Implement opacity for popups by mattn · Pull Request #19272 · vim/vim

mattn · 2026-01-29T11:26:16Z

Popup windows in Vim currently have no transparency support. Users cannot create semi-transparent overlays that allow underlying text to be visible through the popup.

So, add a new opacity option for popup windows that controls transparency level.

2026-01-29.130110.mp4

### Usage

```vim
" Create a popup with 50% opacity (semi-transparent)
let winid = popup_create('Semi-transparent text', #{
    \ line: 5,
    \ col: 10,
    \ opacity: 50,
    \ })

" Change opacity dynamically
call popup_setoptions(winid, #{opacity: 80})

" Get current opacity value
echo popup_getoptions(winid).opacity

Opacity values

0 - Fully transparent (background text fully visible)
100 - Fully opaque (default, no transparency)
1-99 - Partially transparent

Requirements

Requires 'termguicolors' to be enabled for the blending effect to work

chrisbra · 2026-02-15T15:54:51Z

Thanks, can you please squash and rebase? I'd like to see the CI output again.

closes: vim#19272 Signed-off-by: Yasuhiro Matsumoto <mattn.jp@gmail.com>

chrisbra · 2026-02-15T17:12:10Z

Hm, it fails for tiny versions. I suspect we need this on top of it?

diff --git a/src/highlight.c b/src/highlight.c
index cc7715217..9ee925a02 100644
--- a/src/highlight.c
+++ b/src/highlight.c
@@ -3081,6 +3081,7 @@ hl_combine_attr(int char_attr, int prim_attr)
     return get_attr_entry(&term_attr_table, &new_en);
 }

+# if defined(FEAT_GUI) || defined(FEAT_TERMGUICOLORS)
 /*
  * Blend two RGB colors based on blend value (0-100).
  * blend: 0=use popup color, 100=use background color
@@ -3118,6 +3119,7 @@ blend_colors(guicolor_T popup_color, guicolor_T bg_color, int blend_val)

     return (r << 16) | (g << 8) | b;
 }
+#endif

 /*
  * Blend attributes for popup windows with opacity.

chrisbra · 2026-02-18T17:55:02Z

Thanks. I have included this now, fixing the conflict, please double verify. The reason for no screendump test is that this requires 'termguicolors', right?

chrisbra · 2026-02-19T07:18:20Z

I think this caused the following Coverity warnings:

** CID 1681431:       Incorrect expression  (IDENTICAL_BRANCHES)
/src/highlight.c: 3223           in hl_blend_attr()


_____________________________________________________________________________________________
*** CID 1681431:         Incorrect expression  (IDENTICAL_BRANCHES)
/src/highlight.c: 3223             in hl_blend_attr()
3217                popup_aep = syn_cterm_attr2entry(popup_attr);
3218                if (popup_aep != NULL)
3219                {
3220                    // Blend foreground color
3221                    if (popup_aep->ae_u.cterm.fg_color > 0)
3222                    {
>>>     CID 1681431:         Incorrect expression  (IDENTICAL_BRANCHES)
>>>     The same code is executed regardless of whether "new_en.ae_u.cterm.fg_color > 0" is true, because the "then" and "else" branches are identical. Should one of the branches be modified, or the entire "if" statement replaced?
3223                        if (new_en.ae_u.cterm.fg_color > 0)
3224                            new_en.ae_u.cterm.fg_color = popup_aep->ae_u.cterm.fg_color;
3225                        else
3226                            new_en.ae_u.cterm.fg_color = popup_aep->ae_u.cterm.fg_color;
3227                    }
3228                    // Use popup background color (cterm colors don't support blending)

** CID 1681430:       Integer handling issues  (INTEGER_OVERFLOW)
/src/screen.c: 845           in screen_line()


_____________________________________________________________________________________________
*** CID 1681430:         Integer handling issues  (INTEGER_OVERFLOW)
/src/screen.c: 845             in screen_line()
839             else if (  p_wiv
840     #ifdef FEAT_GUI
841                     && !gui.in_use
842     #endif
843                     && col + coloff > 0)
844             {
>>>     CID 1681430:         Integer handling issues  (INTEGER_OVERFLOW)
>>>     Expression "off_to - 1U", where "off_to" is known to be equal to 0, underflows the type of "off_to - 1U", which is type "unsigned int".
845                 if (ScreenAttrs[off_to] == ScreenAttrs[off_to - 1])
846                 {
847                     /*
848                      * Don't output stop-highlight when moving the cursor, it will
849                      * stop the highlighting when it should continue.
850                      */

can you please have a look @mattn ?

Problem: Redundant code in hl_blend_attr() (Coverity, after v9.2.0017) Solution: Remove redundant if/else logic, remove redundant braces. related: #19272 Signed-off-by: Christian Brabandt <cb@256bit.org>

Problem: In screen_line(), there is a potential integer underflow when accessing ScreenAttrs[off_to - 1] if off_to is zero. (Coverity CID 1681430, after v9.2.0017) Solution: Add a check to ensure off_to > 0 before accessing the previous attribute index. related: vim#19272 Signed-off-by: Christian Brabandt <cb@256bit.org>

Problem: syntax highlighting lost in popup with opacity lower than 100 (after v9.2.0017) Solution: Before blending, combine the popup's window color attribute with the character's own attribute using hl_combine_attr() (Yasuhiro Matsumoto). related: #19272 closes: #19478 Signed-off-by: Yasuhiro Matsumoto <mattn.jp@gmail.com> Signed-off-by: Christian Brabandt <cb@256bit.org>

Problem: In screen_line(), there is a potential integer underflow when accessing ScreenAttrs[off_to - 1] if off_to is zero. (Coverity CID 1681430, after v9.2.0017) Solution: Add a check to ensure off_to > 0 before accessing the previous attribute index. related: #19272 closes: #19479 Signed-off-by: Christian Brabandt <cb@256bit.org>

lilydjwg · 2026-02-22T15:43:31Z

Hi, can you check #19485 which happens since this patch?

mattn force-pushed the popup-opacity branch 2 times, most recently from 4191f25 to 775e56c Compare January 29, 2026 11:36

chrisbra added the after-9.2 label Jan 29, 2026

Add opacity option for popup windows

5f4b3d5

closes: vim#19272 Signed-off-by: Yasuhiro Matsumoto <mattn.jp@gmail.com>

mattn force-pushed the popup-opacity branch from 5fa492f to 5f4b3d5 Compare February 15, 2026 16:34

mattn added 2 commits February 16, 2026 02:29

Fix tiny build

efb87c2

Cosmetic change

0d2368b

chrisbra closed this in 95e8faa Feb 18, 2026

chrisbra mentioned this pull request Feb 21, 2026

potential integer underflow in screen_line() #19479

Closed

mattn deleted the popup-opacity branch March 17, 2026 23:40

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mattn commented Jan 29, 2026

Opacity values

Requirements

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