-- CUSTOM SCROLL BAR --
--
-- 27 Oct 1998: written for the D7 Behaviors Palette by James Newton
-- 23 Dec 1999: JN
--  + Scroll to end corrected when the bar is clicked



-- NOTES FOR DEVELOPERS

-- This is the most complex behavior I have written for the Behavior
-- Library.  I have included in one script all the handlers necessary
-- to deal with each of the four elements of a scroll bar.
-- 
-- In practice, this one script works as four separate behaviors. 
-- Each element is identified by its myScrollRole (upArrow, downArrow,
-- dragger or bar).  The behavior acts differently for each 
-- myScrollRole.  Many handlers are divided into section by a 
-- "case myScrollRole of" statement.

-- INSTALLATION
-- Initializing the 4 behaviors cannot be done all at once on
-- beginSprite because the behaviors on the other sprites may not
-- exist.  To get round this, I set a myState property to 0 in the
-- StartInstallation handler (on beginSprite).  The first prepareFrame
-- (which is sent once all behaviors in the current frame have been
-- instanciated) sees that "myState + 0 = 0" (or FALSE) and calls the
-- FinishInstallation handler.

-- Why "myState + 0"?  Because once the installation is finished,
-- myState is set to #done.  This is a symbol.  A symbol is simply an
-- integer with a special tag.  Adding zero to a symbol gives you
-- access to the integer itself.  Later, when the prepareFrame handler
-- encounters "#done + 0" it evaluates this as a positive integer (or
-- TRUE) and doesn't botherd to reinstall the elements.

-- This technique is excessively fast: it slows down the following
-- prepareFrames by something in the order of a millionth of a second.

-- Installation itself is a three step-process.

-- First: the behavior has to check if the sprite and member that it
-- is to scroll do actually appear where it expects to find them.  The
-- ourScrolledElement property returned by the
-- getPropertyDescriptionList handler is a double-barreled affair:
-- "sprite X:field(member Y of castLib Z)".
-- If sprite X contains a Field or Text member, the behavior assumes
-- that this is the right one, and adopts it as myScrolledMember.  If
-- not, it sets out to look for (member Y of castLib Z), via the
-- FindSprite handler.  If it finds this member in one of the sprites
-- in the frame, then it adopts the new sprite as myScrolledSprite.
-- If not, it warns the author (4 times, once for each behavior).

-- Second: the current behavior has to check if all the others are
-- present. The Initialize handler has already prepared a list of all
-- behaviors which treat the same sprite and/or member:
-- ourControlList.  The CheckControl handler ensures that this list
-- contains one behavior for each control element... and only one.

-- Third: the sprite to which the behavior is attached has to be
-- placed correctly beside the sprite it is to scroll.  This is most
-- complex for the Dragger sprite, since it must be placed in
-- accordance with the current scrollTop of myScrolledMember.

-- The scrolling itself is always carried out by the behavior attached
-- to the dragger.  The Move and MoveBar handlers (which deal with
-- clicks on the arrow buttons and on the backing bar) end with a...
-- 
--   call (#SetDraggerShift, ourControlList.dragger)
-- 
-- ... command.  The bar behavior must in addition ask the dragger
-- where it now is, using ...
--
--   call (#GetDraggerData, ourControlList.dragger)
-- 
-- ... so as to update its myActiveZone.

-- EXTERNAL LINGO CALLS

-- * CustomScrollbar_SetScroll me, theScroll

-- If you use standard Lingo to set the scrollTop of myScrolledMember
-- at runtime,  the dragger position will not update until the scroll
-- bar is next used.  Use this call to tell the dragger to do all the
-- work for you

-- * CustomScrollbar_SwapMember me, newMember, currentMemberOrSprite

-- If you use standard Lingo to swap the member of myScrolledSprite at
-- runtime, the behaviors will continually happily to scroll the
-- member which is now off-stage.  Use this call to tell one of the
-- behaviors do the swapping for you.

-- * CustomScrollbar_GetReference me, memberOrSprite, controlOrList

-- Using sendAllSprites with one of the above messages will ensure
-- that the job gets done... four times, once by each behavior that
-- makes up the scroll bar.  If you call one of the behaviors
-- directly, the command will be executed just once.  But first you
-- must get an object reference to the behavior in question.  The
-- following syntax is the simplest:
-- 
--   scrollRef=sendAllSprites(#CustomScrollbar_GetReference,sprite X)
-- 
-- This will give you a reference to the behavior on the highest
-- sprite which controls the scrolling of sprite X.

-- More details on using these external calls are given in the
-- handlers themselves.



