"

 COPYRIGHT (c) 1994 by Claus Gittinger

	      All Rights Reserved

 This software is furnished under a license and may be used

 only in accordance with the terms of that license and with the

 inclusion of the above copyright notice.   This software may not

 be provided or otherwise made available to, or used by, any

 other person.  No title to or ownership of the software is

 hereby transferred.

"

"{ Package: 'stx:libwidg2' }"

SimpleView subclass:#ViewScroller

	instanceVariableNames:'frame scrolledView keepViewsChannel model verticalScrollStep

		horizontalScrollStep resizeScrolledViewVertical

		resizeScrolledViewHorizontal'

	classVariableNames:''

	poolDictionaries:''

	category:'Views-Basic'

!

!ViewScroller class methodsFor:'documentation'!

copyright

"

 COPYRIGHT (c) 1994 by Claus Gittinger

	      All Rights Reserved

 This software is furnished under a license and may be used

 only in accordance with the terms of that license and with the

 inclusion of the above copyright notice.   This software may not

 be provided or otherwise made available to, or used by, any

 other person.  No title to or ownership of the software is

 hereby transferred.

"

!

documentation 

"

    This wrapper view allows scrolling of views (in contrast to scrolling

    of contents which can be done by any view).

    Normally, scrolling is done by putting a view into a ScrollableView (which

    simply wraps the scrollbars around) and have the scrollbars send scrollUp:/

    scrollDown: etc. send to the scrolledView.

    The default implementation of scrolling (in View) modifies the transformation,

    and does a bit-copy of the contents with redraw of the exposed area.

    However, there are situations, where you want to scroll a view itself.

    For example, if you need many buttons in a panel, which do not fit.

    This class provides the basic mechanism to implement this.

    It is a wrapper, which implements scrolling by modifying the origin of its

    single subview when asked to scroll. Thus, it can be put into a ScrollableView

    like any other, but will move its subview when asked to scroll instead.

    (i.e. reimplement all scroll messages by manipulating its subviews origin

     instead of its contents' transformation offset)

    The subview should have a constant extent, which will be taken for the

    scrollbar position/height computation.

    Since the subview is represented directly by the underlying window systems view

    implementation, there may be a limit on the maximum size of that view. For

    example, in X, dimensions may not be larger than 32767 pixels.

    [Instance variables:]

        model                <ValueHolder>      the model which keeps the current scrolledView.

        keepViewsChannel     <ValueHolder>      boolean holder; if the value is false (the default),

                                                the previous scrolled view is destroyed, whenever a

                                                new scrolled view is set. If true, it is unmapped and

                                                kept.

                                                Set this flag, if the application changes the scrolled

                                                view but wants them to be kept for fast switching.

        horizontalScrollStep <SmallInteger>     amount to scroll when stepping left/right in pixels

        verticalScrollStep   <SmallInteger>     amount to scroll when stepping up/down    in pixels

        frame                <SimpleView>       the one and only container of the visible scrolledView

                                                and all invisible scrolledViews if existant.

        scrolledView         <SimpleView | nil> the current scrolled view or nil

    [see also:]

        ScrollableView HVScrollableView

    [author:]

        Claus Gittinger

"

!

examples

"

  scroll a panel of buttons:

                                                                [exBegin]

    |top frame vscroller v panel|

    top := StandardSystemView new.

    top extent:100@400.

    frame := ScrollableView for:ViewScroller in:top.

    frame origin:0.0 @ 0.0 corner:1.0 @ 1.0.

    vscroller := frame scrolledView.

    panel := VerticalPanelView new.

    panel horizontalLayout:#fit.

    1 to:100 do:[:i |

        Button label:(i printString) in:panel

    ].

    vscroller scrolledView:panel.

    top open.

                                                                [exEnd]

  same, defining what a scroll step is:

                                                                [exBegin]

    |top frame vscroller v panel|

    top := StandardSystemView new.

    top extent:100@400.

    frame := ScrollableView for:ViewScroller in:top.

    frame origin:0.0 @ 0.0 corner:1.0 @ 1.0.

    vscroller := frame scrolledView.

    vscroller verticalScrollStep:20.

    panel := VerticalPanelView new.

    panel horizontalLayout:#fit.

    1 to:100 do:[:i |

        Button label:(i printString) in:panel

    ].

    vscroller scrolledView:panel.

    top open.

