Move the page switching code into set currentPageNumber in PDFViewer instead of placing it in the pagechange event handler
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…er` instead of placing it in the `pagechange` event handler The reason that this code can be moved is that the `if (this.loading && page === 1)` check, in the `pagechange` event handler in viewer.js, is never satisfied since `this.loading` is not defined in that scope. This *could* be considered a regression from PR 5295, since prior to that `this.loading` was using the `PDFViewerApplication` scope (or `PDFView` as it were). However, I don't think that we need to fix that since we've been shipping this code in no less than *three* Firefox releases (uplifted in https://bugzilla.mozilla.org/show_bug.cgi?id=1084158), without breaking the world. An explanation of why the `pagechange` code works, despite `this.loading === undefined`, is that `set currentPageNumber` (in `PDFViewer`) returns early whenever `this.pdfDocument` isn't set. This check is, for all intents and purposes, functionally equivalent to checking `PDFViewerApplication.loading`. Hence we can move the page switching code into `PDFViewer`, and also remove `PDFViewerApplication.loading` since it's not used any more. (The `this.loading` property was added in PR 686, which was before the current viewer even existed.) *Note:* The changes in this patch should also be beneficial to the viewer `components`, since requiring every implementer to provide their own `pagechange` event handler just to get `PDFViewer.currentPageNumber` to actually work seems like an unnecessary complication.
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Nice analysis, thanks for catching this. |
yurydelendik
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Jun 30, 2015
…iewer Move the page switching code into `set currentPageNumber` in `PDFViewer` instead of placing it in the `pagechange` event handler
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The reason that this code can be moved is that the
if (this.loading && page === 1)check, in thepagechangeevent handler in viewer.js, is never satisfied sincethis.loadingis not defined in that scope.This could be considered a regression from PR #5295, since prior to that
this.loadingwas using thePDFViewerApplicationscope (orPDFViewas it were).However, I don't think that we need to fix that since we've been shipping this code in no less than three Firefox releases (uplifted in https://bugzilla.mozilla.org/show_bug.cgi?id=1084158), without breaking the world.
An explanation of why the
pagechangecode works, despitethis.loading === undefined, is thatset currentPageNumber(inPDFViewer) returns early wheneverthis.pdfDocumentisn't set. This check is, for all intents and purposes, functionally equivalent to checkingPDFViewerApplication.loading.Hence we can move the page switching code into
PDFViewer, and also removePDFViewerApplication.loadingsince it's not used any more.(The
this.loadingproperty was added in PR #686, which was before the current viewer even existed.)Note: The changes in this patch should also be beneficial to the viewer
components, since requiring every implementer to provide their ownpagechangeevent handler just to getPDFViewer.currentPageNumberto actually work seems like an unnecessary complication.