-- PROPERTIES --

property spriteNum
-- error checking
property getPDLError
-- author-defined parameters
property ourScrolledElement -- "<spriteNum>: <member>" of element to
--                             scroll
property myScrollRole       -- sprite behaves as
--                             upArrow|downArrow|dragger|bar
property myActiveMember     -- member which appears on mouseDown
property myStandardMember   -- member which appears at all other times
property myMultiThreading   -- updates on prepareFrame | while the 
--                             mouseDown
-- internal properties
property mySprite
property myMember
property myRect              -- rect to which all members must be set
--                              to fit
property myScrolledSprite    -- sprite containing myScrolledMember
property myScrolledMember    -- Text or Field member to scroll
property myActiveZone        -- when mouse is in zone, scrolling
--                              continues
property myState             -- #paused if mouse is outside
--                              myActiveZone
property myNextUpdate        -- slows scrollByPage if necessary
-- properties specific to the dragger
property myZeroLoc           -- loc of dragger when scrollTop = 0
property myDraggerShift      -- vertical distance dwon from myZeroLoc
property myClickV            -- vertical coordinate where the dragger
--                              was clicked
property myInterimShift      -- value of shift while the dragger is 
--                             being scrolled
property myMaxDraggerShift   -- maximum value of dragger shift
-- property specific to the bar
property myPageScroll        -- direction of scroll: #up or #down
-- properties shared between behaviors
property ourControlList      -- list of behaviors which collaborate on
--                              scrollbar
property ourMaxScroll        -- list shared by behaviors: [maximum
--                              scrollTop]




-- EVENT HANDLERS --

on beginSprite me
  StartInstallation me
end beginSprite


on prepareFrame me
  if not myState + 0 then
    FinishInstallation me -- First prepareFrame only
  end if
  if myMultiThreading then
    UpdateScroll me
  end if
end prepareFrame


on mouseDown me
  StartScroll me
end mouseDown

on mouseUp me
  EndScroll me
end mouseUp

on mouseUpOutside me
  EndScroll me
end mouseUpOutside



-- CUSTOM HANDLERS --

on StartInstallation me -- sent by beginSprite
  mySprite         = sprite(me.spriteNum)
  myMember         = mySprite.member
  memberType       = myMember.type
  
  -- Error checking
  if voidP (myScrollRole) then
    ErrorAlert (me, #getPDL_Invalid)
  end if
  
  -- The member of the sprite may have changed since getPDL
  myScrolledSprite = value (ourScrolledElement)
  myScrolledMember = myScrolledSprite.member
  
  -- Ensure that the scrolled sprite has not changed or moved
  memberType = myScrolledMember.type
  case memberType of
    #field, #text: -- do nothing
    otherwise
      -- Try to find the expected member in another sprite
      FindSprite (me)
  end case
  -- End of error checking
  
  -- Calculate ideal sprite.rect
  topLeft = point (myScrolledSprite.left, myScrolledSprite.top)
  myRect  = myScrolledSprite.rect - rect (topLeft, topLeft)
  if memberType = #field then
    if myScrolledMember.border then
      myRect[1] = 1
    end if
  end if
  -- Contact other sprites with the same behavior
  ourMaxScroll = []
  set ourControlList = [:]
  sendAllSprites \
(\
 #CustomScrollbar_RollCall, \
 ourScrolledElement, \
 ourControlList, \
 ourMaxScroll \
)
  myState = 0 -- Check will be run on first prepareFrame
end StartInstallation


on FindSprite me -- sent by StartInstallation
  -- Finds highest sprite containing the expected member to scroll
  saveDelimiter = the itemDelimiter
  the itemDelimiter = ":"
  memberData = ourScrolledElement.item[2]
  the itemDelimiter = saveDelimiter
  delete memberData.word[1] -- Remove type information
  delete memberData.char[1] -- Remove remaining space
  memberData = value (memberData)
  myScrolledMember = member (memberData)
  
  scrollSprite = the lastChannel
  repeat while scrollSprite
    if sprite(scrollSprite).member = myScrolledMember then
      -- We've found it!
      myScrolledSprite = sprite (scrollSprite)
      exit
    end if
    scrollSprite = scrollSprite - 1
  end repeat
  if not scrollSprite then
    -- The expected member was not found
    ErrorAlert me, #notScrollable, myScrolledSprite.member.type
  end if
end FindSprite


on FinishInstallation me -- sent by first prepareFrame
  -- Terminates initialization process once all behaviors are in place
  CheckControlList me
  -- Place this sprite to the right of myScrolledSprite
  InstallElement me
end FinishInstallation


