[Scummvm-tracker] [ScummVM] #10765: QFG4 floppy: Assertion Error celobj32.cpp:179 at the swamp

[Vhati]

#10765: QFG4 floppy: Assertion Error celobj32.cpp:179 at the swamp
--------------------------------+-------------------------
  Reporter:  Vhati              |      Owner:  (none)
      Type:  defect             |     Status:  new
  Priority:  high               |  Component:  Engine: SCI
Resolution:                     |   Keywords:  SCI32
      Game:  Quest for Glory 4  |
--------------------------------+-------------------------

Comment (by Vhati):

 The only functional difference I'm seeing between Scaler versions is CD
 avoids recalculating if the y position hasn't changed since last time. And
 I don't think hands ever move.
 \\
 \\
 script 10 - Swamp::init()
 {{{
 (= local7 (IntArray with: 54 48 95 158 132))
 (= local8 (IntArray with: 175 108 119 142 178))
 # ...
 (switch g11_myCurrentRoomNum
 # ...
         (535
                 (= temp0 0)
                 (while (< temp0 5)
                         ((hands new:)
                                 init: temp0 (local7 at: temp0) (local8 at:
 temp0)
                         )
                         (++ temp0)
                 )
         )
 # ...
 )
 }}}
 \\
 \\
 script 10 - hands::init()
 {{{
         (method (init param1 param2 param3)
                 (super init:)
                 (= x param2)
                 (= y param3)
                 (= loop (Random 0 5))
                 ((Timer new:) setReal: self (Random 5 25))
                 (self
                         signal: (| (self signal?) $0001)
                         setScaler: Scaler 100 60 125 65
                 )
         )
 }}}
 \\
 \\
 hands is a TargActor, whose ancestry is Feature/View/Prop/Actor.
 Prop::setScaler() basically forwards args to Scaler::init(self, &rest).
 \\
 \\
 script 64935 - Scaler::init()
 {{{
 (method (init param1 param2 param3 param4 param5)
         (if argc
                 (= client param1)
                 (= frontSize param2)
                 (= backSize param3)
                 (= frontY param4)
                 (= backY param5)
         )
         (= slopeNum (- frontSize backSize))
         (if (not (= slopeDen (- frontY backY)))
                 (proc64921_0 {<Scaler> frontY cannot be equal to backY})
                 (return 0)
         )
         (= const (- backSize (/ (* slopeNum backY) slopeDen)))
         (return (self doit:))
 )
 }}}
 \\
 \\
 A hands scaler would have...
 * frontSize = 100
 * backSize = 60
 * frontY = 125
 * backY = 65
 * slopeNum = 100 - 60 = 40
 * slopeDen = 125 - 65 = 60
 * const = 60 - (100 * 65 / 60) = -48

 Okay. frontY & backY are capping the scale. If a client moves lower/higher
 than those values, it won't get any bigger/smaller.

 The problem hand earlier was at y:108.

 {{{
 (else (= temp1 (+ (/ (* slopeNum temp0) slopeDen) const)))
 }}}

 40 * 108 / 60 + -48 = 24

 If the client's "scaleY" property isn't already 24...
 (Debugger says a hands at that position has scaleY:113. Dunno where 113
 came from.)

 ... the scaler will attempt to set scaleY to 24.

 The assertion doesn't abort anything though.

 "bp_write hands.3::scaleY" isn't stopping as the hand bobs up and down, so
 scaleY isn't constantly being set (or it is constantly set to 113?).
 Confused.

--
Ticket URL: <https://bugs.scummvm.org/ticket/10765#comment:9>
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