This class implements BitBlt, much as specified in the Blue Book spec.

Performance has been enhanced through the use of pointer variables such as sourceIndex and destIndex, and by separating several special cases of the inner loop.

Operation has been extended to color, with support for 1, 2, 4, 8, 16, and 32-bit pixel sizes. Conversion between different pixel sizes is facilitated by accepting an optional color map.

In addition to the original 16 combination rules, this BitBlt supports
16 fail (for old paint mode)
17 fail (for old mask mode)
18 sourceWord + destinationWord
19 sourceWord - destinationWord
20 rgbAdd: sourceWord with: destinationWord
21 rgbSub: sourceWord with: destinationWord
22 OLDrgbDiff: sourceWord with: destinationWord
23 OLDtallyIntoMap: destinationWord -- old vers doesn't clip to bit boundary
24 alphaBlend: sourceWord with: destinationWord
25 pixPaint: sourceWord with: destinationWord
26 pixMask: sourceWord with: destinationWord
27 rgbMax: sourceWord with: destinationWord
28 rgbMin: sourceWord with: destinationWord
29 rgbMin: sourceWord bitInvert32 with: destinationWord
30 alphaBlendConst: sourceWord with: destinationWord -- alpha passed as an arg
31 alphaPaintConst: sourceWord with: destinationWord -- alpha passed as an arg
32 rgbDiff: sourceWord with: destinationWord
33 tallyIntoMap: destinationWord
34 alphaBlendScaled: sourceWord with: destinationWord
35 srcPaint: sourceWord with: destinationWord
36 dstPaint: sourceWord with: destinationWord

This implementation has also been fitted with an experimental "warp drive" that allows abritrary scaling and rotation (and even limited affine deformations) with all BitBlt storage modes supported.

To add a new rule to BitBlt...
1. add the new rule method or methods in the category 'combination rules' of BBSim
2. describe it in the class comment of BBSim and in the class comment for BitBlt
3. add refs to initializeRuleTable in proper positions
4. add refs to initBBOpTable, following the pattern

combination rules

OLDrgbDiff:with: OLDtallyIntoMap:with: addWord:with: alphaBlend:with: alphaBlendConst:with: alphaBlendConst:with:paintMode: alphaBlendScaled:with: alphaPaintConst:with: bitAnd:with: bitAndInvert:with: bitInvertAnd:with: bitInvertAndInvert:with: bitInvertDestination:with: bitInvertOr:with: bitInvertOrInvert:with: bitInvertSource:with: bitInvertXor:with: bitOr:with: bitOrInvert:with: bitXor:with: clearWord:with: destinationWord:with: dstPaint:with: partitionedAND:to:nBits:nPartitions: partitionedAdd:to:nBits:nPartitions: partitionedMax:with:nBits:nPartitions: partitionedMin:with:nBits:nPartitions: partitionedSub:from:nBits:nPartitions: pixMask:with: pixPaint:with: rgbAdd:with: rgbDiff:with: rgbMax:with: rgbMin:with: rgbMinInvert:with: rgbSub:with: sourceWord:with: srcPaint:with: subWord:with: tallyIntoMap:with:

	initialize
	initBBOpTable initialiseModule moduleUnloaded:

	inner loop
	alphaSourceBlendBits16 alphaSourceBlendBits32 alphaSourceBlendBits8 copyLoop copyLoopNoSource copyLoopNoSourcePixels copyLoopPixMap copyLoopPixels merge:with:function: warpLoop

	interpreter interface
	drawLoopX:Y: fetchIntOrFloat:ofObject: fetchIntOrFloat:ofObject:ifNil: loadBitBltClipRect loadBitBltCombinationRule loadBitBltDestForm loadBitBltDestRect loadBitBltFrom: loadBitBltSourceForm loadFXAlphaValues loadFXColorMap loadFXDestMap loadFXShiftOrMaskFrom: loadFXSourceMap loadFXTallyMap loadFXWarpQuad loadFXWarpQuality loadHalftoneForm showDisplayBits version

	memory access
	dstLongAt: dstLongAt:put: dstLongAt:put:mask: halftoneAt: srcLongAt:

	pixel mapping
	default8To32Table deltaFrom:to:nSteps: dither32To16:threshold: isIdentityMap:with: mapDestPixel: mapPixel: mapSourcePixel: pickSourcePixels:srcMask:destMask:paintMode:destWord: pickWarpPixelAtX:y: rgbMapPixel:shifts:masks: warpPickSmoothPixels:xDeltah:yDeltah:xDeltav:yDeltav:paintMode:destWord: warpPickSourcePixels:xDeltah:yDeltah:xDeltav:yDeltav:paintMode:destWord:

