mungeURL worries me a bit -- especially that it allows & without escaping. It
would be better not to use system at all.

actionLaunch should check with the user when opening another file.

actionLaunch can execute arbitrary commands without prompting if launchCommand
is set (e.g. if the params are "`foo`").

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=977182
- Release process?
- How to handle unrecognised config file options -- error or warn?

Things to add to README:
- General philosophy
- Supported Poppler versions
- Compiler requirement (C++11)
  - It's actually C++14 (for make_unique) at the moment...
  - ... and it could be C++17 (for optional) eventually

Check the formatting codes are correct (e.g. error() calls).

PDFCore's doc pointer should be a std::unique_ptr. (One example of many!)

Maybe collapse XPDFCore and PDFCore together, since there are no other
subclasses.

XPDFViewer::cmdFullScreenMode and cmdWindowedMode are nearly identical and
could share a helper function.

Bind the back/forward mouse buttons as in web browsers.

The MULTITHREADED code in GlobalParams could be redone using std::unique_lock,
to match Poppler. (Or removed, since it's not used anyway. Removing it would
mean we could return a const reference from  XPDFParams::getPSFile, etc.)

Add "Copy selection" and, if over a link, "Copy URL" to the context menu.
(Suggested by jidanni in Debian #547090.)

Display an error dialog when opening a file fails, both from the command line
(if an option is given, e.g. when xpdf is being invoked from a web browser) and
from the Open dialog. (Suggested by Vincent Lefevre in Debian #931010.)

Rework PDFHistory: use std::vector rather than an array?

Rework XPDFTreeEntry: use std::vector or std::list rather than homebrew list?

Use checked multiplications where possible (goo/GooCheckedOps.h).

Add PDFCore::getDocFileName() which converts to std::string?

Work out what's going on with PDFCoreTile::bitmap's ownership -- it's treated
as an owning pointer when it's deleted but not in redrawCbk.

Add configure test for libpaper, and ask Florian to remove it from
debian/rules.

Debian bug #505932 - Support selectable checkboxes
  Unclear why this doesn't work. Poppler can render forms/annotations, but
  AnnotAppearanceBuilder::drawFormFieldButton isn't getting called on the
  buttons that have been ticked (!).
