Merge branch 'release/15.2.0'

Author: Andrea Verlicchi

CHANGELOG.md

@@ -2,6 +2,38 @@
 
 ## Version 15
 
+#### 15.2.0
+
+OPTIMIZE FOR SLOW CONNECTIONS WITH `cancel_on_exit`
+
+Want to optimize speed for users who scroll down fast on a slow connection? Just set `cancel_on_exit: true` and LazyLoad will cancel the download of images exiting the viewport while still loading, eventually restoring the original attributes.
+
+-   Introduced the new `cancel_on_exit` option.
+-   Introduced the `callback_cancel` option, just in case you want to perform any additional action whenever a download gets canceled by `cancel_on_exit`.
+-   Created a new demo named `cancel_on_exit.html` so you can try the new `cancel_on_exit` option live.
+-   Set `cancel_on_exit` to `true` in the following demos, so you can test how it behaves...
+    -   `image_ph_inline.html`, with an inline SVG placeholder
+    -   `image_ph_external.html`, with an external SVG placeholder
+    -   `delay_test.html`, in conjuction with the `delay_load` option
+    -   `fade_in.html`, with a beautiful fade-in effect.
+
+The `cancel_on_exit` option applies only to images so to the `img` (and `picture`) tags. It doesn't work for background images, `iframe`s nor `video`s.
+
+The `cancel_on_exit` option will probably default to `true` starting from the next major version, so give it a try! And please report your feedback in the comments of [#438](https://github.com/verlok/lazyload/issues/438).
+
+API
+
+-   Added the `resetElementStatus()` method for when you need to tell LazyLoad to consider an image (or other DOM element) again. This is particularly useful if you change the `data-src` attribute after the previous `data-src` was loaded). See the [API section](README.md#-api) in the README file for more information.
+
+FIX
+
+-   The `callback_exit` callback was called several times (for every images out of the viewport) at instance creation or upon `update()` calls. Now the callback is properly called only when any element exits the viewport.
+
+INTERNALS
+
+-   Improved script performance by reducing the number of event listeners used for loading elements.
+-   Changed the values that the (internally used) `data-ll-status` attribute can take. Removed the status `"observed"` (it was useless) and introduced status `"delayed"`.
+
 #### 15.1.1
 
 Fixed a bug when loading lazy background images on HiDPI screens, `data-bg-hidpi` was mandatory, not it fallbacks to `data-bg`. #430

README.md

@@ -0,0 +1,28 @@
+# Current feature: resetElement
+
+It all started with #438.
+
+1. Ability to reset an element status via `resetElementStatus`, in case you need it
+   (e.g. some users want to change the `data-src` and make LazyLoad reconsider those images)
+2. Introduced a new option `cancel_on_exit` to cancel the download of the exiting images(\*) and restore the original sources (placeholders)
+3. Introduced the new `callback_cancel` option, it will be called whenever a download gets canceled
+4. Created a new demo named `cancel_on_exit.html`
+5. Set the `cancel_on_exit: true` in new demos for cross feature testing
+    - `image_ph_inline.html`,
+    - `image_ph_external.html`,
+    - `delay_test.html`
+    - `fade_in.html`
+6. Better event listeners management and removal (event listeners are temporarily stored inside the DOM elements).
+7. Removed status `"observed"` (it was useless), introduced status `"delayed"` to distinguish exit at landing | exit after delay.
+
+(\*) this technique doesn't work on `iframe` and `video` and it's too complex to manage for background images, it's now restricted only to `img` (and `picture`) tags.
+
+---
+
+Solved issues:
+
+-   The count loading / to load elements works now.
+-   The `isElementLoading` is not exposed anymore.
+-   DOM elements are unobserved when loaded / when start loading (multiple backgrounds)
+-   Canceling the download no longer triggers `callback_error`
+-   Restored `delay_load` functionality