Cached sf::Text attributes

Two optimizations:
- If a value remains the same, nothing happens
- Recompute geometry only before drawing and bound access, not after each set

Closes #413

include/SFML/Graphics/Text.hpp

@@ -275,10 +275,13 @@ private :
     virtual void draw(RenderTarget& target, RenderStates states) const;
 
     ////////////////////////////////////////////////////////////
-    /// \brief Update the text's geometry
+    /// \brief Make sure the text's geometry is updated
+    /// 
+    /// All the attributes related to rendering are cached, such
+    /// that the geometry is only updated when necessary.
     ///
     ////////////////////////////////////////////////////////////
-    void updateGeometry();
+    void ensureGeometryUpdate() const;
 
     ////////////////////////////////////////////////////////////
     // Member data
@@ -288,8 +291,9 @@ private :
     unsigned int        m_characterSize;      ///< Base size of characters, in pixels
     Uint32              m_style;              ///< Text style (see Style enum)
     Color               m_color;              ///< Text color
-    VertexArray   m_vertices;      ///< Vertex array containing the text's geometry
+    mutable VertexArray m_vertices;           ///< Vertex array containing the text's geometry
-    FloatRect     m_bounds;        ///< Bounding rectangle of the text (in local coordinates)
+    mutable FloatRect   m_bounds;             ///< Bounding rectangle of the text (in local coordinates)
+    mutable bool        m_geometryNeedUpdate; ///< Does the geometry need to be recomputed?
 };
 
 } // namespace sf

src/SFML/Graphics/Text.cpp

@@ -41,7 +41,8 @@ m_characterSize(30),
 m_style             (Regular),
 m_color             (255, 255, 255),
 m_vertices          (Quads),
-m_bounds       ()
+m_bounds            (),
+m_geometryNeedUpdate(false)
 {
 
 }
@@ -55,17 +56,21 @@ m_characterSize(characterSize),
 m_style             (Regular),
 m_color             (255, 255, 255),
 m_vertices          (Quads),
-m_bounds       ()
+m_bounds            (),
+m_geometryNeedUpdate(true)
 {
-    updateGeometry();
+
 }
 
 
 ////////////////////////////////////////////////////////////
 void Text::setString(const String& string)
+{
+    if (m_string != string)
     {
         m_string = string;
-    updateGeometry();
+        m_geometryNeedUpdate = true;
+    }
 }
 
 
@@ -75,7 +80,7 @@ void Text::setFont(const Font& font)
     if (m_font != &font)
     {
         m_font = &font;
-        updateGeometry();
+        m_geometryNeedUpdate = true;
     }
 }
 
@@ -86,7 +91,7 @@ void Text::setCharacterSize(unsigned int size)
     if (m_characterSize != size)
     {
         m_characterSize = size;
-        updateGeometry();
+        m_geometryNeedUpdate = true;
     }
 }
 
@@ -97,7 +102,7 @@ void Text::setStyle(Uint32 style)
     if (m_style != style)
     {
         m_style = style;
-        updateGeometry();
+        m_geometryNeedUpdate = true;
     }
 }
 
@@ -108,10 +113,16 @@ void Text::setColor(const Color& color)
     if (color != m_color)
     {
         m_color = color;
+
+        // Change vertex colors directly, no need to update whole geometry
+        // (if geometry is updated anyway, we can skip this step)
+        if (!m_geometryNeedUpdate)
+        {
             for (unsigned int i = 0; i < m_vertices.getVertexCount(); ++i)
                 m_vertices[i].color = m_color;
         }
     }
+}
 
 
 ////////////////////////////////////////////////////////////
@@ -199,6 +210,8 @@ Vector2f Text::findCharacterPos(std::size_t index) const
 ////////////////////////////////////////////////////////////
 FloatRect Text::getLocalBounds() const
 {
+    ensureGeometryUpdate();
+
     return m_bounds;
 }
 
@@ -215,6 +228,8 @@ void Text::draw(RenderTarget& target, RenderStates states) const
 {
     if (m_font)
     {
+        ensureGeometryUpdate();
+
         states.transform *= getTransform();
         states.texture = &m_font->getTexture(m_characterSize);
         target.draw(m_vertices, states);
@@ -223,8 +238,15 @@ void Text::draw(RenderTarget& target, RenderStates states) const
 
 
 ////////////////////////////////////////////////////////////
-void Text::updateGeometry()
+void Text::ensureGeometryUpdate() const
 {
+    // Do nothing, if geometry has not changed
+    if (!m_geometryNeedUpdate)
+        return;
+
+    // Mark geometry as updated
+    m_geometryNeedUpdate = false;
+
     // Clear the previous geometry
     m_vertices.clear();
     m_bounds = FloatRect();