Hi Michael, This is not such an easy feature to implement, though as Daniel says, it's feasible with some caveats. One issue to be aware of is performance-related -- PDF is very heavy to embed on a page because the format is very complex and poppler is therefore slow, so I'm not sure how responsive things will be if someone tries to insert lots of PDF fragments onto the page. Also, we'll have to say goodbye to the legacy PDF export.
Roughly, the plan of action to do this and the surrounding changes needed / warranted in connection to it might look as follows. The biggest structural change is modifying the xournal/poppler interaction so that there can be several PDF files being rendered for a single xournal document -- currently xournal maintains the unique PDF file being annotated in memory as well as bitmap renderings of the pages that have been accessed so far at the display resolution (in the "bgpdf" structure), calling poppler in background as needed to refresh when a page not yet seen becomes visible or when the display zoom level changes. There's some soul-searching to be done to figure out the best data structures to maintain a working relationship with several poppler documents at once (presumably we just want to have multiple struct BgPdf's around, one for each file referenced in the xoj; don't let the "Bg" part of the name fool you, the BgPdf structure is not particularly specific to page backgrounds, it just keeps track of a subset of pages from a PDF document to be rendered through poppler into xournal's data structures as gdk-pixbufs to be inserted into the GnomeCanvas for display, and queues requests for re-rendering the pages at different resolutions). (Right now the updating of PDF background pages is done via calls to rescale_bg_pixmaps() which in turns calls add_bgpdf_request() to schedule a PDF rendering; bgpdf_scheduler_callback() actually does the job. One would presumably add other calls to add_bgpdf_request() to request updates to other embedded PDF pieces). All that said, there are many moving pieces -- besides extending the internal data structures to allow several PDFs at once + PDF fragments that sit on the page rather than serve as background, one needs to take care of various things: * extend the xoj file format, and the struct Item data structure, to be able to include not just png images but also pdf pages onto the xoj page. * allow either embedding or linking to an external file (both for backgrounds and for objects sitting on the page, for consistency, though perhaps we'd hardcode a default behavior in the UI, e.g. embed pngs since they can be copy-pasted into xournal and not necessarily exist as pages, vs. link pdfs since we'd always receive those via a file selection dialog box and not a copy-paste of a bitmap fragment, though one could add a "embed/link" pair of radio buttons to the file selection box). * not sure if this is something you need, but perhaps allow some method to 'crop' to an excerpt of a pdf page when a pdf object placed on the page gets resized, rather than rescaling it and keeping the whole pdf page. If we're going to display PDF bits and pieces, might as well allow the user to display only *part* of a PDF page, eg so they don't have to figure out how to modify the bounding-box of the PDF page on the other end of things (ever tried to produce "bounding box sized" rather than "printer page sized" PDFs from random office software?). * regarding rescaling, one needs to be aware that poppler can only render to bitmaps with a same scaling ratio for x and y directions, so we can't easily allow rescalings of PDF fragments that modify aspect ratio -- or rather, we could but they'll become blurry. The other option is to treat them like the text boxes and always rescale in an aspect-preserving manner. * allow the page backgrounds for different pages to reference more than one PDF file -- if we're allowing fragments of various PDF files to sit on the page then we might as well allow a xoj file to annotate backgrounds taken from more than one PDF. * kill the "legacy export to PDF" feature, which can't handle multiple incoming PDF files. (Or use it only when only one PDF is used as backgrounds and there are no on-page PDF fragments). (There are still some PDF files where it produces a better result than the new export to PDF via poppler). * ideally, design a piece of UI to allow the user to modify what PDF page is being referenced somewhere -- e.g. modify the background of the current page to say "use instead page 46 of this other PDF file". For fragments on the page this is not so crucial (one can always expect the user to delete the item and insert a new one) but for the background we currently lack any kind of decent user interface for changing what PDF page one wants to use. (Conceptually perhaps the right thing to do is to make the PDF background behave just as an inserted PDF fragment, simply it lives on the Background layer instead of on a normal drawable layer, and always occupies the whole page when it is present; but we could want to rescale / crop it or change what it is just as with the PDF items that Michael wants to put on the other layers). I'm probably forgetting some other stuff too. Anyway: I realize doing all this is just a very large undertaking and not realistic. I'm not suggesting either of you try to do all this or even the bulk of it. On the other hand, modifying the code to have multiple BgPdf structures and allowing pdf objects on the page (more specifically, just pasting the whole page 1 of a PDF at unit scale onto the xoj page) (perhaps working within the "Image" tool, but when the user selects a PDF instead of a bitmap format) might be a reasonable goal. Best, Denis On 12/14/2015 06:05 AM, Michael J Gruber wrote: > Hi there, > > I'm wondering what the current state is regarding inclusion of PDFs, and > what the best direction would be. As far as I understand: > > - Xournal can annotate PDFs directly or load them as background. In each > case, the page size is set to the PDFs page size. If you change it then > the PDF gets rescaled. Also, this means one PDF per page, obviously. > > - Xournal can insert an arbitrary number of images and rescale them. > They get embedded into the xoj. > > That get's you only so far if you want to include, say, multiple graphs > into your lecture notes. I can convert PDF to PNG, of course, but that > seems to be moot if Xournal knows how to render PDFs (using poppler), > and besides the unnecessary increase in file size (embedded PNG), this > also makes it difficult to update an xoj with updated graphs. > > So, ideally I would like to "include" PDFs as links to the PDF (just > like the annotated PDFs), multiple ones per xoj page. I don't mind > editing an xoj by hand (vim to the rescue...). > > Michael > > > ------------------------------------------------------------------------------ > _______________________________________________ > Xournal-devel mailing list > Xournal-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/xournal-devel > -- Denis Auroux UC Berkeley, Department of Mathematics 817 Evans Hall, Berkeley CA 94720-3840, USA aur...@math.berkeley.edu ------------------------------------------------------------------------------ _______________________________________________ Xournal-devel mailing list Xournal-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/xournal-devel
