fix(statusline): fill for double-width char after moving items (#24207)

src/nvim/statusline.c

@@ -263,6 +263,7 @@ void stl_fill_click_defs(StlClickDefinition *click_defs, StlClickRecord *click_r
   };
   for (int i = 0; click_recs[i].start != NULL; i++) {
     len += vim_strnsize(buf, (int)(click_recs[i].start - buf));
+    assert(len <= width);
     if (col < len) {
       while (col < len) {
         click_defs[col++] = cur_click_def;
@@ -2052,17 +2053,6 @@ int build_stl_str_hl(win_T *wp, char *out, size_t outlen, char *fmt, char *opt_n
 
       // Put a `<` to mark where we truncated at
       *trunc_p = '<';
-
-      if (width + 1 < maxwidth) {
-        // Advance the pointer to the end of the string
-        trunc_p = trunc_p + strlen(trunc_p);
-      }
-
-      // Fill up for half a double-wide character.
-      while (++width < maxwidth) {
-        MB_CHAR2BYTES(fillchar, trunc_p);
-        *trunc_p = NUL;
-      }
       // }
 
       // { Change the start point for items based on
@@ -2084,6 +2074,17 @@ int build_stl_str_hl(win_T *wp, char *out, size_t outlen, char *fmt, char *opt_n
         }
       }
       // }
+
+      if (width + 1 < maxwidth) {
+        // Advance the pointer to the end of the string
+        trunc_p = trunc_p + strlen(trunc_p);
+      }
+
+      // Fill up for half a double-wide character.
+      while (++width < maxwidth) {
+        MB_CHAR2BYTES(fillchar, trunc_p);
+        *trunc_p = NUL;
+      }
     }
     width = maxwidth;
 

test/functional/ui/tabline_spec.lua

@@ -1,6 +1,9 @@
 local helpers = require('test.functional.helpers')(after_each)
 local Screen = require('test.functional.ui.screen')
 local clear, command, eq = helpers.clear, helpers.command, helpers.eq
+local insert = helpers.insert
+local meths = helpers.meths
+local assert_alive = helpers.assert_alive
 
 describe('ui/ext_tabline', function()
   local screen
@@ -92,6 +95,10 @@ describe("tabline", function()
     clear()
     screen = Screen.new(42, 5)
     screen:attach()
+    screen:set_default_attr_ids({
+      [0] = {bold = true, foreground = Screen.colors.Blue};  -- NonText
+      [1] = {reverse = true};  -- TabLineFill
+    })
   end)
 
   it('redraws when tabline option is set', function()
@@ -100,24 +107,18 @@ describe("tabline", function()
     screen:expect{grid=[[
       {1:asdf                                      }|
       ^                                          |
-      {2:~                                         }|
+      {0:~                                         }|
-      {2:~                                         }|
+      {0:~                                         }|
                                                 |
-    ]], attr_ids={
+    ]]}
-      [1] = {reverse = true};
-      [2] = {bold = true, foreground = Screen.colors.Blue1};
-    }}
     command('set tabline=jkl')
     screen:expect{grid=[[
       {1:jkl                                       }|
       ^                                          |
-      {2:~                                         }|
+      {0:~                                         }|
-      {2:~                                         }|
+      {0:~                                         }|
                                                 |
-    ]], attr_ids={
+    ]]}
-      [1] = {reverse = true};
-      [2] = {bold = true, foreground = Screen.colors.Blue};
-    }}
   end)
 
   it('click definitions do not leak memory #21765', function()
@@ -125,4 +126,52 @@ describe("tabline", function()
     command('set showtabline=2')
     command('redrawtabline')
   end)
+
+  it('clicks work with truncated double-width label #24187', function()
+    insert('tab1')
+    command('tabnew')
+    insert('tab2')
+    command('tabprev')
+    meths.set_option_value('tabline', '%1T口口%2Ta' .. ('b'):rep(38) .. '%999Xc', {})
+    screen:expect{grid=[[
+      {1:<abbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbc }|
+      tab^1                                      |
+      {0:~                                         }|
+      {0:~                                         }|
+                                                |
+    ]]}
+    assert_alive()
+    meths.input_mouse('left', 'press', '', 0, 0, 1)
+    screen:expect{grid=[[
+      {1:<abbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbc }|
+      tab^2                                      |
+      {0:~                                         }|
+      {0:~                                         }|
+                                                |
+    ]]}
+    meths.input_mouse('left', 'press', '', 0, 0, 0)
+    screen:expect{grid=[[
+      {1:<abbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbc }|
+      tab^1                                      |
+      {0:~                                         }|
+      {0:~                                         }|
+                                                |
+    ]]}
+    meths.input_mouse('left', 'press', '', 0, 0, 39)
+    screen:expect{grid=[[
+      {1:<abbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbc }|
+      tab^2                                      |
+      {0:~                                         }|
+      {0:~                                         }|
+                                                |
+    ]]}
+    meths.input_mouse('left', 'press', '', 0, 0, 40)
+    screen:expect{grid=[[
+      tab^1                                      |
+      {0:~                                         }|
+      {0:~                                         }|
+      {0:~                                         }|
+                                                |
+    ]]}
+  end)
 end)