on CheckControlList me -- sent by FinishInstallation
  -- Checks if ourControlList contains one-and-only-one behavior with
  -- each role
  checkList = duplicate (ourControlList)
  roleList  = [#upArrow, #downArrow, #dragger, #bar]
  i = roleList.count()
  repeat while i
    theRole = roleList[i]
    rolePosition = checkList.findPos (theRole)
    if rolePosition then
      roleList.deleteAt(i)
      checkList.deleteAt (rolePosition)
    end if
    i = i - 1
  end repeat
  if checkList.count() then
    ErrorAlert me, #extraControl, checkList.getPropAt (1)   
  end if
  if roleList.count() then
    ErrorAlert me, #missingControls, roleList 
  end if
end CheckControlList


on InstallElement me
  -- sent by FinishInstallation on first prepareFrame, _SwapMembers
  -- Places sprite next to myScrolledSprite and determines
  -- myActiveZone  
  scrollRoof  = myScrolledSprite.top
  scrollFloor = myScrolledSprite.bottom
  scrollLeft  = myScrolledSprite.right
  if myScrolledMember.type = #field then
    scrollLeft = scrollLeft - (myScrolledMember.border <> 0)
  end if
  
  case myScrollRole of
    #upArrow: 
      mySprite.loc = point (scrollLeft, scrollRoof)+myMember.regPoint
      myActiveZone = mySprite.rect
    #downArrow:
      locAdjust    = myMember.regPoint - [0, mySprite.height]
      rectAdjust   = mySprite.rect - rect (mySprite.loc, mySprite.loc)
      mySprite.loc = point (scrollLeft, scrollFloor) + locAdjust
      myActiveZone = rectAdjust + rect (mySprite.loc, mySprite.loc)
    #bar:
      barRoof  = scrollRoof+call(#SpriteHeight,ourControlList.upArrow)
      barRight = scrollLeft+call(#SpriteWidth,ourControlList.upArrow)
      barFloor = scrollFloor-call(#SpriteHeight,ourControlList.downArrow)
      mySprite.rect= rect (scrollLeft, barRoof, barRight, barFloor)
    #dragger:
      case myMember.type of
        #vectorShape:
          regOffset = (myMember.strokeWidth  + 1) / 2
          myMember.regPoint = point (regOffset, regOffset)
        otherwise
          myMember.regPoint = point (0,0)
      end case
      
      upHeight        = call (#SpriteHeight, ourControlList.upArrow)
      upWidth         = call (#SpriteHeight, ourControlList.upArrow)
      downHeight      = call (#SpriteHeight, ourControlList.downArrow)
      
      draggerRoof     = scrollRoof  + upHeight
      myZeroLoc       = point (scrollLeft, draggerRoof)
      barRight        = scrollLeft  + upWidth
      myActiveZone  = rect(scrollLeft,scrollRoof,barRight,scrollFloor)
      myActiveZone  = inflate (myActiveZone, 32, 32)
      
      arrowAdjust     = upHeight + downHeight
      pageHeight      = myScrolledSprite.height
      scrollHeight    = pageHeight - arrowAdjust
      draggerHeight   = mySprite.Height
      
      myMaxDraggerShift = 0 -- pre-emptive measure in case dragger
      --                       can't scroll
      if scrollHeight < 0 then
        -- Adjust length of myScrolledMember so that arrow buttons fit
        minRect               = myScrolledMember.rect
        minRect[4]            = arrowAdjust
        myScrolledMember.rect = minRect
        call (#InstallElement, ourControlList.bar)
      end if
      if scrollHeight < draggerHeight then
        mySprite.loc = point (-999, -999)
      else
        -- Dragger can slide: set myMaxDraggerShift to reflect this
        if myScrolledMember.type = #field then
          theMargin     = myScrolledMember.margin
          theMargin     = theMargin - theMargin mod 2
          borderAdjust  = (myScrolledMember.border * 2) + theMargin
        else
          borderAdjust  = 0
        end if
        myMaxDraggerShift = scrollHeight-draggerHeight+borderAdjust
      end if
      
      ourMaxScroll[1] = GetMaxScroll (me)
      SetDraggerShift me
  end case
  myState = #done
end InstallElement


on GetMaxScroll me
  pageHeight = myScrolledSprite.height
  
  if myScrolledMember.type = #text then
    lastChar   = myScrolledMember.char.count
    textHeight = charPostoloc  (myScrolledMember, lastChar)[2]
  else
    textHeight = myScrolledMember.height
  end if
  
  maxScroll  = textHeight - pageHeight
  if maxScroll < 1 then
    return 0
  else
    return maxScroll
  end if
end GetMaxScroll



