Add Lua SkXfermode skp scraping support

src/utils/SkLua.cpp

Index: src/utils/SkLua.cpp
diff --git a/src/utils/SkLua.cpp b/src/utils/SkLua.cpp
index d85fb91a033a4164046f934e7b6e1f2dbb8232eb..edd336afdf04c5867e6fe512cf67121932013083 100644
--- a/src/utils/SkLua.cpp
+++ b/src/utils/SkLua.cpp
@@ -28,6 +28,7 @@
 #include "SkSurface.h"
 #include "SkTextBlob.h"
 #include "SkTypeface.h"
+#include "SkXfermode.h"
 
 extern "C" {
     #include "lua.h"
@@ -58,6 +59,7 @@ DEF_MTNAME(SkShader)
 DEF_MTNAME(SkSurface)
 DEF_MTNAME(SkTextBlob)
 DEF_MTNAME(SkTypeface)
+DEF_MTNAME(SkXfermode)
 
 template <typename T> T* push_new(lua_State* L) {
     T* addr = (T*)lua_newuserdata(L, sizeof(T));
@@ -1081,6 +1083,22 @@ static int lpaint_getEffects(lua_State* L) {
     return 1;
 }
 
+static int lpaint_getXfermode(lua_State* L) {
+    const SkPaint* paint = get_obj<SkPaint>(L, 1);
+    SkXfermode* xfermode = paint->getXfermode();
+    if (xfermode) {
+        push_ref(L, xfermode);
+        return 1;
+    }
+    return 0;
+}
+
+static int lpaint_setXfermode(lua_State* L) {
+    SkPaint* paint = get_obj<SkPaint>(L, 1);
+    paint->setXfermode(get_ref<SkXfermode>(L, 2));
+    return 0;
+}
+
 static int lpaint_getColorFilter(lua_State* L) {
     const SkPaint* paint = get_obj<SkPaint>(L, 1);
     SkColorFilter* cf = paint->getColorFilter();
@@ -1192,6 +1210,8 @@ static const struct luaL_Reg gSkPaint_Methods[] = {
     { "setColorFilter", lpaint_setColorFilter },
     { "getImageFilter", lpaint_getImageFilter },
     { "setImageFilter", lpaint_setImageFilter },
+    { "getXfermode", lpaint_getXfermode },
+    { "setXfermode", lpaint_setXfermode },
     { "getShader", lpaint_getShader },
     { "setShader", lpaint_setShader },
     { "getPathEffect", lpaint_getPathEffect },
@@ -1314,6 +1334,24 @@ static const struct luaL_Reg gSkPathEffect_Methods[] = {
 
 ///////////////////////////////////////////////////////////////////////////////
 
+static int lpxfermode_getTypeName(lua_State* L) {
+    lua_pushstring(L, get_ref<SkXfermode>(L, 1)->getTypeName());
+    return 1;
+}
+
+static int lpxfermode_gc(lua_State* L) {
+    get_ref<SkXfermode>(L, 1)->unref();
+    return 0;
+}
+
+static const struct luaL_Reg gSkXfermode_Methods[] = {
+    { "getTypeName",    lpxfermode_getTypeName },
+    { "__gc",           lpxfermode_gc },
+    { nullptr, nullptr }
+};
+
+///////////////////////////////////////////////////////////////////////////////
+
 static int lpcolorfilter_gc(lua_State* L) {
     get_ref<SkColorFilter>(L, 1)->unref();
     return 0;
@@ -2095,6 +2133,7 @@ void SkLua::Load(lua_State* L) {
     REG_CLASS(L, SkSurface);
     REG_CLASS(L, SkTextBlob);
     REG_CLASS(L, SkTypeface);
+    REG_CLASS(L, SkXfermode);
 }
 
 extern "C" int luaopen_skia(lua_State* L);