ui: add 'winblend' to support blending of floating windows

Also add `hi blend=` attribute to override transparency of indiviual attributes.

16 files changed, 342 insertions, 30 deletions

diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index 212e686f96..53581179b6 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -4513,6 +4513,13 @@ A jump table for the options with a short description can be found at |Q_op|.
 	the range of 0 for fully opaque popupmenu (disabled) to 100 for fully
 	transparent background. Values between 0-30 are typically most useful.
 
+	It is possible to override the level for individual highlights within
+	the popupmenu using |highlight-blend|. For instance, to enable
+	transparency but force the current selected element to be fully opaque: >
+
+		:set pumblend=15
+		:hi PmenuSel blend=0
+<
 	UI-dependent. Works best with RGB colors. 'termguicolors'
 
 						*'pyxversion'* *'pyx'*
@@ -6693,6 +6700,15 @@ A jump table for the options with a short description can be found at |Q_op|.
 	key is never used for the menu.
 	This option is not used for <F10>; on Win32.
 
+						*'winblend'* *'winbl'*
+'winblend' 'winbl'		number	(default 0)
+			local to window
+	Enables pseudo-transparency for a floating window. Valid values are in
+	the range of 0 for fully opaque window (disabled) to 100 for fully
+	transparent background. Values between 0-30 are typically most useful.
+
+	UI-dependent. Works best with RGB colors. 'termguicolors'
+
 						*'window'* *'wi'*
 'window' 'wi'		number  (default screen height - 1)
 			global
diff --git a/runtime/doc/syntax.txt b/runtime/doc/syntax.txt
index b60a952def..1373aff891 100644
--- a/runtime/doc/syntax.txt
+++ b/runtime/doc/syntax.txt
@@ -4879,6 +4879,11 @@ guisp={color-name}					*highlight-guisp*
 	All values are hexadecimal, range from "00" to "ff".  Examples: >
   :highlight Comment guifg=#11f0c3 guibg=#ff00ff
 <
+blend={integer}					*highlight-blend*
+	Override the blend level for a highlight group within the popupmenu
+	or floating windows. Only takes effect if 'pumblend' or 'winblend'
+	is set for the menu or window. See the help at the respective option.
+
 					*highlight-groups* *highlight-default*
 These are the builtin highlighting groups.  Note that the highlighting depends
 on the value of 'background'.  You can see the current settings with the
diff --git a/src/nvim/buffer_defs.h b/src/nvim/buffer_defs.h
index 4b0e680c25..ad10f6baa2 100644
--- a/src/nvim/buffer_defs.h
+++ b/src/nvim/buffer_defs.h
@@ -252,6 +252,8 @@ typedef struct {
 # define w_p_fcs w_onebuf_opt.wo_fcs    // 'fillchars'
   char_u *wo_lcs;
 # define w_p_lcs w_onebuf_opt.wo_lcs    // 'listchars'
+  long wo_winbl;
+# define w_p_winbl w_onebuf_opt.wo_winbl  // 'winblend'
 
   LastSet wo_scriptID[WV_COUNT];        // SIDs for window-local options
 # define w_p_scriptID w_onebuf_opt.wo_scriptID
diff --git a/src/nvim/globals.h b/src/nvim/globals.h
index 68b2640aa5..0b5fafd7c0 100644
--- a/src/nvim/globals.h
+++ b/src/nvim/globals.h
@@ -756,9 +756,11 @@ EXTERN bool KeyTyped;                    // true if user typed current char
 EXTERN int KeyStuffed;                   // TRUE if current char from stuffbuf
 EXTERN int maptick INIT(= 0);            // tick for each non-mapped char
 
-EXTERN int must_redraw INIT(= 0);           /* type of redraw necessary */
-EXTERN int skip_redraw INIT(= FALSE);       /* skip redraw once */
-EXTERN int do_redraw INIT(= FALSE);         /* extra redraw once */
+EXTERN int must_redraw INIT(= 0);           // type of redraw necessary
+EXTERN bool skip_redraw INIT(= false);      // skip redraw once
+EXTERN bool do_redraw INIT(= false);        // extra redraw once
+EXTERN bool must_redraw_pum INIT(= false);  // redraw pum. NB: must_redraw
+                                            // should also be set.
 