-- SCROLLING --

on StartScroll me -- sent by mouseDown
  -- StartInstallations properties for scroll and either performs one
  -- update (if myMultiThreading is TRUE) or completes the operation
  -- (in repeat loop).
  myState = #active
  ourMaxScroll[1] = GetMaxScroll (me)
  case myScrollRole of
    #dragger:
      -- Determine start of scroll
      myClickV        = the clickLoc[2]
      myInterimShift = 0
    #upArrow, #downArrow:
      -- Swap members
      mySprite.Member = myActiveMember
    #bar:
      -- Determine active zone
      draggerData = call (#GetDraggerData, ourControlList.dragger)
      if the clickLoc[2] < draggerData.top then
        myActiveZone = GetBarZone (me, draggerData, #up)
      else
        myActiveZone = GetBarZone (me, draggerData, #down)
      end if
  end case
  UpdateScroll me
  if myMultiThreading then exit
  
  -- Use a tight repeat loop to scroll as fast as possible
  repeat while the mouseDown
    UpdateScroll me
  end repeat
end StartScroll


on UpdateScroll me -- sent by prepareFrame, StartScroll, ResumeScroll
  -- Determines whether to pause or to scroll (and how to)
  case myState of
    #active:
      if inside (the mouseLoc, myActiveZone) then
        case myScrollRole of
          #dragger:   MoveDragger me
          #upArrow:   Move me, TRUE
          #downArrow: Move me, FALSE
          #bar:       MoveBar me
        end case
      else
        PauseScroll me
      end if
    #paused:
      ResumeScroll me
  end case
end UpdateScroll


on GetBarZone me, draggerData, pageScroll
  -- Determines zone in which the mouse makes the text scroll by page
  if not voidP (pageScroll) then
    myPageScroll  = pageScroll
  end if
  barZone       = mySprite.rect
  if myPageScroll = #up then
    barZone [2] = myScrolledSprite.top
    barZone [4] = draggerData.top
  else 
    barZone [2] = draggerData.bottom
    barZone [4] = myScrolledSprite.bottom
  end if
  return barZone
end GetBarZone


on MoveDragger me
  -- Checks if the dragger has moved, and if so modifies scroll
  newScroll = myDraggerShift + the mouseV - myClickV
  newScroll = max (0, min (newScroll, myMaxDraggerShift))
  if myInterimShift = newScroll then exit
  
  myInterimShift = newScroll      
  SetTextScroll me, myInterimShift
end MoveDragger


on Move me, up
  -- Scrolls one line up or down
  if the ticks < myNextUpdate then exit
  if voidP (myNextUpdate) then
    -- Allow time for a quick single-line click
    myNextUpdate = the ticks + 10
  else
    -- Don't scroll too fast
    myNextUpdate = the ticks + 1
  end if
  
  if up then
    if not myScrolledMember.scrollTop then exit
    scrollByLine myScrolledMember, -1
  else
    maxScroll = ourMaxScroll[1]
    if myScrolledMember.scrollTop = maxScroll then exit
    scrollByLine myScrolledMember, 1
    if myScrolledMember.scrollTop > maxScroll then
      myScrolledMember.scrollTop = maxScroll
    end if
  end if
  call (#SetDraggerShift, ourControlList.dragger)
end MoveUp


on MoveBar me, up
  -- Scrolls one page up or down, leaving one previous line visible
  if the ticks < myNextUpdate then exit
  myNextUpdate = the ticks + 10 -- So as not to scroll too fast
  
  if myPageScroll = #up then
    scrollByPage (myScrolledMember, -1)
    if myScrolledMember.scrollTop then
      -- Leave previous top line visible at bottom
      scrollByLine (myScrolledMember,  1)
    end if
  else -- down
    maxScroll = ourMaxScroll[1]
    if myScrolledMember.scrollTop = maxScroll then exit
    scrollByPage (myScrolledMember,  1)
    
    if myScrolledMember.scrollTop > maxScroll then
      myScrolledMember.scrollTop = maxScroll
    else
      -- Leave previous bottom line visible at top
      scrollByLine (myScrolledMember, -1)
    end if
  end if
  call (#SetDraggerShift, ourControlList.dragger)
  -- The area of the bar where mouse should active just got smaller
  draggerData  = call (#GetDraggerData, ourControlList.dragger)
  myActiveZone = GetBarZone (me, draggerData)
end MoveBar


