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iczelion tut19 (转)

原创 IT生活 作者:worldblog 时间:2007-12-09 08:16:41 0 删除 编辑
iczelion tut19 (转)[@more@]

Tutorial 19: Tree View Control


In this tutorial, we will learn how to use tree view control. Moreover, we will also learn how to do drag and drop under tree view control and how to use an image list with it.
DOWNLOAD the example here.

Theory:

A tree view control is a special kind of window that represents objects in hierarchical order. An example of it is the left pane of windows Explorer. You can use this control to show relationships between objects.
You can create a tree view control by calling CreateWindowEx, passing "SysTreeView32" as the class name or you can incorporate it into a dialog box. Don't forget to put InitCommonControls call in your code.
There are several styles specific to the tree view control. These three are the ones mostly used.
    TVS_HASBUTTONS == Displays plus (+) and minus (-) buttons next to parent items. The user clicks the buttons to expand or collapse a parent item's list of child items. To include buttons with items at the root of the tree view, TVS_LINESATROOT must also be specified.
    TVS_HASLINES == Uses lines to show the hierarchy of items.
    TVS_LINESATROOT == Uses lines to link items at the root of the tree-view control. This value is ignored if TVS_HASLINES is not also specified.
The tree view control, like other common controls, communicates with the parent window via messages. The parent window can send various messages to it and the tree view control can send "notification" messages to its parent window. In this regard, the tree view control is not different that any window.
When something interesting occurs to it, it sends a WM_NOTIFY message to the parent window with accompanying information.
    WM_NOTIFY
    wParam == Control ID, this value is not guaranteed to be unique so we don't use it.
      Instead, we use hwndFrom or IDFrom member of the NMHDR structure
      pointed to by lParam
    lParam == Pointer to NMHDR structure. Some controls may pass a pointer to larger
      structure but it must have a NMHDR structure as its first member.
      That is, when you have lParam, you can be sure that it points to a
      NMHDR structure at least.
Next we will examine NMHDR structure.
    NMHDR struct Dword
      hwndFrom  DWORD ?
      idFrom  DWORD ?
      code  DWORD ?
    NMHDR ends
hwndFrom is the window handle of the control that sends this WM_NOTIFY message.
idFrom is the control ID of the control that sends this WM_NOTIFY message.
code is the actual message the control wants to send to the parent window.
Tree view notifications are those with TVN_ at the beginning of the name. Tree view messages are those with TVM_, like TVM_CREATEDRAGIMAGE. The tree view control sends TVN_xxxx in the code member of NMHDR. The parent window can send TVM_xxxx to control it.