 EXTERN int need_highlight_changed INIT(= true);
 
diff --git a/src/nvim/grid_defs.h b/src/nvim/grid_defs.h
index 38fc513baa..e4021c033b 100644
--- a/src/nvim/grid_defs.h
+++ b/src/nvim/grid_defs.h
@@ -54,6 +54,9 @@ typedef struct {
   int row_offset;
   int col_offset;
 
+  // whether the compositor should blend the grid with the background grid
+  bool blending;
+
   // state owned by the compositor.
   int comp_row;
   int comp_col;
@@ -61,7 +64,7 @@ typedef struct {
   bool comp_disabled;
 } ScreenGrid;
 
-#define SCREEN_GRID_INIT { 0, NULL, NULL, NULL, NULL, 0, 0, false, 0, 0, 0, \
-                           0, 0,  false }
+#define SCREEN_GRID_INIT { 0, NULL, NULL, NULL, NULL, 0, 0, false, 0, 0, \
+                           false, 0, 0, 0,  false }
 
 #endif  // NVIM_GRID_DEFS_H
diff --git a/src/nvim/highlight.c b/src/nvim/highlight.c
index 3ba02be32d..15c3d0eb7b 100644
--- a/src/nvim/highlight.c
+++ b/src/nvim/highlight.c
@@ -7,6 +7,7 @@
 #include "nvim/highlight.h"
 #include "nvim/highlight_defs.h"
 #include "nvim/map.h"
+#include "nvim/popupmnu.h"
 #include "nvim/screen.h"
 #include "nvim/syntax.h"
 #include "nvim/ui.h"
@@ -145,6 +146,16 @@ int hl_get_ui_attr(int idx, int final_id, bool optional)
     attrs = syn_attr2entry(syn_attr);
     available = true;
   }
+
+  if (HLF_PNI <= idx && idx <= HLF_PST) {
+    if (attrs.hl_blend == -1 && p_pb > 0) {
+      attrs.hl_blend = (int)p_pb;
+    }
+    if (pum_drawn()) {
+      must_redraw_pum = true;
+    }
+  }
+
   if (optional && !available) {
     return 0;
   }
@@ -159,20 +170,35 @@ void update_window_hl(win_T *wp, bool invalid)
   }
   wp->w_hl_needs_update = false;
 
+  // If a floating window is blending it always have a named
+  // wp->w_hl_attr_normal group. HL_ATTR(HLF_NFLOAT) is always named.
+  bool has_blend = wp->w_floating && wp->w_p_winbl != 0;
+
   // determine window specific background set in 'winhighlight'
   bool float_win = wp->w_floating && !wp->w_float_config.external;
   if (wp != curwin && wp->w_hl_ids[HLF_INACTIVE] > 0) {
     wp->w_hl_attr_normal = hl_get_ui_attr(HLF_INACTIVE,
-                                          wp->w_hl_ids[HLF_INACTIVE], true);
+                                          wp->w_hl_ids[HLF_INACTIVE],
+                                          !has_blend);
   } else if (float_win && wp->w_hl_ids[HLF_NFLOAT] > 0) {
     wp->w_hl_attr_normal = hl_get_ui_attr(HLF_NFLOAT,
-                                          wp->w_hl_ids[HLF_NFLOAT], true);
+    // 'cursorline'
+                                          wp->w_hl_ids[HLF_NFLOAT], !has_blend);
   } else if (wp->w_hl_id_normal > 0) {
-    wp->w_hl_attr_normal = hl_get_ui_attr(-1, wp->w_hl_id_normal, true);
+    wp->w_hl_attr_normal = hl_get_ui_attr(-1, wp->w_hl_id_normal, !has_blend);
   } else {
     wp->w_hl_attr_normal = float_win ? HL_ATTR(HLF_NFLOAT) : 0;
   }
 
+  // if blend= attribute is not set, 'winblend' value overrides it.
+  if (wp->w_floating && wp->w_p_winbl > 0) {
+    HlEntry entry = kv_A(attr_entries, wp->w_hl_attr_normal);
+    if (entry.attr.hl_blend == -1) {
+      entry.attr.hl_blend = (int)wp->w_p_winbl;
+      wp->w_hl_attr_normal = get_attr_entry(entry);
+    }
+  }
+
   if (wp != curwin) {
     wp->w_hl_attr_normal = hl_combine_attr(HL_ATTR(HLF_INACTIVE),
                                            wp->w_hl_attr_normal);
@@ -240,6 +266,8 @@ void hl_invalidate_blends(void)
 {
   map_clear(int, int)(blend_attr_entries);
   map_clear(int, int)(blendthrough_attr_entries);
+  highlight_changed();
+  update_window_hl(curwin, true);
 }
 
