fix(plines): don't return very large height on very long line (#24260)

2 files changed, 49 insertions, 13 deletions

diff --git a/src/nvim/plines.c b/src/nvim/plines.c
index 46bbbeeb07..615ce9100b 100644
--- a/src/nvim/plines.c
+++ b/src/nvim/plines.c
@@ -98,19 +98,15 @@ int plines_win_nofill(win_T *wp, linenr_T lnum, bool winheight)
 /// "wp".  Does not care about folding, 'wrap' or 'diff'.
 int plines_win_nofold(win_T *wp, linenr_T lnum)
 {
-  char *s;
-  unsigned col;
-  int width;
+  char *s = ml_get_buf(wp->w_buffer, lnum, false);
   chartabsize_T cts;
-
-  s = ml_get_buf(wp->w_buffer, lnum, false);
   init_chartabsize_arg(&cts, wp, lnum, 0, s, s);
   if (*s == NUL && !cts.cts_has_virt_text) {
     return 1;  // be quick for an empty line
   }
   win_linetabsize_cts(&cts, (colnr_T)MAXCOL);
   clear_chartabsize_arg(&cts);
-  col = (unsigned)cts.cts_vcol;
+  int64_t col = cts.cts_vcol;
 
   // If list mode is on, then the '$' at the end of the line may take up one
   // extra column.
@@ -119,17 +115,17 @@ int plines_win_nofold(win_T *wp, linenr_T lnum)
   }
 
   // Add column offset for 'number', 'relativenumber' and 'foldcolumn'.
-  width = wp->w_width_inner - win_col_off(wp);
-  if (width <= 0 || col > 32000) {
-    return 32000;  // bigger than the number of screen columns
+  int width = wp->w_width_inner - win_col_off(wp);
+  if (width <= 0) {
+    return 32000;  // bigger than the number of screen lines
   }
-  if (col <= (unsigned)width) {
+  if (col <= width) {
     return 1;
   }
-  col -= (unsigned)width;
+  col -= width;
   width += win_col_off2(wp);
-  assert(col <= INT_MAX && (int)col < INT_MAX - (width - 1));
-  return ((int)col + (width - 1)) / width + 1;
+  const int64_t lines = (col + (width - 1)) / width + 1;
+  return (lines > 0 && lines <= INT_MAX) ? (int)lines : INT_MAX;
 }
 
 /// Like plines_win(), but only reports the number of physical screen lines
diff --git a/test/functional/legacy/scroll_opt_spec.lua b/test/functional/legacy/scroll_opt_spec.lua
index ae6a409762..b179338665 100644
--- a/test/functional/legacy/scroll_opt_spec.lua
+++ b/test/functional/legacy/scroll_opt_spec.lua
@@ -1109,4 +1109,44 @@ describe('smoothscroll', function()
                                               |
     ]])
   end)
+
+  it('works with very long line', function()
+    screen:set_default_attr_ids({
+      [1] = {foreground = Screen.colors.Brown},
+      [2] = {foreground = Screen.colors.Blue1, bold = true},
+    })
+    exec([[
+      edit test/functional/fixtures/bigfile_oneline.txt
+      setlocal smoothscroll number
+    ]])
+    screen:expect([[
+      {1:  1 }^0000;<control>;Cc;0;BN;;;;;N;NULL;;;|
+      {1:    }; 0001;<control>;Cc;0;BN;;;;;N;START|
+      {1:    } OF HEADING;;;; 0002;<control>;Cc;0;|
+      {1:    }BN;;;;;N;START OF TEXT;;;; 0003;<con|
+      {1:    }trol>;Cc;0;BN;;;;;N;END OF TEXT;;;; |
+      {1:    }0004;<control>;Cc;0;BN;;;;;N;END OF |
+      {1:    }TRANSMISSION;;;; 0005;<control>;Cc;0|
+      {1:    };BN;;;;;N;ENQUIRY;;;; 0006;<control>|
+      {1:    };Cc;0;BN;;;;;N;ACKNOWLEDGE;;;; 0007;|
+      {1:    }<control>;Cc;0;BN;;;;;N;BELL;;;; 000|
+      {1:    }8;<control>;Cc;0;BN;;;;;N;BACKSPACE;|
+                                              |
+    ]])
+    feed('j')
+    screen:expect([[
+      {2:<<<}{1: }CJK COMPATIBILITY IDEOGRAPH-2F91F;Lo|
+      {1:    };0;L;243AB;;;;N;;;;; 2F920;CJK COMPA|
+      {1:    }TIBILITY IDEOGRAPH-2F920;Lo;0;L;7228|
+      {1:    };;;;N;;;;; 2F921;CJK COMPATIBILITY I|
+      {1:    }DEOGRAPH-2F921;Lo;0;L;7235;;;;N;;;;;|
+      {1:    } 2F922;CJK COMPATIBILITY IDEOGRAPH-2|
+      {1:    }F922;Lo;0;L;7250;;;;N;;;;;          |
+      {1:  2 }^2F923;CJK COMPATIBILITY IDEOGRAPH-2F|
+      {1:    }923;Lo;0;L;24608;;;;N;;;;;          |
+      {1:  3 }2F924;CJK COMPATIBILITY IDEOGRAPH-2F|
+      {1:    }924;Lo;0;L;7280;;;;N;;;;;           |
+                                              |
+    ]])
+  end)
 end)