Adding items to a tree view control

After you create a tree view control, you can add items to it. You can do this by sending TVM_INSERTITEM to it.
    TVM_INSERTITEM
    wParam = 0;
    lParam = pointer to a TV_INSERTSTRUCT;
You should know some teRminology at this point about the relationship between items in the tree view control.
An item can be parent, child, or both at the same time. A parent item is the item that has some other subitem(s) associated with it. At the same time, the parent item may be a child of some other item. An item without a parent is called a root item. There can be many root items in a tree view control. Now we examine TV_INSERTSTRUCT structure
    TV_INSERTSTRUCT STRUCT DWORD
      hParent  DWORD  ?
      hInsertAfter  DWORD ?
      ITEMTYPE <>
    TV_INSERTSTRUCT ENDS
hParent = Handle to the parent item. If this member is the TVI_ROOT value or NULL, the item is inserted at the root of the tree-view control.
hInsertAfter = Handle to the item after which the new item is to be inserted or one of the following values:
  • TVI_FIRST ==> Inserts the item at the beginning of the list.
  • TVI_LAST ==> Inserts the item at the end of the list.
  • TVI_SORT ==> Inserts the item into the list in alphabetical order.
    ITEMTYPE UNION
      itemex TVITEMEX <>
      item TVITEM <>
    ITEMTYPE ENDS
We will use only TVITEM here.
    TV_ITEM STRUCT DWORD
      imask  DWORD  ?
      hItem  DWORD  ?
      state  DWORD  ?
      stateMask  DWORD  ?
      pszText  DWORD  ?
      cchTextMax  DWORD  ?
      iImage  DWORD  ?
      iselectedImage  DWORD  ?
      cChildren  DWORD  ?
      lParam  DWORD  ?
    TV_ITEM ENDS
This structure is used to send and receive info about a tree view item, depending on messages. For example, with TVM_INSERTITEM, it is used to specify the attribute of the item to be inserted into the tree view control. With TVM_GETITEM, it'll be filled with information about the selected tree view item.
imask is used to specify which member(s) of the TV_ITEM structure is (are) valid. For example, if the value in imask is TVIF_TEXT, it means only the pszText member is valid. You can combine several flags together.
hItem is the handle to the tree view item. Each item has its own handle, like a window handle. If you want to do something with an item, you must select it by its handle.
pszText is the pointer to a null-terminated string that is the label of the tree view item.
cchTextMax is used only when you want to retrieve the label of the tree view item. Because you will supply the pointer to the buffer in pszText, Windows has to know the size of the provided buffer. You have to give the size of the buffer in this member.
iImage and iSelectedImage refers to the index into an image list that contains the images to be shown when the item is not selected and when it's selected. If you recall Windows Explorer left pane, the folder images are specified by these two members.
In order to insert an item into the tree view control, you must at least fill in the hParent, hInsertAfter and you should fill imask and pszText members as well.

Adding images to the tree view control

If you want to put an image to the left of the tree view item's label, you have to create an image list and associate it with the tree view control. You can create an image list by calling ImageList_Create.
    ImageList_Create PROTO cx:DWORD, cy:DWORD, flags:DWORD,
      cInitial:DWORD,  cGrow:DWORD
This function returns the handle to an empty image list if successful.
cx == width of each image in this image list, in pixels.
cy == height of each image in this image list, in pixels. Every image in an image list must be equal to each other in size. If you specify a large bitmap, Windows will use cx and cy to *cut* it into several pieces. So you should prepare your own image as a strip of pictures with identical dimensions.
flags == specify the type of images in this image list whether they are color or monochrome and their color depth. Consult your win32 api reference for more detail
cInitial == The number of images that this image list will initially contain. Windows will use this info to allocate memory for the images.
cGrow == Amount of images by which the image list can grow when the system needs to resize the list to make room for new images. This parameter represents the number of new images that the resized image list can contain.
An image list is not a window! It's only an image deposit for use by other windows.
After an image list is created, you can add images to it by calling ImageList_Add
    ImageList_Add PROTO himl:DWORD, hbmImage:DWORD, hbmMask:DWORD
This function returns -1 if unsuccessful.
himl == the handle of the image list you want to add images to. It is the value returned by a successful call to ImageList_Create
hbmImage == the handle to the bitmap to be added to the image list. You usually store the bitmap in the resource and load it with Loadbitmap call. Note that you don't have to specify the number of images contained in this bitmap because this information is inferred from cx and cy parameters passed to ImageList_Create call.
hbmMask == Handle to the bitmap that contains the mask. If no mask is used with the image list, this parameter is ignored.
Normally, we will add only two images to the image list for use with the tree view control: one that is used when the tree view item is not selected, and the other when the item is selected.
When the image list is ready, you associate it with the tree view control by sending TVM_SETIMAGELIST to the tree view control.
    TVM_SETIMAGELIST
    wParam = type of image list to set. There are two choices:
    • TVSIL_NORMAL Set the normal image list, which contains the selected and unselected images for the tree-view item.
    • TVSIL_STATE Set the state image list, which contains the images for tree-view items that are in a user-defined state.
    lParam = Handle to the image list

