fix(signs): priority of extmark signs (#19718)

runtime/doc/api.txt

@@ -2610,8 +2610,9 @@ nvim_buf_set_extmark({buffer}, {ns_id}, {line}, {col}, {*opts})
                     the extmark end position (if it exists) will be shifted in
                     when new text is inserted (true for right, false for
                     left). Defaults to false.
-                  • priority: a priority value for the highlight group. For
+                  • priority: a priority value for the highlight group or sign
-                    example treesitter highlighting uses a value of 100.
+                    attribute. For example treesitter highlighting uses a
+                    value of 100.
                   • strict: boolean that indicates extmark should not be
                     placed if the line or column value is past the end of the
                     buffer or end of the line respectively. Defaults to true.

src/nvim/api/extmark.c

@@ -441,8 +441,9 @@ Array nvim_buf_get_extmarks(Buffer buffer, Integer ns_id, Object start, Object e
 ///                   the extmark end position (if it exists) will be shifted
 ///                   in when new text is inserted (true for right, false
 ///                   for left). Defaults to false.
-///               - priority: a priority value for the highlight group. For
+///               - priority: a priority value for the highlight group or sign
-///                   example treesitter highlighting uses a value of 100.
+///                   attribute. For example treesitter highlighting uses a
+///                   value of 100.
 ///               - strict: boolean that indicates extmark should not be placed
 ///                   if the line or column value is past the end of the
 ///                   buffer or end of the line respectively. Defaults to true.

src/nvim/decoration.c

@@ -385,7 +385,7 @@ void decor_redraw_signs(buf_T *buf, int row, int *num_signs, sign_attrs_T sattrs
 
     int j;
     for (j = (*num_signs); j > 0; j--) {
-      if (sattrs[j].sat_prio <= decor->priority) {
+      if (sattrs[j - 1].sat_prio >= decor->priority) {
         break;
       }
       sattrs[j] = sattrs[j - 1];

test/functional/ui/decorations_spec.lua

@@ -1681,7 +1681,7 @@ l5
 
     screen:expect{grid=[[
       S4S1^l1                                            |
-      S2x l2                                            |
+      x S2l2                                            |
       S5{1:  }l3                                            |
       {1:    }l4                                            |
       {1:    }l5                                            |
@@ -1779,6 +1779,34 @@ l5
     ]]}
   end)
 
+  it('works with priority #19716', function()
+    screen:try_resize(20, 3)
+    insert(example_text)
+    feed 'gg'
+
+    helpers.command('sign define Oldsign text=O3')
+    helpers.command([[exe 'sign place 42 line=1 name=Oldsign priority=10 buffer=' . bufnr('')]])
+
+    meths.buf_set_extmark(0, ns, 0, -1, {sign_text='S4', priority=100})
+    meths.buf_set_extmark(0, ns, 0, -1, {sign_text='S2', priority=5})
+    meths.buf_set_extmark(0, ns, 0, -1, {sign_text='S5', priority=200})
+    meths.buf_set_extmark(0, ns, 0, -1, {sign_text='S1', priority=1})
+
+    screen:expect{grid=[[
+      S1S2O3S4S5^l1        |
+      {1:          }l2        |
+                          |
+    ]]}
+
+    -- Check truncation works too
+    meths.win_set_option(0, 'signcolumn', 'auto')
+
+    screen:expect{grid=[[
+      S5^l1                |
+      {1:  }l2                |
+                          |
+    ]]}
+  end)
 end)
 
 describe('decorations: virt_text', function()