Drop Files Components
Information Sheet

Contents

• Overview
• Compatibility
• Installation
• Bugs
• Change log
• License
• About the author

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Overview

Two components are provided that enable applications to support Windows Explorer file drag and drop. The components are:

• TPJDropFiles
  This windowed component catches files dropped anywhere over its window. It can act as a container for other components.
• TPFormDropFiles
  This non-visual component catches files dropped anywhere on its form, including the non-client areas.
• TPJCtrlDropFiles
  This non-visual component catches files dropped on an associated TWinControl or TFrame.

Key features of these components are:

• An OnDropFiles event is triggered when files are dropped.
• The names of dropped files are made available through the Files array property. For convenience, the name of the first file is also stored in the FileName property.
• The list of dropped files can be configured to include only files, only folders or all files and folders.
• Dropped folders can be recursed so that all the files and sub-folders in each of the dropped folders are listed.
• Filters can be applied to the dropped files and folders. This is done in one of two ways:
  • By handling the OnFileFilter event and deciding which files and folders to pass through the filter.
  • By linking the drop file component to a special file filter component, derived from the abstract TPJFileFilter. In this case the dropped files are automatically filtered by the filter component. Two filter components are provided: TPJExtFileFilter that filters according to file extensions and TPJWildCardFileFilter that filters using DOS-style wildcards. Developers can create further filter components by deriving from TPJFileFilter.
• The mouse co-ordinates where the files were dropped can be retrieved, as can a reference to any control under the mouse cursor at the time.
• The OnBeforeDrop event can be used to do pre-processing before the files are actually dropped.
• The IsFolder array property tells if an equivalent item in the Files list is a file or a folder.
• The owning window can be brought to the front when files are dropped.
• Some design time assistance is provided by component and property editors.

Help file

An OpenHelp compatible help file is included that integrates with Delphi 3 to 7. The help file does not integrate with Delphi 2005 and later, but can be used as a stand-alone help file with some loss of functionality. An a-link keyword file is supplied for use with Delphi 6 and 7.

Demo programs

The source code for two demo programs is included. Details are:

1. The main demo program exercises all three drop files components and the filter components. This demo compiles with all the compilers supported by the components.
2. A program that demonstrates how to use TPJCtrlDropFiles with frames. This demo requires Delphi 5 or later to compile, since frames are not supported in Delphi 3 or 4.

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Compatibility

The Drop Files Components compile with Delphi 3 and later. They have been tested with Delphi 3, 4, 6, 7 and 2006.

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Installation

The Drop Files Components, their documentation and the demo program are supplied in a zip file. Before installing you need to extract all the files from the zip file, preserving the directory structure. The following files will be extracted:

• PJDropFiles.pas – component source code.
• PJDropFiles.dcr – resource file containing component palette glyphs.
• PJDropFilesDsgn.pas – source file for component registration and component and property editors.
• PJDropFilesDsgn.dfm – property editor form.
• PJDropFiles.hlp – component help file that integrates with the Delphi 3 to 7 OpenHelp system.
• PJDropFiles.als – a-link keyword file for integration with the Delphi 6 or 7 OpenHelp system.
• ReadMe.htm – this file.
• ChangeLog.txt – component's change log.
• Demo\DelphiDabbler.ico – DelphiDabbler icon used by demo programs.
• Demo\1\DropFilesDemo.dpr – main demo project file.
• Demo\1\DropFilesDemo.res – icon resource for main demo.
• Demo\1\FmDropFilesDemo.pas – main demo form source file.
• Demo\1\FmDropFilesDemo.dfm – main demo form file.
• Demo\2\FrameDemo.dpr – frame demo project file.
• Demo\2\FrameDemo.res – icon resource for frame demo.
• Demo\2\FmFrameDemo.pas – frame demo form source file.
• Demo\2\FmFrameDemo.dfm – frame demo form file.
• Demo\2\FrDemo.pas – frame demo frame source file.
• Demo\2\FrDemo.dfm – frame demo frame file.

You can now proceed to install the components and property editor using the emphasised files above. Installation methods vary between Delphi versions, so follow the instructions that apply to your version below. Note that $(DELPHI) represents the path where the appropriate version of Delphi was installed. Similarly $(BDS) refers to the installation path of a version of the Borland Development System.