Retrieve the info about tree view item

You can retrieve the information about a tree view item by sending TVM_GETITEM message.
    TVM_GETITEM
    wParam = 0
    lParam = pointer to the TV_ITEM structure to be filled with the information
Before you send this message, you must fill imask member with the flag(s) that specifies which member(s) of TV_ITEM you want Windows to fill. And most importantly, you must fill hItem with the handle to the item you want to get information from. And this poses a problem: How can you know the handle of the item you want to retrieve info from? Will you have to store all tree view handles?
The answer is quite simple: you don't have to. You can send TVM_GETNEXTITEM message to the tree view control to retrieve the handle to the tree view item that has the attribute(s) you specified. For example, you can query the handle of the first child item, the root item, the selected item, and so on.
    TVM_GETNEXTITEM
    wParam = flag
    lParam = handle to a tree view item (only necessary for some flag values)
The value in wParam is very important so I present all the flags below:
    • TVGN_CARET Retrieves the currently selected item.
    • TVGN_CHILD Retrieves the first child item of the item specified by the hitem parameter
    • TVGN_DROPHILITE Retrieves the item that is the target of a drag-and-drop operation.
    • TVGN_FIRSTVISIBLE Retrieves the first visible item.
    • TVGN_NEXT Retrieves the next sibling item.
    • TVGN_NEXTVISIBLE Retrieves the next visible item that follows the specified item. The specified item must be visible. Use the TVM_GETITEMRECT message to determine whether an item is visible.
    • TVGN_PARENT Retrieves the parent of the specified item.
    • TVGN_PREVIOUS Retrieves the previous sibling item.
    • TVGN_PREVIOUSVISIBLE Retrieves the first visible item that precedes the specified item. The specified item must be visible. Use the TVM_GETITEMRECT message to determine whether an item is visible.
    • TVGN_ROOT Retrieves the topmost or very first item of the tree-view control.
You can see that, you can retrieve the handle to the tree view item you are interested in from this message. SendMessage returns the handle to the tree view item if successful. You can then fill the returned handle into hItem member of TV_ITEM to be used with TVM_GETITEM message.

Drag and Drop Operation in tree view control

This part is the reason I decided to write this tutorial. When I tried to follow the example in win32 api reference (the win32.hlp from InPrise), I was very frustrated because the vital information is lacking. From trial and error, I finally figured out how to implement drag & drop in a tree view control and I don't want anyone to walk the same path as myself.
Below is the steps in implementing drag & drop operation in a tree view control.
  1. When the user tries to drag an item, the tree view control sends TVN_BEGINDRAG notification to the parent window. You can use this opportunity to create a drag image which is the image that will be used to represent the item while it's being dragged. You can send TVM_CREATEDRAGIMAGE to the tree view control to tell it to create a default drag image from the image that is currently used by the item that will be dragged. The tree view control will create an image list with just one drag image and return the handle to that image list to you.
  2. After the drag image is created, you specify the hotspot of the drag image by calling ImageList_BeginDrag.
      ImageList_BeginDrag PROTO himlTrack:DWORD, 
        iTrack:DWORD ,
        dxHotspot:DWORD,
        dyHotspot:DWORD
      himlTrack is the handle to the image list that contains the drag image.
      iTrack is the index into the image list that specifies the drag image
      dxHotspot specifies the relative distance of the hotspot in horizontal plance in the drag image since this image will be used in place of the mouse cursor, so we need to specify which part of the image is the hotspot.
      dyHotspot specifies the relative distance of the hotspot in the vertical plane.
      Normally, iTrack would be 0 if you tell the tree view control to create the drag image for you. and dxHotspot and dyHotspot can be 0 if you want the left upper corner of the drag image to be the hotspot.
  3. When the drag image is ready to be displayed, we call ImageList_DragEnter to display the drag image in the window.
      ImageList_DragEnter PROTO hwndLock:DWORD, x:DWORD, y:DWORD
      hwndLock is the handle of the window that owns the drag image. The drag image will not be able to move outside that window.
      x and y are the x-and y-coordinate of the place where the drag image should be initially displayed. Note that these values are relative to the left upper corner of the window, not the client area.
  4. Now that the drag image is displayed on the window, you will have to support the drag operation in the tree view control. However, there is a little problem here. We have to monitor the drag path with WM_MOUSEMOVE and the drop location with WM_LBUTTONUP messages. However, if the drag image is over some other child windows, the parent window will never receive any mouse message. The solution is to capture the mouse input with SetCapture. Using the call, the mouse messages will be directed to the specified window regardless of where the mouse cursor is.
  5. Within WM_MOUSEMOVE handler, you will update the drag path with ImageList_DragMove call. This function moves the image that is being dragged during a drag-and-drop operation. Furthermore, if you so desire, you can hilite the item that the drag image is over by sending TVM_HITTEST to check if the drag image is over some item. If it is, you can send TVM_SELECTITEM with TVGN_DROPHILITE flag to hilite that item. Note that before sending TVM_SELECTITEM message, you must hide the drag image first else your drag image will leave ugly traces. You can hide the drag image by calling ImageList_DragShowNolock and, after the hilite operation is finished, call ImageList_DragShowNolock again to show the drag image.
  6. When the user releases the left mouse button, you must do several things. If you hilite an item, you must un-hilite it by sending TVM_SELECTITEM with TVGN_DROPHILITE flag again, but this time, lParam MUST be zero. If you don't un-hilite the item, you will get a strange effect: when you select some other item, that item will be enclosed by a rectangle but the hilite will still be on the last hilited item. Next, you must call ImageList_DragLeave followed by ImageList_EndDrag. You must release the mouse by calling ReleaseCapture. If you create an image list, you must destroy it by calling ImageList_Destroy. After that, you can go on with what your program wants to do when the drag & drop operation is completed.

