$LVS_EX_DOUBLEBUFFER causes freeze

[czardas]

Is this a bug?

Caution don't run this if you don't know what you are doing. Run the script, preferably in SciTE, and select an item in the ListView control. Now we can cause the to GUI freeze by pressing the TAB key. Since the GUI stops responding I figured it must be a bug.

expandcollapse popup

#include <GUIConstants.au3>
#include <WindowsConstants.au3>
#include <GuiListView.au3>
 
_Run()
 
Func _Run()
    Local $sFont = "MS Sans Serif", $iFontSize = 10, $iFontWeight = 500, $iWidthRatio = .9, $iHeightRatio = .8, _
    $bLV_BKColor = 0xFFFFCC
    Local $iWidth = @DesktopWidth*$iWidthRatio, $iHeight = @DesktopHeight*$iHeightRatio, _
    $bStyle = BitOR($GUI_SS_DEFAULT_GUI, $WS_MAXIMIZEBOX)
    Local $hGUI = GUICreate(" Test", $iWidth, $iHeight, Default, Default, $bStyle)
 
    Local $sHeadings = "Col 1|Col 2|Col 3|Col 4|Col 5|Col 6|Col 7"
 
    $hListView = GUICtrlCreateListView($sHeadings, 0, 0, $iWidth, $iHeight -20, _
    BitOR($LVS_REPORT,$LVS_SHOWSELALWAYS), BitOR($LVS_EX_GRIDLINES, $LVS_EX_FULLROWSELECT, $LVS_EX_DOUBLEBUFFER))
    GUICtrlSetBkColor($hListView, $bLV_BKColor)
    GUICtrlSetFont($hListView, $iFontSize, $iFontWeight, Default, $sFont)
    _SetColWidth($hListView, $iWidth/7)
    _SetData($hListView)
 
    GUISetState(@SW_SHOW)
 
    While 1
        $msg = GUIGetMsg()
        If $msg = $GUI_EVENT_CLOSE Then ExitLoop
        If $msg = $GUI_EVENT_MAXIMIZE Then _SetColWidth($hListView, @DesktopWidth/7)
        If $msg = $GUI_EVENT_RESTORE Then _SetColWidth($hListView, $iWidth/7)
    WEnd
EndFunc
 
Func _SetData($hListView)
    For $i = 0 To 1000
        GUICtrlCreateListViewItem( _
        Random(0 ,1000000, 1) &"|"& _
        Random(0 ,1000000, 1) &"|"& _
        Random(0 ,1000000, 1) &"|"& _
        Random(0 ,1000000, 1) &"|"& _
        Random(0 ,1000000, 1) &"|"& _
        Random(0 ,1000000, 1) &"|"& _
        Random(0 ,1000000, 1) , $hListView)
    Next
EndFunc
 
Func _SetColWidth($hListView, $iWidth)
    For $i = 0 To 6
        _GUICtrlListView_SetColumnWidth($hListView, $i, $iWidth -3)
    Next
EndFunc

Removing $LVS_EX_DOUBLEBUFFER resolves the issue. I thought I'd take a look to see what it does, but the help file doesn't give any information. $LVS_EX_DOUBLEBUFFER was left over from an earlier edit using an example from the help file => _GUICtrlListView_SortItems. I don't need it afaict. I'm curious why it has no description.

Edited October 16, 2011 by czardas

[czardas]

>>> Please could someone confirm this.

[JohnOne]

It certainly does freeze with that const in, but I have no idea why, is it not something to do with stopping gui flicker?

[czardas]

I don't know. I guess it's one of those MS options that they never bothered to give a description for. Maybe I'm wrong. I also suspect that another control added to the GUI may stop it from freezing. However, I think I ought to report it as a bug. Thanks JoneOne.

Edited October 16, 2011 by czardas

[JohnOne]

Have you seen by M23?

In it he uses some setextendedlistviwestyle func, and I think he explains why in his wiki entry.

[czardas]

Thanks for the link. When I use _GUICtrlListView_SetExtendedListViewStyle it seems to fix the issue. I don't know why that would be. But if I set $LVS_EX_DOUBLEBUFFER as a parameter for the function GUICtrlCreateListView, it breaks.