on PauseScroll me
  -- Pauses the behavior when the mouse leaves myActiveZone
  myState = #paused
  case myScrollRole of
    #dragger:
      -- Revert to original scroll
      SetTextScroll me, myDraggerShift
    #upArrow, #downArrow:
      -- Revert to original button image
      mySprite.member = myStandardMember
      if not myMultiThreading then
        updateStage
      end if
  end case
end PauseScroll


on ResumeScroll me
  -- Reactivates the behavior when the mouse returns to myActiveZone
  myState = #active
  case myScrollRole of
    #upArrow, #downArrow:
      mySprite.member = myActiveMember
  end case
  UpdateScroll me
end ResumeScroll


on EndScroll me
  -- Tidies up after scroll is over, ready for the next one
  case myScrollRole of
    #dragger:
      if not voidP (myInterimShift) then
        if ourMaxScroll[1] then
          myDraggerShift = myInterimShift
        else
          myDraggerShift = 0
          ShiftDragger me, myDraggerShift
        end if
      end if
      myInterimShift = void
    #upArrow, #downArrow:
      mySprite.member = myStandardMember
      myNextUpdate = void
  end case
  myState = #done
end EndScroll


on SetTextScroll me, draggerShift
  -- Calculates the scrollTop of the text then sets it and moves thumb
  if ourMaxScroll[1] then
    textScroll = (draggerShift * ourMaxScroll[1]) / myMaxDraggerShift
    myScrolledMember.scrollTop = textScroll
  else
    -- draggerShift = 0
  end if
  
  ShiftDragger me, draggerShift
end SetTextScroll


on SetDraggerShift me
  -- Calculates the position of the dragger from
  -- myScrolledMember.scrollTop
  maxScroll = ourMaxScroll[1]
  if maxScroll then
    textScroll = myScrolledMember.scrollTop
    myDraggerShift = (textScroll * myMaxDraggerShift) / maxScroll
  else
    myDraggerShift = 0
  end if
  
  ShiftDragger me, myDraggerShift
end SetDraggerShift


on ShiftDragger me, draggerShift
  if not myMaxDraggerShift then
    -- Don't move dragger if there is no space to move it
    exit
  end if
  
  mySprite.loc = myZeroLoc + [0, draggerShift]
  updateStage
end ShiftDragger



-- PUBLIC METHODS (responses to #sendSprite, #sendAllSprites, #call) --

on CustomScrollbar_SetScroll me, theScroll
  -- Allows an editable field to update its scrolltop via the #dragger
  -- behavior
  
  -- Error check
  case ilk (theScroll) of
    #integer: -- nothing
    #float:   theScroll = integer (theScroll)
    otherwise
      return #invalidTypeError
  end case
  -- End of error check
  
  theScroll = max (0, min (theScroll, ourMaxScroll[1]))
  myScrolledMember.scrollTop = theScroll
  call (#SetDraggerShift, ourControlList.dragger, theScroll)
end CustomScrollbar_SetScroll


on CustomScrollbar_SwapMember me, newMember, currentMemberOrSprite
  -- Allows you to change the member of the scrolled sprite at runtime
  -- newMember is a member reference, name or number.  If you have a
  -- number of custom scrollbars in the frame, then
  -- currentMemberOrSprite identifies  which member to change if you
  -- use a sendAllSprites messsage. You can leave the
  -- currentMemberOrSprite parameter empty if you call a specific
  -- behavior.
  --
  -- The following examples both set the member of sprite 1 to member
  -- 2.  The first example will actually do this four times, once for
  -- each behavior that makes up the scrollbar:
  --
  --   sendAllSprites(#CustomScrollbar_SwapMember, member 2, sprite 1)
  -- OR
  --   scrollBehavior = sendAllSprites (#CustomScrollbar_GetReference,
  --                    sprite 1)
  --   call (#CustomScrollbar_SwapMember, scrollBehavior, member 2)
  
  -- Error check
  case ilk (newMember) of
    #member: -- do nothing
    #integer, #string:   
      memberExists = (the number of member (newMember) > 0)
      if memberExists then
        newMember = member (newMember)
      else
        return #memberInexistant
      end if
    otherwise
      return #invalidType
  end case
  case newMember.type of
    #text, #field: -- do nothing
    otherwise
      return #invalidMemberType
  end case
  -- End of error check
  
  case ilk (currentMemberOrSprite) of
    #sprite: if currentMemberOrSprite <> myScrolledSprite then exit  
    #member: if currentMemberOrSprite <> myScrolledMember then exit
      -- otherwise ignore currentMemberOrSprite
  end case
  
