added assert and more comments

include/ACGL/OpenGL/Data/TextureData.hh

@@ -91,6 +91,7 @@ public:
     // ================================================================================================= SETTERS \/
     // ========================================================================================================= \/
 public:
+    //! _pData has to be created by new GLubyte[...] and will get deleted by this TextureData object!
     void setData  (GLubyte* _pData)  { pData  = _pData;  }
     void setWidth (GLsizei  _width)  { width  = _width;  }
     void setHeight(GLsizei  _height) { height = _height; }

src/ACGL/OpenGL/Data/TextureData.cc

@@ -132,6 +132,7 @@ glm::vec4 TextureData::getTexel( glm::uvec2 _texCoord )
 
 void TextureData::setTexel( glm::uvec2 _texCoord, glm::vec4 _color )
 {
+    assert( pData && "can't set texels if there is no data store, define data using setData()" );
     // clamp negative to 0:
     _texCoord.x = std::max( 0u, _texCoord.x );
     _texCoord.y = std::max( 0u, _texCoord.y );