	primitives
	primitiveCopyBits primitiveDrawLoop primitiveVersion

	setup
	checkSourceOverlap clipDest clipSource copyBits copyBitsFrom:to:at: copyBitsLockedAndClipped copyBitsQuickly destMaskAndPointerInit ignoreSourceOrHalftone: sourceSkewAndPointerInit warpBits warpSetup

	special inner loops
	copyLoopPixMapLsbLsb copyLoopPixMapLsbMsb copyLoopPixMapMsbLsb copyLoopPixMapMsbMsb doCopyLoopPixMap doWarpLoop warpLoopLsbLsb warpLoopLsbMsb warpLoopMsbLsb warpLoopMsbMsb

	surface support
	loadSurfacePlugin lockSurfaces queryDestSurface: querySourceSurface: unlockSurfaces

	system simulation
	copyBitsFrom: fxCopyBitsFrom: simulatorClass warpBitsFrom:

	translation
	declareCVarsIn: moduleName opTable specializeLoopsIn:

	accessing	top
	affectedBottom
	affectedLeft
	affectedRight
	affectedTop
	targetForm Return the destination form of a copyBits or scanCharacters operation.

	combination rules	top
	OLDrgbDiff:with: Subract the pixels in the source and destination and return the number of differing pixels. Note that the region is not clipped to bit boundaries, but only to the nearest (enclosing) word. This is because copyLoop does not do pre-merge masking. For accurate results, you must subtract the values obtained from the left and right fringes.
	OLDtallyIntoMap:with: Tally pixels into the tally map. Note that the source should be specified = destination, in order for the proper color map checks to be performed at setup. Note that the region is not clipped to bit boundaries, but only to the nearest (enclosing) word. This is because copyLoop does not do pre-merge masking. For accurate results, you must subtract the values obtained from the left and right fringes.
	addWord:with:
	alphaBlend:with: Blend sourceWord with destinationWord, assuming both are 32-bit pixels. The source is assumed to have 255*alpha in the high 8 bits of each pixel, while the high 8 bits of the destinationWord will be ignored. The blend produced is alpha*source + (1-alpha)*dest, with the computation being performed independently on each color component. The high byte of the result will be 0.
	alphaBlendConst:with:
	alphaBlendConst:with:paintMode: Blend sourceWord with destinationWord using a constant alpha. Alpha is encoded as 0 meaning 0.0, and 255 meaning 1.0. The blend produced is alpha*source + (1.0-alpha)*dest, with the computation being performed independently on each color component. This function could eventually blend into any depth destination, using the same color averaging and mapping as warpBlt. paintMode = true means do nothing if the source pixel value is zero.
	alphaBlendScaled:with: Blend sourceWord with destinationWord using the alpha value from sourceWord. Alpha is encoded as 0 meaning 0.0, and 255 meaning 1.0. In contrast to alphaBlend:with: the color produced is srcColor + (1-srcAlpha) * dstColor e.g., it is assumed that the source color is already scaled.
	alphaPaintConst:with:
	bitAnd:with:
	bitAndInvert:with:
	bitInvertAnd:with:
	bitInvertAndInvert:with:
	bitInvertDestination:with:
	bitInvertOr:with:
	bitInvertOrInvert:with:
	bitInvertSource:with:
	bitInvertXor:with:
	bitOr:with:
	bitOrInvert:with:
	bitXor:with:
	clearWord:with:
	destinationWord:with:
	dstPaint:with: Replace those pixels in destinationWord where the pixel value is equal to destAlphaKey.
	partitionedAND:to:nBits:nPartitions: AND word1 to word2 as nParts partitions of nBits each. Any field of word1 not all-ones is treated as all-zeroes. Used for erasing, eg, brush shapes prior to ORing in a color
	partitionedAdd:to:nBits:nPartitions: Add word1 to word2 as nParts partitions of nBits each. This is useful for packed pixels, or packed colors
	partitionedMax:with:nBits:nPartitions: Max word1 to word2 as nParts partitions of nBits each
	partitionedMin:with:nBits:nPartitions: Min word1 to word2 as nParts partitions of nBits each
	partitionedSub:from:nBits:nPartitions: Subtract word1 from word2 as nParts partitions of nBits each. This is useful for packed pixels, or packed colors
	pixMask:with:
	pixPaint:with:
	rgbAdd:with:
	rgbDiff:with: Subract the pixels in the source and destination and return the number of differing pixels.
	rgbMax:with:
	rgbMin:with:
	rgbMinInvert:with:
	rgbSub:with:
	sourceWord:with:
	srcPaint:with: Replace those pixels in destinationWord where the associated pixel in sourceWord is different from sourceAlphaKey. Note: This will only work for sourceDepth = destDepth.
	subWord:with:
	tallyIntoMap:with: Tally pixels into the color map. Those tallied are exactly those in the destination rectangle. Note that the source should be specified == destination, in order for the proper color map checks to be performed at setup.

