Usually, properties should call "g_object_notify()" for the property that changed when their value changes. _set_zoom() doesn't do this: http://cgit.freedesktop.org/libreoffice/core/tree/libreofficekit/source/gtk/lokdocview.cxx#n2475
Pranav Kant committed a patch related to this issue. It has been pushed to "master": http://cgit.freedesktop.org/libreoffice/core/commit/?id=398ef76d5dc3ec1ed22fa1d9fd9151b61cce54e2 tdf#96514: Emits a 'notify' signal when zoom changes It will be available in 5.2.0. The patch should be included in the daily builds available at http://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More information about daily builds can be found at: http://wiki.documentfoundation.org/Testing_Daily_Builds Affected users are encouraged to test the fix and report feedback.
Pranav Kant committed a patch related to this issue. It has been pushed to "libreoffice-5-1": http://cgit.freedesktop.org/libreoffice/core/commit/?id=1fb882cb1e2eedbef688cf2b3a2ca9322486c9cb&h=libreoffice-5-1 tdf#96514: Emits a 'notify' signal when zoom changes It will be available in 5.1.0.2. The patch should be included in the daily builds available at http://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More information about daily builds can be found at: http://wiki.documentfoundation.org/Testing_Daily_Builds Affected users are encouraged to test the fix and report feedback.