PixelIterator()

template<typename PixelControllerT>

PixelIterator::PixelIterator ( PixelControllerT * pc, Rgbw rgbw )

inline

Definition at line 88 of file pixel_iterator.h.

         : mPixelController(pc), mRgbw(rgbw) {
      // Manually build up a vtable.
      // Wait... what? Stupid nerds trying to show off how smart they are...
      // Why not just use a virtual function?!
      //
      // Before you think this then you should know that the alternative straight
      // forward way is to have a virtual interface class that PixelController inherits from.
      // ...and that was already tried. And if you try to do this yourself
      // this then let me tell you what is going to happen...
      //
      // EVERY SINGLE PLATFORM THAT HAS A COMPILED BINARY SIZE CHECK WILL IMMEDIATELY
      // FAIL AS THE BINARY BLOWS UP BY 10-30%!!! It doesn't matter if only one PixelController
      // with a vtable is used, gcc seems not to de-virtualize the calls. And we really care
      // about binary size since FastLED needs to run on those tiny little microcontrollers like
      // the Attiny85 (and family) which are in the sub $1 range used for commercial products.
      //
      // So to satisfy these tight memory requirements we make the dynamic dispatch used in PixelIterator
      // an optional zero-cost abstraction which doesn't affect the binary size for platforms that
      // don't use it. So that's why we are using this manual construction of the vtable that is built
      // up using template magic. If your platform has lots of memory then you'll gladly trade
      // a sliver of memory for the convenience of having a concrete implementation of
      // PixelController that you can use without having to make all your driver code a template.
      //
      // Btw, this pattern in C++ is called the "type-erasure pattern". It allows non virtual
      // polymorphism by leveraging the C++ template system to ensure type safety.
      typedef PixelControllerVtable<PixelControllerT> Vtable;
      mLoadAndScaleRGBW = &Vtable::loadAndScaleRGBW;
      mLoadAndScaleRGB = &Vtable::loadAndScaleRGB;
      mLoadAndScale_APA102_HD = &Vtable::loadAndScale_APA102_HD;
      mLoadAndScale_WS2816_HD = &Vtable::loadAndScale_WS2816_HD;
      mStepDithering = &Vtable::stepDithering;
      mAdvanceData = &Vtable::advanceData;
      mSize = &Vtable::size;
      mHas = &Vtable::has;
      #if FASTLED_HD_COLOR_MIXING
      mGetHdScale = &Vtable::getHdScale;
      #endif
    }

References mAdvanceData, mHas, mLoadAndScale_APA102_HD, mLoadAndScale_WS2816_HD, mLoadAndScaleRGB, mLoadAndScaleRGBW, mPixelController, mRgbw, mSize, mStepDithering, and rgbw.