  myScrolledMember = newMember
  idealRect        = myRect
  if myScrolledMember.type = #field then
    hBorder        = myScrolledMember.border
    vBorder        = hBorder - (hBorder <> 0)
    hMargin        = myScrolledMember.margin
    vMargin        = hMargin / 2   --- hMargin - (hMargin mod 2)
    idealRect = inflate(idealRect, -hBorder-hMargin, -hBorder-vMargin)
    if myRect[1] then -- 0riginal meber had a border...
      if hBorder then -- ... and so does this member
        idealRect[1] = idealRect[1] - 1
      end if
    else -- Original member had NO border...
      if hBorder then -- ... but this one has.
        idealRect[1] = idealRect[1] - 1
      end if
    end if
  end if
  
  myScrolledMember.rect   = idealRect
  myScrolledSprite.member = myScrolledMember
  myScrolledMember.boxType = #fixed
  
  i = ourControlList.count()
  repeat while i
    call (#NewMember, ourControlList[i])
    i = i - 1
  end repeat
  updateStage
  call (#InstallElement, ourControlList.dragger)
end CustomScrollbar_SwapMember


on CustomScrollbar_GetReference me, memberOrSprite, controlOrList
  -- Returns a reference to the behavior for Lingo calls.
  -- The parameters are optional: use them to find a specific
  -- behavior. Use 'theElement' to find the scrollbar of a particular
  -- sprite or member Use 'controlOrList' to find a specific behavior
  -- (up|downArrow|dragger|bar) or to return a property list of all
  -- behaviors.
  -- Examples:
  --
  -- put sendAllSprites(#CustomScrollbar_GetReference, sprite 1,
  ---                   #dragger)
  -- -- <offspring "Custom Scrollbar" 3 486bc20>
  --
  -- put sendAllSprites (#CustomScrollbar_GetReference, sprite 1, [:])
  -- -- [#bar:<ref>, #upArrow:<ref>, #dragger:<ref>, #downArrow:<ref>]
  --
  -- You can leave the controlOrList parameter empty.  If you do, the
  -- behavior reference on the highest sprite in the scrollbar will be
  -- returned.
  
  case ilk (memberOrSprite) of
    #sprite: if memberOrSprite <> myScrolledSprite then exit  
    #member: if memberOrSprite <> myScrolledMember then exit
    otherwise
      exit
  end case
  
  if not voidP (controlOrList) then
    if ilk (controlOrList) = #propList then
      controlOrList.addProp(myScrollRole, me)
      return controlOrList
    else
      if controlOrList = myScrollRole then return me
    end if
  else
    return me
  end if
end CustomScrollbar_GetReference



-- INTER-SPRITE COMMUNICATION --
-- (responses to #sendAllSprites) --

on CustomScrollbar_RollCall me, scrolledElement, controlList, maxScrollList
  -- sent on StartInstallation by this and other sprites with the same
  -- behavior
  if scrolledElement <> ourScrolledElement then exit
  
  ourControlList = controlList
  ourControlList.addProp(myScrollRole, me)
  ourMaxScroll   = maxScrollList
end CustomScrollbar_RollCall

-- (responses to #call) --

on SpriteHeight me
  -- Called by InstallElement in behaviors on the bar and the dragger
  -- Dealt with by behavior on the upArrow
  return mySprite.height
end


on SpriteWidth me
  -- Called by InstallElement in behaviors on the bar and the dragger
  -- Dealt with by behavior on the upArrow
  return mySprite.width
end


on GetDraggerData me
  -- Called by  StartScroll, MoveBar in behavior on the bar
  -- Dealt with by behavior on the dragger
  return [#top: mySprite.top, #bottom: mySprite.bottom]
end


on NewMember me
  -- sent by _SwapMember from the behavior that received the call
  myScrolledMember = myScrolledSprite.member
end NewMember



-- ERROR CHECKING --

on ErrorAlert me, theError, data
  -- sent by getPropertyDescriptionList, StartInstallation
  case theError of
    #getPDLError:
      permittedTypes = PermittedMemberTypes(me)
      alert \
"Error: This behavior works only with the following member types: "&\
permittedTypes&RETURN&RETURN&\
"Hit OK and then delete this behavior from the sprite."&RETURN&\
"For more information on deleting Behaviors, see the Help system."
      if the optionDown then
        return \
[ \
 #getPDLError: \
 [ \
  #comment: "ERROR:  Click 'Cancel'. Wrong member type.", \
  #format:  #string, \
  #range:   [""], \
  #default:  "" \
 ] \
]
      end if
      