Code sample:

.386
.model flat,stdcall
option casemap:none
include masm32includewindows.inc
include masm32includeuser32.inc
include masm32includekernel32.inc
include masm32includecomctl32.inc
include masm32includegdi32.inc
includelib masm32libgdi32.lib
includelib masm32libcomctl32.lib
includelib masm32libuser32.lib
includelib masm32libkernel32.lib

WinMain PROTO :DWORD,:DWORD,:DWORD,:DWORD
.const
IDB_TREE equ 4006  ; ID of the bitmap resource
.data
ClassName  db "TreeViewWinClass",0
AppName  db "Tree View Demo",0
TreeViewClass  db "SysTreeView32",0
Parent  db "Parent Item",0
Child1  db "child1",0
Child2  db "child2",0
DragMode  dd FALSE  ; a flag to determine if we are in drag mode

.data?
hInstance  HINSTANCE ?
hwndTreeView dd ?  ; handle of the tree view control
hParent  dd ?  ; handle of the root tree view item
hImageList dd ?  ; handle of the image list used in the tree view control
hDragImageList  dd ?  ; handle of the image list used to store the drag image

.code
start:
  invoke GetModuleHandle, NULL
  mov  hInstance,eax
  invoke WinMain, hInstance,NULL,NULL, SW_SHOWDEFAULT
  invoke ExitProcess,eax
  invoke InitCommonControls

WinMain proc hInst:HINSTANCE,hPrevInst:HINSTANCE,CmdLine:LPSTR,CmdShow:DWORD
  LOCAL wc:WNDCLASSEX
  LOCAL msg:MSG
  LOCAL hwnd:HWND
  mov  wc.cbSize,SIZEOF WNDCLASSEX
  mov  wc.style, CS_HREDRAW or CS_VREDRAW
  mov  wc.lpfnWndProc, OFFSET WndProc
  mov  wc.cbClsExtra,NULL
  mov  wc.cbWndExtra,NULL
  push  hInst
  pop  wc.hInstance
  mov  wc.hbrBackground,COLOR_APPWORKSPACE
  mov  wc.lpszMenuName,NULL
  mov  wc.lpszClassName,OFFSET ClassName
  invoke LoadIcon,NULL,IDI_APPLICATION
  mov  wc.hIcon,eax
  mov  wc.hIconSm,eax
  invoke LoadCursor,NULL,IDC_ARROW
  mov  wc.hCursor,eax
  invoke RegisterClassEx, addr wc
  invoke CreateWindowEx,WS_EX_CLIENTEDGE,ADDR ClassName,ADDR AppName,  WS_OVERLAPPED+WS_CAPTION+WS_SYSMENU+WS_MINIMIZEBOX+WS_MAXIMIZEBOX+WS_VISIBLE,CW_USEDEFAULT,
  CW_USEDEFAULT,200,400,NULL,NULL,
  hInst,NULL
  mov  hwnd,eax
  .while TRUE
  invoke GetMessage, ADDR msg,NULL,0,0
  .BREAK .IF (!eax)
  invoke TranslateMessage, ADDR msg
  invoke DispatchMessage, ADDR msg
  .endw
  mov eax,msg.wParam
  ret
WinMain endp

