Created attachment 291291 [details]
screenshot

Generally, the filechooser is not really as nice as it could be to pick among pictures or video files since the thumbnails are minuscule (bug #141154).

In Pitivi we made our own multimedia preview widget that handles audio files, pictures and video files. The problem is that its design is limited by what  gtk_file_chooser_set_preview_widget() allows us to do (bug #650806) since you can only tell it to set a given widget as the preview pane, and then bump the width by forcing the width of the children widgets.

The thing is that the vast majority of videos nowadays are in widescreen aspect ratio, and most images are too... which means that showing that preview in a "column" on the right of the file list (as shown in the attached screenshot) sucks big time, because you're not making efficient use of the available space: you're wasting a ton of vertical empty space, you're squeezing the filenames in the listview, and you lack enough horizontal space to expand the video preview to a comfortable size.

So I'd like to request some simple ability/API for app developers to set_preview_widget_orientation. It would then look like


----------------------------------------
| shortcuts  | pathbar                 |
| sidebar    |--------------------------
|            | files list              |
|            |                         |
|            |                         |
|            |                         |
|            |                         |
|            |                         |
|            |-------------------------|
|            | preview widget area     |
|            |                         |
|            |                         |
----------------------------------------
| "extra widgets" area                 |
----------------------------------------