 // Combine special attributes (e.g., for spelling) with other attributes
@@ -292,6 +320,10 @@ int hl_combine_attr(int char_attr, int prim_attr)
     new_en.rgb_sp_color = spell_aep.rgb_sp_color;
   }
 
+  if (spell_aep.hl_blend >= 0) {
+    new_en.hl_blend = spell_aep.hl_blend;
+  }
+
   id = get_attr_entry((HlEntry){ .attr = new_en, .kind = kHlCombine,
                                  .id1 = char_attr, .id2 = prim_attr });
   if (id > 0) {
@@ -336,50 +368,59 @@ static HlAttrs get_colors_force(int attr)
 /// This is called per-cell, so cache the result.
 ///
 /// @return the resulting attributes.
-int hl_blend_attrs(int back_attr, int front_attr, bool through)
+int hl_blend_attrs(int back_attr, int front_attr, bool *through)
 {
+  HlAttrs fattrs = get_colors_force(front_attr);
+  int ratio = fattrs.hl_blend;
+  if (ratio <= 0) {
+    *through = false;
+    return front_attr;
+  }
+
   int combine_tag = (back_attr << 16) + front_attr;
-  Map(int, int) *map = through ? blendthrough_attr_entries : blend_attr_entries;
+  Map(int, int) *map = (*through
+                        ? blendthrough_attr_entries
+                        : blend_attr_entries);
   int id = map_get(int, int)(map, combine_tag);
   if (id > 0) {
     return id;
   }
 
   HlAttrs battrs = get_colors_force(back_attr);
-  HlAttrs fattrs = get_colors_force(front_attr);
   HlAttrs cattrs;
-  if (through) {
+
+  if (*through) {
     cattrs = battrs;
-    cattrs.rgb_fg_color = rgb_blend((int)p_pb, battrs.rgb_fg_color,
+    cattrs.rgb_fg_color = rgb_blend(ratio, battrs.rgb_fg_color,
                                     fattrs.rgb_bg_color);
     if (cattrs.rgb_ae_attr & (HL_UNDERLINE|HL_UNDERCURL)) {
-      cattrs.rgb_sp_color = rgb_blend((int)p_pb, battrs.rgb_sp_color,
+      cattrs.rgb_sp_color = rgb_blend(ratio, battrs.rgb_sp_color,
                                       fattrs.rgb_bg_color);
     } else {
       cattrs.rgb_sp_color = -1;
     }
 
     cattrs.cterm_bg_color = fattrs.cterm_bg_color;
-    cattrs.cterm_fg_color = cterm_blend((int)p_pb, battrs.cterm_fg_color,
+    cattrs.cterm_fg_color = cterm_blend(ratio, battrs.cterm_fg_color,
                                         fattrs.cterm_bg_color);
   } else {
     cattrs = fattrs;
-    if (p_pb >= 50) {
+    if (ratio >= 50) {
       cattrs.rgb_ae_attr |= battrs.rgb_ae_attr;
     }
-    cattrs.rgb_fg_color = rgb_blend((int)p_pb/2, battrs.rgb_fg_color,
+    cattrs.rgb_fg_color = rgb_blend(ratio/2, battrs.rgb_fg_color,
                                     fattrs.rgb_fg_color);
     if (cattrs.rgb_ae_attr & (HL_UNDERLINE|HL_UNDERCURL)) {
-      cattrs.rgb_sp_color = rgb_blend((int)p_pb/2, battrs.rgb_bg_color,
+      cattrs.rgb_sp_color = rgb_blend(ratio/2, battrs.rgb_bg_color,
                                       fattrs.rgb_sp_color);
     } else {
       cattrs.rgb_sp_color = -1;
     }
   }
-  cattrs.rgb_bg_color = rgb_blend((int)p_pb, battrs.rgb_bg_color,
+  cattrs.rgb_bg_color = rgb_blend(ratio, battrs.rgb_bg_color,
                                   fattrs.rgb_bg_color);
 
