ActiveX Support In SWT

Summary

OLE Documents, such as Word, Excel or PowerPoint, and ActiveX Controls such as Internet Explorer are COM objects that can be embedded into other applications running on a Microsoft® Windows® platform. This article provides an overview of integrating OLE Documents and ActiveX Controls into an application using SWT.

By Veronika Irvine, OTI
Copyright © 2001 Object Technology International, Inc.
March 22, 2001

Embedding an OLE Object in your SWT Application

OLE Objects can be contained in SWT widgets. From there, they can be activated and deactivated for user interaction, and manipulated by the application according to their specification. For example, edited data and state can be retrieved or saved. If the object is no longer required, it can be disposed.

Create the OLE Object

An OLE Document or ActiveX Control is added to an application by inserting it into a Container. The Container is made up of two parts:

  1. The OleFrame object handles sizing, menu management and window placement.
  2. The OleClientSite (for OLE Documents) or OleControlSite (for ActiveX Controls) handles interactions with a specific OLE Object.

The first step in embedding an OLE Object is to create the OleFrame:

	Display display = new Display();
	Shell shell = new Shell(display);
	OleFrame frame = new OleFrame(shell, SWT.NONE);

When activated, an OLE Document displays its own menu bar over top of the application's menu bar. The application can contribute menus to the OLE Document's menu bar through the OleFrame as follows:

	Menu bar = new Menu(shell, SWT.BAR);
	shell.setMenuBar(bar);
	
	MenuItem fileItem1 = new MenuItem(bar, SWT.CASCADE);
	fileItem1.setText("&File_Item_1");
	MenuItem fileItem2 = new MenuItem(bar, SWT.CASCADE);
	fileItem2.setText("&File_Item_2");

	MenuItem containerItem = new MenuItem(bar, SWT.CASCADE);
	containerItem.setText("&Container_Item");

	MenuItem windowItem1 = new MenuItem(bar, SWT.CASCADE);
	windowItem1.setText("&Window_Item_1");
	MenuItem windowItem2 = new MenuItem(bar, SWT.CASCADE);
	windowItem2.setText("&Window_Item_2");

	frame.setFileMenus(new MenuItem[] {fileItem1, fileItem2});
	frame.setContainerMenus(new MenuItem[] {containerItem});
	frame.setWindowMenus(new MenuItem[] {windowItem1, windowItem2});

The next step is to create an OleClientSite or an OleControlSite. Some COM objects can function as both an OLE Document and an ActiveX Control. Embedding an OLE Document is equivalent to embedding the entire application. The OLE Document provides its own toolbar and menu bar for accessing its behavior. An ActiveX Control only provides the content part and the parent application must manage the behavior of the content through the API of the ActiveX Control. To determine if a COM object supports the OLE Document behavior, look for the IOleDocument interface. To determine if a COM object supports the ActiveX Control behavior, look for the IOleControl interface. To see which interfaces the OLE Object implements, look at the type library.

To embed an OLE Document, create an OleClientSite object. To embed an ActiveX Control, create an OleControlSite object. The parent in either case is the OleFrame. When you create the OleClientSite or the OleControlSite, the associated OLE Document or ActiveX Control will automatically be created and associated with the container site.

There are two ways to create an OleClientSite:

  1. Create an OleClientSite from a ProgramID. A ProgramID is a string that identifies the application. For example, the ProgramID for Word is "Word.Document" and the ProgramID for Excel is "Excel.Chart". The ProgramID for an application can be found in the Windows Registry. Using the following constructor, a blank document is created (similar to choosing File->New from a standalone application):
    2. 	OleClientSite clientSite = new OleClientSite(frame, SWT.NONE, "Word.Document");
  2. Create an OleClientSite from a Storage file. A Storage file is a file with an OLE format that contains information about the type of OLE Object that can view it. It also contains a structured storage format and will store information such as paragraph formats, dictionaries or Author/Title/Description tags. For example, a ".doc" file created by Word is a Storage file. Given a Storage file, OLE will figure out which OLE Document to create.
    3. 	File file = new File("C:\\OleDocumentation.doc");
	OleClientSite clientSite = new OleClientSite(frame, SWT.NONE, file);

