XFT: Forbid XFT rendering on bitmaps (depth-1 pixmaps)
In theory it could work if XFT would just turn gray into
either black or white. But XFT doesn't do it and simply draw
nothing without failing in any way.
To prevent this silent failures, forbid drawing XFT onto bitmaps
(depth-1 pixmaps). After all, the while point of XFT is to use
anti-aliased fonts.
"{ Package: 'stx:libview' }"
Color subclass:#TranslucentColor
instanceVariableNames:'alpha'
classVariableNames:''
poolDictionaries:''
category:'Graphics-Support'
!
!TranslucentColor class methodsFor:'documentation'!
documentation
"
TranslucentColor represents colors with an alpha (transparency)
channel.
This is experimental and not yet used by the system.
[Instance variables:]
alpha <Integer> the internal alpha value (0..255)
"
! !
!TranslucentColor class methodsFor:'instance creation'!
red:r green:g blue:b alpha:alpha
alpha = 1 ifTrue:[
^ super red:r green:g blue:b
].
^ (super
scaledRed:(r * MaxValue // 100)
scaledGreen:(g * MaxValue // 100)
scaledBlue:(b * MaxValue // 100)) alpha:alpha
! !
!TranslucentColor methodsFor:'accessing'!
alpha
"return the alpha value (0..1),
where 0 is completely transparent and 1 is completely opaque"
^ alpha asFloat / 255.0
!
alpha:alphaFraction
"set the alpha value (0..1),
where 0 is completely transparent and 1 is completely opaque"
alpha := (alphaFraction * 255) rounded
!
alphaByte
"return the alpha value as byte 0..255,
where 0 is completely transparent and 255 is completely opaque"
^ alpha
!
privateAlpha
"return the internal alpha value (0..255),
where 0 is completely transparent and 255 is completely opaque"
^ alpha
!
scaledAlpha
"return the alpha value (0..16rFFFF),
where 0 is completely transparent and 16rFFFF is completely opaque"
^ alpha * 16rFFFF // 255
!
setAlphaByte:aByteValuedInteger
"set the alpha value (0..255),
where 0 is completely transparent and 255 is completely opaque"
alpha := aByteValuedInteger
! !
!TranslucentColor methodsFor:'printing & storing'!
storeOn:aStream
"append a string representing an expression to reconstruct the receiver
to the argument, aStream"
|clsName|
clsName := self class name.
aStream nextPutAll:'(' , clsName , ' red:'.
(self red) storeOn:aStream.
aStream nextPutAll:' green:'.
(self green) storeOn:aStream.
aStream nextPutAll:' blue:'.
(self blue) storeOn:aStream.
aStream nextPutAll:' alpha:'.
(self alpha) storeOn:aStream.
aStream nextPut:$).
"
(self red:100 green:100 blue:0 alpha:1) storeOn:Transcript
"
! !
!TranslucentColor methodsFor:'queries'!
isOpaque
"return true, if I represent an opaque color"
^ alpha == 255
!
isTranslucent
"return true, if I represent a translucent color;
that is: not completely opaque"
^ alpha < 255
!
isTranslucentColor
"return true, if I represent a translucent color;
This means: self isTranslucent, but isTransparent not"
^ alpha > 0
!
isTransparent
"return true, if I represent a completely transparent color"
^ alpha == 0
! !
!TranslucentColor class methodsFor:'documentation'!
version
^ '$Header: /cvs/stx/stx/libview/TranslucentColor.st,v 1.5 2014-03-22 09:26:53 cg Exp $'
! !