-  HlKind kind = through ? kHlBlendThrough : kHlBlend;
+  HlKind kind = *through ? kHlBlendThrough : kHlBlend;
   id = get_attr_entry((HlEntry){ .attr = cattrs, .kind = kind,
                                  .id1 = back_attr, .id2 = front_attr });
   if (id > 0) {
diff --git a/src/nvim/highlight_defs.h b/src/nvim/highlight_defs.h
index 746d2c2dfc..60f571ff0f 100644
--- a/src/nvim/highlight_defs.h
+++ b/src/nvim/highlight_defs.h
@@ -25,6 +25,7 @@ typedef struct attr_entry {
   int16_t rgb_ae_attr, cterm_ae_attr;  ///< HlAttrFlags
   RgbValue rgb_fg_color, rgb_bg_color, rgb_sp_color;
   int cterm_fg_color, cterm_bg_color;
+  int hl_blend;
 } HlAttrs;
 
 #define HLATTRS_INIT (HlAttrs) { \
diff --git a/src/nvim/option.c b/src/nvim/option.c
index 8dadf926b9..25b498e3e6 100644
--- a/src/nvim/option.c
+++ b/src/nvim/option.c
@@ -74,6 +74,7 @@
 #include "nvim/strings.h"
 #include "nvim/syntax.h"
 #include "nvim/ui.h"
+#include "nvim/ui_compositor.h"
 #include "nvim/undo.h"
 #include "nvim/window.h"
 #include "nvim/os/os.h"
@@ -4391,11 +4392,10 @@ static char *set_num_option(int opt_idx, char_u *varp, long value,
     }
   } else if (pp == &p_pb) {
     p_pb = MAX(MIN(p_pb, 100), 0);
-    if (old_value != 0) {
-      hl_invalidate_blends();
-    }
+    hl_invalidate_blends();
+    pum_grid.blending = (p_pb > 0);
     if (pum_drawn()) {
-      pum_recompose();
+      pum_redraw();
     }
   } else if (pp == &p_pyx) {
     if (p_pyx != 0 && p_pyx != 2 && p_pyx != 3) {
@@ -4418,6 +4418,11 @@ static char *set_num_option(int opt_idx, char_u *varp, long value,
     }
   } else if (pp == &curwin->w_p_nuw) {
     curwin->w_nrwidth_line_count = 0;
+  } else if (pp == &curwin->w_p_winbl && value != old_value) {
+    // 'floatblend'
+    curwin->w_p_winbl = MAX(MIN(curwin->w_p_winbl, 100), 0);
+    curwin->w_hl_needs_update = true;
+    curwin->w_grid.blending = curwin->w_p_winbl > 0;
   }
 
 
@@ -5713,6 +5718,7 @@ static char_u *get_varp(vimoption_T *p)
   case PV_WINHL:  return (char_u *)&(curwin->w_p_winhl);
   case PV_FCS:    return (char_u *)&(curwin->w_p_fcs);
   case PV_LCS:    return (char_u *)&(curwin->w_p_lcs);
+  case PV_WINBL:  return (char_u *)&(curwin->w_p_winbl);
   default:        IEMSG(_("E356: get_varp ERROR"));
   }
   // always return a valid pointer to avoid a crash!
@@ -5792,6 +5798,7 @@ void copy_winopt(winopt_T *from, winopt_T *to)
   to->wo_winhl = vim_strsave(from->wo_winhl);
   to->wo_fcs = vim_strsave(from->wo_fcs);
   to->wo_lcs = vim_strsave(from->wo_lcs);
+  to->wo_winbl = from->wo_winbl;
   check_winopt(to);             // don't want NULL pointers
 }
 
@@ -5854,7 +5861,8 @@ void didset_window_options(win_T *wp)
   briopt_check(wp);
   set_chars_option(wp, &wp->w_p_fcs);
   set_chars_option(wp, &wp->w_p_lcs);
-  parse_winhl_opt(wp);
+  parse_winhl_opt(wp);  // sets w_hl_needs_update also for w_p_winbl
+  wp->w_grid.blending = wp->w_p_winbl > 0;
 }
 
 
diff --git a/src/nvim/option_defs.h b/src/nvim/option_defs.h
index 8df5039037..35fe3b5b00 100644
--- a/src/nvim/option_defs.h
+++ b/src/nvim/option_defs.h
@@ -816,6 +816,7 @@ enum {
   , WV_WINHL
   , WV_FCS
   , WV_LCS
+  , WV_WINBL
   , WV_COUNT        // must be the last one
 };
 
