From: Hirohito Higashi <h.east.727@gmail.com>
Date: Mon, 20 Jul 2026 17:44:27 +0000 (+0000)
Subject: patch 9.2.0819: MS-Windows: sixel image shown as raw text in the console
X-Git-Tag: v9.2.0819^0
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=5af893b2cd43c5ccf8eea60bfca4198b28536e1b;p=thirdparty%2Fvim.git

patch 9.2.0819: MS-Windows: sixel image shown as raw text in the console

Problem:  On the MS-Windows console a popup image is displayed as the raw
          sixel escape sequence instead of the image, unless
          'termguicolors' is set (Bakudankun).
Solution: Write a DCS sequence with the console API that lets the console
          parse it, no matter which write path the current colors select.
          Keep track of the terminator across writes, since a long
          sequence is split up (Hirohito Higashi).

fixes:  #20795
closes: #20797

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Signed-off-by: Hirohito Higashi <h.east.727@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
---

diff --git a/src/os_win32.c b/src/os_win32.c
index 5e11de231c..4797eed426 100644
--- a/src/os_win32.c
+++ b/src/os_win32.c
@@ -7645,6 +7645,52 @@ sgrn2cn(
     return p && p[0] == 0x0a && p[1] == '\033' ? ++p : NULL;
 }
 
+static bool in_dcs = false;	// inside a DCS (sixel) sequence
+static bool dcs_esc = false;	// last DCS byte written was ESC
+
+/*
+ * Write "len" bytes at "s" with WriteConsoleW, so that the console's own VT
+ * parser processes them.  Needed for DCS sequences when USE_VTP is off.
+ */
+    static void
+write_vt(char_u *s, int len)
+{
+    int		wlen;
+    WCHAR	*ws;
+    DWORD	written;
+
+    wlen = MultiByteToWideChar(CP_UTF8, 0, (LPCSTR)s, len, NULL, 0);
+    if (wlen <= 0)
+	return;
+    ws = ALLOC_MULT(WCHAR, wlen);
+    if (ws == NULL)
+	return;
+    MultiByteToWideChar(CP_UTF8, 0, (LPCSTR)s, len, ws, wlen);
+    WriteConsoleW(g_hConOut, ws, wlen, &written, NULL);
+    vim_free(ws);
+}
+
+/*
+ * Return the pointer just after the ST (ESC '\') that ends a DCS sequence.
+ * Returns "end" when the ST is not in this chunk; "in_dcs" then stays set so
+ * that the next mch_write() call continues the scan.
+ */
+    static char_u *
+skip_dcs(char_u *s, char_u *end)
+{
+    for (char_u *p = s; p < end; ++p)
+    {
+	if (dcs_esc && *p == '\\')
+	{
+	    dcs_esc = false;
+	    in_dcs = false;
+	    return p + 1;
+	}
+	dcs_esc = *p == ESC;
+    }
+    return end;
+}
+
 /*
  * mch_write(): write the output buffer to the screen, translating ESC
  * sequences into calls to console output routines.
@@ -7681,6 +7727,18 @@ mch_write(
 	    return;
 	}
 
+	if (in_dcs)
+	{
+	    // Continuation of a DCS sequence split over several writes.
+	    int	l = (int)(skip_dcs(s, end) - s);
+
+	    if (vtp_working)
+		write_vt(s, l);
+	    len -= l - 1;
+	    s += l;
+	    continue;
+	}
+
 	while (s + ++prefix < end)
 	{
 	    ch = s[prefix];
@@ -7985,6 +8043,20 @@ notsgr:
 	    len -= l - 1;
 	    s += l;
 	}
+	else if (s[0] == ESC && len >= 2-1 && s[1] == 'P')
+	{
+	    // DCS (e.g. sixel image): write_chars() would print it as raw text
+	    // when USE_VTP is off, so let the console's VT parser handle it.
+	    int	l;
+
+	    in_dcs = true;
+	    dcs_esc = false;
+	    l = (int)(skip_dcs(s + 2, end) - s);
+	    if (vtp_working)
+		write_vt(s, l);
+	    len -= l - 1;
+	    s += l;
+	}
 	else
 	{
 	    // Write a single character
diff --git a/src/testdir/test_popupwin.vim b/src/testdir/test_popupwin.vim
index 5e4bc5221f..67babab1b2 100644
--- a/src/testdir/test_popupwin.vim
+++ b/src/testdir/test_popupwin.vim
@@ -5887,6 +5887,40 @@ func Test_popup_image_clear_with_empty_dict()
   call popup_close(winid)
 endfunc
 
+" A popup image is emitted as a DCS (sixel) escape sequence.  On the Windows
+" console it has to go through the VT path, otherwise the escape sequence ends
+" up on the screen as raw text when 'termguicolors' is off.  Send the sequence
+" with echoraw() so that only the console write is under test.  See #20795.
+func Test_dcs_not_written_as_text_windows_cui()
+  CheckFeature terminal
+  if !has('win32') || has('gui_running')
+    throw 'Skipped: only for the Windows CUI'
+  endif
+
+  " Draw the text first, so nothing repairs the cells afterwards in case the
+  " sequence does land on the screen as text.
+  let lines =<< trim END
+      call setline(1, 'READY')
+      redraw
+      call echoraw("\<Esc>P0;1;8q\"1;1;8;8#1;2;100;0;0#1~~~~~~~~-\<Esc>\\")
+  END
+  call writefile(lines, 'XpopupDcs', 'D')
+
+  let buf = term_start(GetVimCommandCleanTerm() .. '-S XpopupDcs',
+        \ #{term_rows: 12, term_cols: 40})
+  call WaitForAssert({-> assert_equal('READY',
+        \ term_scrape(buf, 1)[:4]->map({_, v -> v['chars']})->join(''))})
+  call TermWait(buf, 50)
+
+  let screen = ''
+  for row in range(1, 12)
+    let screen ..= term_scrape(buf, row)->map({_, v -> v['chars']})->join('')
+  endfor
+  call assert_notmatch('0;1;8q', screen)
+
+  call StopVimInTerminal(buf)
+endfunc
+
 func Test_popup_image_set_and_getoptions()
   CheckFeature image
 
diff --git a/src/version.c b/src/version.c
index a1318f49ad..ae605f2431 100644
--- a/src/version.c
+++ b/src/version.c
@@ -759,6 +759,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    819,
 /**/
     818,
 /**/