my vertical scrolling is slow

Hello.

Take a look at visits and tiles in the following:

Strict

Global List_bricks : TList = CreateList()
Global visits
Global tiles

Type TBrick

	Field Col
	Field Row
	
	Field r
	Field g
	Field b
	
	Field x
	Field y
	
	' ----------------------------------------------------------------------------------------------
	
	Function Create:TBrick (X,y)
	
		Local b:TBrick = New TBrick
		
		b.Col = x
		b.Row = y 
		
		b.r = Rand (100,255)
		b.g = Rand (100,255)
		b.b = Rand (100,255)

		ListAddLast List_bricks, b
		
		Return b
		
	End Function

	' ----------------------------------------------------------------------------------------------

	Function Compute_one_row_Scrolling (Row, ScrollY)
		visits:+1	
		For Local b:TBrick = EachIn List_bricks
			tiles:+1
					
			If b.Row = Row Then
				b.x = b.Col * 32
				b.y = ScrollY 
			End If
			
		Next
		
	End Function

	' ----------------------------------------------------------------------------------------------

	Function Draw_one_row (Row)
		visits:+1	
		For Local b:TBrick = EachIn List_bricks
			tiles:+1
			If b.Row = Row Then
			
				SetColor b.r, b.g, b.b
				DrawRect b.x, b.y, 32,32
				
			End If
			
		Next
		
	End Function
	
	' ----------------------------------------------------------------------------------------------

	Function MySort:Int(o1:Object, o2:Object)
	
        Local diff% = TBrick(o1).Row - TBrick(o2).Row
        If diff = 0 Then
             diff = TBrick(o1).Col - TBrick(o2).Col
        EndIf
        Return diff	

	End Function

	' ----------------------------------------------------------------------------------------------

	Function Sort_the_list ()
	
		SortList(List_bricks,True,MySort)
		
	End Function		

	' ----------------------------------------------------------------------------------------------

End Type

' create some tiles for this example (i use an editor for my game)

' if you increase max_row, the scrolling is slow, coz the for-next loop into the 
' Compute_one_row_Scrolling().

Local Max_row = 100

For Local y=0 To Max_Row

	For Local x=0 To 31

		TBrick.Create (x, y)

	Next

Next

' sort them by y and x (not usefull here, but the game editor don't sort them...)

TBrick.Sort_the_list()

' go

Graphics 1024,768


Local t
Local ScrollY = 0
Local Row = 0
Local TimeScroll = MilliSecs()

While Not KeyDown(KEy_ESCAPE)

	' compute scrolling
	
	If TimeScroll + 1 < MilliSecs() Then ' NOTE CHANGE TO 1 MILLISEC HERE TO GIVE FASTEST TRY

		If ScrollY < 31 Then
		
			ScrollY = SCrollY + 1
			
		Else

			ScrollY = 0

			If Row < Max_row + 25 Then
			
				Row = Row + 1
				
			Else
			
				Row = 0
				
			End If
			
		End If
		
		t = MilliSecs()
		
		Local Decal = -32
		
		For Local r = row To (row-24) Step - 1
		
			TBrick.Compute_one_row_Scrolling(r,ScrollY + Decal)
			
			Decal = Decal + 32
			
		Next
		
		t = MilliSecs() - t		
		
		TimeScroll = MilliSecs()
		
	End If
	
	' draw
	
	Cls

	For Local r = row To (row-24) Step - 1
	
		TBrick.Draw_one_row(r)
		
	Next
	
	DrawText "time=" + String(t), 0,0
	DrawText "row=" + String(row), 0,30
	DrawText "Visits=" + String(visits),0,48	
	DrawText "Tiles=" + String(tiles),0,64
	Flip
	visits = 0
	tiles = 0
Wend 

And try changing the number of rows from 100 to 1000 to 10000.

Goodbye.