create and modify matrices in lua

samplecode/SampleLua.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 "SampleCode.h"
 #include "SkView.h"
 #include "SkLua.h"
@@ skipping 82 matching lines @@
                         this->inval(NULL);
                         return true;
                     }
                 }
             }
         }
         return this->INHERITED::onQuery(evt);
     }
 
     virtual void onDrawContent(SkCanvas* canvas) SK_OVERRIDE {
-        SkMatrix matrix;
-        matrix.setRectToRect(SkRect::MakeWH(640, 480),
-                             SkRect::MakeWH(this->width(), this->height()),
-                             SkMatrix::kCenter_ScaleToFit);
-        canvas->concat(matrix);
-
         lua_State* L = this->ensureLua();
 
         lua_getglobal(L, gDrawName);
         if (!lua_isfunction(L, -1)) {
             int t = lua_type(L, -1);
             SkDebugf("--- expected %s function %d, ignoring.\n", gDrawName, t);
             lua_pop(L, 1);
         } else {
             // does it make sense to try to "cache" the lua version of this
             // canvas between draws?
             fLua->pushCanvas(canvas);
-            if (lua_pcall(L, 1, 1, 0) != LUA_OK) {
+            fLua->pushScalar(this->width());
+            fLua->pushScalar(this->height());
+            if (lua_pcall(L, 3, 1, 0) != LUA_OK) {
                 SkDebugf("lua err: %s\n", lua_tostring(L, -1));
             } else {
                 if (lua_isboolean(L, -1) && lua_toboolean(L, -1)) {
                     this->inval(NULL);
                 }
             }
         }
     }
 
     virtual SkView::Click* onFindClickHandler(SkScalar x, SkScalar y,
@@ skipping 21 matching lines @@
 private:
     SkLua* fLua;
 
     typedef SampleView INHERITED;
 };
 
 //////////////////////////////////////////////////////////////////////////////
 
 static SkView* MyFactory() { return new LuaView; }
 static SkViewRegister reg(MyFactory);