    #noScrollableSprites:
      alert \
"Error: Please place a Field or Text member on the Stage before using this \
behavior to create a scroll bar."&RETURN&RETURN&\
"Hit OK and then delete this behavior from the sprite."&RETURN&\
"For more information on deleting Behaviors, see the Help system."
      if the optionDown then
        return \
[ \
 #getPDLError: \
 [ \
  #comment: "ERROR:   Click 'Cancel'.  Place a Text or Field"&RETURN&\
            "member on Stage before creating scroll bar.", \
  #format:  #string, \
  #range:   [""], \
  #default:  "" \
 ] \
]
      end if
      
    otherwise
      -- Determine the behavior's name
      behaviorName = string (me)
      delete word 1 of behaviorName
      delete the last word of behaviorName
      delete the last word of behaviorName
      -- Convert #data to useful value
      case data.ilk of
        #void: data = "<void>"
        #symbol: data = "#"&data
      end case
      if theError <> #getPDL_Invalid then
        -- Determine the name and type of myScrolledMember
        memberName = myScrolledMember.name
        if memberName = EMPTY then
          memberName = myScrolledMember
        else
          memberName = QUOTE&memberName&QUOTE
        end if
        memberName = myScrolledMember.type&&memberName
      end if
      
      case theError of
        #getPDL_Invalid:
          alert \
"BEHAVIOR ERROR: Frame "&the frame&", Sprite "&me.spriteNum&RETURN&RETURN&\
"Parameters for the "&behaviorName&"behavior have not been set."&\
RETURN&RETURN&\
"Please reopen the Behavior Parameters dialog and choose again."
          halt
          
        #notScrollable:
          alert \
"BEHAVIOR ERROR: Frame "&the frame&", Sprite "&me.spriteNum&RETURN&\
"Behavior "&behaviorName&RETURN&RETURN&\
"Sprite "&myScrolledSprite.spriteNum&" does not \
contain a Field or Text member."&RETURN&\
"Choose again in the Behavior Parameters dialog."&\
RETURN&RETURN&\
"Member type = "&data
          halt
          
        #extraControl:
          if the runMode = "Author" then
            alert \
"BEHAVIOR ERROR: Frame "&the frame&", Sprite "&me.spriteNum&RETURN&\
"Behavior "&behaviorName&RETURN&RETURN&\
"There is more than one "&data&" sprite defined for the scroll bar for \
sprite "&myScrolledSprite.spriteNum&", "&memberName&"."
          end if
          
        #missingControls:
          alert \
"BEHAVIOR ERROR: Frame "&the frame&", Sprite "&me.spriteNum&RETURN&\
"Behavior "&behaviorName&RETURN&RETURN&\
"The following elements of the scroll bar for sprite "&\
myScrolledSprite.spriteNum&", "&memberName&" are missing:"&RETURN&RETURN&\
data
          halt
          
      end case
  end case
end ErrorAlert



-- UTILITIES --

on GetScrollableSprites me, permittedTypes
  -- Returns a list of sprites containing Field or Text members, in
  -- the format: ["<spriteNumber>, <type> <member.name|member>",...]
  
  scrollableSprites = []
  repeat with theSprite = 1 to the lastChannel
    theMember = sprite(theSprite).member
    case theMember.type of
      #field, #text:
        memberName = theMember.name
        if memberName = EMPTY then
          memberName = theMember
        else
          memberName = QUOTE&memberName&QUOTE
        end if
        memberName = theMember.type&&memberName
        scrollableSprites.append ("sprite "&theSprite&": "&memberName)
    end case
  end repeat
  return scrollableSprites
end GetScrollableSprites



on PermittedMemberTypes me
  -- sent by:
  -- getBehaviorDescription
  -- getPropertyDescriptionList
  -- ErrorAlert
  return [#animgif, #bitmap, #filmLoop, #flash, #movie, #picture, #shape]
end PermittedMemberTypes



-- AUTHOR-DEFINED PARAMETERS --

on getPropertyDescriptionList me
  
  if not the currentSpriteNum then exit
  
  -- Error check: does current sprite contain appropriate member type?
  theMember = sprite(the currentSpriteNum).member
  memberType = theMember.type
  permittedTypes = PermittedMemberTypes(me)
  if not permittedTypes.getPos(memberType) then
    return ErrorAlert (me, #getPDLError, permittedTypes)
  end if
  -- Find sprites with field or text members
  scrollableList = GetScrollableSprites (me)
  if not scrollableList.count then
    return ErrorAlert (me, #noScrollableSprites)
  end if
  