diff --git a/src/nvim/options.lua b/src/nvim/options.lua
index e892e59ba6..cfdac36990 100644
--- a/src/nvim/options.lua
+++ b/src/nvim/options.lua
@@ -2762,6 +2762,13 @@ return {
       defaults={if_true={vi="menu"}}
     },
     {
+      full_name='winblend', abbreviation='winbl',
+      type='number', scope={'window'},
+      vi_def=true,
+      redraw={'current_window'},
+      defaults={if_true={vi=0}}
+    },
+    {
       full_name='winhighlight', abbreviation='winhl',
       type='string', scope={'window'},
       vi_def=true,
diff --git a/src/nvim/popupmnu.c b/src/nvim/popupmnu.c
index df751b0ca2..ef4330003f 100644
--- a/src/nvim/popupmnu.c
+++ b/src/nvim/popupmnu.c
@@ -376,6 +376,7 @@ void pum_redraw(void)
                                 pum_height, grid_width, false, true);
   bool invalid_grid = moved || pum_invalid;
   pum_invalid = false;
+  must_redraw_pum = false;
 
   if (!pum_grid.chars
       || pum_grid.Rows != pum_height || pum_grid.Columns != grid_width) {
@@ -790,6 +791,7 @@ void pum_undisplay(bool immediate)
 {
   pum_is_visible = false;
   pum_array = NULL;
+  must_redraw_pum = false;
 
   if (immediate) {
     pum_check_clear();
diff --git a/src/nvim/screen.c b/src/nvim/screen.c
index f349304468..d91b832e5a 100644
--- a/src/nvim/screen.c
+++ b/src/nvim/screen.c
@@ -482,13 +482,13 @@ void update_screen(int type)
   }
 
   end_search_hl();
+
   // May need to redraw the popup menu.
-  if (pum_drawn() && redraw_popupmenu) {
+  if (pum_drawn() && must_redraw_pum) {
     pum_redraw();
   }
 
   send_grid_resize = false;
-  redraw_popupmenu = false;
 
   /* Reset b_mod_set flags.  Going through all windows is probably faster
    * than going through all buffers (there could be many buffers). */
diff --git a/src/nvim/syntax.c b/src/nvim/syntax.c
index 38d0e33948..8d846df8b6 100644
--- a/src/nvim/syntax.c
+++ b/src/nvim/syntax.c
@@ -75,6 +75,8 @@ struct hl_group {
   uint8_t *sg_rgb_fg_name;      ///< RGB foreground color name
   uint8_t *sg_rgb_bg_name;      ///< RGB background color name
   uint8_t *sg_rgb_sp_name;      ///< RGB special color name
+
+  int sg_blend;                 ///< blend level (0-100 inclusive), -1 if unset
 };
 
 /// \addtogroup SG_SET
@@ -6879,6 +6881,12 @@ void do_highlight(const char *line, const bool forceit, const bool init)
         }
       } else if (strcmp(key, "START") == 0 || strcmp(key, "STOP") == 0)   {
         // Ignored for now
+      } else if (strcmp(key, "BLEND") == 0)   {
+        if (strcmp(arg, "NONE") != 0) {
+          HL_TABLE()[idx].sg_blend = strtol(arg, NULL, 10);
+        } else {
+          HL_TABLE()[idx].sg_blend = -1;
+        }
       } else {
         emsgf(_("E423: Illegal argument: %s"), key_start);
         error = true;
@@ -6993,6 +7001,7 @@ static void highlight_clear(int idx)
   XFREE_CLEAR(HL_TABLE()[idx].sg_rgb_fg_name);
   XFREE_CLEAR(HL_TABLE()[idx].sg_rgb_bg_name);
   XFREE_CLEAR(HL_TABLE()[idx].sg_rgb_sp_name);
+  HL_TABLE()[idx].sg_blend = -1;
   // Clear the script ID only when there is no link, since that is not
   // cleared.
   if (HL_TABLE()[idx].sg_link == 0) {
@@ -7029,6 +7038,9 @@ static void highlight_list_one(const int id)
   didh = highlight_list_arg(id, didh, LIST_STRING,
                             0, sgp->sg_rgb_sp_name, "guisp");
 