                                                                [exEnd]

  same, horizontally. Also change layout in panel for nicer look

  and make panel adjust its height:

  (since the buttons are defined to fill vertically, the vertical

   scrollbar is useless here - its here as example; not for its function)

                                                                [exBegin]

    |top frame vscroller v panel|

    top := StandardSystemView new.

    top extent:300@100.

    frame := HVScrollableView for:ViewScroller in:top.

    frame origin:0.0 @ 0.0 corner:1.0 @ 1.0.

    vscroller := frame scrolledView.

    panel := HorizontalPanelView new.

    panel verticalLayout:#fit.

    panel horizontalLayout:#fit.

    1 to:100 do:[:i |

        Button label:(i printString) in:panel

    ].

    vscroller scrolledView:panel.

    panel height:1.0.

    top open.

                                                                [exEnd]

  scroll a panel of buttons and other views:

  (not good looking, but a demo that it can be done ...)

                                                                [exBegin]

    |top frame vscroller v panel textView1 textView2|

    top := StandardSystemView new.

    frame := HVScrollableView for:ViewScroller in:top.

    frame origin:0.0 @ 0.0 corner:1.0 @ 1.0.

    vscroller := frame scrolledView.

    panel := VerticalPanelView new.

    panel horizontalLayout:#leftSpace.

    textView1 := ScrollableView for:EditTextView in:panel.

    textView1 extent:2000 @ 300.

    textView1 scrolledView contents:('Makefile' asFilename readStream contents).

    textView2 := ScrollableView for:EditTextView in:panel.

    textView2 extent:500 @ 300.

    textView2 scrolledView contents:('Make.proto' asFilename readStream contents).

    1 to:100 do:[:i |

        Button label:(i printString) in:panel

    ].

    vscroller scrolledView:panel.

    top open.

                                                                [exEnd]

"

! !

!ViewScroller methodsFor:'accessing'!

destroyAllClientViews

    "destroy all client views"

    frame destroySubViews.

    scrolledView ifNotNil:[

        scrolledView := nil.        

        self sizeChanged:nil.

    ].

    model value:scrolledView.

!

keepViews

    "returns the value of the boolean channel: keepViewsChannel.

        for more information see: #keepViewsChannel"

    ^ keepViewsChannel value ? false

!

keepViews:aBool

    "set the value of the boolean channel: keepViewsChannel.

        for more information see: #keepViewsChannel:

    "

    keepViewsChannel value:aBool

!

resizeScrolledViewHorizontal

    ^ resizeScrolledViewHorizontal

!

resizeScrolledViewHorizontal:something

    resizeScrolledViewHorizontal := something.

!

resizeScrolledViewVertical

    ^ resizeScrolledViewVertical

!

resizeScrolledViewVertical:something

    resizeScrolledViewVertical := something.

!

scrolledView

    "return the view which is scrolled"

    ^ scrolledView 

!

scrolledViews

    "Returns the collection of all scrolled views including the current scrolled view

     and all unmapped scrolled views."

    |subviews|

    frame ifNotNil:[

        subviews := frame subViews.

        subviews ifNotNil:[ ^ subviews ]

    ].

    ^ #()

! !

!ViewScroller methodsFor:'accessing-channels'!

keepViewsChannel

    "boolean holder; if the value is false (the default), the previous scrolled view is

     destroyed, whenever a new scrolled view is set.  if true, it is unmapped and kept.

     Set this flag, if the application changes the scrolled view but wants

     them to be kept for fast switching.

    "

    ^ keepViewsChannel

!

keepViewsChannel:aHolder

    "boolean holder; if the value is false (the default), the previous scrolled view is

     destroyed, whenever a new scrolled view is set.  if true, it is unmapped and kept.

     Set this flag, if the application changes the scrolled view but wants

     them to be kept for fast switching.

    "

    |oldValue|

    oldValue := keepViewsChannel value.

    keepViewsChannel removeDependent:self.

    (keepViewsChannel := aHolder) isNil ifTrue:[

        keepViewsChannel := oldValue asValue.

    ].

    keepViewsChannel addDependent:self.

    self update:nil with:nil from:keepViewsChannel.

!

model

    "value holder, which keeps the current scrolledView or nil

    "

    ^ model

!

model:aHolder

    "value holder, which keeps the current scrolledView or nil

    "

    model removeDependent:self.

    aHolder isNil ifTrue:[ model := nil asValue ]

                 ifFalse:[ model := aHolder     ].

    model addDependent:self.

    self update:nil with:nil from:model.

! !

!ViewScroller methodsFor:'accessing-look'!

horizontalScrollStep:something

    "set the value of the instance variable 'horizontalScrollStep' (automatically generated)"

    horizontalScrollStep := something.

!

verticalScrollStep:something

    "set the value of the instance variable 'verticalScrollStep' (automatically generated)"

    verticalScrollStep := something.

