Move scrollback-push feature detection to fish script

A lot of terminals support CSI Ps S.  Currently we only allow them
to use scrollback-up if they advertise it via XTGETTCAP.  This seems
surprising; it's better to make visible in fish script  whether this
is supposed to be working.  The canonical place is in "bind ctrl-l"
output.

The downside here is that we need to expose something that's rarely
useful. But the namespace pollution is not so bad, and this gives
users a nice paper trail instead of having to look in the source code.

CHANGELOG.rst

@@ -69,7 +69,7 @@ New or improved bindings
 - Before clearing the screen and redrawing, :kbd:`ctrl-l` now pushes all text located above the prompt to the terminal's scrollback,
   via a new special input function :ref:`scrollback-push <special-input-functions-scrollback-push>`.
   For compatibility with terminals that do not implement ECMA-48's :ref:`SCROLL UP <term-compat-indn>` command,
-  this function is only enabled if the terminal advertises support for that via :ref:`XTGETTCAP <term-compat-xtgettcap>`.
+  this function is only used if the terminal advertises support for that via :ref:`XTGETTCAP <term-compat-xtgettcap>`.
 - Vi mode has learned :kbd:`ctrl-a` (increment) and :kbd:`ctrl-x` (decrement) (:issue:`11570`).
 
 Completions

doc_src/cmds/bind.rst

@@ -187,9 +187,7 @@ The following special input functions are available:
 
 ``scrollback-push``
     pushes earlier output to the terminal scrollback, positioning the prompt at the top.
-
-    For compatibility with terminals that do not provide the ECMA-48 ``SCROLL UP`` command,
-    this command does nothing unless the terminal advertises support for that command via :ref:`XTGETTCAP <term-compat-xtgettcap>`.
+    This requires the terminal to implement the ECMA-48 :ref:`SCROLL UP <term-compat-indn>` command and :ref:`cursor position reporting <term-compat-cursor-position-report>`.
 
 ``complete``
     guess the remainder of the current token

doc_src/cmds/status.rst

@@ -34,6 +34,7 @@ Synopsis
     status get-file FILE
     status list-files [PATH]
     status terminal
+    status test-terminal-feature FEATURE
 
 Description
 -----------
@@ -118,14 +119,25 @@ The following operations (subcommands) are available:
     This lists the files embedded in the fish binary at compile time. Only files where the path starts with the optional *FILE* argument are shown.
     Returns 0 if something was printed, 1 otherwise.
 
+.. _status-terminal:
+
 **terminal**
     Prints the name and version of the terminal fish is running inside (for example as reported via :ref:`XTVERSION <term-compat-xtversion>`).
-    This is not available during early startup but only just before the first interactive prompt is shown (possibly via builtin :doc:`read <read>`),
-    that is, on the first ``fish_prompt`` or ``fish_read`` :ref:`event <event>`.
+    This is not available during early startup but only starting from when the first interactive prompt is shown, possibly via builtin :doc:`read <read>`,
+    so before the first ``fish_prompt`` or ``fish_read`` :ref:`event <event>`.
+
+.. _status-test-terminal-features:
+
+**test-terminal-feature** *FEATURE*
+    Returns 0 when the terminal was :ref:`detected <term-compat-xtgettcap>` to support the given feature.
+    Like :ref:`status terminal <status-terminal>`, this only works once the first interactive prompt is shown.
+
+    Currently the only available *FEATURE* is :ref:`scroll-content-up <term-compat-indn>`.
+    An error will be printed when passed an unrecognized feature.
 
 Notes
 -----
 
-For backwards compatibility most subcommands can also be specified as a long or short option. For example, rather than ``status is-login`` you can type ``status --is-login``. The flag forms are deprecated and may be removed in a future release (but not before fish 4.0).
+For backwards compatibility most subcommands can also be specified as a long or short option. For example, rather than ``status is-login`` you can type ``status --is-login``. The flag forms are deprecated and may be removed in a future release.
 
