feat: implement nvimpager = "float"

[kkanden]

this implements the "float" option for nvimpager for both R help and example. i have added a utils function for creating floating.

in the future, a user config option could be added to customize the location and size of the floating window. by default it just centers the window.

[jalvesaq]

Thank you! It works!

Some ideas (waiting for comments):

• Limit the maximum width to a not too high value, such as 120?

• Prefer 80 columns as the width of the float window?

• Between 60 and 120 columns, choose a value corresponding to the largest line in the document +1?

• Position of the float window centered on the editor window, not on the full Neovim display?

[kkanden]

good ideas, i'll try to implement these changes later today and see what looks good

[kkanden]

i have implemented the changes:

• floating window is centered relative to the code editor
• if 60 <= cols <= 120 then the width is longest line length + 1, 80 otherwise

one shortcoming (or feature?) compared to the last version is that the example/help window does not get directly overlaid on top of the preview help/example window, but is relative to it. subsequent help->help/example->example windows are overlaid as before.

[jalvesaq]

Thank you, @kkanden!

Some observations:

• Some variables in utils.open_float_win() are always overridden (width, height, col, and row), and the same code to calculate them is repeated in edit.lua and doc.lua. Hence, you can:
  • Pass lines to utils.open_float_win() and let the values of width, height, col, and row be calculated there.
  • Delete the code that calculates the variables from edit.lua and doc.lua.
• If the Object Browser is open, the float window will not be centralized in the editor window.

[kkanden]

* Some variables in `utils.open_float_win()` are always overridden (`width`, `height`, `col`, and `row`), and the same code to calculate them is repeated in `edit.lua` and `doc.lua`. Hence, you can:
  
  * Pass `lines` to `utils.open_float_win()` and let the values of `width`, `height`, `col`, and `row` be calculated there.
  * Delete the code that calculates the variables from `edit.lua` and `doc.lua`.

so in the open_float_win function we want the window to always be calculated from the line lengths of the text to be displayed (given the previous conditions)? i thought of the function to be a generic utils function.

* If the Object Browser is open, the float window will not be centralized in the editor window.

that happens if the editor window is less than 60 and the width of the floating window defaults to 80 columns. this also makes the window look like it's stuck to the side of the editor instead of centered. i thought this looked better than a centered but small and squished window.

[jalvesaq]

I'm sorry, but I'm on a trip now and will need some time to properly review the code again...