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About Text Object Model

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The Text Object Model (TOM) defines a set of text manipulation interfaces that are supported in varying degrees by several Microsoft text solutions, including the rich edit control. This topic provides a high-level overview of the TOM. It discusses the following topics.

TOM Version 2 Objects

TOM version 2 (TOM 2) extends the original text object model; the new interfaces are derived from the old ones. The updated TOM API includes support for new character and paragraph format properties, a table model, multiple selection, and inline object support for math and ruby.

The top-level TOM 2 object is defined by the ITextDocument2 interface, which has methods for creating and retrieving objects lower in the object hierarchy. For simple plain-text processing, you can obtain an ITextRange2 object from an ITextDocument2 object and do most everything with that. If you need to add rich-text formatting, you can obtain ITextFont2 and ITextPara2 objects from an ITextRange2 object. ITextFont2 provides the programming equivalent of the Microsoft Word format-font dialog, and ITextPara2 provides the equivalent of the Word format-paragraph dialog.

In addition to these three lower-level objects, TOM 2 has a selection object (ITextSelection2), which is an ITextRange2 object with selection highlighting and some UI-oriented methods.

The range and selection objects include screen-oriented methods that enable programs to examine text on screen or text that could be scrolled onto the screen. These capabilities help make text accessible to people with impaired vision, for example.

Each interface that has the 2 suffix inherits from the corresponding interface without the 2 suffix. For example, ITextDocument2 inherits from ITextDocument.

The TOM 2 objects have the following hierarchy.

ITextDocument2         Top-level editing object
    ITextRange2        Primary text interface: a range of text
        ITextFont2     Character-attribute interface
        ITextPara2     Paragraph-attribute interface
        ITextRow       Table interface
    ITextSelection2    Screen highlighted text range
        ITextRange2    Selection inherits all range methods
    ITextDisplays      Displays collection (not yet defined)
    ITextStrings       Rich-text strings collection
    ITextStoryRanges2  Enumerator for stories in document

An ITextDocument2 object describes one or more contiguous ranges of text called stories. Stories represent various parts of a document, such as the main text of the document, headers and footers, footnotes, annotations, and rich-text scratch pads. A scratch pad story is used when translating between linearly formatted math expressions and a built-up form. A scratch pad story is also used when saving the contents of a range that is the current copy source when the contents are about to be changed.

An ITextRange2 object is defined by its start and end character-position offsets and a story object. It does not exist independently of its parent story object, although its text can be copied to the clipboard or to other targets. A text range object is different from spreadsheet and other range objects, which are defined by other kinds of offsets; for example, row/column or graphics position (x, y). A text range object can modify itself in various ways, can return a duplicate of itself, and it can be commanded to copy its start and end character positions and its story pointer to the current selection.

An explicit story object is not needed, since an ITextRange object can always be created to represent any given story. In particular, the ITextDocument object can create an ITextStoryRanges object to enumerate the stories in the document in terms of ranges with start and end character position values that describe complete stories (such as, 0 and tomForward).

With an ITextStoryRanges2 object, an explicit story object is not needed, since the each story is described by an ITextRange2 object. In particular, the ITextDocument2 object can create an ITextStoryRanges2 object to enumerate the stories in the document in terms of ranges with start and end character position values that describe complete stories (such as, 0 and tomForward).

The ITextRow interface together with the ITextRange::Move and ITextRange::Expand methods give the capability to insert, query, and change tables.

TOM Interface Conventions

All TOM methods return HRESULT values. In general, the TOM methods return the following standard values.

  • E_OUTOFMEMORY
  • E_INVALIDARG
  • E_NOTIMPL
  • E_FILENOTFOUND
  • E_ACCESSDENIED
  • E_FAIL
  • CO_E_RELEASED
  • NOERROR (same as S_OK)
  • S_FALSE

Be aware that if the editing instance associated with a TOM object such as ITextRange is deleted, the TOM object becomes useless, and all its methods return CO_E_RELEASED.

In addition to the HRESULT return values, many methods include out parameters, which are pointers used to return values. For all interfaces, you should check all pointer parameters to ensure that they are nonzero before using them. If you pass a null value to a method that requires a valid pointer, the method returns E_INVALIDARG. Optional out pointers with null values are ignored.

Use methods with Get and Set prefixes to get and set properties. Boolean variables use tomFalse (0) for FALSE, and tomTrue (-1) for TRUE.

TOM constants are defined in the tomConstants enumeration type and begin with the prefix tom, for example tomWord.

The tomBool Type

Many TOM methods use a special type of variable called "tomBool" for rich-text attributes that have binary states. The tomBool type is different from the Boolean type because it can take four values: tomTrue, tomFalse, tomToggle, and tomUndefined. The tomTrue and tomFalse values indicate true and false. The tomToggle value is used to toggle a property. The tomUndefined value, more traditionally called NINCH, is a special no-input, no-change value that works with longs, floats, and COLORREFs. For strings, tomUndefined (or NINCH) is represented by the null string. For property setting operations, using tomUndefined does not change the target property. For property getting operations, tomUndefined means that the characters in the range have different values (it gives the grayed check box in property dialog boxes).

Math BuildUp and Build Down

You can use the ITextRange2::BuildUpMath method to convert linearly formatted math expressions into built-up versions. The ITextRange2::Linearize method does the opposite conversion, called linearization or build down, to convert built-up versions of math expressions back to linear format. The math build down capability is useful when you need to export plain text or to enable certain types of editing.

TOM RTF

In TOM, rich-text exchange can be accomplished by sets of explicit method calls or by transfers of rich text in the Rich Text Format (RTF). This section gives tables of RTF control words for paragraph properties and for character properties.

