From f064acbdd9fac8a417067a244d008e4177e265f7 Mon Sep 17 00:00:00 2001
From: Nikolay Sivov <nsivov@codeweavers.com>
Date: Fri, 22 Jan 2021 15:25:17 +0300
Subject: [PATCH] dwrite/arabic: Mark some features for fallback.

Signed-off-by: Nikolay Sivov <nsivov@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>
---
 dlls/dwrite/dwrite_private.h |  3 +++
 dlls/dwrite/opentype.c       |  2 +-
 dlls/dwrite/shape.c          |  3 ++-
 dlls/dwrite/shapers/arabic.c | 25 +++++++++++++++++++++++--
 4 files changed, 29 insertions(+), 4 deletions(-)

diff --git a/dlls/dwrite/dwrite_private.h b/dlls/dwrite/dwrite_private.h
index 76d49ae5104..4a4229e1dc0 100644
--- a/dlls/dwrite/dwrite_private.h
+++ b/dlls/dwrite/dwrite_private.h
@@ -543,6 +543,7 @@ enum shaping_feature_flags
     FEATURE_MANUAL_ZWNJ = 0x4,
     FEATURE_MANUAL_ZWJ = 0x8,
     FEATURE_MANUAL_JOINERS = FEATURE_MANUAL_ZWNJ | FEATURE_MANUAL_ZWJ,
+    FEATURE_HAS_FALLBACK = 0x10,
 };
 
 struct shaping_feature
@@ -575,6 +576,8 @@ extern const struct shaper arabic_shaper DECLSPEC_HIDDEN;
 
 extern void shape_enable_feature(struct shaping_features *features, unsigned int tag,
         unsigned int flags) DECLSPEC_HIDDEN;
+extern void shape_add_feature_full(struct shaping_features *features, unsigned int tag, unsigned int flags,
+        unsigned int value) DECLSPEC_HIDDEN;
 extern void shape_start_next_stage(struct shaping_features *features) DECLSPEC_HIDDEN;
 
 struct scriptshaping_context
diff --git a/dlls/dwrite/opentype.c b/dlls/dwrite/opentype.c
index 20534460d09..256218663fb 100644
--- a/dlls/dwrite/opentype.c
+++ b/dlls/dwrite/opentype.c
@@ -4553,7 +4553,7 @@ static void opentype_layout_collect_lookups(struct scriptshaping_context *contex
             }
         }
 
-        if (!found)
+        if (!found && !(features->features[i].flags & FEATURE_HAS_FALLBACK))
             continue;
 
         if (feature->flags & FEATURE_GLOBAL && feature->max_value == 1)
diff --git a/dlls/dwrite/shape.c b/dlls/dwrite/shape.c
index 53b392c88e2..2dbea825216 100644
--- a/dlls/dwrite/shape.c
+++ b/dlls/dwrite/shape.c
@@ -115,7 +115,7 @@ static DWORD shape_select_language(const struct scriptshaping_cache *cache, DWOR
     return 0;
 }
 
-static void shape_add_feature_full(struct shaping_features *features, unsigned int tag, unsigned int flags, unsigned int value)
+void shape_add_feature_full(struct shaping_features *features, unsigned int tag, unsigned int flags, unsigned int value)
 {
     unsigned int i = features->count;
 
@@ -193,6 +193,7 @@ static void shape_merge_features(struct scriptshaping_context *context, struct s
                     features->features[j].flags ^= FEATURE_GLOBAL;
                 features->features[j].max_value = max(features->features[j].max_value, features->features[i].max_value);
             }
+            features->features[j].flags |= features->features[i].flags & FEATURE_HAS_FALLBACK;
             features->features[j].stage = min(features->features[j].stage, features->features[i].stage);
         }
     }
diff --git a/dlls/dwrite/shapers/arabic.c b/dlls/dwrite/shapers/arabic.c
index d8c6c9495c0..32588b9c796 100644
--- a/dlls/dwrite/shapers/arabic.c
+++ b/dlls/dwrite/shapers/arabic.c
@@ -18,6 +18,7 @@
  */
 
 #include "dwrite_private.h"
+#include "scripts.h"
 
 static const unsigned int arabic_features[] =
 {
@@ -30,6 +31,24 @@ static const unsigned int arabic_features[] =
     DWRITE_MAKE_OPENTYPE_TAG('i','n','i','t'),
 };
 
+enum arabic_shaping_action
+{
+    ISOL,
+    FINA,
+    FIN2,
+    FIN3,
+    MEDI,
+    MED2,
+    INIT,
+    NONE,
+};
+
+static BOOL feature_is_syriac(unsigned int tag)
+{
+    return tag == arabic_features[FIN2] || tag == arabic_features[FIN3] ||
+            tag == arabic_features[MED2];
+}
+
 static void arabic_collect_features(struct scriptshaping_context *context,
         struct shaping_features *features)
 {
@@ -41,11 +60,13 @@ static void arabic_collect_features(struct scriptshaping_context *context,
 
     for (i = 0; i < ARRAY_SIZE(arabic_features); ++i)
     {
-        shape_enable_feature(features, arabic_features[i], 0);
+        unsigned int flags = context->script == Script_Arabic && !feature_is_syriac(arabic_features[i]) ?
+                FEATURE_HAS_FALLBACK : 0;
+        shape_add_feature_full(features, arabic_features[i], flags, 1);
         shape_start_next_stage(features);
     }
 
-    shape_enable_feature(features, DWRITE_MAKE_OPENTYPE_TAG('r','l','i','g'), FEATURE_MANUAL_ZWJ);
+    shape_enable_feature(features, DWRITE_MAKE_OPENTYPE_TAG('r','l','i','g'), FEATURE_MANUAL_ZWJ | FEATURE_HAS_FALLBACK);
 
     shape_enable_feature(features, DWRITE_MAKE_OPENTYPE_TAG('r','c','l','t'), FEATURE_MANUAL_ZWJ);
     shape_enable_feature(features, DWRITE_MAKE_OPENTYPE_TAG('c','a','l','t'), FEATURE_MANUAL_ZWJ);