+  didh = highlight_list_arg(id, didh, LIST_INT,
+                            sgp->sg_blend+1, NULL, "blend");
+
   if (sgp->sg_link && !got_int) {
     (void)syn_list_header(didh, 9999, id);
     didh = true;
@@ -7252,6 +7264,7 @@ static void set_hl_attr(int idx)
   at_en.rgb_fg_color = sgp->sg_rgb_fg_name ? sgp->sg_rgb_fg : -1;
   at_en.rgb_bg_color = sgp->sg_rgb_bg_name ? sgp->sg_rgb_bg : -1;
   at_en.rgb_sp_color = sgp->sg_rgb_sp_name ? sgp->sg_rgb_sp : -1;
+  at_en.hl_blend = sgp->sg_blend;
 
   sgp->sg_attr = hl_get_syn_attr(idx+1, at_en);
 
@@ -7377,6 +7390,7 @@ static int syn_add_group(char_u *name)
   hlgp->sg_rgb_bg = -1;
   hlgp->sg_rgb_fg = -1;
   hlgp->sg_rgb_sp = -1;
+  hlgp->sg_blend = -1;
   hlgp->sg_name_u = vim_strsave_up(name);
 
   return highlight_ga.ga_len;               /* ID is index plus one */
diff --git a/src/nvim/ui_compositor.c b/src/nvim/ui_compositor.c
index f6573e7488..0c3e771eb8 100644
--- a/src/nvim/ui_compositor.c
+++ b/src/nvim/ui_compositor.c
@@ -330,10 +330,10 @@ static void compose_line(Integer row, Integer startcol, Integer endcol,
     memcpy(attrbuf+(col-startcol), grid->attrs+off, n * sizeof(*attrbuf));
 
