Very poor performance on full-screen 1x1 landscape images

With geeqie in full-screen mode (under xfce4), viewing fairly large-resolution images, at full resolution (i.e., after hitting "z"), and with landscape format images, screen updates are very slow. That is, though image updates are essentially instantaneous (like, going back and forth through a directory of images) when the above conditions are not met - when the image is a portrait-format image (greater height than width), or when the image is not viewed at 1x magnification, or when the application is not full-screen - updates are very slow when the conditions *are* met.

The "eye of Gnome" application, a comparable image viewer, is able to paint full-screen 1x landscape format images quickly on the same platform.

The problem seems very similar to this: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=762257

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: geeqie 1:1.2-3
ProcVersionSignature: Ubuntu 3.19.0-22.22-generic 3.19.8-ckt1
Uname: Linux 3.19.0-22-generic x86_64
ApportVersion: 2.17.2-0ubuntu1.1
Architecture: amd64
Date: Sat Jul 18 11:06:57 2015
InstallationDate: Installed on 2014-03-27 (477 days ago)
InstallationMedia: Ubuntu 13.10 "Saucy Salamander" - Release amd64 (20131016.1)
ProcEnviron:
 LANGUAGE=en_US
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/zsh
SourcePackage: geeqie
UpgradeStatus: Upgraded to vivid on 2015-07-09 (8 days ago)