WndProc proc uses edi hWnd:HWND, uMsg:UINT, wParam:WPARAM, lParam:LPARAM
  LOCAL tvinsert:TV_INSERTSTRUCT
  LOCAL hBitmap:DWORD
  LOCAL tvhit:TV_HITTESTINFO
  .if uMsg==WM_CREATE
  invoke CreateWindowEx,NULL,ADDR TreeViewClass,NULL,
  WS_CHILD+WS_VISIBLE+TVS_HASLINES+TVS_HASBUTTONS+TVS_LINESATROOT,0,
  0,200,400,hWnd,NULL,
  hInstance,NULL  ; Create the tree view control
  mov hwndTreeView,eax
  invoke ImageList_Create,16,16,ILC_COLOR16,2,10  ; create the associated image list
  mov hImageList,eax
  invoke LoadBitmap,hInstance,IDB_TREE  ; load the bitmap from the resource
  mov hBitmap,eax
  invoke ImageList_Add,hImageList,hBitmap,NULL  ; Add the bitmap into the image list
  invoke DeleteObject,hBitmap  ; always delete the bitmap resource
  invoke SendMessage,hwndTreeView,TVM_SETIMAGELIST,0,hImageList
  mov tvinsert.hParent,NULL
  mov tvinsert.hInsertAfter,TVI_ROOT
  mov tvinsert.item.imask,TVIF_TEXT+TVIF_IMAGE+TVIF_SELECTEDIMAGE
  mov tvinsert.item.pszText,offset Parent
  mov tvinsert.item.iImage,0
  mov tvinsert.item.iSelectedImage,1
  invoke SendMessage,hwndTreeView,TVM_INSERTITEM,0,addr tvinsert
  mov hParent,eax
  mov tvinsert.hParent,eax
  mov tvinsert.hInsertAfter,TVI_LAST
  mov tvinsert.item.pszText,offset Child1
  invoke SendMessage,hwndTreeView,TVM_INSERTITEM,0,addr tvinsert
  mov tvinsert.item.pszText,offset Child2
  invoke SendMessage,hwndTreeView,TVM_INSERTITEM,0,addr tvinsert
  .elseif uMsg==WM_MOUSEMOVE
  .if DragMode==TRUE
  mov eax,lParam
  and eax,0ffffh
  mov ecx,lParam
  shr ecx,16
  mov tvhit.pt.x,eax
  mov tvhit.pt.y,ecx
  invoke ImageList_DragMove,eax,ecx
  invoke ImageList_DragShowNolock,FALSE
  invoke SendMessage,hwndTreeView,TVM_HITTEST,NULL,addr tvhit
  .if eax!=NULL
  invoke SendMessage,hwndTreeView,TVM_SELECTITEM,TVGN_DROPHILITE,eax
  .endif
  invoke ImageList_DragShowNolock,TRUE
  .endif
  .elseif uMsg==WM_LBUTTONUP
  .if DragMode==TRUE
  invoke ImageList_DragLeave,hwndTreeView
  invoke ImageList_EndDrag
  invoke ImageList_Destroy,hDragImageList
  invoke SendMessage,hwndTreeView,TVM_GETNEXTITEM,TVGN_DROPHILITE,0
  invoke SendMessage,hwndTreeView,TVM_SELECTITEM,TVGN_CARET,eax
  invoke SendMessage,hwndTreeView,TVM_SELECTITEM,TVGN_DROPHILITE,0
  invoke ReleaseCapture
  mov DragMode,FALSE
  .endif
  .elseif uMsg==WM_NOTIFY
  mov edi,lParam
  assume edi:ptr NM_TREEVIEW
  .if [edi].hdr.code==TVN_BEGINDRAG
  invoke SendMessage,hwndTreeView,TVM_CREATEDRAGIMAGE,0,[edi].itemNew.hItem
  mov hDragImageList,eax
  invoke ImageList_BeginDrag,hDragImageList,0,0,0
  invoke ImageList_DragEnter,hwndTreeView,[edi].ptDrag.x,[edi].ptDrag.y
  invoke SetCapture,hWnd
  mov DragMode,TRUE
  .endif
  assume edi:nothing
  .elseif uMsg==WM_DESTROY
  invoke PostQuitMessage,NULL
  .else
  invoke DefWindowProc,hWnd,uMsg,wParam,lParam
  ret
  .endif
  xor eax,eax
  ret
WndProc endp
end start

