Add load progress callback

[pj-r]

Would it be hard to add an event emitter for progress of loading pdf document?
I did quick research and looks like it could be done.

from pdfjs src/display/api.js we can find:

loadingTask.onProgress({
  loaded: data.loaded,
  total: data.total,
});

add an event emitter to pdf-viewer.component.ts:

@Output('on-progress') onProgress = new EventEmitter<any>();

change the line in pdf-viewer.component.ts to handle progress event:

PDFJS.getDocument(src).then((pdf: PDFDocumentProxy) => {

---->

PDFDocumentLoadingTask task = PDFJS.getDocument(src);
task.onProgress = (any) => { this.onProgress(any); };
task.then((pdf: PDFDocumentProxy) => {

Note: Just pseudo code. Havent tested if it works.

[VadimDez]

You can use different approach, by just settings isLoading = true; before and then change to isLoading = false once after-load-complete event is called.

[pj-r]

Thats good approach but in my case the problem is that for example with IE loading some bigger pdf files can take up to 3 minutes and it would be nice to show progress for the user so he/she can determine how long the coffee break will be.

There is one example file: https://github.com/mozilla/pdf.js/issues/7989

[pj-r]

Nice work, Thanks!