! !

!ViewScroller methodsFor:'change & update'!

resizeScrolledView

    "forces a recomputation of the scrolled view"

    |oldExtent newExtent xIsRelative yIsRelative|

    scrolledView isNil ifTrue:[

        ^ self

    ].

    oldExtent   := scrolledView extent copy.

    newExtent   := scrolledView preferredExtent copy.

    xIsRelative := resizeScrolledViewHorizontal.

    yIsRelative := resizeScrolledViewVertical.

    scrolledView isScrollWrapper ifTrue:[

        scrolledView isHorizontalScrollable ifTrue:[

            xIsRelative := true.

        ].     

        scrolledView isVerticalScrollable ifTrue:[

            yIsRelative := true.

        ].

    ].

    resizeScrolledViewHorizontal ifTrue:[ newExtent x:1.0 ].

    resizeScrolledViewVertical   ifTrue:[ newExtent y:1.0 ].

    xIsRelative ifTrue:[

        newExtent x:1.0.

        oldExtent x:1.0.

    ].

    yIsRelative ifTrue:[

        newExtent y:1.0.

        oldExtent y:1.0.

    ].

    oldExtent ~= newExtent ifTrue:[

        scrolledView extent:newExtent.

        realized ifTrue:[

            self sizeChanged:nil.

        ].

    ].

!

update:something with:aParameter from:changedObject

    changedObject == model ifTrue:[

        self scrolledView:(model value).

        ^ self

    ].

    changedObject == keepViewsChannel ifTrue:[

        self keepViews ifFalse:[ |views|

            "destroy all client views other than the actuel scrolled view

            "

            views := frame subViews.

            views size ~~ 0 ifTrue:[

                views copy do:[:v | v ~~ scrolledView ifTrue:[ v destroy ] ].

            ]

        ].

        ^ self

    ].

    super update:something with:aParameter from:changedObject

! !

!ViewScroller methodsFor:'event handling'!

sizeChanged:how

    "reposition the scrolledView, if required"

    |newOrigin|

    super sizeChanged:how.

    self changed:#sizeOfContents.        "update possible scrollers"

    "

     if we are beyond the end, scroll up a bit

    "

    ((self viewOrigin y + self height) > self heightOfContents) ifTrue:[

        newOrigin := self heightOfContents - self height.

        newOrigin < 0 ifTrue:[

            newOrigin := 0

        ].

        self scrollVerticalTo: newOrigin.

    ].

    "

     if we are right of the end, scroll left a bit

    "

    ((self viewOrigin x + self width) > self widthOfContents) ifTrue:[

        newOrigin := self widthOfContents - self width.

        newOrigin < 0 ifTrue:[

            newOrigin := 0

        ].

        self scrollHorizontalTo: newOrigin.

    ].

    "Modified: 24.5.1996 / 17:48:44 / cg"

! !

!ViewScroller methodsFor:'focus handling'!

canTab

    ^ false

! !

!ViewScroller methodsFor:'initialization & release'!

initialize

    "initialize all models of the view"

    super initialize.

    resizeScrolledViewVertical := false.

    resizeScrolledViewHorizontal := false.

    frame := SimpleView origin:0.0@0.0 corner:1.0@1.0 in:self.

    frame borderWidth:0; level:0.

    keepViewsChannel := false asValue.

    keepViewsChannel addDependent:self.

    model := nil asValue.

    model addDependent:self.

!

release

    "release all dependencies"

    keepViewsChannel removeDependent:self.

    model            removeDependent:self.

    super release.

! !

!ViewScroller methodsFor:'queries-contents'!

heightOfContents

    "return my contents' height; this is the scrolledViews height"

    scrolledView isNil ifTrue:[^ super heightOfContents].

    ^ scrolledView height

    "Modified: 24.5.1996 / 17:34:48 / cg"

!

viewOrigin

    "the viewOrigin (for scrollBars) is based upon the scrolledViews origin"

    scrolledView isNil ifTrue:[^ 0@0].

    ^ scrolledView origin negated

    "Modified: 24.5.1996 / 17:48:13 / cg"

!

widthOfContents

    "return my contents' width; this is the scrolledViews width"

    scrolledView isNil ifTrue:[^ super widthOfContents].

    ^ scrolledView width

    "Modified: 24.5.1996 / 17:34:56 / cg"

! !

!ViewScroller methodsFor:'scrolling'!

horizontalScrollStep

    "return the amount by which to step-scroll horizontally"

    ^ horizontalScrollStep ? (self width // 2)