Gamedev Framework (gf)
0.6.0
A C++11 framework for 2D games

Decomposed transform defined by a position, a rotation and a scale. More...
#include <gf/Transformable.h>
Public Member Functions  
Transformable ()  
Default constructor. More...  
void  setOrigin (Vector2f origin) 
Set the local origin of the object. More...  
Vector2f  getOrigin () const 
Get the local origin of the object. More...  
void  setPosition (Vector2f position) 
Set the position of the object. More...  
Vector2f  getPosition () const 
Get the position of the object. More...  
void  move (Vector2f offset) 
Move the object by a given offset. More...  
void  setRotation (float angle) 
Set the orientation of the object. More...  
float  getRotation () const 
Get the orientation of the object. More...  
void  rotate (float angle) 
Rotate the object. More...  
void  setScale (Vector2f factors) 
Set the scale factors of the object. More...  
void  setScale (float factor) 
Set the scale factor of the object. More...  
Vector2f  getScale () const 
Get the current scale of the object. More...  
void  scale (Vector2f factors) 
Scale the object. More...  
void  scale (float factor) 
Scale the object. More...  
Matrix3f  getTransform () const 
Get the combined transform of the object. More...  
Matrix3f  getInverseTransform () const 
Get the inverse of the combined transform of the object. More...  
Public Member Functions inherited from gf::Drawable  
virtual  ~Drawable () 
Virtual desctructor. More...  
virtual void  draw (RenderTarget &target, RenderStates states)=0 
Draw the object to a render target. More...  
Protected Member Functions  
void  setOriginFromAnchorAndBounds (Anchor anchor, const RectF &bounds) 
Set the origin from an anchor and bounds. More...  
Decomposed transform defined by a position, a rotation and a scale.
gf::Matrix3f, as a lowlevel class, offers a great level of flexibility but it is not always convenient to manage. Indeed, one can easily combine any kind of operation, such as a translation followed by a rotation followed by a scaling, but once the result transform is built, there's no way to go backward and, let's say, change only the rotation without modifying the translation and scaling. The entire transform must be recomputed, which means that you need to retrieve the initial translation and scale factors as well, and combine them the same way you did before updating the rotation. This is a tedious operation, and it requires to store all the individual components of the final transform.
That's exactly what gf::Transformable was written for: it hides these variables and the composed transform behind an easy to use interface. You can set or get any of the individual components without worrying about the others. It also provides the composed transform (as a gf::Matrix3f), and keeps it uptodate.
In addition to the position, rotation and scale, gf::Transformable provides an "origin" component, which represents the local origin of the three other components. Let's take an example with a 10x10 pixels sprite. By default, the sprite is positioned/rotated/scaled relatively to its topleft corner, because it is the local point \((0, 0)\). But if we change the origin to be \((5, 5)\), the sprite will be positioned/rotated/scaled around its center instead. And if we set the origin to \((10, 10)\), it will be transformed around its bottomright corner.
To keep the gf::Transformable class simple, there's only one origin for all the components. You cannot position the sprite relatively to its topleft corner while rotating it around its center, for example. To do such things, use gf::Matrix3f directly.
gf::Transformable can be used as a base class. That's what gf's sprites, texts, curves and shapes do.
gf::Transformable::Transformable  (  ) 
Default constructor.
By default:
Matrix3f gf::Transformable::getInverseTransform  (  )  const 
Get the inverse of the combined transform of the object.

inline 

inline 

inline 

inline 
Matrix3f gf::Transformable::getTransform  (  )  const 
Get the combined transform of the object.
The combined transform of the object is (in this order):
void gf::Transformable::move  (  Vector2f  offset  ) 
Move the object by a given offset.
This function adds to the current position of the object, unlike setPosition() which overwrites it. Thus, it is equivalent to the following code:
offset  Offset 
void gf::Transformable::rotate  (  float  angle  ) 
Rotate the object.
This function adds to the current rotation of the object, unlike setRotation() which overwrites it. Thus, it is equivalent to the following code:
angle  Angle of rotation, in radians 
void gf::Transformable::scale  (  Vector2f  factors  ) 
Scale the object.
This function multiplies the current scale of the object, unlike setScale() which overwrites it. Thus, it is equivalent to the following code:
factors  Scale factors 

inline 
Scale the object.
This function is a shortcut when the scale factors for \( x \) and \( y \) are the same. It is equivalent to:
factor  Scale factor 
void gf::Transformable::setOrigin  (  Vector2f  origin  ) 
Set the local origin of the object.
The origin of an object defines the center point for all transformations (position, scale, rotation). The coordinates of this point must be relative to the topleft corner of the object, and ignore all transformations (position, scale, rotation).
The default origin of a transformable object is \((0, 0)\).
origin  New origin 

protected 
Set the origin from an anchor and bounds.
This function can be called from derived classes for setting the origin properly thanks to an anchor and the bounds they computed.
anchor  An anchor 
bounds  The bounds of the entity 
void gf::Transformable::setPosition  (  Vector2f  position  ) 
Set the position of the object.
This function completely overwrites the previous position. See the move() function to apply an offset based on the previous position instead.
The default position of a transformable object is \((0, 0)\).
position  New position 
void gf::Transformable::setRotation  (  float  angle  ) 
Set the orientation of the object.
This function completely overwrites the previous rotation. See the rotate() function to add an angle based on the previous rotation instead.
The default rotation of a transformable object is \( 0 \).
angle  New rotation, in radians 
void gf::Transformable::setScale  (  Vector2f  factors  ) 
Set the scale factors of the object.
This function completely overwrites the previous scale. See the scale() function to add a factor based on the previous scale instead.
The default scale of a transformable object is \((1, 1)\).
factors  New scale factors 

inline 
Set the scale factor of the object.
This function is a shortcut when the scale factors for \( x \) and \( y \) are the same. It is equivalent to:
factor  New scale factor 