Give scroll-forward a less confusing name

ECMA-48 calls CSI S "scroll up", so use something like that but try
to avoid ambiguity.

doc_src/terminal-compatibility.rst

@@ -198,7 +198,7 @@ Optional Commands
 
        ``\e[ Ps S``
      - indn
-     - Scroll up Ps lines (aka ``SU`` but terminfo calls it "scroll forward")
+     - Scroll up the content (not the viewport) Ps lines (aka ``SU`` but terminfo calls it "scroll forward")
        This enables the :ref:`scrollback-push <special-input-functions-scrollback-push>` special input function which is used by :kbd:`ctrl-l`.
      - ECMA-48
    * - ``\e[= Ps u``, ``\e[? Ps u``

src/input_common.rs

@@ -11,7 +11,7 @@
     function_key, shift, Key, Modifiers, ViewportPosition,
 };
 use crate::reader::reader_test_and_clear_interrupted;
-use crate::terminal::{SCROLL_FORWARD_SUPPORTED, SCROLL_FORWARD_TERMINFO_CODE};
+use crate::terminal::{SCROLL_CONTENT_UP_SUPPORTED, SCROLL_CONTENT_UP_TERMINFO_CODE};
 use crate::threads::iothread_port;
 use crate::tty_handoff::{
     get_kitty_keyboard_capability, maybe_set_kitty_keyboard_capability, XTVERSION,
@@ -1505,9 +1505,9 @@ fn parse_dcs(&mut self, buffer: &mut Vec<u8>) -> Option<KeyEvent> {
                 format!("Received XTGETTCAP response: {}", str2wcstring(&key))
             );
         }
-        if key == SCROLL_FORWARD_TERMINFO_CODE.as_bytes() {
-            SCROLL_FORWARD_SUPPORTED.store(true);
-            FLOG!(reader, "Scroll forward is supported");
+        if key == SCROLL_CONTENT_UP_TERMINFO_CODE.as_bytes() {
+            SCROLL_CONTENT_UP_SUPPORTED.store(true);
+            FLOG!(reader, "SCROLL UP is supported");
         }
         return None;
     }

src/reader.rs

@@ -134,7 +134,7 @@
     QueryCursorPosition, QueryKittyKeyboardProgressiveEnhancements, QueryPrimaryDeviceAttribute,
     QueryXtgettcap, QueryXtversion,
 };
-use crate::terminal::{SCROLL_FORWARD_SUPPORTED, SCROLL_FORWARD_TERMINFO_CODE};
+use crate::terminal::{SCROLL_CONTENT_UP_SUPPORTED, SCROLL_CONTENT_UP_TERMINFO_CODE};
 use crate::termsize::{termsize_invalidate_tty, termsize_last, termsize_update};
 use crate::text_face::parse_text_face;
 use crate::text_face::TextFace;
@@ -2678,7 +2678,7 @@ fn query_capabilities_via_dcs(out: &mut impl Output) {
         return;
     }
     out.write_command(DecsetAlternateScreenBuffer); // enable alternative screen buffer
-    send_xtgettcap_query(out, SCROLL_FORWARD_TERMINFO_CODE);
+    send_xtgettcap_query(out, SCROLL_CONTENT_UP_TERMINFO_CODE);
     out.write_command(DecrstAlternateScreenBuffer); // disable alternative screen buffer
 }
 
@@ -3946,7 +3946,7 @@ fn handle_readline_command(&mut self, c: ReadlineCmd) {
                 self.clear_screen_and_repaint();
             }
             rl::ScrollbackPush => {
-                if !SCROLL_FORWARD_SUPPORTED.load() {
+                if !SCROLL_CONTENT_UP_SUPPORTED.load() {
                     return;
                 }
                 let query = self.blocking_query();

src/screen.rs

@@ -34,7 +34,7 @@
 use crate::highlight::{HighlightColorResolver, HighlightSpec};
 use crate::terminal::TerminalCommand::{
     self, ClearToEndOfLine, ClearToEndOfScreen, CursorDown, CursorLeft, CursorMove, CursorRight,
-    CursorUp, EnterDimMode, ExitAttributeMode, Osc133PromptStart, ScrollForward,
+    CursorUp, EnterDimMode, ExitAttributeMode, Osc133PromptStart, ScrollContentUp,
 };
 use crate::terminal::{use_terminfo, BufferedOutputter, CardinalDirection, Output, Outputter};
 use crate::termsize::{termsize_last, Termsize};
@@ -588,8 +588,8 @@ pub fn push_to_scrollback(&mut self, cursor_y: usize) {
             return;
         }
         let mut out = BufferedOutputter::new(self.outp);
-        // Scroll down.
-        out.write_command(ScrollForward(lines_to_scroll));
+        // Move everything to scrollback.
+        out.write_command(ScrollContentUp(lines_to_scroll));
         // Reposition cursor.
         out.write_command(CursorMove(CardinalDirection::Up, lines_to_scroll));
     }

src/terminal.rs

@@ -109,7 +109,7 @@ pub(crate) enum TerminalCommand<'a> {
 
     // Other terminal features
     QueryCursorPosition,
-    ScrollForward(usize),
+    ScrollContentUp(usize),
 
     DecsetShowCursor,
     DecrstMouseTracking,
@@ -182,7 +182,7 @@ fn write(out: &mut impl Output, sequence: &'static [u8]) -> bool {
             Osc133CommandStart(command) => osc_133_command_start(self, command),
             Osc133CommandFinished(s) => osc_133_command_finished(self, s),
             QueryCursorPosition => write(self, b"\x1b[6n"),
-            ScrollForward(lines) => scroll_forward(self, lines),
+            ScrollContentUp(lines) => scroll_content_up(self, lines),
             DecsetShowCursor => write(self, b"\x1b[?25h"),
             DecrstMouseTracking => write(self, b"\x1b[?1000l"),
             DecsetFocusReporting => write(self, b"\x1b[?1004h"),
@@ -216,8 +216,8 @@ fn maybe_terminfo(
     true
 }
 
-pub(crate) static SCROLL_FORWARD_SUPPORTED: RelaxedAtomicBool = RelaxedAtomicBool::new(false);
-pub(crate) static SCROLL_FORWARD_TERMINFO_CODE: &str = "indn";
+pub(crate) static SCROLL_CONTENT_UP_SUPPORTED: RelaxedAtomicBool = RelaxedAtomicBool::new(false);
+pub(crate) static SCROLL_CONTENT_UP_TERMINFO_CODE: &str = "indn";
 
 pub(crate) fn use_terminfo() -> bool {
     !future_feature_flags::test(FeatureFlag::ignore_terminfo) && TERM.lock().unwrap().is_some()
@@ -412,8 +412,8 @@ fn osc_133_command_finished(out: &mut impl Output, exit_status: libc::c_int) ->
     true
 }
 
-fn scroll_forward(out: &mut impl Output, lines: usize) -> bool {
-    assert!(SCROLL_FORWARD_SUPPORTED.load());
+fn scroll_content_up(out: &mut impl Output, lines: usize) -> bool {
+    assert!(SCROLL_CONTENT_UP_SUPPORTED.load());
     write_to_output!(out, "\x1b[{}S", lines);
     true
 }