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Thanks to Roberto Valois for his Virtual ListView program posted
in the source code forum July 26, 2001. With this elegant technique
the time otherwise used for filling the total listview grid with data
is eliminated. Only the lines presented in the listview window at
any one time are just being picked by listview when needed. This
is a major advantage with large amounts of data.
Another issue affecting performance speed of listview (virtual or
not) is the number of subitems or columns. With many columns the
scrolling speed is markedly reduced. The listview (virtual or
not) seems to process each entire row even if only few of the
subitems are actually being displayed at any one time.
The question is: How can you limit the listview processing to
displayed subitems and thereby improve the scrolling performance?
Regards,
Erik
[email protected]
The code below, which is a shortened version of the program of
Roberto Valois, illustrates the slow scrolling performance
(the column number is set to 234 which seems to be the maximum
allowed).
[email protected]
------------------
[This message has been edited by Erik Christensen (edited August 18, 2001).]
in the source code forum July 26, 2001. With this elegant technique
the time otherwise used for filling the total listview grid with data
is eliminated. Only the lines presented in the listview window at
any one time are just being picked by listview when needed. This
is a major advantage with large amounts of data.
Another issue affecting performance speed of listview (virtual or
not) is the number of subitems or columns. With many columns the
scrolling speed is markedly reduced. The listview (virtual or
not) seems to process each entire row even if only few of the
subitems are actually being displayed at any one time.
The question is: How can you limit the listview processing to
displayed subitems and thereby improve the scrolling performance?
Regards,
Erik
[email protected]
The code below, which is a shortened version of the program of
Roberto Valois, illustrates the slow scrolling performance
(the column number is set to 234 which seems to be the maximum
allowed).
Code:
#DIM ALL
#COMPILE EXE
#INCLUDE "WIN32API.INC"
#INCLUDE "COMMCTRL.INC"
%ID_LISTVIEW = 300
'
' **********************
' You can change this to lower values to see the effect on scrolling performance
' Try for example %COLUMN_COUNT = 5 and see the difference.
%COLUMN_COUNT = 234
' **********************
%ITEM_COUNT = 20000 ' This number does not affect scrolling performance
'
DECLARE FUNCTION InitApplication() AS LONG
DECLARE FUNCTION InitInstance(LONG) AS LONG
DECLARE FUNCTION MainWndProc(BYVAL LONG, BYVAL LONG, BYVAL LONG, BYVAL LONG) AS LONG
DECLARE FUNCTION ListViewNotify(BYVAL LONG, BYVAL LONG) AS LONG
DECLARE FUNCTION CreateListView(BYVAL LONG, BYVAL DWORD) AS LONG
DECLARE SUB ResizeListView(BYVAL LONG, BYVAL LONG)
DECLARE SUB InitListView(BYVAL LONG)
DECLARE FUNCTION MakeFont(Font AS ASCIIZ, Charset AS LONG, Bold AS LONG, Italic AS LONG, PointSize AS LONG) AS LONG
'*******************************************************************************
GLOBAL g_hInst AS LONG
GLOBAL g_szClassName AS ASCIIZ * 32
GLOBAL hFont AS LONG