	initialize	top
	initBBOpTable
	initialiseModule
	moduleUnloaded: The module with the given name was just unloaded. Make sure we have no dangling references.

	inner loop	top
	alphaSourceBlendBits16 This version assumes combinationRule = 34 sourcePixSize = 32 destPixSize = 16 sourceForm ~= destForm.
	alphaSourceBlendBits32 This version assumes combinationRule = 34 sourcePixSize = destPixSize = 32 sourceForm ~= destForm. Note: The inner loop has been optimized for dealing with the special cases of srcAlpha = 0.0 and srcAlpha = 1.0
	alphaSourceBlendBits8 This version assumes combinationRule = 34 sourcePixSize = 32 destPixSize = 8 sourceForm ~= destForm. Note: This is not real blending since we don't have the source colors available.
	copyLoop This version of the inner loop assumes sourceDepth = destDepth, noSource = false, noColorMap = noSourceMap = noDestMap = true
	copyLoopNoSource Faster copyLoop when source not used. hDir and vDir are both positive, and perload and skew are unused. Note: This is the common fill loop without any fancy stuff.
	copyLoopNoSourcePixels This version of the inner loop maps dest pixels one at a time. Note: This loop is typically used for filling with alpha values. Note2: There is probably some significant speedup in here but for now I just need a version that does the job...
	copyLoopPixMap This version of the inner loop maps source pixels to a destination form with different depth. Note: Special care is taken to handle source paint mode correctly.
	copyLoopPixels This version of the inner loop maps source pixels and dest pixels one at a time. This is the most general (and slowest) version which must also keep track of source and dest paint mode by itself.
	merge:with:function:
	warpLoop This version of the inner loop traverses an arbirary quadrilateral source, thus producing a general affine transformation.

	interpreter interface	top
	drawLoopX:Y: This is the primitive implementation of the line-drawing loop. See the comments in BitBlt>>drawLoopX:Y:
	fetchIntOrFloat:ofObject:
	fetchIntOrFloat:ofObject:ifNil:
	loadBitBltClipRect Load the clipping rectangle from a BitBlt oop.
	loadBitBltCombinationRule Load the combination rule from a BitBlt oop
	loadBitBltDestForm Load the dest form for BitBlt. Return false if anything is wrong, true otherwise.
	loadBitBltDestRect Load the destination rectangle from a BitBlt oop
	loadBitBltFrom: Load context from BitBlt instance. Return false if anything is amiss
	loadBitBltSourceForm Load the source form for BitBlt. Return false if anything is wrong, true otherwise.
	loadFXAlphaValues Load the source/destination transparency keys
	loadFXColorMap Load a color map from FXBlt
	loadFXDestMap Load a destination map from destForm to canonical 32bit RGBA values
	loadFXShiftOrMaskFrom:
	loadFXSourceMap Load a source map from sourceForm to canonical 32bit RGBA values
	loadFXTallyMap Load the tally map
	loadFXWarpQuad Load the new warp quad (used, e.g., for warping)
	loadFXWarpQuality Load the warp quality (used, e.g., for warping)
	loadHalftoneForm Load the halftone form
	showDisplayBits
	version Return the version of FXBlt

	memory access	top
	dstLongAt:
	dstLongAt:put:
	dstLongAt:put:mask: Store the given value back into destination form, using dstMask to mask out the bits to be modified. This is an essiantial read-modify-write operation on the destination form.
	halftoneAt: Return a value from the halftone pattern.
	srcLongAt:

