Add WASM build (resolves #28)

.github/workflows/build.yml

@@ -89,6 +89,11 @@ jobs:
             target_cpu: x86
             runner: windows-2019
 
+          - artifact: pdfium-wasm
+            target_os: wasm
+            target_cpu: wasm
+            runner: ubuntu-20.04
+
     runs-on: ${{ matrix.runner }}
     steps:
       - name: Checkout this repo

README.md

@@ -90,8 +90,15 @@ Here are the download links for latest release:
     <td>x86</td>
     <td><a href="https://github.com/bblanchon/pdfium-binaries/releases/latest/download/pdfium-win-x86.tgz">pdfium-win-x86.tgz</a></td>
   </tr>
+
+  <tr>
+    <td colspan="2">WebAssembly<sup>1</sup></td>
+    <td><a href="https://github.com/bblanchon/pdfium-binaries/releases/latest/download/pdfium-wasm.tgz">pdfium-wasm.tgz</a></td>
+  </tr>
 </table>
 
+<small>1: WebAssembly build is experimental; please [provide feedback](https://github.com/bblanchon/pdfium-binaries/issues/28).</small>
+
 See the [Releases page](https://github.com/bblanchon/pdfium-binaries/releases) to download older versions of PDFium.
 
 Several [NuGet packages](https://www.nuget.org/packages/bblanchon.PDFium/) are also available.

patches/wasm/build.patch

@@ -0,0 +1,72 @@
+diff --git a/config/BUILDCONFIG.gn b/config/BUILDCONFIG.gn
+index fcc7e1283..a6e65682d 100644
+--- a/config/BUILDCONFIG.gn
++++ b/config/BUILDCONFIG.gn
+@@ -262,6 +262,8 @@ if (target_os == "android") {
+   _default_toolchain = "//build/toolchain/aix:$target_cpu"
+ } else if (target_os == "zos") {
+   _default_toolchain = "//build/toolchain/zos:$target_cpu"
++} else if (target_cpu == "wasm") {
++  _default_toolchain = "//build/toolchain/wasm:emscripten"
+ } else {
+   assert(false, "Unsupported target_os: $target_os")
+ }
+@@ -300,9 +302,10 @@ is_linux = current_os == "linux"
+ is_mac = current_os == "mac"
+ is_nacl = current_os == "nacl"
+ is_win = current_os == "win" || current_os == "winuwp"
++is_wasm = current_os == "wasm"
+
+ is_apple = is_ios || is_mac
+-is_posix = !is_win && !is_fuchsia
++is_posix = !is_win && !is_fuchsia && !is_wasm
+
+ # =============================================================================
+ # TARGET DEFAULTS
+@@ -377,7 +380,6 @@ if (is_android) {
+
+ if (is_clang && !is_nacl) {
+   default_compiler_configs += [
+-    "//build/config/clang:find_bad_constructs",
+     "//build/config/clang:extra_warnings",
+   ]
+ }
+diff --git a/config/compiler/BUILD.gn b/config/compiler/BUILD.gn
+index 10937225b..5fed442e4 100644
+--- a/config/compiler/BUILD.gn
++++ b/config/compiler/BUILD.gn
+@@ -287,6 +287,8 @@ config("compiler") {
+     configs += [ "//build/config/aix:compiler" ]
+   } else if (current_os == "zos") {
+     configs += [ "//build/config/zos:compiler" ]
++  } else if (current_os == "wasm") {
++    configs += [ "//build/config/wasm:compiler" ]
+   }
+
+   configs += [
+diff --git a/config/compiler/compiler.gni b/config/compiler/compiler.gni
+index 8e7bdd8f0..124dbd963 100644
+--- a/config/compiler/compiler.gni
++++ b/config/compiler/compiler.gni
+@@ -221,7 +221,7 @@ declare_args() {
+   # (which lld doesn't support either).
+   # The default linker everywhere else.
+   use_lld = is_clang && !(is_mac && is_gpu_fyi_bot) && current_os != "zos" &&
+-            !(is_ios && (is_cronet_build || target_environment == "catalyst"))
++            !(is_ios && (is_cronet_build || target_environment == "catalyst")) && !is_wasm
+ }
+
+ declare_args() {
+diff --git a/toolchain/toolchain.gni b/toolchain/toolchain.gni
+index 9874c7a12..59f84c36f 100644
+--- a/toolchain/toolchain.gni
++++ b/toolchain/toolchain.gni
+@@ -52,6 +52,8 @@ if (is_apple) {
+   shlib_extension = ".so"
+ } else if (is_win) {
+   shlib_extension = ".dll"
++} if (is_wasm) {
++  shlib_extension = ".so"
+ } else {
+   assert(false, "Platform not supported")
+ }

