| This code the first installment in the TreeView Common Control API series, tackles some of the easier treeview messages - those providing 'special effects' without resorting to owner-drawn controls. The treeview is a special beast ... compared to the listview, in my opinion, a lot more complicated to manipulate via API. Instead of referring to items as simple indices based on order, each treeview item has an item handle, and it is this that is used when manipulating treeview items (see the code for the 'Bold Selected' option). And, like the listview, some changes to items in the control via API are not reflected in VB's internal collection of treeview items, making maintaining the control's API-affected contents and VB's internal-collection contents of the control cumbersome. So we start with the easy ones; ones that don't affect the collection. Windows' common control header contains the definitions of the calls to manipulate aspects of the treeview control. For applying changes to the colours used in the control, the header file defines the methods as : #define TreeView_SetBkColor(hwnd, clr) \ (COLORREF)SNDMSG((hwnd), TVM_SETBKCOLOR, 0, (LPARAM)clr) #define TreeView_SetTextColor(hwnd, clr) \ (COLORREF)SNDMSG((hwnd), TVM_SETTEXTCOLOR, 0, (LPARAM)clr) #define TreeView_GetBkColor(hwnd) \ (COLORREF)SNDMSG((hwnd), TVM_GETBKCOLOR, 0, 0) #define TreeView_GetTextColor(hwnd) \ (COLORREF)SNDMSG((hwnd), TVM_GETTEXTCOLOR, 0, 0) When using methods that need to deal with the control on a per-item basis (as in the Bold method), the header defines a message to return the control item identifier (hTreeItem) relative to a 'passed relationship' (in wParam): #define TreeView_GetNextItem(hwnd, hitem, code) \ (HTREEITEM)SNDMSG((hwnd), TVM_GETNEXTITEM, (WPARAM)code, (LPARAM)(HTREEITEM)(hitem)) These 'relation identifiers' passed in wParam can be one of TVGN_ROOT, TVGN_NEXT, TVGN_PREVIOUS, TVGN_PARENT, TVGN_CHILD, TVGN_FIRSTVISIBLE, TVGN_NEXTVISIBLE, TVGN_PREVIOUSVISIBLE, TVGN_DROPHILITE, and TVGN_CARET. Finally, note that there is no message is identified providing a means to change the colour of the treeview connecting lines or +- signs; these are based on the system setting for 3D objects. This limits the setting of fore/back colours to ones that not only are visually appealing, but provide enough contrast to clearly identify the tree lines. BAS Module Code Place the following code into the general declarations area of a bas module: -------------------------------------------------------------------------------- Option Explicit Public Const GWL_STYLE As Long = (-16) Public Const COLOR_WINDOW As Long = 5 Public Const COLOR_WINDOWTEXT As Long = 8 Public Const TVI_ROOT As Long = &HFFFF0000 Public Const TVI_FIRST As Long = &HFFFF0001 Public Const TVI_LAST As Long = &HFFFF0002 Public Const TVI_SORT As Long = &HFFFF0003 Public Const TVIF_STATE As Long = &H8 'treeview styles Public Const TVS_HASLINES As Long = 2 Public Const TVS_FULLROWSELECT As Long = &H1000 'treeview style item states Public Const TVIS_BOLD As Long = &H10 Public Const TV_FIRST As Long = &H1100 Public Const TVM_GETNEXTITEM As Long = (TV_FIRST + 10) Public Const TVM_GETITEM As Long = (TV_FIRST + 12) Public Const TVM_SETITEM As Long = (TV_FIRST + 13) Public Const TVM_SETBKCOLOR As Long = (TV_FIRST + 29) Public Const TVM_SETTEXTCOLOR As Long = (TV_FIRST + 30) Public Const TVM_GETBKCOLOR As Long = (TV_FIRST + 31) Public Const TVM_GETTEXTCOLOR As Long = (TV_FIRST + 32) Public Const TVGN_ROOT As Long = &H0 Public Const TVGN_NEXT As Long = &H1 Public Const TVGN_PREVIOUS As Long = &H2 Public Const