PDF page not rendering properly if the page is changed

[Радомир Хаџић <radomirhadzic46 gmail com>]

Hello.

I've sent as an attachment a code for a very simple PDF viewer. It is
not that well written but that's because I wanted it to be simple and
easy to understand. The purpose of the program is to illustrate a
problem that I'm having with my larger project.

The problem is that if a user changes page (by clicking "Previous
Page" or "Next Page") and the page when scaled accordingly is bigger
than the visible portion of the page rendering area (GtkDrawingArea),
then only the part of the page will render. You can try this yourself:
1. Open a document 2. Make sure that the next page is not completely
visible on the screen (so the scrollbars appear, this can be usually
achieved by clicking "Fit Width") 3. Click "Next page" and try
scrolling. You'll notice that one part of the page is not rendered.

So, why is this happening and how can I solve it? What also confuses
me is that rendering() function is definitely called when I scroll but
the page does not render (though it does render as it should when I
scroll the first page of a just opened document) properly, but if I
then resize the window the page renders properly.