Single page forward/backward step in 2 page view?

[Petra Roosen]

Hello @all,

being a hobby musician, I want to get rid of the heavy paper score sheet
packs to be carried around by using a light-weight computer (like the
Raspi) with a larger, but light, 20+" display that is able to tackle two
score pages side-by-side. Of course this approach needs a "special" page
turning function, typically realized by foot pedal.

Problem: I would like to show two pages of a multi-page score sheet on
the display, placed horizontally on a music stand. This size is large
enough to display the equivalent of 2 conventional paper pages side by
side in one view. A page turn should now forward the view only by one
"paper" page, i.e. half of the display width. The reason: reading
musical scores you frequently need to stay on the presently played page
but need to have a look forward on the score to see what comes next.
Additionally there are repeat phrases frequently, so you need to
"fine-tune" the required 2-page section to be displayed at a given time.

Okular, as all other PDF viewers, only allows to "turn pages" in 2-page
mode modulo 2: You replace the complete 2 page view with the next one,
so the "one paper page forward with display overlap" is not feasible.
Among the other PDF viewers there is just one exception that I found so
far: PDF viewing in Firefox: If you forward to next page, the currently
displayed pages are shifted just by one to the left. But Firefox won't
let you edit your sheets which is necessary for musicians, as they
"work" with the sheets and need to annotate the document graphically.

There are multiple keyboard shortcut commands in Okular presently to
turn pages: PAGE_UP/DN, CURSOR_UP/DN, CURSOR_Left/Right all do the same,
which is a pity. Could the behaviour of Okular be changed in a way to
discriminate between "one logical page forward" and "complete present
view forward". Or is this already realized and I just didn't find the
feature?

Just a side remark: Using PAGE_UP/DN for the requested feature would be
very fine, as this would create some compatibility with typical settings
of Bluetooth foot pedals that are frequently used for the page turning
process while playing. But most pedals have the possibility to use the
other mentioned combinations as well.

Kind regards,
Petra