test(extmarks): add test for virt_text_win_col with cpo+=n (#24328)

runtime/doc/api.txt

@@ -2615,15 +2615,16 @@ nvim_buf_set_extmark({buffer}, {ns_id}, {line}, {col}, {*opts})
                     string or as an integer, the latter which can be obtained
                     using |nvim_get_hl_id_by_name()|.
                   • virt_text_pos : position of virtual text. Possible values:
-                    • "eol": right after eol character (default)
+                    • "eol": right after eol character (default).
                     • "overlay": display over the specified column, without
                       shifting the underlying text.
                     • "right_align": display right aligned in the window.
                     • "inline": display at the specified column, and shift the
-                      buffer text to the right as needed
+                      buffer text to the right as needed.
 
                   • virt_text_win_col : position the virtual text at a fixed
-                    window column (starting from the first text column)
+                    window column (starting from the first text column of the
+                    screen line) instead of "virt_text_pos".
                   • virt_text_hide : hide the virtual text when the background
                     text is selected or hidden because of scrolling with
                     'nowrap' or 'smoothscroll'. Currently only affects

src/nvim/api/extmark.c

@@ -473,15 +473,16 @@ Array nvim_buf_get_extmarks(Buffer buffer, Integer ns_id, Object start, Object e
 ///                   either as a string or as an integer, the latter which
 ///                   can be obtained using |nvim_get_hl_id_by_name()|.
 ///               - virt_text_pos : position of virtual text. Possible values:
-///                 - "eol": right after eol character (default)
+///                 - "eol": right after eol character (default).
 ///                 - "overlay": display over the specified column, without
 ///                              shifting the underlying text.
 ///                 - "right_align": display right aligned in the window.
 ///                 - "inline": display at the specified column, and
-///                             shift the buffer text to the right as needed
+///                             shift the buffer text to the right as needed.
 ///               - virt_text_win_col : position the virtual text at a fixed
 ///                                     window column (starting from the first
-///                                     text column)
+///                                     text column of the screen line) instead
+///                                     of "virt_text_pos".
 ///               - virt_text_hide : hide the virtual text when the background
 ///                                  text is selected or hidden because of
 ///                                  scrolling with 'nowrap' or 'smoothscroll'.

test/functional/ui/decorations_spec.lua

@@ -1130,7 +1130,45 @@ describe('extmark decorations', function()
                                                         |
     ]]}
 
-    command 'set nowrap'
+    command 'set number'
+    screen:expect{grid=[[
+      {2:  1 }for _,item in ipairs(items) do                |
+      {2:  2 }    local text, hl_id_cell, cou{4:Very} unpack{4:VERY}|
+      {2:    }m)                                            |
+      {2:  3 }    if                                        |
+      {2:  4 }hl_id_cell ~= nil then         {4:Much}       {4:MUCH}|
+      {2:  5 }        --^ -- -- -- -- -- -- -- -- -- -- -- hl|
+      {2:    }_id = hl_id_cell               {4:Error}     {4:ERROR}|
+      {2:  6 }    end                                       |
+      {2:  7 }    for _ = 1, (count or 1) do                |
+      {2:  8 }        local cell = line[colpos]             |
+      {2:  9 }    {1:-}   cell.text = text                     {1:-}|
+      {2: 10 }        cell.hl_id = hl_id                    |
+      {2: 11 }        colpos = colpos+1                     |
+      {2: 12 }    end                                       |
+                                                        |
+    ]]}
+
+    command 'set cpoptions+=n'
+    screen:expect{grid=[[
+      {2:  1 }for _,item in ipairs(items) do                |
+      {2:  2 }    local text, hl_id_cell, cou{4:Very} unpack{4:VERY}|
+      m)                                                |
+      {2:  3 }    if                                        |
+      {2:  4 }hl_id_cell ~= nil then         {4:Much}       {4:MUCH}|
+      {2:  5 }        --^ -- -- -- -- -- -- -- -- -- -- -- hl|
+      _id = hl_id_cell               {4:Error}         {4:ERROR}|
+      {2:  6 }    end                                       |
+      {2:  7 }    for _ = 1, (count or 1) do                |
+      {2:  8 }        local cell = line[colpos]             |
+      {2:  9 }    {1:-}   cell.text = text                     {1:-}|
+      {2: 10 }        cell.hl_id = hl_id                    |
+      {2: 11 }        colpos = colpos+1                     |
+      {2: 12 }    end                                       |
+                                                        |
+    ]]}
+
+    command 'set cpoptions-=n nonumber nowrap'
     screen:expect{grid=[[
       for _,item in ipairs(items) do                    |
           local text, hl_id_cell, cou{4:Very} unpack(ite{4:VERY}|
@@ -1149,7 +1187,7 @@ describe('extmark decorations', function()
                                                         |
     ]]}
 
-    feed('8zl')
+    feed '8zl'
     screen:expect{grid=[[
       em in ipairs(items) do                            |
       l text, hl_id_cell, count = unp{4:Very}item)      {4:VERY}|