Preserve top/bottom lines on PageUp/PageDown keypresses

[john-cj]

Consider a file with 100 lines. How many lines do you see on your screen? On my screen there are 42 ones. Place the mouse cursor to the first line and press PageDown key. On the next screen I see the lines 43, 44, 45, and so on, the line 42 isn't visible. Sometimes it's more preferable to see the bottom line from the 1st screen as the top line on the 2nd screen.

In other words, we need to have a setting to control how many lines will be preserved on PageUp/PageDown keypresses.

[FHTheron]

A crude small plugin:
https://forum.sublimetext.com/t/move-up-or-down-by-n-lines/42193/3
https://forum.sublimetext.com/t/a-better-paging-behaviour/42454/8

Should be possible to edit it to work by line counts.

[john-cj]

@FHTheron Thanks, I will look at them.

[john-cj]

@FHTheron

Here is my version, feel free to test and improve it if you find it useful:

import sublime
import sublime_plugin

class ScrollUpCommand(sublime_plugin.TextCommand):
    def run(self, edit, amount):
        view = self.view

        physical_lines_per_viewport = float(view.rowcol(view.visible_region().end())[0] -
                                            view.rowcol(view.visible_region().begin())[0])
        viewport_height = view.viewport_extent()[1]
        line_height = view.line_height()
        visual_lines_per_viewport = round(viewport_height / line_height)
        x = visual_lines_per_viewport + amount
        cursor_position = view.rowcol(view.sel()[0].begin())[0]

        # print(cursor_position, physical_lines_per_viewport)
        if cursor_position > physical_lines_per_viewport:
            view.run_command("scroll_lines", {"amount": x})
            view.run_command("move", {"by": "lines", "forward": False})
            # print("a")
        else:
            view.run_command("move_to", {"to": "bof", "extend": False})
            # print("b")

class ScrollDownCommand(sublime_plugin.TextCommand):
    def run(self, edit, amount):
        view = self.view

        physical_lines_per_viewport = float(view.rowcol(view.visible_region().end())[0] -
                                            view.rowcol(view.visible_region().begin())[0])
        viewport_height = view.viewport_extent()[1]
        line_height = view.line_height()
        visual_lines_per_viewport = round(viewport_height / line_height)
        x = visual_lines_per_viewport + amount
        cursor_position = view.rowcol(view.sel()[0].begin())[0]
        physical_lines_per_layout = view.rowcol(view.size())[0]

        # print(cursor_position, physical_lines_per_layout, physical_lines_per_viewport)
        if cursor_position < physical_lines_per_layout - physical_lines_per_viewport:
            view.run_command("scroll_lines", {"amount": -x})
            view.run_command("move", {"by": "lines", "forward": True})
            # print("a2")
        else:
            view.run_command("move_to", {"to": "eof", "extend": False})
            # print("b2")

[
    { "keys": ["pageup"], "command": "scroll_up", "args": {"amount": -2.0} },
    { "keys": ["pagedown"], "command": "scroll_down", "args": {"amount": -2.0} },
]

scroll_past_end and word_wrap can have any values.

Though it works for me, it will be better to have polished built-in option, as in VS Code.

[BenjaminSchaaf]

Fixed in 4075: The "scroll_context_lines" setting controls this behaviour.

[john-cj]

@BenjaminSchaaf I have just tested "scroll_context_lines" and it seems that it works differently.

"scroll_context_lines" does not work for me with Page Up and Page Down keys, which were the sole purpose of writing the plugin above. It works perfectly for simple Up and Down arrow keys, though.

I have tested it with ST 4.1.1.3 32-bit. Although they are not officially presented, 32-bit versions can be download from the site by "hacking" the address in the URL bar. I don't know whether it is the issue. Could you test it with ST 4.1.1.3 64-bit?