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Merge pull request #785 from matrix-org/luke/fix-scroll-past-big-event

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Fix scroll token selection logic
This commit is contained in:
Luke Barnard 2017-04-06 12:36:30 +01:00 committed by GitHub
commit 880a48494b
2 changed files with 39 additions and 33 deletions
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68
src/components/structures/ScrollPanel.js
View file

@ -333,33 +333,27 @@ module.exports = React.createClass({
if (excessHeight <= 0) {
return;
}
var itemlist = this.refs.itemlist;
var tiles = itemlist.children;
const tiles = this.refs.itemlist.children;
// The scroll token of the first/last tile to be unpaginated
let markerScrollToken = null;
// Subtract clientHeights to simulate the events being unpaginated whilst counting
// the events to be unpaginated.
if (backwards) {
// Iterate forwards from start of tiles, subtracting event tile height
let i = 0;
while (i < tiles.length && excessHeight > tiles[i].clientHeight) {
excessHeight -= tiles[i].clientHeight;
if (tiles[i].dataset.scrollToken) {
markerScrollToken = tiles[i].dataset.scrollToken;
}
i++;
// Subtract heights of tiles to simulate the tiles being unpaginated until the
// excess height is less than the height of the next tile to subtract. This
// prevents excessHeight becoming negative, which could lead to future
// pagination.
//
// If backwards is true, we unpaginate (remove) tiles from the back (top).
for (let i = 0; i < tiles.length; i++) {
const tile = tiles[backwards ? tiles.length - 1 - i : i];
// Subtract height of tile as if it were unpaginated
excessHeight -= tile.clientHeight;
// The tile may not have a scroll token, so guard it
if (tile.dataset.scrollToken) {
markerScrollToken = tile.dataset.scrollToken;
}
} else {
// Iterate backwards from end of tiles, subtracting event tile height
let i = tiles.length - 1;
while (i > 0 && excessHeight > tiles[i].clientHeight) {
excessHeight -= tiles[i].clientHeight;
if (tiles[i].dataset.scrollToken) {
markerScrollToken = tiles[i].dataset.scrollToken;
}
i--;
if (tile.clientHeight > excessHeight) {
break;
}
}
@ -589,24 +583,34 @@ module.exports = React.createClass({
var itemlist = this.refs.itemlist;
var wrapperRect = ReactDOM.findDOMNode(this).getBoundingClientRect();
var messages = itemlist.children;
let newScrollState = null;
for (var i = messages.length-1; i >= 0; --i) {
var node = messages[i];
if (!node.dataset.scrollToken) continue;
var boundingRect = node.getBoundingClientRect();
if (boundingRect.bottom < wrapperRect.bottom) {
this.scrollState = {
stuckAtBottom: false,
trackedScrollToken: node.dataset.scrollToken,
pixelOffset: wrapperRect.bottom - boundingRect.bottom,
};
debuglog("ScrollPanel: saved scroll state", this.scrollState);
return;
newScrollState = {
stuckAtBottom: false,
trackedScrollToken: node.dataset.scrollToken,
pixelOffset: wrapperRect.bottom - boundingRect.bottom,
};
// If the bottom of the panel intersects the ClientRect of node, use this node
// as the scrollToken.
// If this is false for the entire for-loop, we default to the last node
// (which is why newScrollState is set on every iteration).
if (boundingRect.top < wrapperRect.bottom) {
// Use this node as the scrollToken
break;
}
}
debuglog("ScrollPanel: unable to save scroll state: found no children in the viewport");
// This is only false if there were no nodes with `node.dataset.scrollToken` set.
if (newScrollState) {
this.scrollState = newScrollState;
debuglog("ScrollPanel: saved scroll state", this.scrollState);
} else {
debuglog("ScrollPanel: unable to save scroll state: found no children in the viewport");
}
},
_restoreSavedScrollState: function() {

4
src/components/structures/TimelinePanel.js
View file

@ -251,10 +251,12 @@ var TimelinePanel = React.createClass({
},
onMessageListUnfillRequest: function(backwards, scrollToken) {
// If backwards, unpaginate from the back (i.e. the start of the timeline)
let dir = backwards ? EventTimeline.BACKWARDS : EventTimeline.FORWARDS;
debuglog("TimelinePanel: unpaginating events in direction", dir);
// All tiles are inserted by MessagePanel to have a scrollToken === eventId
// All tiles are inserted by MessagePanel to have a scrollToken === eventId, and
// this particular event should be the first or last to be unpaginated.
let eventId = scrollToken;
let marker = this.state.events.findIndex(