An OleControlSite is created from the ProgramID for the ActiveX Control. For example, the ProgramID for the Internet Explorer is "Shell.Explorer". The web browser can be embedded in an application as follows:

	OleControlSite controlSite = new OleControlSite(frame, SWT.NONE, "Shell.Explorer");

Activate the OLE Object

The final step before an OLE Document or ActiveX control becomes visible inside the application is to activate the OLE Object (often referred to as in-place activation). This is done by invoking the "doVerb" action on the OleClientSite or OleControlSite. The "doVerb" syntax is as follows:

	public int doVerb(int verb)

where

Further Reading on "doVerb": MSDN Library: Windows CE Documentation->Application Development->API Reference->Core ->Interfaces->IOleObject::IUnknown->IOleObject::DoVerb

Saving changes to an OLE Document

The changes made to the OLE Document can be saved to a Storage file or an ordinary file. As described above, a Storage file contains information in the header that is specific to OLE.

Applications like Word save additional information in the Storage file such as paragraph formats, Author's name and Company. If you save a Word Document to an ordinary file, only the text will be saved.

Some applications edit resources which are not OLE specific and therefore can not save their contents into a Storage file because then other applications will not understand the contents. For example, a bitmap can be edited with Microsoft's Paint application which can be embedded as an OLE Document. A bitmap, however, has a format that does not include an OLE header. In this case, the contents must be saved to an ordinary file.

Before saving the file, check that a save is necessary using the method isDirty() on the OleClientSite. If a save is required, invoke the method save(File file, boolean includeOleInfo) on the OleClientSite. The boolean includeOleInfo should be set to true to save to a Storage file and false to save to an ordinary file.

	File file = new File("C:\\OleDocumentation.doc");
	OleClientSite clientSite = new OleClientSite(frame, SWT.NONE, file);

	// ... edit the document ...

	if (clientSite.isDirty()) {
		File tempFile = new File(file.getAbsolutePath() + ".tmp");
		file.renameTo(tempFile);
		if (clientSite.save(file, true)){
			// save was successful so discard the backup
			tempFile.delete();
		} else {
			// save failed so restore the backup
			tempFile.renameTo(file);
		}
	}

Deactivating the OLE Object

If several OLE Documents or ActiveX Controls are embedded in an application, it may be preferable to have only one OLE Object "active" at a time. The OLE Object that is not currently being used can be deactivated. When the OLE Object is deactivated, it is placed in a "Running" state, its contents are visible but the toolbar and menu bar have been removed and the content does not respond to mouse or keyboard actions. In this state, the object is still alive. If modifications have been made to the object, when the object is returned to the active state, those changes will still be present.

NOTE: In the case of OLE Documents, the order of activating and deactivating is very important; first deactivate the old document and then activate the new document otherwise the menu bar will not appear correctly.

Deactivating an OLE Document or ActiveX Control is done by calling deactivateInPlaceClient on the OleClientSite or OleControlSite:

	currentSite.deactivateInPlaceClient();

Disposing the OLE Object

Because OleFrame, OleClientSite and OleControlSite are SWT Widgets, when the parent is disposed, the children will be disposed automatically. To terminate an OLE Document or ActiveX Control while other OLE Objects are still running in the same OleFrame, directly dispose of the object:

	myClientSite.dispose();

or

	myControlSite.dispose();

Note: When an OLE Object is terminated, saving is not performed automatically, nor will there be any checking for a "dirty" state (no checking for unsaved changes before closing). The application must write this code.

Using Customized Behavior

ActiveX Controls and OLE Documents can provide customized behavior. To see what kinds of customized behavior are available refer to the type library associated with the OLE Object. SWT provides access to several different types of customized behavior: the "Exec Command", the "IDispatch interface", Events and Property Change Notification.

