one last bit of iterator weirdness

[Boudewijn Rempt]

On Thu, 26 Apr 2012, Boudewijn Rempt wrote:

> Apart from the blur filters not giving exactly the same result as before -- 
> which breaks the KisConvolutionFilterTest and KisProcessingsTest -- there is 
> one last bit of weirdness.
>
> In KisPainter::bitBltImpl, we used to create a CONST iterator on the
> srcDev:
>
> KisRandomConstAccessorPixel srcIt = srcDev->createRandomConstAccessor(srcX, 
> srcY);
>
> and then we would, depending on template parameter take either the rawData or 
> the oldRawData of that const iterator. NG const iterators only have 
> oldRawData.
>
> If I change the iterator to non-const, suddenly undo is broken on other 
> layers than the first!
>
> I'm really scratching my head here -- I cannot explain what is happening.
>

I still cannot explain what is going on here exactly, there's a huge lack
of documentation in this area, but I managed to "fix" it...

diff --git a/krita/image/kis_painter.cc b/krita/image/kis_painter.cc
index bf75cd0..b9c0bb1 100644
--- a/krita/image/kis_painter.cc
+++ b/krita/image/kis_painter.cc
@@ -64,6 +64,7 @@
  #include "kis_paint_information.h"
  #include "kis_paintop_registry.h"
  #include "kis_perspective_math.h"
+#include "tiles3/kis_random_accessor.h"

  // Maximum distance from a Bezier control point to the line through the 
start
  // and end points for the curve to be considered flat.
@@ -465,7 +466,7 @@ void KisPainter::bitBltImpl(qint32 dstX, qint32 dstY,
      qint32 rowsRemaining = srcHeight;

      // Read below
-    KisRandomAccessorSP srcIt = srcDev->createRandomAccessorNG(srcX, 
srcY);
+    KisRandomConstAccessorSP srcIt = 
srcDev->createRandomConstAccessorNG(srcX, srcY);
      KisRandomAccessorSP dstIt = d->device->createRandomAccessorNG(dstX, 
dstY);

      /* Here be a huge block of verbose code that does roughly the same 
than
@@ -509,7 +510,8 @@ void KisPainter::bitBltImpl(qint32 dstX, qint32 dstY,

                  d->paramInfo.dstRowStart   = dstIt->rawData();
                  d->paramInfo.dstRowStride  = dstRowStride;
-                d->paramInfo.srcRowStart   = useOldSrcData ? srcIt->oldRawData() : srcIt->rawData();
+                // if we don't use the oldRawData, we need to access the rawData of the source device.
+                d->paramInfo.srcRowStart   = useOldSrcData ? srcIt->oldRawData() : static_cast<KisRandomAccessor2*>(srcIt.data())->rawData();
                  d->paramInfo.srcRowStride  = srcRowStride;
                  d->paramInfo.maskRowStart  = maskIt->oldRawData();
                  d->paramInfo.maskRowStride = maskRowStride;
@@ -556,7 +558,8 @@ void KisPainter::bitBltImpl(qint32 dstX, qint32 dstY,

                  d->paramInfo.dstRowStart   = dstIt->rawData();
                  d->paramInfo.dstRowStride  = dstRowStride;
-                d->paramInfo.srcRowStart   = useOldSrcData ? srcIt->oldRawData() : srcIt->rawData();
+                // if we don't use the oldRawData, we need to access the rawData of the source device.
+                d->paramInfo.srcRowStart   = useOldSrcData ? srcIt->oldRawData() : static_cast<KisRandomAccessor2*>(srcIt.data())->rawData();
                  d->paramInfo.srcRowStride  = srcRowStride;
                  d->paramInfo.maskRowStart  = 0;
                  d->paramInfo.maskRowStride = 0;
@@ -576,6 +579,7 @@ void KisPainter::bitBltImpl(qint32 dstX, qint32 dstY,
      }

      addDirtyRect(QRect(dstX, dstY, srcWidth, srcHeight));
+
  }

  void KisPainter::bitBlt(qint32 dstX, qint32 dstY,

...