 You can only specify one subcommand per invocation even if you use the flag form of the subcommand.

doc_src/terminal-compatibility.rst

@@ -198,8 +198,9 @@ Optional Commands
 
        ``\e[ Ps S``
      - indn
-     - Scroll up the content (not the viewport) Ps lines (called ``SCROLL UP`` / ``SU`` by ECMA-48 and "scroll forward" by terminfo)
-       This enables the :ref:`scrollback-push <special-input-functions-scrollback-push>` special input function which is used by :kbd:`ctrl-l`.
+     - Scroll up the content (not the viewport) Ps lines (called ``SCROLL UP`` / ``SU`` by ECMA-48 and "scroll forward" by terminfo).
+       When fish detects support for this feature, :ref:`status test-terminal-features scroll-content-up <status-test-terminal-features>` will return 0,
+       which enables the :kbd:`ctrl-l` binding to use the :ref:`scrollback-push <special-input-functions-scrollback-push>` special input function.
      - ECMA-48
    * - ``\e[= Ps u``, ``\e[? Ps u``
      - n/a
@@ -215,10 +216,8 @@ Optional Commands
        and the second parameter is the column number.
        Both start at 1.
 
-       This is used inside terminals that either
-
-       - implement the OSC 133 :ref:`click_events <term-compat-osc-133>` feature.
-       - advertise the :ref:`indn <term-compat-indn>` capability via :ref:`XTGETTCAP <term-compat-xtgettcap>`
+       This is used by the :ref:`scrollback-push <special-input-functions-scrollback-push>` special input function,
+       and inside terminals that implement the OSC 133 :ref:`click_events <term-compat-osc-133>` feature.
      - VT100
    * - ``\e[ \x20 q``
      - Se

po/de.po

@@ -265,10 +265,6 @@ msgstr ""
 msgid "%ls: --set-cursor option requires --add\n"
 msgstr ""
 
-#, c-format
-msgid "%ls: -S requires a non-empty string\n"
-msgstr "%ls: -S erfordert eine nicht leere Zeichenkette\n"
-
 #, c-format
 msgid "%ls: -l requires a non-empty string\n"
 msgstr ""
@@ -811,6 +807,11 @@ msgstr ""
 msgid "%s"
 msgstr ""
 
+#
+#, c-format
+msgid "%s %s: unrecognized feature '%ls'"
+msgstr ""
+
 #
 #, c-format
 msgid "%s and %s are mutually exclusive"
@@ -65152,6 +65153,9 @@ msgstr ""
 msgid "Test if snap has yet to be given the subcommand"
 msgstr ""
 
+msgid "Test if the terminal suports the given feature"
+msgstr ""
+
 msgid "Test if there is a subcommand given"
 msgstr ""
 

po/en.po

@@ -263,10 +263,6 @@ msgstr ""
 msgid "%ls: --set-cursor option requires --add\n"
 msgstr ""
 
-#, c-format
-msgid "%ls: -S requires a non-empty string\n"
-msgstr ""
-
 #, c-format
 msgid "%ls: -l requires a non-empty string\n"
 msgstr ""
@@ -809,6 +805,11 @@ msgstr ""
 msgid "%s"
 msgstr ""
 
+#
+#, c-format
+msgid "%s %s: unrecognized feature '%ls'"
+msgstr ""
+
 #
 #, c-format
 msgid "%s and %s are mutually exclusive"
@@ -65148,6 +65149,9 @@ msgstr ""
 msgid "Test if snap has yet to be given the subcommand"
 msgstr ""
 
+msgid "Test if the terminal suports the given feature"
+msgstr ""
+
 msgid "Test if there is a subcommand given"
 msgstr ""
 

po/fr.po

@@ -364,10 +364,6 @@ msgstr ""
 msgid "%ls: --set-cursor option requires --add\n"
 msgstr ""
 
-#, c-format
-msgid "%ls: -S requires a non-empty string\n"
-msgstr ""
-
 #, c-format
 msgid "%ls: -l requires a non-empty string\n"
 msgstr "%ls : -l requiert une chaîne non-vide\n"
@@ -910,6 +906,11 @@ msgstr ""
 msgid "%s"
 msgstr ""
 
+#
+#, c-format
+msgid "%s %s: unrecognized feature '%ls'"
+msgstr ""
+
 #
 #, c-format
 msgid "%s and %s are mutually exclusive"
@@ -65249,6 +65250,9 @@ msgstr ""
 msgid "Test if snap has yet to be given the subcommand"
 msgstr ""
 
+msgid "Test if the terminal suports the given feature"
+msgstr ""
+
 msgid "Test if there is a subcommand given"
 msgstr ""
 

po/pl.po

@@ -259,10 +259,6 @@ msgstr ""
 msgid "%ls: --set-cursor option requires --add\n"
 msgstr ""
 
