Drop Files Components

Contents

• Description
• Compatibility
• Installation
• Known Issues
• Update History
• License and Disclaimer
• About the Author

Description

This unit provides two components that can handle files dragged and dropped from Windows Explorer, along with two additional helper components that can optionally be used to filter the files dropped:

TPJDropFiles

TPJDropFiles provides a window which can accept files dragged and dropped from Windows Explorer. The window takes on the appearance of its parent window, although anything drawn on the parent's canvas is obliterated.

The control can contain child components (in a similar way to TPanel components). Files dropped over any such child component are accepted by the parent TPJDropFiles component. The TPJDropFiles component can be aligned with the form on which it is placed using the Align property.

When files are dropped over this component the OnBeforeDrop event is first triggered. The dropped files are then processed and dropped folders and optionally recursed. Files and folders can be filtered using either by handling the OnFileFilter event or by using the component in association with one of special "filter" components (see below). Once the files have been processed and filtered the OnDropFiles event is triggered. The names of the files are recorded in the Files property and the number of files is held in the Count property.

The point at which the files were dropped is given by the DropPoint property (in coordinates relative to the control). The DropControl property identifies any child control that was under the mouse cursor when the files were dropped.

The window containing the control can optionally be given the focus when files are dropped.

TPJFormDropFiles

TPJFormDropFiles is a non-visual component that enables the form where it is dropped to accept files dragged and dropped from Explorer. Whenever files are dropped anywhere on the form's window, the OnDropFiles event is triggered.

As with TPJDropFiles files can be filtered and the number and names of dropped files, the drop coordinates and any control under the mouse cursor can be found.

The Filters

There are two filter components provided that can be used with either of the above components. They are:

• TPJExtFileFilter - filters files and/or folders according to their file extension.
• TPJWildCardFileFilter - filters file and folders using DOS-like wild cards, using the * and ? wild card characters.

Compatibility

This component is compatible with Delphi 3 to 7 and has been tested with all but v5.

Installation

Installation with Delphi 3 to 7

In these instructions $(DELPHI) is to be taken to represent the path where the appropriate version of Delphi was installed. For example, if you have Delphi 7 installed on the default installation path then $(DELPHI) is equivalent to \Program Files\Borland\Delphi7.

1. Unzip the component's .zip into a folder of your choice, preserving the directory structure.
2. Copy the files PJDropFiles.pas and PJDropFiles.dcr to where you wish to install into Delphi. This will probably be a sub-folder of the $(DELPHI)\lib folder.
3. Install the unit's components and property editor into the palette by chosing the Component | Install Component menu option to display the Install Component dialog box. Then:
   • Select the Into existing package tab.
   • Click the Browse button next to the Unit file name edit box to display the Unit file name dialog box.
   • Select PJDropFiles.pas from the file dialog and click OK to return to the Install Component dialog box.
   • Choose the package into you wish to install from the Package file name drop down list.
   • Click OK.
   • A confirmation dialog box, querying whether it is OK to rebuild and reinstall the package may displayed. Click Yes to proceed.
   • The package will now be built and a dialog box will be displayed stating that the TPJDropFiles, TPJFormDropFiles, TPJExtFileFilter and TPJWidlCardFileFilter components have been installed. Click OK to dismiss the dialog box.
4. You can now delete PJDropFiles.pas from the place where you copied it if you wish (but ensure that the .dcu file is not deleted). The component will appear on a palette called DelphiDabbler. The other code in the unit can be made available simply by use-ing the unit in your projects. You can move the components to a different palette as required.
5. The simplest way to install the help file is to use my Component Help Installer Expert. To install manually, proceed as follows:
   • Copy PJDropFiles.hlp to whichever folder you wish to install it to.
   • In Delphi 3 to 6 (where X is the Delphi version 3..6):
     • Edit DelphiX.ohl (in $(DELPHI)\Help), adding the line :Link PJDropFiles.hlp to the end of the section labelled "Third party help".
     • Edit DelphiX.ohi (in $(DELPHI)\Help), adding the line :Index DelphiDabbler Drop Files=PJDropFiles.hlp towards the end of the index section.
     • Edit DelphiX.cnt (in $(DELPHI)\Help), ensuring that the lines :Include delphiX.ohi and :Include delphiX.ohl appear somewhere in the file.
   • In Delphi 7
     • Edit D7.ohl (in $(DELPHI)\Help), adding the line :Link PJDropFiles.hlp to the end of the section labelled "Third party help".
     • Edit D7.ohi (in $(DELPHI)\Help), adding the line :Index DelphiDabbler Drop Files=PJDropFiles.hlp towards the end of the index section.
     • Edit D7.cnt (in $(DELPHI)\Help), ensuring that the lines :Include d7.ohi and :Include d7.ohl appear somewhere in the file.
   • Using RegEdit open the key HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\Help and add a new string value named PJDropFiles.hlp whose value is the path where you copied the help file (probably ($DELPHI)\Help).
6. The supplied demo programs can be loaded into Delphi and compiled and run as required.