• Installation with Delphi 2005 & 2006
• Installation with Delphi 3 to 7

Installation with Delphi 2005 & 2006

The components must be installed into a Delphi Win32 design package. It is assumed that you will be installing into an existing package. You may decide to install into the "user" package: $(BDS)\Lib\dclusr.dpk.

1. Decide upon a suitable location into which to install the components. This may be a subdirectory of your Borland Studio Projects or $(BDS)\lib folders.
2. Copy PJDropFiles.pas, PJDropFiles.dcr, PJDropFilesDsgn.pas and PJDropFilesDsgn.dfm to the chosen installation folder.
3. Start the Development System (selecting the Delphi Win32 personality if appropriate) then:
   • Open the required package. Select File | Open menu and choose a suitable package source file.
   • The package will now be displayed in the Project Manager with a .bpl extension. Right click the package's entry and select Add to display the Add dialog box. Enter the full path to PJDropFiles.pas in the Unit file name edit box (use the Browse button to navigate to the file). Click OK to add the component to the package.
   • Repeat the previous step for PJDropFilesDsgn.pas.
   • Back in the Project Manager, check that all the added files appear under the package's Contains node. If so, right click the package's entry again and select Compile. If the resulting compilation succeeds a message should be displayed confirming that TPJDropFiles, TPJFormDropFiles, TPJExtFileFilter and TPJWildCardFileFilter have been registered. The components should now appear in the "DelphiDabbler" section of the Tool Palette. (Note this will only appear when a form is selected in the designer).
   • If the components do not appear the package may not have been installed. Install it from the Project Manager by selecting the package's Install right click menu option.
   • Close the package project using the File | Close menu item. Accept any prompt that offers to save the package project.
4. If you wish you can now delete PJDropFiles.pas and PJDropFilesDsgn.pas from the chosen installation folder.
5. The supplied help file cannot be integrated with the IDE's help system. However it can be used independently of the IDE, albeit with reduced functionality.
6. The demo programs can be loaded into Delphi and compiled and run as required.

Installation with Delphi 3 to 7

The components must be installed into a design package. It is assumed that you will be installing into an existing package. You may wish to use the "user" package named dclusr.dpk or dclusrXX.dpk (where XX is a version number). This package can be found in $(DELPHI)\Lib.

1. Decide upon a suitable location into which to install the components. This may be a subdirectory of your $(DELPHI)\lib folder.
2. Copy PJDropFiles.pas, PJDropFiles.dcr, PJDropFilesDsgn.pas and PJDropFilesDsgn.dfm to the chosen installation folder.
3. Start Delphi then:
   • Choose the Component | Install Component menu option to display the Install Component dialog box. Ensure the Into existing package tab is selected. Enter the full path to PJDropFiles.pas in the Unit file name edit box (use the adjacent Browse button to navigate to the file). Repeat the previous step for PJDropFilesDsgn.pas. Choose the required package from the Package description combo box, or by navigating to the package using Browse. Click OK to confirm your selections.
   • A confirmation dialog box may displayed, querying whether it is OK to rebuild and reinstall the package. Click Yes to proceed.
   • The package will now be built and a dialog box should be displayed stating that the TPJDropFiles, TPJFormDropFiles, TPJExtFileFilter and TPJWildCardFileFilter components have been installed. Click OK to dismiss the dialog box.
   • The components will appear on the "DelphiDabbler" palette.
4. If you wish you can now delete PJDropFiles.pas and PJDropFilesDsgn.pas from the chosen installation folder.
5. The provided help file can be integrated with the IDE's OpenHelp system. Delphi 6 and 7 also require the use of the supplied .als file. The simplest way to install help is to use my Component Help Installer Expert (v2.2.1 or later). If you prefer to install manually, this article explains the process.
6. The demo programs can be loaded into Delphi and compiled and run as required. The frame demo requires Delphi 5 and higher.

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Bugs

There are no known outstanding bugs.

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

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

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

In release 4 there was a minor bug in the wildcard file filter where a change of wildcard was sometimes ignored. This was fixed in release 5.0.

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Change log

A complete change log is provided in a text file that is included in the download.

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License

This source code is subject to the Mozilla Public License Version 1.1 (the "License"); you may not use this program 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 © 1998-2006 Peter Johnson. All Rights Reserved.

All relevant trademarks are acknowledged.

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About the author

I'm Peter Johnson – a hobbyist programmer living in Ceredigion in West Wales, UK, writing write mainly in Delphi. My programs are available for download from: http://www.delphidabbler.com/.