-#, c-format
-msgid "%ls: -S requires a non-empty string\n"
-msgstr ""
-
 #, c-format
 msgid "%ls: -l requires a non-empty string\n"
 msgstr ""
@@ -805,6 +801,11 @@ msgstr ""
 msgid "%s"
 msgstr ""
 
+#
+#, c-format
+msgid "%s %s: unrecognized feature '%ls'"
+msgstr ""
+
 #
 #, c-format
 msgid "%s and %s are mutually exclusive"
@@ -65144,6 +65145,9 @@ msgstr ""
 msgid "Test if snap has yet to be given the subcommand"
 msgstr ""
 
+msgid "Test if the terminal suports the given feature"
+msgstr ""
+
 msgid "Test if there is a subcommand given"
 msgstr ""
 

po/pt_BR.po

@@ -264,10 +264,6 @@ msgstr ""
 msgid "%ls: --set-cursor option requires --add\n"
 msgstr ""
 
-#, c-format
-msgid "%ls: -S requires a non-empty string\n"
-msgstr ""
-
 #, c-format
 msgid "%ls: -l requires a non-empty string\n"
 msgstr ""
@@ -810,6 +806,11 @@ msgstr ""
 msgid "%s"
 msgstr ""
 
+#
+#, c-format
+msgid "%s %s: unrecognized feature '%ls'"
+msgstr ""
+
 #
 #, c-format
 msgid "%s and %s are mutually exclusive"
@@ -65171,6 +65172,9 @@ msgstr ""
 msgid "Test if snap has yet to be given the subcommand"
 msgstr ""
 
+msgid "Test if the terminal suports the given feature"
+msgstr ""
+
 msgid "Test if there is a subcommand given"
 msgstr ""
 

po/sv.po

@@ -260,10 +260,6 @@ msgstr ""
 msgid "%ls: --set-cursor option requires --add\n"
 msgstr ""
 
-#, c-format
-msgid "%ls: -S requires a non-empty string\n"
-msgstr ""
-
 #, c-format
 msgid "%ls: -l requires a non-empty string\n"
 msgstr ""
@@ -806,6 +802,11 @@ msgstr ""
 msgid "%s"
 msgstr ""
 
+#
+#, c-format
+msgid "%s %s: unrecognized feature '%ls'"
+msgstr ""
+
 #
 #, c-format
 msgid "%s and %s are mutually exclusive"
@@ -65147,6 +65148,9 @@ msgstr ""
 msgid "Test if snap has yet to be given the subcommand"
 msgstr ""
 
+msgid "Test if the terminal suports the given feature"
+msgstr ""
+
 msgid "Test if there is a subcommand given"
 msgstr ""
 

po/zh_CN.po

@@ -257,10 +257,6 @@ msgstr "%ls: --set-cursor 参数不能为空\n"
 msgid "%ls: --set-cursor option requires --add\n"
 msgstr "%ls: --set-cursor 选项需要 --add\n"
 
-#, c-format
-msgid "%ls: -S requires a non-empty string\n"
-msgstr "%ls: -S 需要非空字符串\n"
-
 #, c-format
 msgid "%ls: -l requires a non-empty string\n"
 msgstr "%ls: -l 需要一个非空字符串\n"
@@ -803,6 +799,11 @@ msgstr "%lu\n"
 msgid "%s"
 msgstr ""
 
+#
+#, c-format
+msgid "%s %s: unrecognized feature '%ls'"
+msgstr ""
+
 #
 #, c-format
 msgid "%s and %s are mutually exclusive"
@@ -65147,6 +65148,9 @@ msgstr "测试Snap命令是否应该有文件作为可能的补全"
 msgid "Test if snap has yet to be given the subcommand"
 msgstr "测试是否尚未给定 snap 命令"
 
+msgid "Test if the terminal suports the given feature"
+msgstr ""
+
 msgid "Test if there is a subcommand given"
 msgstr "测试是否有一个子命令"
 

share/completions/status.fish

@@ -28,7 +28,8 @@ set -l __fish_status_all_commands \
     print-stack-trace \
     stack-trace \
     terminal \
-    test-feature
+    test-feature \
+    test-terminal-feature
 