Known Issues

There was a bug in release 2.0 where length of strings containing names of dropped files was being set incorrectly. This was fixed from release 2.0.1.

In v3.0 and v3.1 the DropControl property did not always return the correct control - this was been fixed in v3.2

There was a small memory leak in all release 3 versions. This has been fixed in release 4.0

Update History

Release 4.0 of 12 Apr 2004
PJDropFiles v4.0 of 12 Apr 2004

• Added ability to filter files dropped on the controls, either via the new OnFileFilter event or by using a separate file filter component.
• Added abstract base class for new file filter components.
• Added filter component that filters on file extensions.
• Added filter component that filters file names on wildcards.
• Fixed a memory leak in TPJAbstractDropFilesHelper.Destroy.
• Created component glyphs for new filter components.
• Updated help file.

Release 3.2 of 09 Feb 2004
PJDropFiles v3.2 of 09 Feb 2004

• Fixed bug in code that determines control under drop point that was often returning the parent of the actual control under the cursor.
• Corrected errors and typos in help file.
• Changed to Mozilla public license.

Release 3.1 of 29 Jul 2003
PJDropFiles v3.1 of 29 Jul 2003

• Prevented compiler warnings when compiling the component under Delphi 6 and 7.
• Updated copyright information in help file.

Release 3.0 of 27 Oct 2002
PJDropFiles v3.0 of 27 Oct 2002

• Major update (backwards compatible with v2)
• Added new Options property to determine how dropped files are handled. Options are:
  • to include or exclude folders from list
  • to include or exclude ordinary files from list
  • to add files and/or folders contained in dropped folders and their subfolders.
• Added new OnBeforeDrop event that is triggered before dropped files are processed.
• Added new IsFolder array property that informs if a dropped file is a file or folder.
• Fixed a bug in TPJFormDropFiles that was causing program to halt on exceptions.

Release 2.0.1 of 13 May 2001
PJDropFiles v2.0.1 of 13 May 2001

• Fixed minor bug where strings holding names of dropped files had incorrect length set.

Release 2.0 of 29 Apr 2001
PJDropFiles v2.0 of 29 Apr 2001

• Completely rewrote TPJDropFiles component and added FileName, PassThrough and ForegroundOnDrop properties.
• Added new TPJFormDropFiles component.
• Changed OnDropFiles events so no longer provided drop coordinates: use DropPoint properties instead.
• Rewrote help file for OpenHelp compatibility.
• Broke backwards compatibility with Delph 1.
• Changed unit name from DrpFiles to PJDropFiles.

Release 1.1.1a of 28 Nov 1999
DrpFiles v1.1.1 of 09 Apr 1999

• Updated HTML documentation to include installation notes for Delphi 3/4 and added update history.

Release 1.1.1 of 10 Jul 1999
DrpFiles v1.1.1 of 09 Jul 1999

• Changed installation palette from "Own" to "PJ Stuff".
• Added HTML documentation.

Un-released
DrpFiles v1.1 of 22 Oct 1998

• Changed 2nd parameter to DragQueryFile when used to find number of files dropped from $FFFF to Cardinal(-1) to make it portable across 16 and 32 bit platforms. This was needed to allow the component to compile under Delphi 2.

Un-released
DrpFiles v1.0 of 15 May 1998

• Original version - 16 bit only.

License & Disclaimer

This component is copyright © P.D.Johnson, 1998-2004. It is released under the Mozilla Public License:

Version: MPL 1.1

The contents of this file are subject to the Mozilla Public License Version 1.1 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.mozilla.org/MPL/.

Software distributed under the License is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License for the specific language governing rights and limitations under the License.

The Original Code is Drop Files Components.

The Initial Developer of the Original Code is Peter Johnson (http://www.delphidabbler.com/).

Portions created by the Initial Developer are Copyright © 1997-2003 Peter Johnson. All Rights Reserved.

Contributor(s):

About the Author

I'm Peter Johnson - a hobbyist programmer living in Ceredigion in West Wales, UK. I write mainly in Delphi. My programs are available for download on my web-site: http://www.delphidabbler.com/.

I can be contacted via the website.