Exec Command

The "exec" command is a generic way of sending a predefined set of commands to either an OLE Document or an ActiveX Control. The command syntax is as follows:

	int OleClientSite.exec(int cmdID, int options, Variant in, Variant out)

where

In and out parameters are defined using a Variant, which is the OLE mechanism for generically passing around any type of data. A Variant may contain an integer, a boolean, a string or many other different types of objects.

The OLE Object may or may not recognize the command. Before sending a command, you can ask an OLE Object if it recognizes the command using OleClientSite.queryStatus(int cmdID). This will return some combination of the following values:

Here is an example of how the Exec command is used:

	int result = controlSite.queryStatus(OLE.OLECMDID_PRINT);
	if ((result & OLE.OLECMDF_ENABLED) == OLE.OLECMDF_ENABLED) {
		controlSite.exec(OLE.OLECMDID_PRINT, OLE.OLECMDEXECOPT_PROMPTUSER, null, null);
	}

Further Reading on "exec": MSDN Library: Platform SDK->Component Services ->COM ->OLE and Data Transfer->Reference ->Interfaces->IOleCommandTarget

IDispatch or OLE Automation

An OLE Document or ActiveX Control can also provide a much richer set of commands than the generic set defined for the "exec" command. To access these, use the IDispatch interface. IDispatch provides access to get and set property values and invoke methods. For example, Word provides the entire Word Basic interface that gives you access to all sorts of commands and properties like cut/copy/paste, print, spell check, select text, change paragraph format, etc. In SWT the IDispatch capabilities are accessed using the OleAutomation object.

Creating the Automation object:

An OleAutomation object can be created from a client or control site or it can be obtained as the return value from a method invocation.

A simple case is the Web Browser. It provides commands like navigate, back, forward, home which you can access like this:

	OleControlSite controlSite = new OleControlSite(frame, SWT.NONE, "Shell.Explorer");
	OleAutomation automation = new OleAutomation(controlSite );

Get a Property

A Property is obtained from an OLE Object using the OleAutomation method getProperty:

	
	Variant getProperty(int dispIdMember)

where

For example:

	OleControlSite controlSite = new OleControlSite(frame, SWT.NONE, "Shell.Explorer");
	OleAutomation automation = new OleAutomation(controlSite);
	int[] rgdispid = automation.getIDsOfNames(new String[]{"LocationName"});
	int dispIdMember = rgdispid[0];
	Variant result = automation.getProperty(dispIdMember);
	System.out.println("The Web Browser is currently viewing the URL "+result.getString());

Matching type library record:

interface IWebBrowser : IDispatch {
	...
	[id(0x000000d2), propget, helpstring("Gets the short (UI-friendly) name of the URL/file currently viewed.")]
	HRESULT LocationName([out, retval] BSTR* LocationName);
	...
}

Set a Property

This is very similar to "Get a Property". In this case the method is:

	boolean OleAutomation.setProperty(int dispIdMember, Variant rgvarg).

where

For example:

	// Allow multiple selection in an embedded Calendar Control
	OleControlSite controlSite = new OleControlSite(frame, SWT.NONE, "MSComCtl2.MonthView");
	OleAutomation automation = new OleAutomation(controlSite);
	int[] rgdispid = automation.getIDsOfNames(new String[]{"MultiSelect"});
	int dispIdMember = rgdispid[0];
	Variant multiSelect = new Variant((short)1); // set to true (0 = false)
	automation.setProperty(dispIdMember, multiSelect);

Matching type library record:

interface IMonthView : IDispatch {
	...
	[id(0x000000013), propput, helpstring("Allow multiple selection."), helpcontext(0x00030da8)]
	HRESULT MultiSelect([in] BSTR pbMultiSelect);
	...
}