 # These are the recognized flags.
 complete -c status -s h -l help -d "Display help and exit"
@@ -66,6 +67,8 @@ complete -f -c status -n "not __fish_seen_subcommand_from $__fish_status_all_com
 complete -f -c status -n "not __fish_seen_subcommand_from $__fish_status_all_commands" -a list-files -d "List embedded files contained in the fish binary"
 complete -f -c status -n "not __fish_seen_subcommand_from $__fish_status_all_commands" -a fish-path -d "Print the path to the current instance of fish"
 complete -f -c status -n "not __fish_seen_subcommand_from $__fish_status_all_commands" -a terminal -d "Print name and version of the terminal fish is running in"
+complete -f -c status -n "not __fish_seen_subcommand_from $__fish_status_all_commands" -a test-terminal-feature -d "Test if the terminal suports the given feature"
+complete -f -c status -n "__fish_seen_subcommand_from test-terminal-feature" -a 'scroll-content-up\t"Command for scrolling up terminal contents"'
 
 # The job-control command changes fish state.
 complete -f -c status -n "not __fish_seen_subcommand_from $__fish_status_all_commands" -a job-control -d "Set which jobs are under job control"

share/functions/__fish_shared_key_bindings.fish

@@ -80,7 +80,9 @@ function __fish_shared_key_bindings -d "Bindings shared between emacs and vi mod
     bind --preset $argv alt-l __fish_list_current_token
     bind --preset $argv alt-o __fish_preview_current_file
     bind --preset $argv alt-w __fish_whatis_current_token
-    bind --preset $argv ctrl-l scrollback-push clear-screen
+    bind --preset $argv ctrl-l \
+        'status test-terminal-feature scroll-content-up && commandline -f scrollback-push' \
+        clear-screen
     bind --preset $argv ctrl-c clear-commandline
     bind --preset $argv ctrl-u backward-kill-line
     bind --preset $argv ctrl-k kill-line

src/builtins/status.rs

@@ -7,7 +7,7 @@
     get_job_control_mode, get_login, is_interactive_session, set_job_control_mode, JobControl,
 };
 use crate::reader::reader_in_interactive_read;
-use crate::tty_handoff::xtversion;
+use crate::tty_handoff::{get_scroll_content_up_capability, xtversion};
 use crate::wutil::{waccess, wbasename, wdirname, wrealpath, Error};
 use libc::F_OK;
 use nix::errno::Errno;
@@ -65,6 +65,7 @@ enum StatusCmd {
     STATUS_GET_FILE,
     STATUS_LIST_FILES,
     STATUS_TERMINAL,
+    STATUS_TEST_TERMINAL_FEATURE,
 }
 
 str_enum!(
@@ -101,6 +102,7 @@ enum StatusCmd {
     (STATUS_STACK_TRACE, "stack-trace"),
     (STATUS_TERMINAL, "terminal"),
     (STATUS_TEST_FEATURE, "test-feature"),
+    (STATUS_TEST_TERMINAL_FEATURE, "test-terminal-feature"),
 );
 
 /// Values that may be returned from the test-feature option to status.
@@ -539,6 +541,33 @@ pub fn status(parser: &Parser, streams: &mut IoStreams, args: &mut [&wstr]) -> B
                 return Err(STATUS_CMD_ERROR);
             }
         }
+        c @ STATUS_TEST_TERMINAL_FEATURE => {
+            if args.len() != 1 {
+                streams.err.append(wgettext_fmt!(
+                    BUILTIN_ERR_ARG_COUNT2,
+                    cmd,
+                    c.to_wstr(),
+                    1,
+                    args.len()
+                ));
+                return Err(STATUS_INVALID_ARGS);
+            }
+            if args[0] != "scroll-content-up" {
+                streams.err.appendln(wgettext_fmt!(
+                    "%s %s: unrecognized feature '%ls'",
+                    cmd,
+                    c.to_wstr(),
+                    args[0]
+                ));
+                return Err(STATUS_INVALID_ARGS);
+            };
+            return if get_scroll_content_up_capability() == Some(true) {
+                Ok(SUCCESS)
+            } else {
+                Err(STATUS_CMD_ERROR)
+            };
+        }
+
         ref s => {
             if !args.is_empty() {
                 streams.err.append(wgettext_fmt!(
@@ -733,7 +762,8 @@ pub fn status(parser: &Parser, streams: &mut IoStreams, args: &mut [&wstr]) -> B
                 | STATUS_FEATURES
                 | STATUS_TEST_FEATURE
                 | STATUS_GET_FILE
-                | STATUS_LIST_FILES => {
+                | STATUS_LIST_FILES
+                | STATUS_TEST_TERMINAL_FEATURE => {
                     unreachable!("")
                 }
             }