patches/wasm/config.gn

@@ -0,0 +1,7 @@
+config("compiler") {
+  defines = [
+    # Enable fseeko() and ftello() (required by libopenjpeg20)
+    # https://github.com/emscripten-core/emscripten/issues/4932
+    "_POSIX_C_SOURCE=200112",
+  ]
+}

patches/wasm/pdfium.patch

@@ -0,0 +1,26 @@
+diff --git a/core/fxcrt/BUILD.gn b/core/fxcrt/BUILD.gn
+index ffa1b60..92224c5 100644
+--- a/core/fxcrt/BUILD.gn
++++ b/core/fxcrt/BUILD.gn
+@@ -125,7 +125,7 @@ source_set("fxcrt") {
+     "//third_party/icu:icuuc",
+   ]
+
+-  if (is_posix || is_fuchsia) {
++  if (is_posix || is_fuchsia || is_wasm) {
+     sources += [
+       "cfx_fileaccess_posix.cpp",
+       "cfx_fileaccess_posix.h",
+diff --git a/core/fxge/BUILD.gn b/core/fxge/BUILD.gn
+index 7dafd7d..6d1fff9 100644
+--- a/core/fxge/BUILD.gn
++++ b/core/fxge/BUILD.gn
+@@ -162,7 +162,7 @@ source_set("fxge") {
+     ]
+   }
+
+-  if (is_linux || is_chromeos) {
++  if (is_linux || is_chromeos || is_wasm) {
+     sources += [ "linux/fx_linux_impl.cpp" ]
+   }
+

patches/wasm/toolchain.gn

@@ -0,0 +1,16 @@
+import("//build/toolchain/gcc_toolchain.gni")
+
+gcc_toolchain("emscripten") {
+  cc = "emcc"
+  cxx = "em++"
+
+  readelf = "llvm-readobj"
+  ar = "emar"
+  ld = cxx
+  nm = "emnm"
+
+  toolchain_args = {
+    current_cpu = "wasm"
+    current_os = "wasm"
+  }
+}

steps/01-install.sh

@@ -1,6 +1,6 @@
 #!/bin/bash -eux
 
-PATH_FILE=${GITHUB_PATH:-.path}
+PATH_FILE=${GITHUB_PATH:-$PWD/.path}
 TARGET_OS=${PDFium_TARGET_OS:?}
 TARGET_CPU=${PDFium_TARGET_CPU:?}
 CURRENT_CPU=${PDFium_CURRENT_CPU:-x64}
@@ -30,4 +30,15 @@ case "$TARGET_OS-$TARGET_CPU" in
     sudo apt-get update
     sudo apt-get install -y g++-aarch64-linux-gnu
     ;;
+
+  wasm-wasm)
+    git clone https://github.com/emscripten-core/emsdk.git
+    pushd emsdk
+    ./emsdk install latest
+    ./emsdk activate latest
+    echo "$PWD/upstream/emscripten" >> "$PATH_FILE"
+    echo "$PWD/upstream/bin" >> "$PATH_FILE"
+    popd
+    ;;
+
 esac

steps/03-patch.sh

@@ -6,7 +6,7 @@ OS="${PDFium_TARGET_OS:?}"
 
 pushd "${SOURCE}"
 
-git apply -v "$PATCHES/shared_library.patch"
+[ "$OS" != "wasm" ] && git apply -v "$PATCHES/shared_library.patch"
 git apply -v "$PATCHES/public_headers.patch"
 
