible to resize an `amp-iframe` in runtime. To do so: -1. The `amp-iframe` must be defined with `resizable` attribute; -2. The `amp-iframe` must have `overflow` child element; -3. The IFrame document has to send a `embed-size` request as a window message. + 1. The `amp-iframe` must be defined with the `resizable` attribute. + 2. The `amp-iframe` must have an `overflow` child element. + 3. The iframe document must send an `embed-size` request as a window message. -Notice that `resizable` overrides `scrolling` value to `no`. +Note that the `resizable` attribute forces the `scrolling` attribute value to `no`. Example of `amp-iframe` with `overflow` element: ```html @@ -73,7 +72,7 @@ Example of `amp-iframe` with `overflow` element: ``` -Example of Iframe resize request: +Example of iframe resize request: ```javascript window.parent.postMessage({ sentinel: 'amp', @@ -82,20 +81,16 @@ window.parent.postMessage({ }, '*'); ``` -Once this message is received the AMP runtime will try to accommodate this request as soon as -possible, but it will take into account where the reader is currently reading, whether the scrolling -is ongoing and any other UX or performance factors. If the runtime cannot satisfy the resize events -the `amp-iframe` will show an `overflow` element. Clicking on the `overflow` element will immediately -resize the `amp-iframe` since it's triggered by a user action. +When this message is received, the AMP runtime will try to accommodate it as soon as possible, but it will take into account where the reader is on the page, whether the scrolling is ongoing, and any other UX or performance factors. If the runtime cannot satisfy the resize request, the `amp-iframe` will show an `overflow` element. Clicking the `overflow` element immediately resizes the `amp-iframe` because it is triggered by a user action. Here are some factors that affect how fast the resize will be executed: -- Whether the resize is triggered by the user action; -- Whether the resize is requested for a currently active Iframe; -- Whether the resize is requested for an Iframe below the viewport or above the viewport. + - Whether the resize is triggered by a user action + - Whether the resize is requested for a currently active iframe + - Whether the resize is requested for an iframe below or above the viewport -#### Iframe with Placeholder -It is possible to have an `amp-iframe` appear on the top of a document when the `amp-iframe` has a `placeholder` element as shown in the example below. +### Iframe with Placeholder +It is possible to have an `amp-iframe` appear on the top of a document when the `amp-iframe` has a `placeholder` element: ```html ``` -- The `amp-iframe` must contain an element with the `placeholder` attribute, (for instance an `amp-img` element) which would be rendered as a placeholder till the iframe is ready to be displayed. -- Iframe readiness can be known by listening to `onload` of the iframe or an `embed-ready` postMessage which would be sent by the Iframe document, whichever comes first. -Example of Iframe embed-ready request: + - The `amp-iframe` must contain an element with the `placeholder` attribute (such as an `amp-img` element) which would be rendered as a placeholder until the iframe is ready to be displayed. + - Iframe readiness can be determined by listening to the iframe's `onload` event or an `embed-ready` postMessage which would be sent by the iframe document, whichever comes first. + +Example of iframe embed-ready request: ```javascript window.parent.postMessage({ sentinel: 'amp', @@ -116,11 +112,11 @@ window.parent.postMessage({ }, '*'); ``` -#### Iframe viewability +### Iframe Viewability -Iframes can send a `send-intersection` message to its parent to start receiving IntersectionObserver style [change records](http://rawgit.com/slightlyoff/IntersectionObserver/master/index.html#intersectionobserverentry) of the iframe's intersection with the parent viewport. +An iframe can send a `send-intersection` message to its parent to start receiving IntersectionObserver style [change records](http://rawgit.com/slightlyoff/IntersectionObserver/master/index.html#intersectionobserverentry) of the iframe's intersection with the parent viewport. -Example of Iframe `send-intersection` request: +Example of iframe `send-intersection` request: ```javascript window.parent.postMessage({ sentinel: 'amp', @@ -128,9 +124,9 @@ window.parent.postMessage({ }, '*'); ``` -The Iframe can listen to an `intersection` message from the parent window to receive the intersection data. +The iframe can listen to an `intersection` message from the parent window to receive the intersection data. -Example of Iframe `send-intersection` request: +Example of iframe listening for an `intersection` message: ```javascript window.addEventListener('message', function(event) { const listener = function(event) { @@ -147,4 +143,4 @@ window.addEventListener('message', function(event) { }); ``` -The intersection message would be sent by the parent to the iframe when the iframe moves in or out of the viewport (or is partially visibile), when the iframe is scrolled or resized. +The intersection message would be sent by the parent to the iframe when the iframe moves in or out of the viewport (or is partially visibile) when the iframe is scrolled or resized.