gimp: Fix AVIF/HEIC support (#341914)

pkgs/applications/graphics/gimp/default.nix

@@ -42,6 +42,7 @@
 , mypaint-brushes1
 , libwebp
 , libheif
+, libxslt
 , libgudev
 , openexr
 , desktopToDarwinBundle
@@ -76,6 +77,14 @@ in stdenv.mkDerivation (finalAttrs: {
     # Use absolute paths instead of relying on PATH
     # to make sure plug-ins are loaded by the correct interpreter.
     ./hardcode-plugin-interpreters.patch
+
+    # GIMP queries libheif.pc for builtin encoder/decoder support to determine if AVIF/HEIC files are supported
+    # (see https://gitlab.gnome.org/GNOME/gimp/-/blob/a8b1173ca441283971ee48f4778e2ffd1cca7284/configure.ac?page=2#L1846-1852)
+    # These variables have been removed since libheif 1.18.0
+    # (see https://github.com/strukturag/libheif/commit/cf0d89c6e0809427427583290547a7757428cf5a)
+    # This has already been fixed for the upcoming GIMP 3, but the fix has not been backported to 2.x yet
+    # (see https://gitlab.gnome.org/GNOME/gimp/-/issues/9080)
+    ./force-enable-libheif.patch
   ];
 
   nativeBuildInputs = [
@@ -85,6 +94,7 @@ in stdenv.mkDerivation (finalAttrs: {
     gettext
     makeWrapper
     gtk-doc
+    libxslt
   ] ++ lib.optionals stdenv.isDarwin [
     desktopToDarwinBundle
   ];

pkgs/applications/graphics/gimp/force-enable-libheif.patch

@@ -0,0 +1,22 @@
+diff --git a/configure.ac b/configure.ac
+index 48c3c77892..3189781817 100644
+--- a/configure.ac
++++ b/configure.ac
+@@ -1843,13 +1843,13 @@ can_export_heic=no
+ can_import_avif=no
+ can_export_avif=no
+ if test "x$have_libheif" = xyes; then
+-  can_import_heic=`$PKG_CONFIG --variable=builtin_h265_decoder libheif`
+-  can_export_heic=`$PKG_CONFIG --variable=builtin_h265_encoder libheif`
++  can_import_heic=yes
++  can_export_heic=yes
+   if test "x$can_import_heic" = xyes; then
+     MIME_TYPES="$MIME_TYPES;image/heif;image/heic"
+   fi
+-  can_import_avif=`$PKG_CONFIG --variable=builtin_avif_decoder libheif`
+-  can_export_avif=`$PKG_CONFIG --variable=builtin_avif_encoder libheif`
++  can_import_avif=yes
++  can_export_avif=yes
+   if test "x$can_import_avif" = xyes; then
+     MIME_TYPES="$MIME_TYPES;image/avif"
+   fi