# HG changeset patch
# User Michael Davis <mcarsondavis@gmail.com>
# Date 1668963417 21600
# Node ID 0cde36878b49229eeb240ebee329b060355b2075
# Parent  01d5c96e4e85cb09174e4f63c5d5c1c70c1792cf
Use a scrolloff-based margin for page scrolling

I'm not totally sure about the numbers here:

Is the +1 doing what I think it is?

What about the division by 2 in the half variants: should the +1 be
done after the division?

~Is this all dependent on whether the height of the viewport is even or
odd?~ Tested and this is not the case.

diff -r 01d5c96e4e85 -r 0cde36878b49 helix-term/src/commands.rs
--- a/helix-term/src/commands.rs	Tue Apr 09 08:13:22 2024 +0200
+++ b/helix-term/src/commands.rs	Sun Nov 20 10:56:57 2022 -0600
@@ -1915,51 +1915,63 @@
     doc.set_selection(view.id, sel);
 }
 
+// The `margin` in the next eight commands allows you to "undo" the view change
+// even if you have scrolloff set: (half_)page_down and then (half_)page_up should
+// keep the cursor in the same place. The `+ 1` accounts for the current line.
+
 fn page_up(cx: &mut Context) {
     let view = view!(cx.editor);
-    let offset = view.inner_height();
+    let margin = cx.editor.config().scrolloff * 2 + 1;
+    let offset = view.inner_height().saturating_sub(margin);
     scroll(cx, offset, Direction::Backward, false);
 }
 
 fn page_down(cx: &mut Context) {
     let view = view!(cx.editor);
-    let offset = view.inner_height();
+    let margin = cx.editor.config().scrolloff * 2 + 1;
+    let offset = view.inner_height().saturating_sub(margin);
     scroll(cx, offset, Direction::Forward, false);
 }
 
 fn half_page_up(cx: &mut Context) {
     let view = view!(cx.editor);
-    let offset = view.inner_height() / 2;
+    let margin = cx.editor.config().scrolloff * 2 + 1;
+    let offset = view.inner_height().saturating_sub(margin) / 2;
     scroll(cx, offset, Direction::Backward, false);
 }
 
 fn half_page_down(cx: &mut Context) {
     let view = view!(cx.editor);
-    let offset = view.inner_height() / 2;
+    let margin = cx.editor.config().scrolloff * 2 + 1;
+    let offset = view.inner_height().saturating_sub(margin) / 2;
     scroll(cx, offset, Direction::Forward, false);
 }
 
 fn page_cursor_up(cx: &mut Context) {
     let view = view!(cx.editor);
-    let offset = view.inner_height();
+    let margin = cx.editor.config().scrolloff * 2 + 1;
+    let offset = view.inner_height().saturating_sub(margin);
     scroll(cx, offset, Direction::Backward, true);
 }
 
 fn page_cursor_down(cx: &mut Context) {
     let view = view!(cx.editor);
-    let offset = view.inner_height();
+    let margin = cx.editor.config().scrolloff * 2 + 1;
+    let offset = view.inner_height().saturating_sub(margin);
     scroll(cx, offset, Direction::Forward, true);
 }
 
 fn page_cursor_half_up(cx: &mut Context) {
     let view = view!(cx.editor);
-    let offset = view.inner_height() / 2;
+    let margin = cx.editor.config().scrolloff * 2 + 1;
+    let offset = view.inner_height().saturating_sub(margin) / 2;
     scroll(cx, offset, Direction::Backward, true);
 }
 
 fn page_cursor_half_down(cx: &mut Context) {
     let view = view!(cx.editor);
-    let offset = view.inner_height() / 2;
+    let margin = cx.editor.config().scrolloff * 2 + 1;
+    let offset = view.inner_height().saturating_sub(margin) / 2;
     scroll(cx, offset, Direction::Forward, true);
 }