[navigation] setting to adjust pagination to be fractions of a page

[synapticlee]

I love visidata, thank you so much for developing it. I had a feature request for pagination using ctrl+f and ctrl+b. Rather than going through one full page, I would love it if, like vim, one could paginate only about 50% or some fraction down or up. It would make it far easier to scroll through if there was some overlap between pages. Thank you!

[midichef]

Hi, I think that is a useful suggestion! Here are some commands for your .visidatarc that should do what you want. They are modified versions of the standard movement commands in movement.py and mouse.py.

#commands that are similar to vim's ^D and ^U movements
# put cursor in middle of page, then use these to scroll forward by half a page, keeping the cursor in the middle of the screen
# to change the motion size, change n to:  n = int(nScreenRows * fraction)
Sheet.addCommand('', 'scroll-up-half',   'n = -nScreenRows//2; cursorDown(n); sheet.topRowIndex += n', 'scroll half page up', replay=False)
Sheet.addCommand('', 'scroll-down-half', 'n =  nScreenRows//2; cursorDown(n); sheet.topRowIndex += n', 'scroll half page down', replay=False)
Sheet.bindkey('^B', 'scroll-up-half')
Sheet.bindkey('^F', 'scroll-down-half')

Also, without creating any new commands, you can use the mouse scrollwheel bindings to move similarly:

visidata/visidata/mouse.py

Lines 139 to 140 in d5c082f

	Sheet.addCommand('ScrollUp', 'scroll-up', 'cursorDown(options.scroll_incr); sheet.topRowIndex += options.scroll_incr', 'scroll one row up')
	Sheet.addCommand('ScrollDown', 'scroll-down', 'cursorDown(-options.scroll_incr); sheet.topRowIndex -= options.scroll_incr', 'scroll one row down')

They move a fixed number of lines, instead of a percentage of the screen. You can change the number of lines by setting options.scroll_incr.