TVGN_PARENT As Long = &H3 Public Const TVGN_CHILD As Long = &H4 Public Const TVGN_FIRSTVISIBLE As Long = &H5 Public Const TVGN_NEXTVISIBLE As Long = &H6 Public Const TVGN_PREVIOUSVISIBLE As Long = &H7 Public Const TVGN_DROPHILITE As Long = &H8 Public Const TVGN_CARET As Long = &H9 Public Type TV_ITEM mask As Long hItem As Long state As Long stateMask As Long pszText As String cchTextMax As Long iImage As Long iSelectedImage As Long cChildren As Long lParam As Long End Type Public Declare Function SendMessage Lib "user32" _ Alias "SendMessageA" _ (ByVal hwnd As Long, _ ByVal wMsg As Long, _ ByVal wParam As Long, _ lParam As Any) As Long Public Declare Function GetWindowLong Lib "user32" _ Alias "GetWindowLongA" _ (ByVal hwnd As Long, _ ByVal nIndex As Long) As Long Public Declare Function SetWindowLong Lib "user32" _ Alias "SetWindowLongA" _ (ByVal hwnd As Long, _ ByVal nIndex As Long, _ ByVal dwNewLong As Long) As Long Public Declare Function GetSysColor Lib "user32" _ (ByVal nIndex As Long) As Long '--end block--' Form Code Add a treeview (TV1), the common dialog control (CommonDialog1), and five command buttons to a form (Command1, Command2, Command3, Command4 and Command5). Add the following code: -------------------------------------------------------------------------------- Option Explicit Private Sub Form_Load() Dim nodX As Node 'add some test items Set nodX = TV1.Nodes.Add(, , "R", "Root") Set nodX = TV1.Nodes.Add("R", tvwChild, "C1", "Child 1") Set nodX = TV1.Nodes.Add("R", tvwChild, "C2", "Child 2") Set nodX = TV1.Nodes.Add("R", tvwChild, "C3", "Child 3") Set nodX = TV1.Nodes.Add("R", tvwChild, "C4", "Child 4") nodX.EnsureVisible Set nodX = TV1.Nodes.Add("C3", tvwChild, "C31", "Child 3 SubC 1") Set nodX = TV1.Nodes.Add("C3", tvwChild, "C32", "Child 3 SubC 2") nodX.EnsureVisible Set nodX = TV1.Nodes.Add("C31", tvwChild, "C321", "Child 3 SubC 1 SubC 1") Set nodX = TV1.Nodes.Add("C4", tvwChild, "C41", "Child 4 Subchild 1") nodX.EnsureVisible Command1.Caption = "Set Background" Command2.Caption = "Set Foreground" Command3.Caption = "Bold Selected" Command4.Caption = "Full Row Select" Command5.Caption = "End" End Sub Private Sub Command5_Click() Unload Me End Sub Private Function GetTVBackColour() As Long Dim clrref As Long Dim hwndTV As Long hwndTV = TV1.hwnd 'try for the treeview backcolor clrref = SendMessage(hwndTV, TVM_GETBKCOLOR, 0, ByVal 0) 'if clrref = -1, then the color is a system color. 'In theory, system colors need to be Or'd with &HFFFFFF 'to retrieve the actual RGB value, but not Or'ing 'seems to work for me. The default system colour for 'a treeview background is COLOR_WINDOW. If clrref = -1 Then clrref = GetSysColor(COLOR_WINDOW) ' Or &HFFFFFF End If 'one way or another, pass it back GetTVBackColour = clrref End Function Private Function GetTVForeColour() As Long Dim clrref As Long Dim hwndTV As Long hwndTV = TV1.hwnd 'try for the treeview text colour clrref = SendMessage(hwndTV, TVM_GETTEXTCOLOR, 0, ByVal 0) 'if clrref = -1, then the color is a system color. 'In theory, system colors need to be Or'd with &HFFFFFF 'to retrieve the actual RGB value, but not Or'ing 'seems to work for me. The default system colour for 'treeview text is COLOR_WINDOWTEXT. If clrref = -1 Then clrref = GetSysColor(COLOR_WINDOWTEXT) ' Or &HFFFFFF End If 'one way or another, pass it back GetTVForeColour = clrref End Function Private Sub SetTVBackColour(clrref As Long) Dim hwndTV As Long Dim style As Long hwndTV = TV1.hwnd 'Change the background Call SendMessage(hwndTV, TVM_SETBKCOLOR, 0, ByVal clrref) 'reset the treeview style so the 