Marcel Taeumel uploaded a new version of Graphics to project The Trunk:
http://source.squeak.org/trunk/Graphics-mt.506.mcz

==================== Summary ====================

Name: Graphics-mt.506
Author: mt
Time: 30 March 2022, 10:14:23.797457 am
UUID: 1934ae70-75f2-9041-a4b6-aa12b4125cc3
Ancestors: Graphics-mt.505

Adds commentary about the side effects of #copyBits and #deferUpdates:.

=============== Diff against Graphics-mt.505 ===============

Item was changed:
  ----- Method: BitBlt>>copyBits (in category 'copying') -----
  copyBits
  	"Primitive. Perform the movement of bits from the source form to the 
  	destination form. Fail if any variables are not of the right type (Integer, 
  	Float, or Form) or if the combination rule is not implemented. 
+ 
+ 	NOTE THAT this method has the side effect of showing the copied bits on
+ 	screen if the destination form happens to be Display. The mechanism is
+ 	similar to calling #primShowRectLeft:right:top:bottom: manually.
+ 
  	In addition to the original 16 combination rules, this BitBlt supports
  	16	fail (to simulate paint)
  	17	fail (to simulate mask)
  	18	sourceWord + destinationWord
  	19	sourceWord - destinationWord
  	20	rgbAdd: sourceWord with: destinationWord
  	21	rgbSub: sourceWord with: destinationWord
  	22	rgbDiff: sourceWord with: destinationWord
  	23	tallyIntoMap: destinationWord
  	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
  "
  	<primitive: 'primitiveCopyBits' module: 'BitBltPlugin' error: ec>
  
  	(combinationRule >= 30 and: [combinationRule <= 31]) ifTrue:
  		["No alpha specified -- re-run with alpha = 1.0"
  		^ self copyBitsTranslucent: 255].
  	"Check for object movement during a surface callback, compressed source, destination or halftone forms.
  	 Simply retry."
  	(ec == #'object moved'
  	 or: [(sourceForm isForm and: [sourceForm unhibernate])
  	 or: [(destForm isForm and: [destForm unhibernate])
  	 or: [halftoneForm isForm and: [halftoneForm unhibernate]]]]) ifTrue:
  		[^self copyBits].
  
  	"Check for unimplmented rules"
  	combinationRule = Form oldPaint ifTrue: [^self paintBits].
  	combinationRule = Form oldErase1bitShape ifTrue: [^self eraseBits].
  
  	"Check if BitBlt doesn't support full color maps"
  	(colorMap notNil and: [colorMap isColormap]) ifTrue:
  		[colorMap := colorMap colors.
  		^self copyBits].
  	"Check if clipping got way out of range"
  	self clipRange.
  	"Convert all numeric parameters to integers and try again."
  	self roundVariables.
  	^self copyBitsAgain!

Item was changed:
  ----- Method: DisplayScreen>>deferUpdates: (in category 'other') -----
  deferUpdates: aBoolean
+ 	"Set the deferUpdates flag in the virtual machine. When this flag is true, BitBlt operations on the Display are not automatically propagated to the screen. If this underlying platform does not support deferred updates, this primitive will fail. Answer whether updates were deferred before if the primitive succeeds, nil if it fails.
+ 	
+ 	Note that when disabling deferred upates again after modifying the receiver, it is advisable to call #forceDisplayUpdate so that the deferred updates can actually be displayed on the screen."
- 	| wasDeferred |
- 	"Set the deferUpdates flag in the virtual machine. When this flag is true, BitBlt operations on the Display are not automatically propagated to the screen. If this underlying platform does not support deferred updates, this primitive will fail. Answer whether updates were deferred before if the primitive succeeds, nil if it fails."
  
+ 	| wasDeferred |
  	wasDeferred := DeferringUpdates == true.
  	DeferringUpdates := aBoolean.
  	^(self primitiveDeferUpdates: aBoolean) ifNotNil: [wasDeferred]!