Added support for vertex shaders in sf::Shader

Rewrote the Shader example

examples/shader/Effect.hpp

@@ -0,0 +1,74 @@
+#ifndef EFFECT_HPP
+#define EFFECT_HPP
+
+////////////////////////////////////////////////////////////
+// Headers
+////////////////////////////////////////////////////////////
+#include <SFML/Graphics.hpp>
+#include <string>
+
+
+////////////////////////////////////////////////////////////
+// Base class for effects
+////////////////////////////////////////////////////////////
+class Effect : public sf::Drawable
+{
+public :
+
+    virtual ~Effect()
+    {
+    }
+
+    const std::string& GetName() const
+    {
+        return myName;
+    }
+
+    void Load()
+    {
+        myIsLoaded = sf::Shader::IsAvailable() && OnLoad();
+    }
+
+    void Update(float time, float x, float y)
+    {
+        if (myIsLoaded)
+            OnUpdate(time, x, y);
+    }
+
+    void Draw(sf::RenderTarget& target, sf::RenderStates states) const
+    {
+        if (myIsLoaded)
+        {
+            OnDraw(target, states);
+        }
+        else
+        {
+            sf::Text error("Shader not\nsupported");
+            error.SetPosition(320.f, 200.f);
+            error.SetCharacterSize(36);
+            target.Draw(error, states);
+        }
+    }
+
+protected :
+
+    Effect(const std::string& name) :
+    myName(name),
+    myIsLoaded(false)
+    {
+    }
+
+private :
+
+    // Virtual functions to be implemented in derived effects
+    virtual bool OnLoad() = 0;
+    virtual void OnUpdate(float time, float x, float y) = 0;
+    virtual void OnDraw(sf::RenderTarget& target, sf::RenderStates states) const = 0;
+
+private :
+
+    std::string myName;
+    bool myIsLoaded;
+};
+
+#endif // EFFECT_HPP