Analysis:

Within WM_CREATE handler, you create the tree view control
      invoke CreateWindowEx,NULL,ADDR TreeViewClass,NULL,
      WS_CHILD+WS_VISIBLE+TVS_HASLINES+TVS_HASBUTTONS+TVS_LINESATROOT,0,
      0,200,400,hWnd,NULL,
      hInstance,NULL
Note the styles. TVS_xxxx are the tree view specific styles.
      invoke ImageList_Create,16,16,ILC_COLOR16,2,10
      mov hImageList,eax
      invoke LoadBitmap,hInstance,IDB_TREE
      mov hBitmap,eax
      invoke ImageList_Add,hImageList,hBitmap,NULL
      invoke DeleteObject,hBitmap
      invoke SendMessage,hwndTreeView,TVM_SETIMAGELIST,0,hImageList
Next, you create an empty image list with will accept images of 16x16 pixels in size, 16-bit color and initially, it will contain 2 images but can be expanded to 10 if need arises. We then load the bitmap from the resource and add it to the image list just created. After that, we delete the handle to the bitmap since it will not be used anymore. When the image list is all set, we associate it with the tree view control by sending TVM_SETIMAGELIST to the tree view control.
      mov tvinsert.hParent,NULL
      mov tvinsert.hInsertAfter,TVI_ROOT
      mov tvinsert.u.item.imask,TVIF_TEXT+TVIF_IMAGE+TVIF_SELECTEDIMAGE
      mov tvinsert.u.item.pszText,offset Parent
      mov tvinsert.u.item.iImage,0
      mov tvinsert.u.item.iSelectedImage,1
      invoke SendMessage,hwndTreeView,TVM_INSERTITEM,0,addr tvinsert
We insert items into the tree view control, beginning from the root item. Since it will be root item, hParent member is NULL and hInsertAfter is TVI_ROOT. imask member specifies that pszText, iImage and iSelectedImage members of the TV_ITEM structure is valid. We fill those three members with appropriate value. pszText contains the label of the root item, iImage is the index into the image in the image list that will be displayed to the left of the unselected item, and iSelectedImage is the index into the image in the image list that will be displayed when the item is selected. When all appropriate members are filled in, we send TVM_INSERTITEM message to the tree view control to add the root item to it.
      mov hParent,eax
      mov tvinsert.hParent,eax
      mov tvinsert.hInsertAfter,TVI_LAST
      mov tvinsert.u.item.pszText,offset Child1
      invoke SendMessage,hwndTreeView,TVM_INSERTITEM,0,addr tvinsert
      mov tvinsert.u.item.pszText,offset Child2
      invoke SendMessage,hwndTreeView,TVM_INSERTITEM,0,addr tvinsert
After the root item is added, we can attach the child items to it. hParent member is now filled with the handle of the parent item. And we will use identical images in the image list so we don't change iImage and iSelectedImage member.
      .elseif uMsg==WM_NOTIFY
      mov edi,lParam
      assume edi:ptr NM_TREEVIEW
      .if [edi].hdr.code==TVN_BEGINDRAG
      invoke SendMessage,hwndTreeView,TVM_CREATEDRAGIMAGE,0,[edi].itemNew.hItem
      mov hDragImageList,eax
      invoke ImageList_BeginDrag,hDragImageList,0,0,0
      invoke ImageList_DragEnter,hwndTreeView,[edi].ptDrag.x,[edi].ptDrag.y
      invoke SetCapture,hWnd
      mov DragMode,TRUE
