From 6aea77c643777b7ed550edc63f65859c05430e53 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Sun, 26 Feb 2023 12:28:25 -0700
Subject: [PATCH] [wasm-shape] Add (disabled) module support

---
 meson.build                |  1 +
 src/hb-wasm-shape.cc       | 66 +++++++++++++++++++++++++++++++++++++-
 src/wasm/graphite/Makefile |  2 +-
 3 files changed, 67 insertions(+), 2 deletions(-)

diff --git a/meson.build b/meson.build
index 70ba6a26c..4b2df6c58 100644
--- a/meson.build
+++ b/meson.build
@@ -234,6 +234,7 @@ endif
 
 if wasm_dep.found()
   conf.set('HAVE_WASM', 1)
+  conf.set('HB_WASM_MODULE_DIR', '"'+get_option('prefix')+'/'+get_option('libdir')+'/harfbuzz/wasm"')
 endif
 
 if graphite2_dep.found() or graphite_dep.found()
diff --git a/src/hb-wasm-shape.cc b/src/hb-wasm-shape.cc
index 439de4704..b1313b3e2 100644
--- a/src/hb-wasm-shape.cc
+++ b/src/hb-wasm-shape.cc
@@ -25,14 +25,74 @@
  */
 
 #define HB_DEBUG_WASM 1
+#define HB_WASM_NO_MODULES
 
 #include "hb-shaper-impl.hh"
 
 #ifdef HAVE_WASM
 
+/* Compile wasm-micro-runtime with:
+ *
+ * $ cmake -DWAMR_BUILD_MULTI_MODULE=1 -DWAMR_BUILD_REF_TYPES=1 -DWAMR_BUILD_FAST_JIT=1
+ * $ make
+ *
+ * If you manage to build a wasm shared module successfully and want to use it,
+ * do the following:
+ *
+ *   - Add -DWAMR_BUILD_MULTI_MODULE=1 to your cmake build for wasm-micro-runtime,
+ *
+ *   - Remove the #define HB_WASM_NO_MODULES line below,
+ *
+ *   - Install your shared module with name ending in .wasm in
+ *     $(prefix)/$(libdir)/harfbuzz/wasm/
+ *
+ *   - Build your font's wasm code importing the shared modules with the desired
+ *     name. This can be done eg.: __attribute__((import_module("graphite2")))
+ *     before each symbol in the the shared-module's headers.
+ *
+ *   - Try shaping your font and hope for the best...
+ *
+ * I haven't been able to get this to work since emcc's support for shared libraries
+ * requires support from the host that seems to be missing from wasm-micro-runtime?
+ */
+
 #include "hb-wasm-api.hh"
 #include "hb-wasm-api-list.hh"
 
+#define HB_WASM_NO_MODULES
+
+static bool HB_UNUSED
+_hb_wasm_module_reader (const char *module_name,
+		       uint8_t **p_buffer, uint32_t *p_size)
+{
+  char path[sizeof (HB_WASM_MODULE_DIR) + 64] = HB_WASM_MODULE_DIR "/";
+  strncat (path, module_name, sizeof (path) - sizeof (HB_WASM_MODULE_DIR) - 16);
+  strncat (path, ".wasm", 6);
+
+  auto *blob = hb_blob_create_from_file (path);
+
+  unsigned length;
+  auto *data = hb_blob_get_data (blob, &length);
+
+  *p_buffer = (uint8_t *) hb_malloc (length);
+
+  if (length && !p_buffer)
+    return false;
+
+  memcpy (*p_buffer, data, length);
+  *p_size = length;
+
+  hb_blob_destroy (blob);
+
+  return true;
+}
+
+static void HB_UNUSED
+_hb_wasm_module_destroyer (uint8_t *buffer, uint32_t size)
+{
+  hb_free (buffer);
+}
+
 
 /*
  * shaper face data
@@ -85,6 +145,11 @@ _hb_wasm_init ()
     return false;
   }
 
+#ifndef HB_WASM_NO_MODULES
+  wasm_runtime_set_module_reader(_hb_wasm_module_reader,
+				 _hb_wasm_module_destroyer);
+#endif
+
   initialized = true;
   return true;
 }
@@ -311,7 +376,6 @@ retry:
   auto *module_inst = plan->module_inst;
   auto *exec_env = plan->exec_env;
 
-  // cmake -DWAMR_BUILD_REF_TYPES=1 for these to work
   HB_OBJ2REF (font);
   HB_OBJ2REF (buffer);
   if (unlikely (!fontref || !bufferref))
diff --git a/src/wasm/graphite/Makefile b/src/wasm/graphite/Makefile
index db40901fe..cdd44dcb3 100644
--- a/src/wasm/graphite/Makefile
+++ b/src/wasm/graphite/Makefile
@@ -12,8 +12,8 @@ all: $(FONTS)
 		-Wl,--no-entry \
 		-Wl,--strip-all \
 		-sERROR_ON_UNDEFINED_SYMBOLS=0 \
-		~/graphite/src/libgraphite2.a \
 		-Wl,--export=malloc -Wl,--export=free \
+		~/graphite/src/libgraphite2.a \
 		~/wasm/wasi-sdk-19.0/share/wasi-sysroot/lib/wasm32-wasi/libc.a \
 		$< \
 		-o $@