From f8c9221afea4516c0719ebfac8d7853ae01e405f Mon Sep 17 00:00:00 2001
From: David Capello <david@igara.com>
Date: Mon, 23 Sep 2024 19:29:05 -0300
Subject: [PATCH] Add way to disable ligatures when shaping text

Related to: https://github.com/aseprite/aseprite/issues/4679
---
 examples/text_shape.cpp        |  5 ++++-
 text/skia_text_blob.h          |  3 ++-
 text/skia_text_blob_shaper.cpp | 11 ++++++++++-
 text/text_blob.h               |  8 +++++++-
 text/text_blob_shaper.cpp      |  6 ++++--
 5 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/examples/text_shape.cpp b/examples/text_shape.cpp
index ce1289020..448425ad9 100644
--- a/examples/text_shape.cpp
+++ b/examples/text_shape.cpp
@@ -63,8 +63,11 @@ struct TextEdit {
   }
 
   void makeBlob(FontMgrRef& fontMgr, FontRef& font) {
+    // Create a blob without ligatures (to edit char by char)
     BoxBuilder handler;
-    blob = TextBlob::MakeWithShaper(fontMgr, font, text, &handler);
+    TextBlob::ShaperFeatures features;
+    features.ligatures = false;
+    blob = TextBlob::MakeWithShaper(fontMgr, font, text, &handler, features);
     boxes = handler.boxes();
   }
 };
diff --git a/text/skia_text_blob.h b/text/skia_text_blob.h
index a53a7abd7..7bd179fc1 100644
--- a/text/skia_text_blob.h
+++ b/text/skia_text_blob.h
@@ -32,7 +32,8 @@ class SkiaTextBlob : public TextBlob {
     const FontMgrRef& fontMgr,
     const FontRef& font,
     const std::string& text,
-    TextBlob::RunHandler* handler);
+    TextBlob::RunHandler* handler,
+    const TextBlob::ShaperFeatures features);
 
 private:
   sk_sp<SkTextBlob> m_skTextBlob;
diff --git a/text/skia_text_blob_shaper.cpp b/text/skia_text_blob_shaper.cpp
index 19bb56404..cc7c72204 100644
--- a/text/skia_text_blob_shaper.cpp
+++ b/text/skia_text_blob_shaper.cpp
@@ -23,6 +23,7 @@
 #include "modules/skshaper/include/SkShaper.h"
 
 #include <limits>
+#include <vector>
 
 namespace text {
 
@@ -125,7 +126,8 @@ TextBlobRef SkiaTextBlob::MakeWithShaper(
   const FontMgrRef& fontMgr,
   const FontRef& font,
   const std::string& text,
-  TextBlob::RunHandler* handler)
+  TextBlob::RunHandler* handler,
+  const TextBlob::ShaperFeatures features)
 {
   ASSERT(font);
   ASSERT(font->type() == FontType::Native);
@@ -150,12 +152,19 @@ TextBlobRef SkiaTextBlob::MakeWithShaper(
                                                     SkFontStyle::Normal(),
                                                     &*languageRun);
 
+    std::vector<SkShaper::Feature> ft;
+    if (!features.ligatures) {
+      ft.emplace_back(SkShaper::Feature{
+        SkSetFourByteTag('l', 'i', 'g', 'a'), 0, 0, text.size() });
+    }
+
     shaper->shape(text.c_str(),
                   text.size(),
                   *fontRun,
                   *bidiRun,
                   *scriptRun,
                   *languageRun,
+                  ft.data(), ft.size(),
                   std::numeric_limits<float>::max(),
                   &shaperHandler);
 
diff --git a/text/text_blob.h b/text/text_blob.h
index bbffd0ac3..12a45e18c 100644
--- a/text/text_blob.h
+++ b/text/text_blob.h
@@ -57,6 +57,11 @@ namespace text {
       gfx::RectF getGlyphBounds(size_t i) const;
     };
 
+    struct ShaperFeatures {
+      bool ligatures = true;
+      ShaperFeatures() { }
+    };
+
     class RunHandler {
     public:
       virtual ~RunHandler() = default;
@@ -94,7 +99,8 @@ namespace text {
       const FontMgrRef& fontMgr,
       const FontRef& font,
       const std::string& text,
-      RunHandler* handler = nullptr);
+      RunHandler* handler = nullptr,
+      const ShaperFeatures features = {});
 
   private:
     gfx::RectF m_bounds;
diff --git a/text/text_blob_shaper.cpp b/text/text_blob_shaper.cpp
index f33553748..60adecb65 100644
--- a/text/text_blob_shaper.cpp
+++ b/text/text_blob_shaper.cpp
@@ -23,7 +23,8 @@ TextBlobRef TextBlob::MakeWithShaper(
   const FontMgrRef& fontMgr,
   const FontRef& font,
   const std::string& text,
-  TextBlob::RunHandler* handler)
+  TextBlob::RunHandler* handler,
+  const TextBlob::ShaperFeatures features)
 {
   ASSERT(font);
   switch (font->type()) {
@@ -37,7 +38,8 @@ TextBlobRef TextBlob::MakeWithShaper(
 
 #if LAF_SKIA
     case FontType::Native:
-      return SkiaTextBlob::MakeWithShaper(fontMgr, font, text, handler);
+      return SkiaTextBlob::MakeWithShaper(
+        fontMgr, font, text, handler, features);
 #endif
 
     default: