Multiple Recognizers Sample

This sample demonstrates advanced features of the MicrosoftTablet PC Automation application programming interface (API) used for handwriting recognition.

It includes the following:

• Enumerating the installed recognizers
• Creating a recognizer context with a specific language recognizer
• Serializing recognition results with a stroke collection
• Organizing stroke collections into a custom collection within the InkDisp object
• Serializing ink objects to and retrieving them from an ink serialized format (ISF) file
• Setting recognizer input guides
• Using synchronous and asynchronous recognition

Ink Headers

First, include the headers for Tablet PC Automation interfaces. These are installed with the Microsoft Windows XP Tablet PC Edition Software Development Kit (SDK).

#include <msinkaut.h>
#include <msinkaut_i.c>

The EventSinks.h file defines the IInkEventsImpl and IInkRecognitionEventsImpl interfaces.

#include "EventSinks.h"

Enumerating the Installed Recognizers

The application's LoadMenu method populates the Create New Strokes menu with the available recognizers. An InkRecognizers is created. If the Languages property of an InkRecognizers object is not empty, then the recognizer is a text recognizer, and the value of its Name property is added to the menu.

// Create the enumerator for the installed recognizers
hr = m_spIInkRecognizers.CoCreateInstance(CLSID_InkRecognizers);
...
    // Filter out non-language recognizers by checking for
    // the languages supported by the recognizer - there is not
    // any if it is a gesture or object recognizer.
    CComVariant vLanguages;
    if (SUCCEEDED(spIInkRecognizer->get_Languages(&vLanguages)))
    {
        if ((VT_ARRAY == (VT_ARRAY & vLanguages.vt))           // it should be an array
            && (NULL != vLanguages.parray)
            && (0 < vLanguages.parray->rgsabound[0].cElements)) // with at least one element
        {
            // This is a language recognizer. Add its name to the menu.
            CComBSTR bstrName;
            if (SUCCEEDED(spIInkRecognizer->get_Name(&bstrName)))
                ...
        }
    }

Creating an Ink Collector

The application's OnCreate method creates an InkCollector object, connects it to its event source, and enables ink collection.

// Create an ink collector object.
hr = m_spIInkCollector.CoCreateInstance(CLSID_InkCollector);

// Establish a connection to the collector's event source.
hr = IInkCollectorEventsImpl<CMultiRecoApp>::DispEventAdvise(m_spIInkCollector);

// Enable ink input in the m_wndInput window
hr = m_spIInkCollector->put_hWnd((long)m_wndInput.m_hWnd);
hr = m_spIInkCollector->put_Enabled(VARIANT_TRUE);

Creating a Recognizer Context

The application's CreateRecoContext method creates and initializes a new recognizer context, and sets up the guides supported by the associated language. The IInkRecognizer object's CreateRecognizerContext method creates a IInkRecognizerContext2 object for the language. If necessary, the old recognizer context is replaced. The context is connected to its event source. Finally, the Capabilities property of the recognizer context is checked for which guides the recognizer context supports.

// Create a recognizer context
CComPtr<IInkRecognizerContext2> spNewContext;
if (FAILED(pIInkRecognizer2->CreateRecognizerContext(&spNewContext)))
    return false;

// Replace the current context with the new one
if (m_spIInkRecoContext != NULL)
{
    // Close the connection to the recognition events source
    IInkRecognitionEventsImpl<CMultiRecoApp>::DispEventUnadvise(m_spIInkRecoContext);
}
m_spIInkRecoContext.Attach(spNewContext.Detach());

// Establish a connection with the recognizer context's event source
if (FAILED(IInkRecognitionEventsImpl<CMultiRecoApp>::DispEventAdvise(m_spIInkRecoContext)))
    ...

// Set the guide if it's supported by the recognizer and has been created 
int cRows = 0, cColumns = 0;
InkRecognizerCapabilities dwCapabilities = IRC_DontCare;
if (SUCCEEDED(pIInkRecognizer->get_Capabilities(&dwCapabilities)))
    ...

Collecting Strokes and Displaying Recognition Results

The application's OnStroke method updates the InkStrokes of the ink collector, cancels existing asynchronous recognition requests, and creates a recognition request on the recognizer context.

// Add the new stroke to the current collection
hr = m_spIInkStrokes->Add(pIInkStroke);

if (SUCCEEDED(hr))
{
    // Cancel the previous background recognition requests
    // which have not been processed yet
    m_spIInkRecoContext->StopBackgroundRecognition();

    // Ask the context to update the recognition results with newly added strokes
    // When the results are ready, the recognizer context returns them
    // through the corresponding event RecognitionWithAlternates
    CComVariant vCustomData;
    m_spIInkRecoContext->BackgroundRecognize(vCustomData);
}

The application's OnRecognition method sends the results of the recognition request to the output window's UpdateString method.

// Update the output window with the new results
m_wndResults.UpdateString(bstrRecognizedString);

Deleting Strokes and Recognition Results

The application's OnClear method deletes all strokes and recognition results from the InkDisp object and clears the windows. The recognizer context's association with its InkStrokes collection is removed.

// Detach the current stroke collection from the recognizer context and release it
if (m_spIInkRecoContext != NULL)
    m_spIInkRecoContext->putref_Strokes(NULL);

m_spIInkStrokes.Release();

// Clear the custom strokes collection
if (m_spIInkCustomStrokes != NULL)
    m_spIInkCustomStrokes->Clear();

// Delete all strokes from the Ink object
// Passing NULL as a stroke collection pointer means asking to delete all strokes
m_spIInkDisp->DeleteStrokes(NULL);

// Get a new stroke collection from the ink object
...
// Ask for an empty collection by passing an empty variant 
if (SUCCEEDED(m_spIInkDisp->CreateStrokes(v, &m_spIInkStrokes)))
{
    // Attach it to the recognizer context
    if (FAILED(m_spIInkRecoContext->putref_Strokes(m_spIInkStrokes)))
        ...
}

Changing Recognizer Contexts

The application's OnNewStrokes method is called when the user selects a recognizer in the Create New Strokes menu. The current InkStrokes is saved. If a different language recognizer was selected, a new recognizer context is created. Then, a new InkStrokes is attached to the new recognizer context.

// Save the current stroke collection if there is any
if (m_spIInkRecoContext != NULL)
{
    // Cancel the previous background recognition requests
    // which have not been processed yet
    m_spIInkRecoContext->StopBackgroundRecognition();
    
    // Let the context know that there'll be no more input 
    // for the attached stroke collection
    m_spIInkRecoContext->EndInkInput();

    // Add the stroke collection to the Ink object's CustomStrokes collection
    SaveStrokeCollection();
}
...
// If a different recognizer was selected, create a new recognizer context
// Else, reuse the same recognizer context
if (wID != m_nCmdRecognizer)
{
    // Get a pointer to the recognizer object from the recognizer collection  
    CComPtr<IInkRecognizer> spIInkRecognizer;
    if ((m_spIInkRecognizers == NULL)
        || FAILED(m_spIInkRecognizers->Item(wID - ID_RECOGNIZER_FIRST,
                                             &spIInkRecognizer))
        || (false == CreateRecoContext(spIInkRecognizer)))
    {
        // restore the cursor
        ::SetCursor(hCursor);
        return 0;
    }

    // Update the status bar
    m_bstrCurRecoName.Empty();
    spIInkRecognizer->get_Name(&m_bstrCurRecoName);
    UpdateStatusBar();

    // Store the selected recognizer's command id
    m_nCmdRecognizer = wID;
}

It then calls StartNewStrokeCollection, which creates an empty InkStrokes and attaches it to the recognizer context.

Saving the Strokes Collection for a Recognizer Context

The application's SaveStrokeCollection method checks for an existing recognizer context, and finalizes the recognition of the current strokes collection. Then the InkStrokes collection is added to the CustomStrokes of the ink object.

if (m_spIInkRecoContext != NULL)
{
    if (SUCCEEDED(m_spIInkStrokes->get_Count(&lCount)) && 0 != lCount)
    {
        CComPtr<IInkRecognitionResult> spIInkRecoResult;
        InkRecognitionStatus RecognitionStatus;
        if (SUCCEEDED(m_spIInkRecoContext->Recognize(&RecognitionStatus, &spIInkRecoResult)))
        {
            if (SUCCEEDED(spIInkRecoResult->SetResultOnStrokes()))
            {
                CComBSTR bstr;
                spIInkRecoResult->get_TopString(&bstr);
                m_wndResults.UpdateString(bstr);
            }
            ...
        }
    }
    // Detach the stroke collection from the old recognizer context
    m_spIInkRecoContext->putref_Strokes(NULL);
}

// Now add it to the ink's custom strokes collection
// Each item (stroke collection) of the custom strokes must be identified
// by a unique string. Here we generate a GUID for this.
if ((0 != lCount) && (m_spIInkCustomStrokes != NULL))
{
    GUID guid;
    WCHAR szGuid[40]; // format: "{xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}"
    if (SUCCEEDED(::CoCreateGuid(&guid)) 
        && (::StringFromGUID2(guid, szGuid, countof(szGuid)) != 0))
    {
        CComBSTR bstrGuid(szGuid);
        if (FAILED(m_spIInkCustomStrokes->Add(bstrGuid, m_spIInkStrokes)))
            ...