How to force scrollable bitmap window back to top?

[qwert]

I have a scrollable child GUI that contains a large bitmap that sometimes needs to be loaded with a different bitmap. The _SetHImage works fine, except that if the original bitmap has been scrolled downward, the replacement bitmap displays in the same "already scrolled down" position.

What is the proper way to force a "Home" on the child window before I load the new bitmap? I've tried a GUIScrollBars_Scroll Window function but could not get any worthwhile result.

Thanks in advance for any assistance.

[martin]

I have a scrollable child GUI that contains a large bitmap that sometimes needs to be loaded with a different bitmap. The _SetHImage works fine, except that if the original bitmap has been scrolled downward, the replacement bitmap displays in the same "already scrolled down" position.

What is the proper way to force a "Home" on the child window before I load the new bitmap? I've tried a GUIScrollBars_Scroll Window function but could not get any worthwhile result.

Thanks in advance for any assistance.

Are the scrollbars in the child gui created using GuiScrollBars.au3?

[qwert]

Are the scrollbars in the child gui created using GuiScrollBars.au3?

Yes, with a _GUIScrollBars_Init plus ...InfoMax, ...InfoPage, etc.

[martin]

Yes, with a _GUIScrollBars_Init plus ...InfoMax, ...InfoPage, etc.

You could just use a sawn-off version of the WM_VSCROLL combined with WM_HSCROLL supplied in the help

like this

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;To set to top and left of window call VHSCROLLToTopLeft($GuiID)


Func VSCROLLToTopLeft($hWnd)
    Local $index = -1, $xChar, $yChar, $xPos, $yPos
    Local $Min, $Pos
     Local $tSCROLLINFO

    For $x = 0 To UBound($aSB_WindowInfo) - 1
        If $aSB_WindowInfo[$x][0] = $hWnd Then
            $index = $x
            $yChar = $aSB_WindowInfo[$index][3]
             $xChar = $aSB_WindowInfo[$index][2]
            ExitLoop
        EndIf
    Next
    If $index = -1 Then Return 0


    ; Get all the vertial scroll bar information
    $tSCROLLINFO = _GUIScrollBars_GetScrollInfoEx($hWnd, $SB_VERT)
    $Min = DllStructGetData($tSCROLLINFO, "nMin")

    ; Save the position for comparison later on
    $yPos = DllStructGetData($tSCROLLINFO, "nPos")
    $Pos = $yPos

    DllStructSetData($tSCROLLINFO, "nPos", $Min)

;~    // Set the position and then retrieve it.  Due to adjustments
;~    //   by Windows it might not be the same as the value set.

    DllStructSetData($tSCROLLINFO, "fMask", $SIF_POS)
    _GUIScrollBars_SetScrollInfo($hWnd, $SB_VERT, $tSCROLLINFO)
    _GUIScrollBars_GetScrollInfo($hWnd, $SB_VERT, $tSCROLLINFO)
    ;// If the position has changed, scroll the window and update it
    $Pos = DllStructGetData($tSCROLLINFO, "nPos")

    If ($Pos <> $yPos) Then  _GUIScrollBars_ScrollWindow($hWnd, 0, $yChar * ($yPos - $Pos))


    ;now the HSCROLL
    ; Get all the horizontal scroll bar information
    $tSCROLLINFO = _GUIScrollBars_GetScrollInfoEx($hWnd, $SB_HORZ)
    $Min = DllStructGetData($tSCROLLINFO, "nMin")

    ; Save the position for comparison later on
    $xPos = DllStructGetData($tSCROLLINFO, "nPos")
    $Pos = $xPos

    DllStructSetData($tSCROLLINFO, "nPos", $Min)

;~    // Set the position and then retrieve it.  Due to adjustments
;~    //   by Windows it might not be the same as the value set.

    DllStructSetData($tSCROLLINFO, "fMask", $SIF_POS)
    _GUIScrollBars_SetScrollInfo($hWnd, $SB_HORZ, $tSCROLLINFO)
    _GUIScrollBars_GetScrollInfo($hWnd, $SB_HORZ, $tSCROLLINFO)
    ;// If the position has changed, scroll the window and update it
    $Pos = DllStructGetData($tSCROLLINFO, "nPos")
    If ($Pos <> $xPos) Then _GUIScrollBars_ScrollWindow($hWnd, $xChar * ($xPos - $Pos), 0)


EndFunc   ;==>VSCROLLToTopLeft

Edited August 14, 2009 by martin

[qwert]

You could just use a sawn-off version of the WM_VSCROLL ...

Martin, thanks.

I should be able to adapt that pretty easily, especially since I only have to work with vertical scrolling. I was hoping I had overlooked some "Home" function, but I suppose scrolling a bitmap comes with some necessary complexity.

[qwert]

I should be able to adapt that pretty easily ...

Well ... almost. It introduced a different problem.

My Child GUI can bring up a different bitmap but it's visible only if the original bitmap is in the "home" position. If it's in the "scrolled down" state, the area goes blank -- even though the new bitmap is being loaded (I can tell it loaded by the change in the scroll box size).

Any ideas?

[qwert]

the area goes blank ... Any ideas?

In investigating alternatives, I found that since WM_VSCROLL is handling the user's scroll bar actions, I can call it locally with a $SB_TOP flag and it "homes" the bitmap.

The only downside is that there's a flash/redisplay cycle on the original bitmap as it gets homed. Ideally, the second bitmap would just appear "homed", without any intermediate action.

I would still like to understand what causes VSCROLLToTopLeft to blank out the area. Maybe it will still turn out to be the best solution.

Thanks for your help so far.

UPDATE: I solved the flash problem by bracketing the bitmap home and change with a @SW_LOCK and @SW_UNLOCK. It works perfectly ... EXCEPT that afterwards the scroll box is still in the down postion. But it magically jumps to the top if I mouse anywhere over the scroll bar.

How can I cause a refresh of the scroll bar after the new bitmap is ready?

UPDATE TWO: I fashioned a workaround to refresh the scroll bar using a MouseGetPos + MouseMove + MouseMove(original position). I'm sure there's a better way, but this one does work.

Edited August 17, 2009 by qwert