 [ "${PDFium_V8:-}" == "enabled" ] && git apply -v "$PATCHES/v8_init.patch"
@@ -22,6 +22,15 @@ case "$OS" in
     git -C third_party/libjpeg_turbo apply -v "$PATCHES/ios/libjpeg_turbo.patch"
     ;;
 
+  wasm)
+    git apply -v "$PATCHES/wasm/pdfium.patch"
+    git -C build apply -v "$PATCHES/wasm/build.patch"
+    mkdir -p "build/toolchain/wasm"
+    cp "$PATCHES/wasm/toolchain.gn" "build/toolchain/wasm/BUILD.gn"
+    mkdir -p "build/config/wasm"
+    cp "$PATCHES/wasm/config.gn" "build/config/wasm/BUILD.gn"
+    ;;
+
   win)
     git apply -v "$PATCHES/win/pdfium.patch"
     git -C build apply -v "$PATCHES/win/build.patch"

steps/05-configure.sh

@@ -39,6 +39,9 @@ mkdir -p "$BUILD"
     win)
       echo 'pdf_use_win32_gdi = true'
       ;;
+    wasm):
+      echo 'pdf_is_complete_lib = true'
+      ;;
   esac
 
 ) | sort > "$BUILD/args.gn"

steps/06-build.sh

@@ -2,5 +2,19 @@
 
 SOURCE=${PDFium_SOURCE_DIR:-pdfium}
 BUILD_DIR=${PDFium_BUILD_DIR:-$SOURCE/out}
+TARGET_CPU=${PDFium_TARGET_CPU:?}
 
-ninja -C "$BUILD_DIR" pdfium
+ninja -C "$BUILD_DIR" pdfium
+
+if [ "$TARGET_CPU" == "wasm" ]; then
+  LIBPDFIUMA="$BUILD_DIR/obj/libpdfium.a"
+  EXPORTED_FUNCTIONS=$(emnm $LIBPDFIUMA --format=just-symbols | grep "^FPDF" | sed 's/^/_/' | paste -sd "," -)
+  em++ \
+    -s EXPORTED_FUNCTIONS="$EXPORTED_FUNCTIONS" \
+    -s LLD_REPORT_UNDEFINED \
+    -s WASM=1 \
+    -s EXPORTED_RUNTIME_METHODS='["ccall", "cwrap"]' \
+    -o "$BUILD_DIR/pdfium.html" \
+    "$LIBPDFIUMA" \
+    --no-entry
+fi

steps/07-pack.sh

@@ -36,6 +36,14 @@ case "$OS" in
     mv "$BUILD/libpdfium.dylib" "$STAGING_LIB"
     ;;
 
+  wasm)
+    mv "$BUILD/pdfium.html" "$STAGING_LIB"
+    mv "$BUILD/pdfium.js" "$STAGING_LIB"
+    mv "$BUILD/pdfium.wasm" "$STAGING_LIB"
+    rm -rf "$STAGING/include/cpp"
+    rm "$STAGING/PDFiumConfig.cmake"
+    ;;
+
   win)
     mv "$BUILD/pdfium.dll.lib" "$STAGING_LIB"
     mkdir -p "$STAGING_BIN"
@@ -57,7 +65,11 @@ BUILD=$(echo "$VERSION" | cut -d. -f3)
 PATCH=$(echo "$VERSION" | cut -d. -f4)
 END
 
-ARTIFACT_BASE="$PWD/pdfium-$OS-$CPU"
+if [ "$OS" != "$CPU" ]; then
+  ARTIFACT_BASE="$PWD/pdfium-$OS-$CPU"
+else
+  ARTIFACT_BASE="$PWD/pdfium-$OS"
+fi
 [ "$V8" == "enabled" ] && ARTIFACT_BASE="$ARTIFACT_BASE-v8"
 [ "$CFG" == "Debug" ] && ARTIFACT_BASE="$ARTIFACT_BASE-debug"
 ARTIFACT="$ARTIFACT_BASE.tgz"

steps/08-test.sh

@@ -99,6 +99,11 @@ case "$OS" in
       -A "$ARCH"
     )
     ;;
+
+  wasm)
+    # TODO: add test for Wasm
+    exit
+    ;;
 esac
 
 CMAKE_ARGS+=("$SOURCE_DIR")