Fix show_last_command_output not working when the output is stored partially in the scrollback pager history buffer

Fixes #4435

docs/changelog.rst

@@ -86,6 +86,9 @@ Detailed list of changes
 
 - Fix a regression in the previous release that broke :opt:`active_tab_foreground` (:iss:`4620`)
 
+- Fix :ac:`show_last_command_output` not working when the output is stored
+  partially in the scrollback pager history buffer (:iss:`4435`)
+
 - Improve CWD detection when there are multiple foreground processes in the TTY process group
 
 - A new option :opt:`narrow_symbols` to turn off opportunistic wide rendering of private use codepoints

kitty/fast_data_types.pyi

@@ -987,7 +987,7 @@ class HistoryBuf:
     def as_text(self, callback: Callable[[str], None], as_ansi: bool, insert_wrap_markers: bool) -> None:
         pass
 
-    def pagerhist_as_text(self) -> str:
+    def pagerhist_as_text(self, upto_output_start: bool = False) -> str:
         pass
 
     def pagerhist_as_bytes(self) -> bytes:
@@ -1137,7 +1137,7 @@ class Screen:
     as_text_non_visual = as_text
     as_text_alternate = as_text
 
-    def cmd_output(self, which: int, callback: Callable[[str], None], as_ansi: bool, insert_wrap_markers: bool) -> None:
+    def cmd_output(self, which: int, callback: Callable[[str], None], as_ansi: bool, insert_wrap_markers: bool) -> bool:
         pass
 
     def scroll_until_cursor_prompt(self) -> None:

kitty/history.c

@@ -418,8 +418,21 @@ pagerhist_write(HistoryBuf *self, PyObject *what) {
     Py_RETURN_NONE;
 }
 
+static const uint8_t*
+reverse_find(const uint8_t *haystack, size_t haystack_sz, const uint8_t *needle) {
+    const size_t needle_sz = strlen((const char*)needle);
+    if (!needle_sz || needle_sz > haystack_sz) return NULL;
+    const uint8_t *p = haystack + haystack_sz - (needle_sz - 1);
+    while (--p >= haystack) {
+        if (*p == needle[0] && memcmp(p, needle, MIN(needle_sz, haystack_sz - (p - haystack))) == 0) return p;
+    }
+    return NULL;
+}
+
 static PyObject*
-pagerhist_as_bytes(HistoryBuf *self, PyObject *args UNUSED) {
+pagerhist_as_bytes(HistoryBuf *self, PyObject *args) {
+    int upto_output_start = 0;
+    if (!PyArg_ParseTuple(args, "|p", &upto_output_start)) return NULL;
 #define ph self->pagerhist
     if (!ph || !ringbuf_bytes_used(ph->ringbuf)) return PyBytes_FromStringAndSize("", 0);
     pagerhist_ensure_start_is_valid_utf8(ph);
@@ -433,6 +446,13 @@ pagerhist_as_bytes(HistoryBuf *self, PyObject *args UNUSED) {
     uint8_t *buf = (uint8_t*)PyBytes_AS_STRING(ans);
     ringbuf_memcpy_from(buf, ph->ringbuf, sz);
     if (!l.attrs.continued) buf[sz-1] = '\n';
+    if (upto_output_start) {
+        const uint8_t *p = reverse_find(buf, sz, (const uint8_t*)"\x1b]133;C\x1b\\");
+        if (p) {
+            PyObject *t = PyBytes_FromStringAndSize((const char*)p, sz - (p - buf));
+            Py_DECREF(ans); ans = t;
+        }
+    }
     return ans;
 #undef ph
 }
@@ -501,8 +521,8 @@ static PyMethodDef methods[] = {
     METHOD(as_ansi, METH_O)
     METHODB(pagerhist_write, METH_O),
     METHODB(pagerhist_rewrap, METH_O),
-    METHODB(pagerhist_as_text, METH_NOARGS),
-    METHODB(pagerhist_as_bytes, METH_NOARGS),
+    METHODB(pagerhist_as_text, METH_VARARGS),
+    METHODB(pagerhist_as_bytes, METH_VARARGS),
     METHODB(as_text, METH_VARARGS),
     METHOD(dirty_lines, METH_NOARGS)
     METHOD(push, METH_VARARGS)

kitty/options/definition.py

@@ -326,7 +326,7 @@ Separate scrollback history size, used only for browsing the scrollback buffer
 (in MB). This separate buffer is not available for interactive scrolling but
 will be piped to the pager program when viewing scrollback buffer in a separate
 window. The current implementation stores the data in UTF-8, so approximatively
-10000 lines per megabyte at 100 chars per line, for pure ASCII text, unformatted
+10000 lines per megabyte at 100 chars per line, for pure ASCII, unformatted
 text. A value of zero or less disables this feature. The maximum allowed size is
 4GB. Note that on config reload if this
 is changed it will only affect newly created windows, not existing ones.