Invoke a Command

Invoking a command is a bit more complicated because you can pass in multiple parameters and because some of these parameters may be optional, you must pass an identifier for the parameter as well as the value of the parameter. There are three variants on the OleAutomation.invoke method to accommodate this:

where

Example 1:

The "GoForward" command on the Web Browser takes no parameters:

	OleControlSite webSite = new OleControlSite(frame, SWT.NONE, "Shell.Explorer");
	OleAutomation automation = new OleAutomation(webSite);
	int[] rgdispid = automation.getIDsOfNames(new String[]{"GoForward"});
	int dispIdMember = rgdispid[0];
	Variant pVarResult = automation.invoke(dispIdMember);
Note: Call getIDsOfNames to get the ID of the command

Matching type library record:

interface IWebBrowser : IDispatch {
	...
	[id(0x00000065), helpstring("Navigates to the next item in the history list.")]
	HRESULT GoForward();
	...
}

Example 2:

The "Navigate" command of the Web Browser takes several arguments but there is only one mandatory parameter and that is the "URL". In this example we are not going to send any of the optional arguments:

	OleControlSite controlSite = new OleControlSite(frame, SWT.NONE, "Shell.Explorer");
	OleAutomation automation = new OleAutomation(controlSite);
	int[] rgdispid = automation.getIDsOfNames(new String[]{"Navigate"});
	int dispIdMember = rgdispid[0];
	Variant[] rgvarg = new Variant[1]; // this is the URL parameter
	rgvarg[0] = new Variant("www.ibm.com");
	Variant pVarResult = automation.invoke(dispIdMember, rgvarg);

Matching type library record:

interface IWebBrowser : IDispatch {
	...
	[id(0x00000068), helpstring("Navigates to a URL or file.")]
	HRESULT Navigate(
		[in] BSTR URL, 
		[in, optional] VARIANT* Flags,
		[in, optional] VARIANT* TargetFrameName, 
		[in, optional] VARIANT* PostData, 
		[in, optional] VARIANT* Headers);
	...
}

Example 3:

The "FormatFont" command in Word Basic takes several optional parameters and we are interested in just a few of them:

	// This is a helper method for getting access to Word's WordBasic IDispatch interface
	// because it is rather complicated
	private OleAutomation getWordBasic(OleClientSite clientSite) {
		// Get generic IDispatch interface
		OleAutomation dispInterface = new OleAutomation(clientSite);
	
		// Get Application
		int[] appId = dispInterface.getIDsOfNames(new String[]{"Application"}); 
		if (appId == null) OLE.error(OLE.ERROR_APPLICATION_NOT_FOUND);
		Variant pVarResult = dispInterface.getProperty(appId[0]);
		if (pVarResult == null) OLE.error(OLE.ERROR_APPLICATION_NOT_FOUND);
		OleAutomation application = pVarResult.getAutomation();

		// Get Word Basic
		int[] wbId = application.getIDsOfNames(new String[]{"WordBasic"});
		if (wbId == null) OLE.error(OLE.ERROR_APPLICATION_NOT_FOUND);
		Variant pVarResult2 = application.getProperty(wbId[0]);
		if (pVarResult2 == null) OLE.error(OLE.ERROR_APPLICATION_NOT_FOUND);
		return pVarResult2.getAutomation();
	}

	OleClientSite clientSite = new OleClientSite(frame, SWT.NONE, "Word.Document");
	OleAutomation automation = getWordBasic(clientSite);
	// set the font to 12 point, Italic, Bold - ignore Color and Font name
	int[] rgdispid = automation.getIDsOfNames(new String[]{"FormatFont", "Points", "Color", "Font", "Bold", "Italic"});
	int dispIdMember = rgdispid[0];
	Variant[] rgvarg = new Variant[3];
	int[] rgdispidNamedArgs = new int[3];
	rgvarg[0] = new Variant(12); // this is the Points parameter
	rgdispidNamedArgs[0] = rgdispid[1];
	rgvarg[1] = new Variant(1); // this is the Bold parameter
	rgdispidNamedArgs[1] = rgdispid[4];
	rgvarg[2] = new Variant(1); // this is the Italic
	rgdispidNamedArgs[2] = rgdispid[5];
	automation.invokeNoReply(dispIdMember, rgvarg, rgdispidNamedArgs);

