common loader: return viewbox info from the vector resource.

if a scene loads a vector resource, it must have viewbox info from the design,
That viewbox will be used as bounding box so that user can scale up/down
the scene by its requirements.

Change-Id: Iafa39af23118a03de207c745364d56c837892e1b

src/lib/tvgLoader.h

@@ -23,6 +23,12 @@ namespace tvg
 class Loader
 {
 public:
+    //default view box, if any.
+    float vx = 0;
+    float vy = 0;
+    float vw = 0;
+    float vh = 0;
+
     virtual ~Loader() {}
 
     virtual bool open(const char* path) = 0;

src/lib/tvgSceneImpl.h

@@ -74,11 +74,12 @@ struct Scene::Impl
     {
         if (loader) {
             auto scene = loader->data();
+            if (scene) {
                 auto p = scene.release();
                 if (!p) return false;
                 paints.push_back(p);
                 loader->close();
-            loader.reset(nullptr);
+            }
         }
 
         if (flag & RenderUpdateFlag::Transform) {
@@ -121,6 +122,12 @@ struct Scene::Impl
 
     bool bounds(float* px, float* py, float* pw, float* ph)
     {
+        if (loader) {
+            if (px) *px = loader->vx;
+            if (py) *py = loader->vy;
+            if (pw) *pw = loader->vw;
+            if (ph) *ph = loader->vh;
+        } else {
             auto x = FLT_MAX;
             auto y = FLT_MAX;
             auto w = 0.0f;
@@ -152,7 +159,7 @@ struct Scene::Impl
             if (py) *py = y;
             if (pw) *pw = w;
             if (ph) *ph = h;
-
+        }
         return true;
     }
 

src/loaders/svg_loader/tvgSvgLoader.cpp

@@ -2262,6 +2262,13 @@ bool SvgLoader::open(const char* path)
         if (content.empty()) return false;
     }
 
+    //FIXME: Verify this resource is normal SVG, otherwise return false
+    //Also, return the brief resource info such as viewbox:
+    //this->vx = ?
+    //this->vy = ?
+    //this->vw = ?
+    //this->vh = ?
+
     return true;
 }