feat(firefox): blur the new tab background

The new tab showed the wallpaper verbatim, so it read as a hole onto
the desktop. write_firefox now scales the wallpaper to 1920 wide and
applies a Gaussian blur (FIREFOX_BLUR, radius 24) with PIL before
saving it into FF Ultima's darknix.png slot. Saving through PIL also
makes the file a real PNG whatever the wallpaper's format.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

2 files changed, 21 insertions, 8 deletions

diff --git a/AGENTS.md b/AGENTS.md
index 3a7401d..92f8894 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -270,9 +270,10 @@ the terminal palette follows the scheme and never the wallpaper. The
 write lands after `wallp` has already run `wal --theme`, so it wins; reorder
 those two and pywal's wallpaper-derived colours come back.
 
-Firefox's new tab shows the wallpaper itself, not a colour. FF Ultima picks
-the new tab background from a fixed list of images by pref, and `udt-accent`
-copies the wallpaper over its `walls/darknix.png` slot; selecting it once
+Firefox's new tab shows the wallpaper, blurred so it reads as a page and not
+as the desktop. FF Ultima picks the new tab background from a fixed list of
+images by pref, and `udt-accent` writes a blurred copy (PIL, `FIREFOX_BLUR`)
+over its `walls/darknix.png` slot; selecting it once
 (`user.theme.wallpaper.darknix` in `about:config`) is the only manual step.
 A copy, not a symlink: Firefox's sandbox will not follow a link out of the
 profile, and the new tab stays blank.
diff --git a/bin/udt-accent b/bin/udt-accent
index 17a225d..8f85b4c 100755
--- a/bin/udt-accent
+++ b/bin/udt-accent
@@ -19,7 +19,6 @@ import json
 import math
 import os
 import re
-import shutil
 import subprocess
 import sys
 import tempfile
@@ -66,6 +65,8 @@ PALETTE_RASI = Path.home() / ".config" / "rofi" / "udt" / "palette.rasi"
 COLORS_JSON = CACHE / "colors.json"
 # FF Ultima's new tab background slots. darknix.png is the one udt fills.
 FIREFOX_WALLS = "chrome/theme/color-schemes/walls"
+# Gaussian radius in px at 1920 wide, for the new tab background.
+FIREFOX_BLUR = 24
 
 # The SDDM theme's live palette. ~/.cache is 0700 and unreachable to the sddm
 # user, ~/.local/share is 0755, so the file has to live here. Root symlinks
@@ -396,18 +397,29 @@ def write_colors_json(name, image):
 
 
 def write_firefox(image):
-    """Copy the wallpaper into FF Ultima's darknix.png new tab slot.
+    """Write a blurred wallpaper into FF Ultima's darknix.png new tab slot.
 
-    A copy, not a link: Firefox's sandbox refuses to follow a symlink out of
+    Blurred so the new tab reads as Firefox, not as a hole onto the desktop.
+    A file, not a link: Firefox's sandbox refuses to follow a symlink out of
     the profile, and the new tab shows nothing. Every profile without FF
     Ultima is skipped.
     """
+    from PIL import Image, ImageFilter
+
+    blurred = None
     for walls in (Path.home() / ".mozilla" / "firefox").glob(f"*/{FIREFOX_WALLS}"):
+        if blurred is None:
+            with Image.open(image) as im:
+                im = im.convert("RGB")
+                # Detail is blurred away anyway, so 1920 wide is plenty and
+                # keeps the blur fast on a 4K wallpaper.
+                im.thumbnail((1920, 1920))
+                blurred = im.filter(ImageFilter.GaussianBlur(FIREFOX_BLUR))
         dest = walls / "darknix.png"
-        # A leftover link would make copyfile write through it into the
+        # A leftover link would make save write through it into the
         # wallpaper itself.
         dest.unlink(missing_ok=True)
-        shutil.copyfile(image, dest)
+        blurred.save(dest, "PNG")
 
 
 def rewrite(path, pattern, value):