#include <GUIConstants.au3>
#include <WindowsConstants.au3>
#include <GuiListView.au3>
 
_Run()
 
Func _Run()
    ;$bStyle = BitOR($GUI_SS_DEFAULT_GUI, $WS_MAXIMIZEBOX)
    Local $hGUI = GUICreate(" Test", 400, 300)
    Local $sHeadings = "Col 1|Col 2|Col 3"
    $hListView = GUICtrlCreateListView($sHeadings, 0, 0, 400, 300)
    _GUICtrlListView_SetExtendedListViewStyle($hListView, _
    BitOR($LVS_EX_FULLROWSELECT, $LVS_EX_DOUBLEBUFFER))
 
    _SetData($hListView)
    GUISetState()
 
    While 1
        $msg = GUIGetMsg()
        If $msg = $GUI_EVENT_CLOSE Then ExitLoop
    WEnd
EndFunc
 
Func _SetData($hListView)
    For $i = 0 To 3
        GUICtrlCreateListViewItem( _
        Random(0 ,1000000, 1) &"|"& _
        Random(0 ,1000000, 1) &"|"& _
        Random(0 ,1000000, 1) , $hListView)
    Next
EndFunc

I think I'll wait a while to see if someone else can shed some light on this.

Edited October 16, 2011 by czardas

[Melba23]

czardas,

It seems that some of the $LVS_EX_* styles have the same numerical values as certain $WS_EX_* styles. When you use the $LVS_EX_* styles in the ListView creation line as extended styles, they are interpreted as the $WS_EX_* styles - you need to use _GUICtrlListView_SetExtendedListViewStyle function to get them accepted as the $LVS_EX_* styles. So I imagine you were trying to set some unsupported extended style value which froze the GUI.

Top tip: Only ever set $LVS_EX_* styles using the UDF function - leave the ListView creation line to the $WS_EX_* ones!

M23

[czardas]

Thanks for the tip Melba23. I'm currently just trying out different ideas. There are so many ListView functions that seem to work differently than expected and I find that somewhat confusing, and also a little overwhelming. I'm currently writing some custom functions to hopefully make life a little easier, but it's slow progress.

I understand arrays, so this is what I have so far.

#include <GuiListView.au3>
 
Func _ListViewToArray($hListView)
    Local $iCols = _GUICtrlListView_GetColumnCount($hListView), _
    $iRows = _GUICtrlListView_GetItemCount($hListView)
    Local $aLVData[$iRows][$iCols]
    For $i = 0 To $iRows -1
        For $j = 0 To $iCols -1
            $aLVData[$i][$j] = _GUICtrlListView_GetItemText($hListView, $i, $j)
        Next
    Next
    ;_ArrayDisplay($aLVData)
    Return $aLVData
EndFunc

Edited October 17, 2011 by czardas

[Melba23]

czardas,

You might want to take a look here.

M23

[guinness]

You beat me to it Melba23!

[czardas]

Nice example Guiness.

Okay I'm digressing a little, but I think I'm making progress. After trying out a few examples in the help file I got totally confused: I felt a little dumbstruck when _GUICtrlListView_SetColumnOrder just changed the column headers. Then after looking a little deeper I realized that it is only the display that changes, so saving the changes will also involve saving additional information about the display order, and that's something I wish to avoid for a reason.

I personally think the end user will feel more at ease with just swapping the positions of two columns.at a time, rather than messing around with delimited strings. Now I have three custom functions I can understand.

; Swap two columns in a ListView control
Func _LVCols_Swap($hListView, $iCol1, $iCol2)
    Local $sTemp, $aLVData = _GUICtrlListView_GetColumn($hListView, $iCol1)
    $sTemp = $aLVData[5]
    $aLVData = _GUICtrlListView_GetColumn($hListView, $iCol2)
    _GUICtrlListView_SetColumn($hListView, $iCol2, $sTemp)
    _GUICtrlListView_SetColumn($hListView, $iCol1, $aLVData[5])
 
    Local $iRows = _GUICtrlListView_GetItemCount($hListView)
    For $i = 0 To $iRows
        $sTemp = _GUICtrlListView_GetItemText($hListView, $i, $iCol1)
        _GUICtrlListView_SetItemText($hListView, $i, _
        _GUICtrlListView_GetItemText($hListView, $i, $iCol2), $iCol1)
        _GUICtrlListView_SetItemText($hListView, $i, $sTemp, $iCol2)
    Next
EndFunc ;==> _LVCols_Swap
 
; Justifies column width according to the width of the ListView control... 2nd Param ... $iWidth
; Avoids horizontal scroll bar appearing - Needs further testing
Func _LVCols_Justify($hListView, $iWidth)
    Local $iCols = _GUICtrlListView_GetColumnCount($hListView)
    $iWidth = Floor($iWidth/$iCols)
    Local $iReserve = 0 ; Reserved area for vertical scroll bar
    Do
        $iReserve += 1
    Until $iReserve*$iCols > 20
 
    For $i = 0 To $iCols -1
        _GUICtrlListView_SetColumnWidth($hListView, $i, $iWidth - $iReserve)
    Next
EndFunc ;==> _LVCols_Justify

Edited October 17, 2011 by czardas