      .endif
      assume edi:nothing
Now when the user tries to drag an item, the tree view control sends WM_NOTIFY message with TVN_BEGINDRAG as the code. lParam is the pointer to an NM_TREEVIEW structure which contains several pieces of information we need so we put its value into edi and use edi as the pointer to NM_TREEVIEW structure. assume edi:ptr NM_TREEVIEW is a way to tell MASM to treat edi as the pointer to NM_TREEVIEW structure. We then create a drag image by sending TVM_CREATEDRAGIMAGE to the tree view control. It returns the handle to the newly created image list with a drag image inside. We call ImageList_BeginDrag to set the hotspot in the drag image. Then we enter the drag operation by calling ImageList_DragEnter. This function displays the drag image at the specified location in the specified window. We use ptDrag structure that is a member of NM_TREEVIEW structure as the point where the drag image should be initially displayed.After that, we capture the mouse input and set the flag to indicate that we now enter drag mode.
      .elseif uMsg==WM_MOUSEMOVE
      .if DragMode==TRUE
      mov eax,lParam
      and eax,0ffffh
      mov ecx,lParam
      shr ecx,16
      mov tvhit.pt.x,eax
      mov tvhit.pt.y,ecx
      invoke ImageList_DragMove,eax,ecx
      invoke ImageList_DragShowNolock,FALSE
      invoke SendMessage,hwndTreeView,TVM_HITTEST,NULL,addr tvhit
      .if eax!=NULL
      invoke SendMessage,hwndTreeView,TVM_SELECTITEM,TVGN_DROPHILITE,eax
      .endif
      invoke ImageList_DragShowNolock,TRUE
      .endif
Now we concentrate on WM_MOUSEMOVE. When the user drags the drag image along, our parent window receives WM_MOUSEMOVE messages. In response to these messages, we update the drag image position with ImageList_DragMove. After that, we check if the drag image is over some item. We do that by sending TVM_HITTEST message to the tree view control with a point for it to check. If the drag image is over some item, we hilite that item by sending TVM_SELECTITEM message with TVGN_DROPHILITE flag to the tree view control. During the hilite operation, we hide the drag image so that it will not leave unsightly blots on the tree view control.
      .elseif uMsg==WM_LBUTTONUP
      .if DragMode==TRUE
      invoke ImageList_DragLeave,hwndTreeView
      invoke ImageList_EndDrag
      invoke ImageList_Destroy,hDragImageList
      invoke SendMessage,hwndTreeView,TVM_GETNEXTITEM,TVGN_DROPHILITE,0
      invoke SendMessage,hwndTreeView,TVM_SELECTITEM,TVGN_CARET,eax
      invoke SendMessage,hwndTreeView,TVM_SELECTITEM,TVGN_DROPHILITE,0
      invoke ReleaseCapture
      mov DragMode,FALSE
      .endif
When the user releases the left mouse button, the drag operation is at the end. We leave the drag mode by calling ImageList_DragLeave, followed by ImageList_EndDrag and ImageList_Destroy. To make the tree view items look good, we also check the last hilited item, and select it. We must also un-hilite it else the other items will not get hilited when they are selected. And lastly, we release the mouse capture.

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