fixes #857, keeping the current photos in view when adjusting the thumbnail slider
fixes #857, keeping the current photos in view when adjusting the thumbnail slider

h4ck3rm1k3/shotwell,damianmoore/shotwell,Sanva/shotwell-gsoc,Sanva/shotwell-gsoc,jof/shotwell,ritchiewilson/shotwell,jimbonator/shotwell,ritchiewilson/shotwell,abrauchli/shotwell,ritchiewilson/shotwell,h4ck3rm1k3/shotwell,jimbonator/shotwell,polymeris/shotwell,Sanva/shotwell-gsoc,polymeris/shotwell,jimbonator/shotwell,damianmoore/shotwell,polymeris/shotwell,jof/shotwell,damianmoore/shotwell,h4ck3rm1k3/shotwell,abrauchli/shotwell,jof/shotwell,abrauchli/shotwell