	pixel mapping	top
	default8To32Table Return the default translation table from 1..8 bit indexed colors to 32bit
	deltaFrom:to:nSteps: Utility routine for computing Warp increments.
	dither32To16:threshold: Dither the given 32bit word to 16 bit. Ignore alpha.
	isIdentityMap:with: Return true if shiftTable/maskTable define an identity mapping.
	mapDestPixel: Expand the given destination pixel value into canonical RGBA space.
	mapPixel: Color map the given source pixel.
	mapSourcePixel: Expand the given source pixel value into canonical RGBA space.
	pickSourcePixels:srcMask:destMask:paintMode:destWord: Pick nPix pixels starting at srcBitIndex from the source, map by the color map, and justify them according to dstBitIndex in the resulting destWord.
	pickWarpPixelAtX:y: Pick a single pixel from the source for WarpBlt. Note: This method is crucial for WarpBlt speed w/o smoothing and still relatively important when smoothing is used.
	rgbMapPixel:shifts:masks: Perform the RGBA conversion for the given source pixel
	warpPickSmoothPixels:xDeltah:yDeltah:xDeltav:yDeltav:paintMode:destWord: Pick n (sub-) pixels from the source form, mapped by sourceMap, average the RGB values, map by colorMap and return the new word. This version is only called from WarpBlt with smoothingCount > 1
	warpPickSourcePixels:xDeltah:yDeltah:xDeltav:yDeltav:paintMode:destWord: Pick n pixels from the source form, map by colorMap and return aligned by dstBitShift. This version is only called from WarpBlt with smoothingCount = 1

	primitives	top
	primitiveCopyBits
	primitiveDrawLoop Invoke the line drawing primitive.
	primitiveVersion Return the version of FXBlt

	setup	top
	checkSourceOverlap check for possible overlap of source and destination
	clipDest clip and adjust source origin and extent appropriately
	clipSource clip and adjust source origin and extent appropriately
	copyBits
	copyBitsFrom:to:at: Support for the balloon engine.
	copyBitsLockedAndClipped Perform the actual copyBits operation. Assume: Surfaces have been locked and clipping was performed.
	copyBitsQuickly Shortcut for stuff that's being run from the balloon engine. Since we do this at each scan line we should avoid the expensive setup for source and destination.
	destMaskAndPointerInit Compute masks for left and right destination words
	ignoreSourceOrHalftone:
	sourceSkewAndPointerInit This is only used when source and dest are same depth, ie, when the barrel-shift copy loop is used.
	warpBits obsolete
	warpSetup Setup values for faster pixel fetching in WarpBlt.

	special inner loops	top
	copyLoopPixMapLsbLsb Note: This loop is specialized by the CCodeGenerator.
	copyLoopPixMapLsbMsb Note: This loop is specialized by the CCodeGenerator.
	copyLoopPixMapMsbLsb Note: This loop is specialized by the CCodeGenerator.
	copyLoopPixMapMsbMsb Note: This loop is specialized by the CCodeGenerator.
	doCopyLoopPixMap
	doWarpLoop
	warpLoopLsbLsb Note: This loop is specialized by the CCodeGenerator.
	warpLoopLsbMsb Note: This loop is specialized by the CCodeGenerator.
	warpLoopMsbLsb Note: This loop is specialized by the CCodeGenerator.
	warpLoopMsbMsb Note: This loop is specialized by the CCodeGenerator.

	surface support	top
	loadSurfacePlugin Load the surface support plugin
	lockSurfaces Get a pointer to the bits of any OS surfaces.
	queryDestSurface: Query the dimension of an OS surface. This method is provided so that in case the inst vars of the source form are broken, *actual* values of the OS surface can be obtained. This might, for instance, happen if the user resizes the main window. Note: Moved to a separate function for better inlining of the caller.
	querySourceSurface: Query the dimension of an OS surface. This method is provided so that in case the inst vars of the source form are broken, *actual* values of the OS surface can be obtained. This might, for instance, happen if the user resizes the main window. Note: Moved to a separate function for better inlining of the caller.
	unlockSurfaces Unlock the bits of any OS surfaces.

	initialization	top
	initialize BitBltSimulation initialize
	initializeRuleTable BitBltSimulation initializeRuleTable
	test2 BitBltSimulation test2
	timingTest: BitBltSimulation timingTest: 640@480

	system simulation	top
	copyBitsFrom: Simulate the copyBits primitive
	fxCopyBitsFrom: Simulate the copyBits primitive
	simulatorClass For running from Smalltalk - answer a class that can be used to simulate the receiver. By default every plugin can simulate itself.
	warpBitsFrom: Simulate the warpBits primitive

	translation	top
	declareCVarsIn: Note: This method must be implemented by all subclasses to declare variables.
	moduleName FXBltScanner translateLocally
	opTable
	specializeLoopsIn: FXBltScanner translate