kitty/screen.c

@@ -2736,6 +2736,7 @@ typedef struct OutputOffset {
     Screen *screen;
     int start;
     unsigned num_lines;
+    bool reached_upper_limit;
 } OutputOffset;
 
 static Line*
@@ -2788,7 +2789,10 @@ find_cmd_output(Screen *self, OutputOffset *oo, index_type start_screen_y, unsig
             }
             y1--;
         }
-        if (y1 < upward_limit) start = upward_limit;
+        if (y1 < upward_limit) {
+            oo->reached_upper_limit = true;
+            start = upward_limit;
+        }
         found_output = true; found_prompt = true;
     }
 
@@ -2848,8 +2852,12 @@ cmd_output(Screen *self, PyObject *args) {
             PyErr_Format(PyExc_KeyError, "%u is not a valid type of command", which);
             return NULL;
     }
-    if (found) return as_text_generic(as_text_args, &oo, get_line_from_offset, oo.num_lines, &self->as_ansi_buf);
-    Py_RETURN_NONE;
+    if (found) {
+        DECREF_AFTER_FUNCTION PyObject *ret = as_text_generic(as_text_args, &oo, get_line_from_offset, oo.num_lines, &self->as_ansi_buf);
+        if (!ret) return NULL;
+    }
+    if (oo.reached_upper_limit && self->linebuf == self->main_linebuf && OPT(scrollback_pager_history_size) > 0) Py_RETURN_TRUE;
+    Py_RETURN_FALSE;
 }
 
 bool

kitty/window.py

@@ -157,6 +157,14 @@ def call_watchers(windowref: Callable[[], Optional['Window']], which: str, data:
     add_timer(callback, 0, False)
 
 
+def pagerhist(screen: Screen, as_ansi: bool = False, add_wrap_markers: bool = True, upto_output_start: bool = False) -> str:
+    pht = screen.historybuf.pagerhist_as_text(upto_output_start)
+    if pht and (not as_ansi or not add_wrap_markers):
+        sanitizer = text_sanitizer(as_ansi, add_wrap_markers)
+        pht = sanitizer(pht)
+    return pht
+
+
 def as_text(
     screen: Screen,
     as_ansi: bool = False,
@@ -186,13 +194,8 @@ def as_text(
             ctext += f'\x1b[{code} q'
 
     if add_history:
-        h: List[str] = []
-        pht = screen.historybuf.pagerhist_as_text()
-        if pht:
-            h.append(pht)
-        if h and (not as_ansi or not add_wrap_markers):
-            sanitizer = text_sanitizer(as_ansi, add_wrap_markers)
-            h = list(map(sanitizer, h))
+        pht = pagerhist(screen, as_ansi, add_wrap_markers)
+        h: List[str] = [pht] if pht else []
         screen.historybuf.as_text(h.append, as_ansi, add_wrap_markers)
         if h:
             if not screen.linebuf.is_continued(0):
@@ -1064,7 +1067,11 @@ class Window:
 
     def cmd_output(self, which: CommandOutput = CommandOutput.last_run, as_ansi: bool = False, add_wrap_markers: bool = False) -> str:
         lines: List[str] = []
-        self.screen.cmd_output(which, lines.append, as_ansi, add_wrap_markers)
+        search_in_pager_hist = self.screen.cmd_output(which, lines.append, as_ansi, add_wrap_markers)
+        if search_in_pager_hist:
+            pht = pagerhist(self.screen, as_ansi, add_wrap_markers, True)
+            if pht:
+                lines.insert(0, pht)
         return ''.join(lines)
 
     @property

kitty_tests/screen.py

@@ -5,6 +5,7 @@ from kitty.fast_data_types import (
     DECAWM, DECCOLM, DECOM, IRM, Cursor, parse_bytes
 )
 from kitty.marks import marker_from_function, marker_from_regex
+from kitty.window import pagerhist
 
 from . import BaseTest
 
@@ -998,7 +999,10 @@ class TestScreen(BaseTest):
 
         def lco(as_ansi=False):
             a = []
-            s.cmd_output(0, a.append, as_ansi)
+            if s.cmd_output(0, a.append, as_ansi):
+                pht = pagerhist(s, as_ansi=as_ansi, upto_output_start=True)
+                if pht:
+                    a.insert(0, pht)
             return ''.join(a)
 
         def fco():
@@ -1076,3 +1080,9 @@ class TestScreen(BaseTest):
         self.ae(lvco(), '0\n1\n2')
         s.scroll_to_prompt(1)
         self.ae(lvco(), '0x\n1x')
+
+        # last command output from pager history
+        s = self.create_screen()
+        draw_prompt('p1')
+        draw_output(30)
+        self.ae(tuple(map(int, lco()[len('\x1b]133;C\x1b\\'):].split())), tuple(range(0, 30)))