Second try of my previous pull request, which was partially reverted due to caused crashes and memory leaks

src/guiengine/widgets/icon_button_widget.cpp

@@ -42,6 +42,7 @@ IconButtonWidget::IconButtonWidget(ScaleMode scale_mode, const bool tab_stop,
     m_label = NULL;
     m_font = NULL;
     m_texture = NULL;
+    m_deactivated_texture = NULL;
     m_highlight_texture = NULL;
     m_custom_aspect_ratio = 1.0f;
 
@@ -270,6 +271,49 @@ void IconButtonWidget::unfocused(const int playerID, Widget* new_focus)
         m_label->setVisible(false);
     }
 }
+// -----------------------------------------------------------------------------
+const video::ITexture* IconButtonWidget::getTexture()
+{
+    if (Widget::isActivated())
+    {
+        return m_texture;
+    }
+    else
+    {
+        if (m_deactivated_texture == NULL)
+            m_deactivated_texture = getDeactivatedTexture(m_texture);
+        return m_deactivated_texture;
+    }
+}
+
+// -----------------------------------------------------------------------------
+video::ITexture* IconButtonWidget::getDeactivatedTexture(video::ITexture* texture)
+{
+    SColor c;
+    u32 g;
+
+    video::IVideoDriver* driver = irr_driver->getVideoDriver();
+    video::IImage* image = driver->createImageFromData (texture->getColorFormat(),
+        texture->getSize(), texture->lock(), false);
+    texture->unlock();
+
+    //Turn the image into grayscale
+    for (u32 x = 0; x < image->getDimension().Width; x++)
+    {
+        for (u32 y = 0; y < image->getDimension().Height; y++)
+        {
+            c = image->getPixel(x, y);
+            g = ((c.getRed() + c.getGreen() + c.getBlue()) / 3);
+            c.set(std::max (0, (int)c.getAlpha() - 120), g, g, g);
+            image->setPixel(x, y, c);
+        }
+    }
+
+    texture = driver->addTexture(texture->getName().getPath() + "_disabled", image);
+    image->drop();
+
+    return texture;
+}
 
 // -----------------------------------------------------------------------------
 void IconButtonWidget::setTexture(video::ITexture* texture)
@@ -277,6 +321,7 @@ void IconButtonWidget::setTexture(video::ITexture* texture)
     m_texture = texture;
     if (texture == NULL)
     {
+        m_deactivated_texture = NULL;
         m_texture_w = 0;
         m_texture_h = 0;
     }

src/guiengine/widgets/icon_button_widget.hpp

@@ -43,9 +43,11 @@ namespace GUIEngine
     {
     private:
         irr::video::ITexture* m_texture;
+        irr::video::ITexture* m_deactivated_texture;
         irr::video::ITexture* m_highlight_texture;
         int m_texture_w, m_texture_h;
 
+        video::ITexture* getDeactivatedTexture(video::ITexture* texture);
         void setLabelFont();
 
     public:
@@ -158,7 +160,7 @@ namespace GUIEngine
         virtual void unfocused(const int playerID, Widget* new_focus);
         // --------------------------------------------------------------------
         /** Returns the texture of this button. */
-        const video::ITexture* getTexture() const { return m_texture; }
+        const video::ITexture* getTexture();
     };
 }