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:

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. Once the files have been processed 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 the number and names of dropped files, the drop coordinates and any control under the mouse cursor can be found.

Compatibility

This component has been tested with Delphi 4. It may work correctly in Delphi 2, 3, 5, 6 and 7 but this has not been tested.

Unlike version 1, which included only TPJDropFiles, this version does not work with 16 bit Delphi. The original version continues to be available from my website.

The help file provided with the components is not compatible with Delphi 2.

Existing projects that use the earlier version of TPJDropFiles will need to use the PJDropFiles instead of DrpFiles in order to be recompiled.

Installation

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 2 installed on the default installation path then $(DELPHI) is equivalent to C:\Program Files\Borland\Delphi 2.0.

Installation with Delphi 2

Note that although the provided help file gives information about using the component it cannot be linked into the Delphi 2 environment.

1. Unzip the file pjdropfiles.zip into a folder, preserving the directory structure.
2. Copy the files PJDropFiles.pas and PJDropFiles.dcr to the folder from where you wish to install it into the Delphi Component Palette. This will probably be an existing folder where you keep the library components - say the default $(DELPHI)\lib folder.
3. Start Delphi. Select the Options | Install Components menu option. Click the Add button, then the Browse button and navigate to the PJDropFiles.pas file in the folder where you placed it. Click OK to recompile the components library.
4. You can now delete PJDropFiles.pas from the place where you copied it if you wish. The component will appear on a palette called Delphi Dabbler . You can move the component to a different palette as required, or hack the source code (before installing the component) by finding the Register procedure at the end of the code and changing the string 'PJ stuff' to the name of the required palette.

Installation with Delphi 3 & 4

1. Unzip the file pjdropfiles.zip into a folder.
2. Copy the files PJDropFiles.pas and PJDropFiles.dcr to the folder from where you wish to install the component into the Delphi Component Palette. This will probably be a sub-folder of the $(DELPHI)\lib folder.
3. Install the component into the palette by chosing the Component | Install Component menu option. The following instructions assume you are installing into the default "users components" package:
   • Select the "Into exisiting package" page of the Install Components dialogue box.
   • Browse to the folder where you saved PJDropFiles.pas and select the file.
   • Ensure that the "Package file name" edit box contains $(DELPHI)\lib\dclusrXX.dpk (where XX=30 for Delphi 3 and XX=40 for Delphi 4).
   • Accept that the package will be rebuilt.
   • A dialogue box should be displayed saying that TPJDropFiles and TPJFormDropFiles have been added to the component palette.
4. You can now delete PJDropFiles.pas from the place where you copied it if you wish. The component will appear on a palette called Delphi Dabbler . You can move the component to a different palette as required, or hack the source code (before installing the program) by finding the Register procedure at the end of the code and changing the string 'PJ stuff' to the name of the required palette.
5. The simplest way to install the help file is to use my Component Help Installer Expert, available from my website. To install manually, proceed as follows (where X=3 or 4 depending on the version of Delphi):
   • Copy PJDropFiles.hlp to whichever folder you wish to install it to.
   • Edit DelphiX.cfg (in $(DELPHI)\Help), adding the line :Link PJDropFiles.hlp to the end of the section labelled "Third party help".
   • Edit DelphiX.cnt (in $(DELPHI)\Help), adding the line :Index DelphiDabbler DropFiles Components=PJDropFiles.hlp towards the end of the index section.
   • Using RegEdit open the key HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\Help and add a new string value named PJDropFiles.hlp whose value is the path where you copied the help file (probably ($DELPHI)\Help).

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.

Update History

Un-released
DrpFiles v1.0 of 15/05/1998

• Original version - 16 bit only.

Un-released
DrpFiles v1.1 of 22/10/1998

• 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.

Release 1.1.1 of 10/07/1999
DrpFiles v1.1.1 of 09/04/1999

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

Release 1.1.1a of 28/11/1999
DrpFiles v1.1.1 of 09/04/1999

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

Release 2.0 of 29/04/2001
PJDropFiles v2.0 of 29/04/2001

• 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 2.0.1 of 13/05/2001
PJDropFiles v2.0.1 of 13/05/2001

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

Release 3.0 of 27/10/2002
PJDropFiles v3.0 of 27/10/2002

• 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

License & Disclaimer

This component is copyright © P.D.Johnson, 1998-2001.

The source code and help files can be freely distributed on a not-for-profit basis providing that:

1. the source code is not altered.
2. this readme file is distributed with it unchanged

By not-for-profit I mean that you may recover out of pocket expenses incurred in distributing the code, but should not make a profit from this.

If you discover any bugs in this implementation, or if you have any update suggestions, please contact me on peter.johnson@openlink.org.

Please do modify the code for you own use. I'd like to see any changes you make - I could incorporate them into future versions. Please notify me of changes on at the above e-mail address.

This software is provided as is - no warranty is given as to its suitability for any purposes to which you may wish to put it.

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 by e-mail on peter.johnson@openlink.org.