'*******************************************************************************
FUNCTION WINMAIN (BYVAL hInstance AS LONG, _
BYVAL hPrevInstance AS LONG, _
lpCmdLine AS ASCIIZ PTR, _
BYVAL nCmdShow AS LONG) AS LONG
LOCAL Msg AS tagMSG
LOCAL i AS LONG, j AS LONG
LOCAL InitCommCtrl AS INIT_COMMON_CONTROLSEX
g_hInst = hInstance
IF (ISFALSE(InitApplication())) THEN
FUNCTION = %False
EXIT FUNCTION
END IF
InitCommCtrl.dwICC = %ICC_LISTVIEW_CLASSES
InitCommCtrl.dwSize = SIZEOF(InitCommCtrl)
InitCommonControlsEx InitCommCtrl
IF (ISFALSE(InitInstance(nCmdShow))) THEN
FUNCTION = %False
EXIT FUNCTION
END IF
WHILE GetMessage(Msg, %NULL, 0, 0)
TranslateMessage Msg
DispatchMessage Msg
WEND
FUNCTION = msg.wParam
END FUNCTION
'*******************************************************************************
FUNCTION InitApplication() AS LONG
LOCAL wcex AS WNDCLASSEX
g_szClassName = "GridClass"
wcex.cbSize = SIZEOF(wcex)
wcex.style = 0
wcex.lpfnWndProc = CODEPTR( MainWndProc )
wcex.cbClsExtra = 0
wcex.cbWndExtra = 0
wcex.hInstance = g_hInst
wcex.hCursor = LoadCursor( %NULL, BYVAL %IDC_ARROW )
wcex.hbrBackground = GetStockObject( %WHITE_BRUSH )
wcex.lpszMenuName = %NULL
wcex.lpszClassName = VARPTR( g_szClassName )
wcex.hIcon = LoadIcon( %NULL, BYVAL %IDI_APPLICATION )
wcex.hIconSm = LoadIcon( %NULL, BYVAL %IDI_APPLICATION )
FUNCTION = RegisterClassEx (wcex)
END FUNCTION
'*******************************************************************************
FUNCTION InitInstance(nCmdShow AS LONG) AS LONG
LOCAL hWnd AS LONG
LOCAL szTitle AS ASCIIZ * 64
szTitle = "Grid.bas - Virtual ListView Sample with Fonts and Colors"
hWnd = CreateWindowEx( 0, _
g_szClassName, _
szTitle, _
%WS_OVERLAPPEDWINDOW, _
%CW_USEDEFAULT, _
%CW_USEDEFAULT, _
%CW_USEDEFAULT, _
%CW_USEDEFAULT, _
BYVAL %NULL, _
BYVAL %NULL, _
g_hInst, _
BYVAL %NULL)
IF (ISFALSE(hWnd)) THEN
FUNCTION = %False
EXIT FUNCTION
END IF
ShowWindow hWnd, nCmdShow
UpdateWindow hWnd
FUNCTION = %True
END FUNCTION
'*******************************************************************************
FUNCTION MainWndProc ( BYVAL hWnd AS LONG, _
BYVAL uMessage AS LONG, _
BYVAL wParam AS LONG, _
BYVAL lParam AS LONG) EXPORT AS LONG
STATIC hwndListView AS LONG
LOCAL pnmh AS NMHDR PTR
SELECT CASE uMessage
CASE %WM_CREATE
hwndListView = CreateListView(hWnd, %ID_LISTVIEW)
InitListView hwndListView
hFont =MakeFont ("Times New Roman", %ANSI_CHARSET, %FW_BOLD, %False, 12)
CASE %WM_NOTIFY
pnmh = lParam
IF @pnmh.idFrom = %ID_LISTVIEW THEN
FUNCTION = ListViewNotify(@pnmh.hwndFrom, lParam)
END IF
EXIT FUNCTION
CASE %WM_SIZE
ResizeListView hwndListView, hWnd
CASE %WM_COMMAND
SELECT CASE LOWRD(wParam)
END SELECT
CASE %WM_DESTROY
PostQuitMessage 0
END SELECT
FUNCTION = DefWindowProc(hWnd, uMessage, wParam, lParam)
END FUNCTION
'*******************************************************************************
FUNCTION CreateListView( BYVAL hwndParent AS LONG, _
BYVAL ListViewID AS DWORD) AS LONG
LOCAL dwStyle AS DWORD
LOCAL dwExStyle AS DWORD
LOCAL hwndListView AS LONG
dwStyle = %WS_TABSTOP OR _
%WS_CHILD OR _
%WS_BORDER OR _
%WS_VISIBLE OR _
%LVS_AUTOARRANGE OR _
%LVS_REPORT OR _
%LVS_OWNERDATA 'Virtual ListView will request for items when needed
'through %LVN_GETDISPINFO message
hwndListView = CreateWindowEx ( %WS_EX_CLIENTEDGE, _