Note: Here we have used invokeNoReply instead of invoke. Word was the first OLE Document ever written and as such it is written slightly differently than other OLE Documents. If a Word command does not return a value, you should use the "InvokeNoReply" variations of invoke. For most other OLE Objects, you can always use "invoke" even if there is no value returned.

Further Reading: MSDN Library: Books->Inside OLE->Chapter 14->The Mechanics of OLE Automation->The IDispatch Interface

Events and Property changes in Controls

addEventListener – allows the user to listen for Events on the Control.

Example:

	// Respond to ProgressChange events in the Web Browser by updating the applications Progress bar
	OleControlSite controlSite = new OleControlSite(frame, SWT.NONE, "Shell.Explorer");
	OleAutomation automation = new OleAutomation(controlSite);
	int ProgressChange = 108; //0x6C - obtained from the type library
	ProgressBar progressBar = new ProgressBar(shell, SWT.BORDER);
	controlSite.addEventListener(ProgressChange, new OleListener() {
		public void handleEvent(OleEvent event) {
			if (event.detail != ProgressChange) return;
			Variant progress = event.arguments[0];
			Variant maxProgress = event.arguments[1];
			if (progress == null || maxProgress == null) return;
			
			progressBar.setMaximum(maxProgress.getInt());
			progressBar.setSelection(progress.getInt());
		}
	});

Note: The application must know the identifier for the event (ProgressChange) and what kind of data it is being given in the event.argument (In our example event.arguments[0] is the current progress value and event.arguments[1] is the maximum progress value)– You can find this out from the type library:

dispinterface DWebBrowserEvents {
	...

	[id(0x0000006c), helpstring("Fired when download progress is updated.")]
		void ProgressChange(
			[in] long Progress, 
			[in] long ProgressMax);
	...
}

addPropertyListener – allows the user to be notified before property changes occur—with the option to veto the change—and after property change has occurred.

Example:

	
	OleControlSite controlSite = new OleControlSite(frame, SWT.NONE, "Shell.Explorer");
	OleAutomation automation = new OleAutomation(controlSite);
	int[] rgdispid = automation.getIDsOfNames(new String[]{"ReadyState"});
	int READYSTATE = rgdispid[0];
	
	// Listen for changes to the ready state and print out the current state
	controlSite.addPropertyListener(READYSTATE, new OleListener() {
		public void handleEvent(OleEvent event) {
			if (event.detail == OLE.PROPERTY_CHANGING) {
				// Print out the old state
				Variant state = automation.getProperty(READYSTATE);
				System.out.println("Web State changing from " + state.getInt());
				event.doit = true; // allow property change to happen

			}
			if (event.detail == OLE.PROPERTY_CHANGED) {
				Variant state = automation.getProperty(READYSTATE);
				System.out.println("Web State changed to " + state.getInt());
			}
		}
	});

You can listen for a change to any property defined in the type library.

The type library also contains enumerations that can be used to interpret the property values. For example the "ReadyState" values in the previous example are integer values belonging to the following enumeration:

	typedef enum {
		READYSTATE_UNINITIALIZED = 0,
		READYSTATE_LOADING = 1,
		READYSTATE_LOADED = 2,
		READYSTATE_INTERACTIVE = 3,
		READYSTATE_COMPLETE = 4
	} tagREADYSTATE;

Summary

On the Windows platform, adding OLE Objects to your application expands the user experience. SWT makes this easy to do by allowing OLE Objects to be embedded in SWT Container widgets, making the Object's interface available to your application, and therefore to your users.

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