src/reader.rs

@@ -147,7 +147,6 @@
     tok_command, MoveWordStateMachine, MoveWordStyle, TokenType, Tokenizer, TOK_ACCEPT_UNFINISHED,
     TOK_SHOW_COMMENTS,
 };
-use crate::tty_handoff::get_scroll_content_up_capability;
 use crate::tty_handoff::SCROLL_CONTENT_UP_TERMINFO_CODE;
 use crate::tty_handoff::{
     get_tty_protocols_active, initialize_tty_metadata, safe_deactivate_tty_protocols, TtyHandoff,
@@ -3988,9 +3987,6 @@ fn handle_readline_command(&mut self, c: ReadlineCmd) {
                 self.clear_screen_and_repaint();
             }
             rl::ScrollbackPush => {
-                if !get_scroll_content_up_capability().unwrap() {
-                    return;
-                }
                 let query = self.blocking_query();
                 let Some(query) = &*query else {
                     drop(query);

src/terminal.rs

@@ -6,7 +6,6 @@
 use crate::screen::{is_dumb, only_grayscale};
 use crate::text_face::{TextFace, TextStyling, UnderlineStyle};
 use crate::threads::MainThread;
-use crate::tty_handoff::get_scroll_content_up_capability;
 use crate::wchar::prelude::*;
 use crate::FLOGF;
 use bitflags::bitflags;
@@ -410,7 +409,6 @@ fn osc_133_command_finished(out: &mut impl Output, exit_status: libc::c_int) ->
 }
 
 fn scroll_content_up(out: &mut impl Output, lines: usize) -> bool {
-    assert!(get_scroll_content_up_capability().unwrap());
     write_to_output!(out, "\x1b[{}S", lines);
     true
 }

tests/checks/status.fish

@@ -134,3 +134,15 @@ printf "%s\n" (test-stack-trace-copy | string replace \t '<TAB>')[1..4]
 # CHECK: <TAB>called on line {{\d+}} of file {{.*}}/status.fish
 # CHECK: in function 'test-stack-trace-copy'
 # CHECK: <TAB>called on line {{\d+}} of file {{.*}}/status.fish
+
+status test-terminal-feature
+and should have failed on missing arg
+# CHECKERR: status: test-terminal-feature: expected 1 arguments; got 0
+status test-terminal-feature 1 2
+and should have failed on too many args
+# CHECKERR: status: test-terminal-feature: expected 1 arguments; got 2
+status test-terminal-feature unrecognized-feature
+and should have failed on unrecognized feature
+# CHECKERR: status test-terminal-feature: unrecognized feature 'unrecognized-feature'
+status test-terminal-feature scroll-content-up
+and should have failed when running without a TTY

tests/pexpect_helper.py

@@ -154,7 +154,7 @@ class SpawnedProc(object):
         name="fish",
         timeout=TIMEOUT_SECS,
         env=os.environ.copy(),
-        scroll_up_content_supported: bool = False,
+        scroll_content_up_supported: bool = False,
         **kwargs,
     ):
         """Construct from a name, timeout, and environment.
@@ -184,7 +184,7 @@ class SpawnedProc(object):
         )
         self.spawn.delaybeforesend = None
         self.prompt_counter = 0
-        if scroll_up_content_supported:
+        if scroll_content_up_supported:
             # XTGETTCAP
             key = bytes.hex(b"indn")
             value = bytes.hex(b"dont-care")

tests/pexpects/scrollback.py

@@ -5,7 +5,7 @@ import os
 env = os.environ.copy()
 env["TERM"] = "not-dumb"
 
-sp = SpawnedProc(env=env, scroll_up_content_supported=True)
+sp = SpawnedProc(env=env, scroll_content_up_supported=True)
 sendline, expect_prompt = sp.sendline, sp.expect_prompt
 expect_prompt()
 
@@ -14,5 +14,9 @@ expect_prompt()
 sp.send(control("g"))
 sp.send_cursor_position_report(y=10, x=5)
 sp.send_primary_device_attribute()
-
 sp.expect_str("\x1b[9S\x1b[9A")
+
+sp.send(control("l"))
+sp.send_cursor_position_report(y=15, x=5)
+sp.send_primary_device_attribute()
+sp.expect_str("\x1b[14S\x1b[14A")