     // 'pumblend'
-    if (grid == &pum_grid && p_pb) {
+    if (grid->blending) {
       for (int i = col-(int)startcol; i < until-startcol; i++) {
         bool thru = strequal((char *)linebuf[i], " ");  // negative space
-        attrbuf[i] = (sattr_T)hl_blend_attrs(bg_attrs[i], attrbuf[i], thru);
+        attrbuf[i] = (sattr_T)hl_blend_attrs(bg_attrs[i], attrbuf[i], &thru);
         if (thru) {
           memcpy(linebuf[i], bg_line[i], sizeof(linebuf[i]));
         }
@@ -419,7 +419,7 @@ static void ui_comp_raw_line(UI *ui, Integer grid, Integer row,
   assert(clearcol <= default_grid.Columns);
   if (flags & kLineFlagInvalid
       || kv_size(layers) > curgrid->comp_index+1
-      || (p_pb && curgrid == &pum_grid)) {
+      || curgrid->blending) {
     compose_line(row, startcol, clearcol, flags);
   } else {
     ui_composed_call_raw_line(1, row, startcol, endcol, clearcol, clearattr,
diff --git a/test/functional/ui/float_spec.lua b/test/functional/ui/float_spec.lua
index a567fbb941..3c7418167c 100644
--- a/test/functional/ui/float_spec.lua
+++ b/test/functional/ui/float_spec.lua
@@ -3764,6 +3764,196 @@ describe('floating windows', function()
         end
       end)
     end)
+
+    it("'winblend' option", function()
+      screen:try_resize(50,9)
+      screen:set_default_attr_ids({
+        [1] = {background = Screen.colors.LightMagenta},
+        [2] = {foreground = Screen.colors.Grey0, background = tonumber('0xffcfff')},
+        [3] = {foreground = tonumber('0xb282b2'), background = tonumber('0xffcfff')},
+        [4] = {foreground = Screen.colors.Red, background = Screen.colors.LightMagenta},
+        [5] = {foreground = tonumber('0x990000'), background = tonumber('0xfff1ff')},
+        [6] = {foreground = tonumber('0x332533'), background = tonumber('0xfff1ff')},
+      })
+      insert([[
+        Lorem ipsum dolor sit amet, consectetur
+        adipisicing elit, sed do eiusmod tempor
+        incididunt ut labore et dolore magna aliqua.
+        Ut enim ad minim veniam, quis nostrud
+        exercitation ullamco laboris nisi ut aliquip ex
+        ea commodo consequat. Duis aute irure dolor in
+        reprehenderit in voluptate velit esse cillum
+        dolore eu fugiat nulla pariatur. Excepteur sint
+        occaecat cupidatat non proident, sunt in culpa
+        qui officia deserunt mollit anim id est
+        laborum.]])
+      local buf = meths.create_buf(false,false)
+      meths.buf_set_lines(buf, 0, -1, true, {"test", "", "popup    text"})
+      local win = meths.open_win(buf, false, {relative='editor', width=15, height=3, row=2, col=5})
+      if multigrid then
+        screen:expect{grid=[[
+        ## grid 1
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+                                                            |
+        ## grid 2
+          Ut enim ad minim veniam, quis nostrud             |
+          exercitation ullamco laboris nisi ut aliquip ex   |
+          ea commodo consequat. Duis aute irure dolor in    |
+          reprehenderit in voluptate velit esse cillum      |
+          dolore eu fugiat nulla pariatur. Excepteur sint   |
+          occaecat cupidatat non proident, sunt in culpa    |
+          qui officia deserunt mollit anim id est           |
+          laborum^.                                          |
+        ## grid 4
+          {1:test           }|
+          {1:               }|
+          {1:popup    text  }|
+        ]], float_pos={[4] = {{id = 1002}, "NW", 1, 2, 5, true}}}
+      else
+        screen:expect([[
+          Ut enim ad minim veniam, quis nostrud             |
+          exercitation ullamco laboris nisi ut aliquip ex   |
+          ea co{1:test           }. Duis aute irure dolor in    |
+          repre{1:               }uptate velit esse cillum      |
+          dolor{1:popup    text  }la pariatur. Excepteur sint   |
+          occaecat cupidatat non proident, sunt in culpa    |
+          qui officia deserunt mollit anim id est           |
+          laborum^.                                          |
+                                                            |
+        ]])
+      end
+
+      meths.win_set_option(win, "winblend", 30)
+      if multigrid then
+        screen:expect{grid=[[
+        ## grid 1
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+                                                            |
+        ## grid 2
+          Ut enim ad minim veniam, quis nostrud             |
+          exercitation ullamco laboris nisi ut aliquip ex   |
+          ea commodo consequat. Duis aute irure dolor in    |
+          reprehenderit in voluptate velit esse cillum      |
+          dolore eu fugiat nulla pariatur. Excepteur sint   |
+          occaecat cupidatat non proident, sunt in culpa    |
+          qui officia deserunt mollit anim id est           |
+          laborum^.                                          |
+        ## grid 4
+          {1:test           }|
+          {1:               }|
+          {1:popup    text  }|
+        ]], float_pos={[4] = {{id = 1002}, "NW", 1, 2, 5, true}}, unchanged=true}
+      else
+        screen:expect([[
+          Ut enim ad minim veniam, quis nostrud             |
+          exercitation ullamco laboris nisi ut aliquip ex   |
+          ea co{2:test}{3:o consequat}. Duis aute irure dolor in    |
+          repre{3:henderit in vol}uptate velit esse cillum      |
+          dolor{2:popup}{3:fugi}{2:text}{3:ul}la pariatur. Excepteur sint   |
+          occaecat cupidatat non proident, sunt in culpa    |
+          qui officia deserunt mollit anim id est           |
+          laborum^.                                          |
+                                                            |
+        ]])
+      end
+
+      command('hi SpecialRegion guifg=Red blend=0')
+      meths.buf_add_highlight(buf, -1, "SpecialRegion", 2, 0, -1)
+      if multigrid then
+        screen:expect{grid=[[
+        ## grid 1
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+                                                            |
+        ## grid 2
+          Ut enim ad minim veniam, quis nostrud             |
+          exercitation ullamco laboris nisi ut aliquip ex   |
+          ea commodo consequat. Duis aute irure dolor in    |
+          reprehenderit in voluptate velit esse cillum      |
+          dolore eu fugiat nulla pariatur. Excepteur sint   |
+          occaecat cupidatat non proident, sunt in culpa    |
+          qui officia deserunt mollit anim id est           |
+          laborum^.                                          |
+        ## grid 4
+          {1:test           }|
+          {1:               }|
+          {4:popup    text}{1:  }|
+        ]], float_pos={[4] = {{id = 1002}, "NW", 1, 2, 5, true}}}
+      else
+        screen:expect([[
+          Ut enim ad minim veniam, quis nostrud             |
+          exercitation ullamco laboris nisi ut aliquip ex   |
+          ea co{2:test}{3:o consequat}. Duis aute irure dolor in    |
+          repre{3:henderit in vol}uptate velit esse cillum      |
+          dolor{4:popup    text}{3:ul}la pariatur. Excepteur sint   |
+          occaecat cupidatat non proident, sunt in culpa    |
+          qui officia deserunt mollit anim id est           |
+          laborum^.                                          |
+                                                            |
+        ]])
+      end
+
+      command('hi SpecialRegion guifg=Red blend=80')
+      if multigrid then
+        screen:expect{grid=[[
+        ## grid 1
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+                                                            |
+        ## grid 2
+          Ut enim ad minim veniam, quis nostrud             |
+          exercitation ullamco laboris nisi ut aliquip ex   |
+          ea commodo consequat. Duis aute irure dolor in    |
+          reprehenderit in voluptate velit esse cillum      |
+          dolore eu fugiat nulla pariatur. Excepteur sint   |
+          occaecat cupidatat non proident, sunt in culpa    |
+          qui officia deserunt mollit anim id est           |
+          laborum^.                                          |
+        ## grid 4
+          {1:test           }|
+          {1:               }|
+          {4:popup    text}{1:  }|
+        ]], float_pos={[4] = {{id = 1002}, "NW", 1, 2, 5, true}}, unchanged=true}
+      else
+        screen:expect([[
+          Ut enim ad minim veniam, quis nostrud             |
+          exercitation ullamco laboris nisi ut aliquip ex   |
+          ea co{2:test}{3:o consequat}. Duis aute irure dolor in    |
+          repre{3:henderit in vol}uptate velit esse cillum      |
+          dolor{5:popup}{6:fugi}{5:text}{3:ul}la pariatur. Excepteur sint   |
+          occaecat cupidatat non proident, sunt in culpa    |
+          qui officia deserunt mollit anim id est           |
+          laborum^.                                          |
+                                                            |
+        ]])
+      end
+    end)
   end
 
