add canvas:clear to lua

src/utils/SkLua.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkLua.h"
 
 #if SK_SUPPORT_GPU
@@ skipping 406 matching lines @@
 }
 
 static SkRect* lua2rect(lua_State* L, int index, SkRect* rect) {
     rect->set(getfield_scalar_default(L, index, "left", 0),
               getfield_scalar_default(L, index, "top", 0),
               getfield_scalar(L, index, "right"),
               getfield_scalar(L, index, "bottom"));
     return rect;
 }
 
+static int lcanvas_clear(lua_State* L) {
+    get_ref<SkCanvas>(L, 1)->clear(0);
+    return 0;
+}
+
 static int lcanvas_drawColor(lua_State* L) {
     get_ref<SkCanvas>(L, 1)->drawColor(lua2color(L, 2));
     return 0;
 }
 
 static int lcanvas_drawRect(lua_State* L) {
     SkRect rect;
     get_ref<SkCanvas>(L, 1)->drawRect(*lua2rect(L, 2, &rect),
                                       *get_obj<SkPaint>(L, 3));
     return 0;
@@ skipping 11 matching lines @@
                                         lua2scalar(L, 3),
                                         lua2scalar(L, 4),
                                         *get_obj<SkPaint>(L, 5));
     return 0;
 }
 
 static SkPaint* lua2OptionalPaint(lua_State* L, int index, SkPaint* paint) {
     if (lua_isnumber(L, index)) {
         paint->setAlpha(SkScalarRoundToInt(lua2scalar(L, index) * 255));
         return paint;
-    } else {
+    } else if (lua_isuserdata(L, index)) {
         const SkPaint* ptr = get_obj<SkPaint>(L, index);
         if (ptr) {
             *paint = *ptr;
             return paint;
         }
     }
     return NULL;
 }
 
 static int lcanvas_drawImage(lua_State* L) {
@@ skipping 147 matching lines @@
     }
     return 1;
 }
 
 static int lcanvas_gc(lua_State* L) {
     get_ref<SkCanvas>(L, 1)->unref();
     return 0;
 }
 
 const struct luaL_Reg gSkCanvas_Methods[] = {
+    { "clear", lcanvas_clear },
     { "drawColor", lcanvas_drawColor },
     { "drawRect", lcanvas_drawRect },
     { "drawOval", lcanvas_drawOval },
     { "drawCircle", lcanvas_drawCircle },
     { "drawImage", lcanvas_drawImage },
     { "drawImageRect", lcanvas_drawImageRect },
     { "drawPath", lcanvas_drawPath },
     { "drawText", lcanvas_drawText },
     { "getSaveCount", lcanvas_getSaveCount },
     { "getTotalMatrix", lcanvas_getTotalMatrix },
@@ skipping 1019 matching lines @@
     REG_CLASS(L, SkSurface);
     REG_CLASS(L, SkTypeface);
     REG_CLASS(L, SkMatrix);
 }
 
 extern "C" int luaopen_skia(lua_State* L);
 extern "C" int luaopen_skia(lua_State* L) {
     SkLua::Load(L);
     return 0;
 }