Using the Drag-Drop Feature - Win32 Programmer's Reference

Custom Search

Using the Drag-Drop Feature

When an application implements the drag-drop feature, a user can select one or more files in File Manager, drag them to an open application, and drop them there. The application in which the files were dropped receives a message it can use to retrieve the filenames and the coordinates of the point at which the files were dropped.

An application that can accept dropped files from File Manager calls the DragAcceptFiles function for one or more of its windows. When the user releases the mouse button to drop a file or files in the window specified in the call to DragAcceptFiles, File Manager sends the application a WM_DROPFILES message. (File Manager does not send the WM_DROPFILES message to an application unless the application calls DragAcceptFiles.) WM_DROPFILES contains a handle of a structure the application can query to retrieve the name of the dropped file and the coordinates of the cursor when the file was dropped. The application can use the DragQueryFile function to retrieve a count of the files that were dropped and their names. The DragQueryPoint function returns the window coordinates of the cursor when the user released the mouse button.

To free the memory allocated by the system for the WM_DROPFILES message, an application calls the DragFinish function when it is finished.

For example, an application can call the DragAcceptFiles function when it starts and call a drag-drop function when it receives a WM_DROPFILES message, as shown in the following example.

case WM_CREATE:

DragAcceptFiles(hwnd, TRUE);

break;

case WM_DROPFILES:

DragFunc(hwnd, wParam); /* application-defined function */

break;

case WM_DESTROY:

DragAcceptFiles(hwnd, FALSE);

break;

The following example uses the DragQueryPoint function to determine where to begin to write text. The first call to the DragQueryFile function determines the number of dropped files. The loop writes the name of each file, beginning at the point returned by DragQueryPoint.

POINT pt;

WORD cFiles, a;

char lpszFile[80];

DragQueryPoint((HANDLE) wParam, &pt);

cFiles = DragQueryFile((HANDLE) wParam, 0xFFFF, (LPSTR) NULL, 0);

for(a = 0; a < cFiles; pt.y += 20, a++) {

DragQueryFile((HANDLE) wParam, a, lpszFile, sizeof(lpszFile));

TextOut(hdc, pt.x, pt.y, lpszFile, lstrlen(lpszFile));

}

DragFinish((HANDLE) wParam);

Last news from Greatis Software

    Nostalgia .Net     .Net is powerful, but not all-powerful, so sometimes we need to use Win32 API for our .Net applications. It's simple enough with Platform Invoke if you have Win32 skill, but we do not always have time to dig the ancient documentation, declare the special types that are compatible with Win32, find the values of the Win32's constants and so on. Nostalgia .Net offers several simple-to-use classes, and components that will allow you to forget about the headache of Win32 and just use the power of Win32 in your application the same way as you use the native. Net classes. More »

Recommended software for developers

    Ultimate Pack     Component pack for Delphi and C++ Builder that contains runtime form designer, runtime object inspector, print suite and much more for the very special price. More »

    Form Designer .Net     Unique runtime form design solution that allows to edit any form in .Net WinForms application at runtime with full source codes for only 300 euro! More »

    Print Suite .Net     Print Suite .Net is a set of components for easy printing texts, images and grids from your WinForms applications. Full C# source codes are available More »

    Gradient Controls .Net     Gradient Controls .Net offers controls with gradient background feature. Labels, panels and so on... Full C# source codes are available More »

    Greatis iGrid     iGrid plots drawing grid right over your desktop, so you can use it everywhere, with any drawing application without any special plugins for different graphic editors. More »

All the contacts and projects

Dmitry Vasiliev (just.dmitry)

More Online Helps

Win32 Programmer's Reference
Win32 Multimedia Programmer's Reference
OLE Programmer's Reference
Microsoft Windows Pen API Programmer's Reference
Microsoft Windows Sockets 2 Reference
Microsoft Windows Telephony API (TAPI) Programmer's Reference
Unix Manual Pages

greatis just4fun network