   describe('with ext_multigrid', function()
diff --git a/test/functional/ui/popupmenu_spec.lua b/test/functional/ui/popupmenu_spec.lua
index b457ebebab..466e078277 100644
--- a/test/functional/ui/popupmenu_spec.lua
+++ b/test/functional/ui/popupmenu_spec.lua
@@ -1662,6 +1662,26 @@ describe('builtin popupmenu', function()
       {20:-- Keyword Local completion (^N^P) }{21:match 1 of 65}            |
     ]])
 
+    -- can disable blending for indiviual attribute. For instance current
+    -- selected item. (also tests that `hi Pmenu*` take immediate effect)
+    command('hi PMenuSel blend=0')
+    screen:expect([[
+      Lorem ipsum d{1:ol}or sit amet, consectetur                     |
+      adipisicing elit, sed do eiusmod tempor                     |
+      bla bla incididunt^                                          |
+      incidid{22: incididunt     }{27: }d{1:ol}ore magna aliqua.                |
+      Ut enim{28: }{29:ut}{28: minim veniam}{25:,} quis nostrud                       |
+      exercit{28:a}{29:labore}{28:llamco la}{25:b}oris nisi ut aliquip ex             |
+      {2:[No Nam}{30:e}{43:et}{30:[+]          }{32: }{2:                                    }|
+      incidid{28:u}{29:dol}{41:or}{29:e}{28:labore et}{25: }d{1:ol}ore magna aliqua.                |
+      Ut enim{28: }{29:magna}{28:nim veniam}{25:,} quis nostrud                       |
+      exercit{28:a}{29:aliqua}{28:llamco la}{25:b}oris nisi {4:ut} aliquip ex             |
+      ea comm{28:o}{29:Ut}{28: consequat. D}{25:u}is a{4:ut}e irure d{1:ol}or in              |
+      reprehe{28:n}{29:enim}{28:t in v}{34:ol}{28:upt}{25:a}te v{3:el}it esse cillum                |
+      {5:[No Nam}{38:e}{44:ad}{38:[+]          }{40: }{5:                                    }|
+      {20:-- Keyword Local completion (^N^P) }{21:match 1 of 65}            |
+    ]])
+
     feed('<c-e>')
     screen:expect([[
       Lorem ipsum d{1:ol}or sit amet, consectetur                     |