$WC_LISTVIEW, _
"", _
dwStyle, _
0, _
0, _
0, _
0, _
hwndParent, _
ListViewID, _
g_hInst, _
BYVAL %NULL )
IF (ISFALSE(hwndListView)) THEN
FUNCTION = %NULL
EXIT FUNCTION
END IF
ResizeListView hwndListView, hwndParent
dwExStyle = %LVS_EX_GRIDLINES OR %LVS_EX_FULLROWSELECT
ListView_SetExtendedListViewStyleEx hwndListView, dwExStyle, dwExStyle
FUNCTION = hwndListView
END FUNCTION
'*******************************************************************************
SUB ResizeListView( BYVAL hwndListView AS LONG, _
BYVAL hwndParent AS LONG)
LOCAL rc AS RECT
GetClientRect hwndParent, rc
MoveWindow hwndListView, _
rc.nleft, _
rc.ntop, _
rc.nright - rc.nleft, _
rc.nbottom - rc.ntop, _
%TRUE
END SUB
'*******************************************************************************
SUB InitListView (BYVAL hwndListView AS LONG)
LOCAL lvColumn AS LV_COLUMN
LOCAL i AS LONG
LOCAL szString AS ASCIIZ * 16
lvColumn.fmt = %LVCFMT_LEFT
lvColumn.cx = 130
lvColumn.mask = %LVCF_FMT OR _
%LVCF_WIDTH OR _
%LVCF_TEXT OR _
%LVCF_SUBITEM
FOR i = 0 TO %COLUMN_COUNT
szString = "Column " & STR$(i)
lvColumn.pszText = VARPTR(szString)
ListView_InsertColumn hwndListView, i, lvColumn
NEXT i
ListView_DeleteAllItems hwndListView
ListView_SetItemCountEx hwndListView, %ITEM_COUNT, %LVSICF_NOINVALIDATEALL
END SUB
'*******************************************************************************
FUNCTION ListViewNotify( BYVAL hwndListView AS LONG, _
BYVAL lParam AS LONG) AS LONG
LOCAL pnmh AS NMHDR PTR
LOCAL lpLVDispInfo AS LV_DISPINFO PTR
LOCAL row AS LONG, column AS LONG
LOCAL lplvcd AS NMLVCUSTOMDRAW PTR
LOCAL szString AS ASCIIZ * 256
pnmh = lParam
SELECT CASE @pnmh.code
CASE %NM_CUSTOMDRAW ' = -12
lplvcd = lParam
IF(@lplvcd.nmcd.dwDrawStage = %CDDS_PREPAINT) THEN
FUNCTION = %CDRF_NOTIFYITEMDRAW
EXIT FUNCTION
END IF
IF(@lplvcd.nmcd.dwDrawStage = %CDDS_ITEMPREPAINT) THEN
' IF (@lplvcd.nmcd.dwItemSpec MOD 2) = 0 THEN
' SelectObject @lplvcd.nmcd.hdc, hFont 'Item Font
' ELSE
' @lplvcd.clrTextBk = RGB(200,200,200) 'Item Text Background Color
' @lplvcd.clrText = RGB(128,0,0) 'Item Text Color
' END IF
FUNCTION = %CDRF_NEWFONT 'Return CDRF_NOTIFYSUBITEMREDRAW
'to customize the item's subitems individually then
'case CDDS_SUBITEM | CDDS_ITEMPREPAINT
EXIT FUNCTION
END IF
CASE %LVN_GETDISPINFO '= -150 'Virtual ListView ask for Item text
lpLVDispInfo = lParam
IF (@lpLVDispInfo.item.mask AND %LVIF_TEXT) THEN
szString = "Item " & STR$(@lpLVDispInfo.item.iItem) & _
" - Column " & STR$(@lpLVDispInfo.item.iSubItem)
@lpLVDispInfo.item.pszText = VARPTR(szString)
END IF
CASE %LVN_ODCACHEHINT
END SELECT
FUNCTION = 0
END FUNCTION
'*******************************************************************************
FUNCTION MakeFont(Font AS ASCIIZ, Charset AS LONG, Bold AS LONG, Italic AS LONG, PointSize AS LONG) AS LONG
LOCAL hDC AS LONG
LOCAL CyPixels AS LONG
hDC = GetDC(%HWND_DESKTOP)
CyPixels = GetDeviceCaps(hDC, %LOGPIXELSY)
ReleaseDC %HWND_DESKTOP, hDC
FUNCTION = CreateFont(MulDiv(PointSize, CyPixels, 72), 0, 0, 0, Bold, Italic, 0, 0, _
CharSet, %OUT_TT_PRECIS, %CLIP_DEFAULT_PRECIS, %DEFAULT_QUALITY, %FF_DONTCARE, Font)
END FUNCTION
------------------
[This message has been edited by Erik Christensen (edited August 18, 2001).]
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