  return \
[ \
 #myScrollRole: \
 [ \
  #comment: "Current sprite acts as:", \
  #format:  #symbol, \
  #range:  [#upArrow, #downArrow, #dragger, #bar], \
  #default:  1 \
 ], \
 #ourScrolledElement: \
 [ \
  #comment: "Scroll the member of", \
  #format:  #string, \
  #range:    scrollableList, \
  #default:  scrollableList[1] \
 ], \
 #myStandardMember: \
 [ \
  #comment: "Standard member:", \
  #format:  #graphic, \
  #default:  theMember \
 ], \
 #myActiveMember: \
 [ \
  #comment: "(Arrows only) mouseDown member:", \
  #format:  #graphic, \
  #default:  theMember \
 ], \
 #myMultiThreading: \
 [ \
  #comment: "Allow animations to continue (slower)?", \
  #format:  #boolean, \
  #default:  TRUE \
 ] \
]
end getPropertyDescriptionList



on getBehaviorTooltip me
  return \
"Use 4 graphic members (dragger, bar, up and down arrows)"&RETURN&\
"to create a dynamic scrollbar for Text or Field members."\
&RETURN&RETURN&\
"Drop this behavior on each sprite separately."&RETURN&RETURN&\
"  Sprites can pass over the scrollbar and animations can"&RETURN&\
"continue while the user scrolls."&RETURN&RETURN&\
"The behavior accepts Lingo calls to:"&RETURN&\
"+ set the scrolltop of the scrolled member to a given value."&\
RETURN&\
"+ swap the current member of the sprite."
end getBehaviorTooltip



on getBehaviorDescription me
  return \
"CUSTOM SCROLL BAR"&RETURN&RETURN&\
"Create dynamic scrollbars with your own artwork.  Such scrollbars are not Direct-To-Stage, so other sprites can appear over the top of them."&RETURN&RETURN&\
"You will need to create four graphic members:"&RETURN&\
"+ up arrow"&RETURN&\
"+ down arrow"&RETURN&\
"+ dragger"&RETURN&\
"+ backing bar"&RETURN&RETURN&\
"You may wish to use two additional members, to indicate that the arrow buttons have been pressed:"&RETURN&\
"+ up arrow (pressed state)"&RETURN&\
"+ down arrow (pressed state)"&RETURN&RETURN&\
"Place the four standard members on the Stage, and drop this behavior onto each of them.  Choose how the current sprite is to act in the appropriate pop-up menu in the Behavior Parameters dialog."&RETURN&RETURN&\
"For each element you can choose whether animations should continue in the background.  This option will tend to slow both the animations and the scrolling process, especially if applied to the arrow buttons."&RETURN&RETURN&\
"The various sprites will position themselves automatically to the right of the sprite-to-be-scrolled when the movie runs.  They revert to their original positions when it stops.  To avoid flashes, it would be a good idea to position them by hand in their intended positions."&RETURN&RETURN&\
"If you use a border on your field members, the scrollbar will sit outside the border.  Field box shadows are not recommended.  You can always fake external borders and box shadows with shape members (this even gives you a choice of colors)."&RETURN&RETURN&\
"To make authoring easier, this behavior will continue to work if you change EITHER the sprite channel OR the member in the chosen channel.  If you change both, the behavior will no longer know what to scroll."&RETURN&RETURN&\
"If you do change either the sprite or the member, and then reopen the Behavior Parameters dialog for one of the elements, this will put that behavior out of synch with the others.  Simply reopen and close the Parameters dialogs for each of the other elements.  If you do not do so, you will receive multiple alerts."&RETURN&RETURN&\
"This behavior can be used to scroll both editable and non-editable Fields and Text members.  For editable members, however, it does not automatically update the dragger position when the length of the text changes, nor does it make the editable member scroll automatically when the user drags the mouse to create a selection."&RETURN&RETURN&\
"PERMITTED MEMBER TYPES:"&RETURN&PermittedMemberTypes (me)&RETURN&RETURN&\
"PARAMETERS:"&RETURN&\
"* Current sprite acts as (up|down arrow | dragger | bar)"&RETURN&\
"* Scroll the member of <sprite>: <the member of sprite>"&RETURN&\
"* Standard member (this should not need to be set)"&RETURN&\
"* Member to display when arrow buttons are pressed"&RETURN&\
"* Allow animations to continue"&RETURN&RETURN&\
"PUBLIC METHODS"&RETURN&\
"=> Scroll the text/field member to a given position"&RETURN&\
"=> Swap the text/field  member to be scrolled"&RETURN&\
"=> Get the behavior reference"
end getBehaviorDescription