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Add spread modes to web viewer

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This builds on the scrolling mode work to add three buttons for joining
page spreads together: one for the default view, with no page spreads,
and two for spreads starting on odd-numbered or even-numbered pages.
This commit is contained in:
Ryan Hendrickson 2018-05-14 23:10:32 -04:00
parent 91cbc185da
commit 3d83c646c6
16 changed files with 168 additions and 25 deletions
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26
web/ui_utils.js
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@ -316,9 +316,10 @@ function getPageSizeInches({ view, userUnit, rotate, }) {
*/
function backtrackBeforeAllVisibleElements(index, views, top) {
// binarySearchFirstItem's assumption is that the input is ordered, with only
// one index where the conditions flips from false to true:
// [false ..., true...]. With wrapped scrolling, it is possible to have
// [false ..., true, false, true ...].
// one index where the conditions flips from false to true: [false ...,
// true...]. With vertical scrolling and spreads, it is possible to have
// [false ..., true, false, true ...]. With wrapped scrolling we can have a
// similar sequence, with many more mixed true and false in the middle.
//
// So there is no guarantee that the binary search yields the index of the
// first visible element. It could have been any of the other visible elements
@ -451,10 +452,11 @@ function getVisibleElements(scrollEl, views, sortByVisibility = false,
isElementBottomAfterViewTop);
if (views.length > 0 && !horizontal) {
// In wrapped scrolling, with some page sizes, isElementBottomAfterViewTop
// doesn't satisfy the binary search condition: there can be pages with
// bottoms above the view top between pages with bottoms below. This
// function detects and corrects that error; see it for more comments.
// In wrapped scrolling (or vertical scrolling with spreads), with some page
// sizes, isElementBottomAfterViewTop doesn't satisfy the binary search
// condition: there can be pages with bottoms above the view top between
// pages with bottoms below. This function detects and corrects that error;
// see it for more comments.
firstVisibleElementInd =
backtrackBeforeAllVisibleElements(firstVisibleElementInd, views, top);
}
@ -462,11 +464,11 @@ function getVisibleElements(scrollEl, views, sortByVisibility = false,
// lastEdge acts as a cutoff for us to stop looping, because we know all
// subsequent pages will be hidden.
//
// When using wrapped scrolling, we can't simply stop the first time we reach
// a page below the bottom of the view; the tops of subsequent pages on the
// same row could still be visible. In horizontal scrolling, we don't have
// that issue, so we can stop as soon as we pass `right`, without needing the
// code below that handles the -1 case.
// When using wrapped scrolling or vertical scrolling with spreads, we can't
// simply stop the first time we reach a page below the bottom of the view;
// the tops of subsequent pages on the same row could still be visible. In
// horizontal scrolling, we don't have that issue, so we can stop as soon as
// we pass `right`, without needing the code below that handles the -1 case.
let lastEdge = horizontal ? right : -1;
for (let i = firstVisibleElementInd, ii = views.length; i < ii; i++) {