tvg_saver: verify view size earlier before the job is started.

src/savers/tvg/tvgTvgSaver.cpp

@@ -69,10 +69,7 @@ bool TvgSaver::writeHeader()
     buffer.count += (TVG_HEADER_SIGNATURE_LENGTH + TVG_HEADER_VERSION_LENGTH);
 
     //3. View Size
-    float var[2];
+    writeData(vsize, SIZE(vsize));
-    paint->bounds(nullptr, nullptr, &var[0], &var[1]);
-    if (var[0] <= FLT_EPSILON || var[1] <= FLT_EPSILON) return false;
-    writeData(var, SIZE(var));
 
     return true;
 }
@@ -449,6 +446,12 @@ bool TvgSaver::save(Paint* paint, const string& path)
     this->path = strdup(path.c_str());
     if (!this->path) return false;
 
+    paint->bounds(nullptr, nullptr, &vsize[0], &vsize[1]);
+    if (vsize[0] <= FLT_EPSILON || vsize[1] <= FLT_EPSILON) {
+        TVGLOG("TVG_SAVER", "Saving paint(%p) has zero view size.", paint);
+        return false;
+    }
+
     this->paint = paint;
 
     TaskScheduler::request(this);

src/savers/tvg/tvgTvgSaver.h

@@ -35,6 +35,7 @@ private:
     Array<TvgBinByte> buffer;
     Paint* paint = nullptr;
     char *path = nullptr;
+    float vsize[2] = {0.0f, 0.0f};
 
     bool flushTo(const std::string& path);
     void reserveCount();