'tree lines appear properly style = GetWindowLong(TV1.hwnd, GWL_STYLE) 'if the treeview has lines, temporarily 'remove them so the back repaints to the 'selected colour, then restore If style And TVS_HASLINES Then Call SetWindowLong(hwndTV, GWL_STYLE, style Xor TVS_HASLINES) Call SetWindowLong(hwndTV, GWL_STYLE, style) End If End Sub Private Sub SetTVForeColour(clrref As Long) Dim hwndTV As Long Dim style As Long hwndTV = TV1.hwnd 'Change the background Call SendMessage(hwndTV, TVM_SETTEXTCOLOR, 0, ByVal clrref) 'reset the treeview style so the 'tree lines appear properly style = GetWindowLong(TV1.hwnd, GWL_STYLE) 'if the treeview has lines, temporarily 'remove them so the back repaints to the 'selected colour, then restore If style And TVS_HASLINES Then Call SetWindowLong(hwndTV, GWL_STYLE, style Xor TVS_HASLINES) Call SetWindowLong(hwndTV, GWL_STYLE, style) End If End Sub Private Sub Command1_Click() Dim newclr As Long With CommonDialog1 .Flags = cdlCCRGBInit 'using RGB colours .Color = GetTVBackColour() 'pre-select the current colour .ShowColor 'get the user's choice newclr = .Color 'and assign to a var End With SetTVBackColour newclr 'set the backcolour End Sub Private Sub Command3_Click() Dim TVI As TV_ITEM Dim hitemTV As Long Dim hwndTV As Long 'get the handle to the treeview item. 'If the item is selected, use TVGN_CARET. 'To highlight the first item in the root, use TVGN_ROOT 'To hilight the first visible, use TVGN_FIRSTVISIBLE 'To hilight the selected item, use TVGN_CARET hwndTV = TV1.hwnd hitemTV = SendMessage(hwndTV, TVM_GETNEXTITEM, TVGN_CARET, ByVal 0&) 'if a valid handle get and set the 'item's state attributes If hitemTV > 0 Then With TVI .hItem = hitemTV .mask = TVIF_STATE .stateMask = TVIS_BOLD Call SendMessage(hwndTV, TVM_GETITEM, 0&, TVI) 'flip the bold mask state .state = TVIS_BOLD End With Call SendMessage(hwndTV, TVM_SETITEM, 0&, TVI) End If End Sub Private Sub Command4_Click() Dim hwndTV As Long Dim style As Long 'get the window style style = GetWindowLong(TV1.hwnd, GWL_STYLE) 'toggle the fullrow select If style And TVS_FULLROWSELECT Then style = style Xor TVS_FULLROWSELECT Else: style = style Or TVS_FULLROWSELECT End If 'and set it Call SetWindowLong(TV1.hwnd, GWL_STYLE, style) End Sub Private Sub Command2_Click() Dim newclr As Long With CommonDialog1 .Flags = cdlCCRGBInit 'using RGB colours .Color = GetTVForeColour() 'pre-select the current colour .ShowColor 'get the user's choice newclr = .Color 'and assign to a var End With SetTVForeColour newclr 'set the text colour End Sub '--end block--' Comments Run the project. Selecting either of the colour options will bring up the common dialog. Select a colour - either from the available colours or a custom colour. The appropriate part of the treeview will take the selected colour. If you've installed IE4 (or the newer Java preview), you also have the comctl version required to bold selected items or select using Full Row Select. At this time, there appears to be no means to italicize individual treeview items, change the font of individual items, set individual item colours, or add images as treeview backgrounds without resorting to subclassing and owner-drawing the control. In addition, an apparent bug with this control and the full row select will highlight past the left side of a child if that child is the last item in the treeview, as in the illustration above. |
Applying Special Effects to a TreeView |
Freelance ASP PHP web development | Web developer India Web development India| Prayagasoft - web designer India, Ecommerce developer india, Ecommerce design