Fix application of force-load-at-top (#243)

Currently force-load-at-top is checked in the 'scroll to the fragment'
steps. This is wrong since it shouldn't apply on same-document
navigations and it should also affect history scroll restoration.

Move this check to happen in the 'update document for history step
application' where history scroll is restored and where we can
differentiate between new- and same-document cases.

Fixes #186

index.bs

@@ -845,37 +845,35 @@ prevent fragment scrolling if the force-load-at-top policy is enabled. Make the
 >                   What should be set as target if inside a shadow tree?
 >                   <a href="https://github.com/WICG/scroll-to-text-fragment/issues/190">#190</a>
 >               </div>
->       4. <span class="diff">Assert: |target| is an [=element=].</span>
->       5. Set |document|'s target element to |target|.
->       6. Run the ancestor details revealing algorithm on |target|.
->       7. Run the ancestor hidden-until-found revealing algorithm on |target|.
+>       5. <span class="diff">Assert: |target| is an [=element=].</span>
+>       6. Set |document|'s target element to |target|.
+>       7. Run the ancestor details revealing algorithm on |target|.
+>       8. Run the ancestor hidden-until-found revealing algorithm on |target|.
 >           <div class="issue">
 >               These revealing algorithms currently wont work well since |target| could be an
 >               ancestor or even the root document node. Issue
 >               <a href="https://github.com/WICG/scroll-to-text-fragment/issues/89">#89</a> proposes
 >               restricting matches to `contain:style layout` blocks which would resolve this
 >               problem.
 >           </div>
->       8. <span class="diff"><a href="https://wicg.github.io/document-policy#algo-get-policy-value">Get the policy
->           value</a> for `force-load-at-top` for |document|. If the result is false:</span>
->           1. <span class="diff">[=scroll a target into view=],
->               with <em>target</em> set to |scrollTarget|, <em>behavior</em> set to "auto", <em>block</em> set to "center", and
->               <em>inline</em> set to "nearest".</span>
->
->               <span class="diff">Implementations MAY avoid scrolling to the target if it is
->               produced from a [=text directive=].</span>
->
->           <div class="issue">
->               <code>force-load-at-top</code> should be checked only when a new document is being
->               loaded.
->               <a href="https://github.com/WICG/scroll-to-text-fragment/issues/186">#186</a>
+>       9. <span class="diff">Let |blockPosition| be "center" if |scrollTarget| is a [=range=],
+>           "start" otherwise.</span>
+>           <div class="note">
+>             Scrolling to a text directive centers it in the block flow direction.
 >           </div>
->       9. <strike class="diff">Scroll target into view, with behavior set to "auto", block set to
+>       10. <strike class="diff">Scroll target into view, with behavior set to "auto", block set to
 >           "start", and inline set to "nearest".</strike>
->       10. Run the focusing steps for target, with the Document's viewport as the fallback target.
+>
+>           <li value="10"><span class="diff">[=scroll a target into view=],
+>           with <em>target</em> set to |scrollTarget|, <em>behavior</em> set to "auto",
+>           <em>block</em> set to |blockPosition|, and <em>inline</em> set to "nearest".</span>
+>
+>           <span class="diff">Implementations MAY avoid scrolling to the target if it is
+>           produced from a [=text directive=].</span></li>
+>       11. Run the focusing steps for target, with the Document's viewport as the fallback target.
 >           <div class="issue">Implementation note: Blink doesn’t currently set focus for text
 >           fragments, it probably should? TODO: file crbug.</div>
->       11. Move the sequential focus navigation starting point to target.
+>       12. Move the sequential focus navigation starting point to target.
 >
 >   </div>
 
@@ -1255,6 +1253,67 @@ steps of the task queued in step 2:
 >       document.
 >   3. Set <em>document</em>'s [=document/allow text fragment scroll=] to false.
 
+### Restricting Scroll on Load ### {#restricting-scroll-on-load}
+
+This section defines how the `force-load-at-top` policy is used to prevent all
+types of scrolling when loading a new document, including but not limited to
+text directives.
+
+ISSUE(WICG/scroll-to-text-fragment#242): Need to decide how `force-load-at-top`
+interacts with the Navigation API.
+
+Amend the <a spec=HTML>restore persisted state</a> steps to take a new boolean
+parameter which suppresses scroll restoration:
+
+> <strong>Monkeypatching [[HTML]]:</strong>
+>
+> <div class="monkeypatch">
+>   To restore persisted state from a session history entry <var ignore>entry</var>
+>   <span class="diff">, and boolean |suppressScrolling|</span>:
+>
+>  1. If entry's scroll restoration mode is "auto", <span class="diff">|suppressScrolling|
+>     is false,</span> and entry's document's relevant global object's navigation API's suppress
+>     normal scroll restoration during ongoing navigation is false, then restore scroll position
+>     data given entry.
+>  2. ...
+
+
+Amend the <a spec=HTML>update document for history step application</a> steps
+to check the `force-load-at-top` policy and avoid scrolling in a new document
+if it's set.
+
+> <strong>Monkeypatching [[HTML]]:</strong>
+>
+> <div class="monkeypatch">
+>   1. ...
+>       <li value="4">Set document's history object's length to scriptHistoryLength.</li>
+>   5. <span class="diff">Let |scrollingBlockedInNewDocument| be the result of
+>       <a href="https://wicg.github.io/document-policy#algo-get-policy-value">getting the policy
+>       value</a> for `force-load-at-top` for |document|.</span>
+>   5. If documentsEntryChanged is true, then:
+>       1. Let oldURL be document's latest entry's URL.
+>       2. ...
+>           <li value="5"> If documentIsNew is false, then:
+>           1. Update the navigation API entries for a same-document navigation given navigation,
+>               entry, and "traverse".
+>           2. Fire an event named popstate...
+>           3. Restore persisted state given entry <span class="diff">and
+>               |suppressScrolling| set to false.</span>
+>           4. If oldURL's fragment is not equal to...
+>       6. Otherwise,
+>           1. Assert: entriesForNavigationAPI is given.
+>           2. Restore persisted state given entry <span class="diff">and
+>               |scrollingBlockedInNewDocument|.</span>
+>           3. Initialize the navigation API entries for a new document given navigation,
+>               entriesForNavigationAPI, and entry.
+>   6. If documentIsNew is true, then:
+>       1. <span class="diff">If |scrollingBlockedInNewDocument| is false,</span> try to scroll to
+>           the fragment for document.
+>       2. At this point scripts may run for the newly-created document document.
+>   7. Otherwise, if documentsEntryChanged is false and doNotReactivate is false, then:
+>       1. ...
+>
+> </div>
 
 ## Navigating to a Text Fragment ## {#navigating-to-text-fragment}