TOM RTF Paragraph Control Words

Control word Meaning
\ fi n First-line indent (the default is zero).
\ keep Keep paragraph intact.
\ keepn Keep with the next paragraph.
\ li n Left indent (the default is zero).
\ noline No line numbering.
\ nowidctlpar Turn off widow/orphan control.
\ pagebb Break page before paragraph.
\ par New paragraph.
\ pard Resets to default paragraph properties.
\ ql Left aligned (the default).
\ qr Right aligned.
\ qj Justified.
\ qc Centered.
\ ri n Right indent (the default is zero).
\ s n Style n.
\ sa n Space after (the default is zero).
\ sb n Space before (the default is zero).
\ sl n If missing or if n=1000, line spacing is determined by the tallest character in the line (single-line spacing); if n> zero, at least this size is used; if n is < zero, exactly |n| is used. The line spacing is multiple-line spacing if \ slmult 1 follows.
\ slmult m Follows \ sl. m = zero: At Least or Exactly line spacing as described by \ sl n. m = 1: line spacing = n/240 times single-line spacing.
\ tb n Bar tab position, in twips, from the left margin.
\ tldot Tab leader dots.
\ tleq Tab leader equal sign.
\ tlhyph Tab leader hyphens.
\ tlth Tab leader thick line.
\ tlul Tab leader underline.
\ tqc Centered tab.
\ tqdec Decimal tab.
\ tqr Flush-right tab.
\ tx n Tab position, in twips, from the left margin.

 

TOM RTF Character Format Control Words

Control word Meaning
\ animation n Sets animation type to n.
\ b Bold.
\ caps All capitals.
\ cf n Foreground color (the default is tomAutocolor).
\ cs n Character style n.
\ dn n Subscript position in half-points (the default is 6).
\ embo Embossed.
\ f n Font number, n refers to an entry in the font table.
\ fs n Font size in half-points (the default is 24).
\ highlight n Background color (the default is tomAutocolor).
\ i Italic.
\ impr Imprint.
\ lang n Applies a language to a character. n is a number corresponding to a language. The \ plain control word resets the language property to the language defined by \ deflang n in the document properties.
\ nosupersub Turns off superscript or subscript.
\ outl Outline.
\ plain Resets character formatting properties to a default value defined by the application. The associated character-formatting properties (described in the section Associated Character Properties in the RTF specification) are also reset.
\ scaps Small capitals.
\ shad Shadow.
\ strike Strikethrough.
\ sub Applies subscript to text and reduces point size according to font information.
\ super Applies superscript to text and reduces point size according to font information.
\ ul Continuous underline. \ ul0 turns off all underlining.
\ uld Dotted underline.
\ uldb Double underline.
\ ulnone Stops all underlining.
\ ulw Word underline.
\ up n Superscript position in half-points (the default is 6).
\ v Hidden text.

 

Finding Rich Text

You can use TOM methods to find rich text as defined by a range of text. Finding such rich text exactly is often needed in word processing, although it has never been fulfilled in a "what you see is what you get" (WYSIWYG) word processor. There is clearly a larger domain of rich-text matching that allows for some character formatting properties to be ignored (or to include paragraph formatting and/or object content), but such generalizations are beyond the scope of this section.

One purpose for this functionality is to use a rich-text Find dialog box to define the rich text you want to locate in a document. The dialog box would be implemented using a rich edit control and TOM methods would be used to carry out the search through the document. You could either copy the desired rich text from the document into the Find dialog box, or enter and format it directly in the Find dialog box.

The following example shows how to use TOM methods to find text containing combinations of exact character formatting. The algorithm searches for the plain text in the match range, which is named pr1. If the plain text is found, it is pointed to by a trial range, which is named pr2. Then, two insertion-point ranges (prip1 and prip2) are used to walk through the trial range comparing its character formatting to that of pr1. If they match exactly, the input range (given by ppr) is updated to point at the trial range's text and the function returns the count of characters in the matched range. Two ITextFont objects, pf1 and pf2, are used in the character-formatting comparison. They are attached to the insertion-point ranges prip1 and prip2.

LONG FindRichText (
    ITextRange **ppr,             // Ptr to range to search
    ITextRange *pr1)              // Range with rich text to find
{
    BSTR        bstr;             // pr1 plain-text to search for
    LONG        cch;              // Text string count
    LONG        cch1, cch2;       // tomCharFormat run char counts
    LONG        cchMatch = 0;     // Nothing matched yet
    LONG        cp;               // Handy char position
    LONG        cpFirst1;         // pr1 cpFirst
    LONG        cpFirst2;         // pr2 cpFirst
    ITextFont  *    pf1, *pf      // Fonts corresponding to IPs prip1 and prip2
    ITextRange *pr2;              // Range duplicate to search with
    ITextRange *prip1, *prip      // Insertion points to walk pr1, pr2

    if (!ppr || !*ppr || !pr1)
        return E_INVALIDARG;

    // Initialize range and font objects used in search
    if ((*ppr)->GetDuplicate(&pr2)    != NOERROR ||
        pr1->GetDuplicate(&prip1)     != NOERROR ||
        pr2->GetDuplicate(&prip2)     != NOERROR ||
        prip1->GetFont(&pf1)          != NOERROR ||
        prip2->GetFont(&pf2)          != NOERROR ||
        pr1->GetText(&bstr)           != NOERROR )
    {
        return E_OUTOFMEMORY;
    }

    pr1->GetStart(&cpFirst1);

    // Keep searching till rich text is matched or no more plain-text hits
    while(!cchMatch && pr2->FindText(bstr, tomForward, 0, &cch) == NOERROR)
    {
        pr2->GetStart(&cpFirst2);                 // pr2 is a new trial range
        prip1->SetRange(cpFirst1, cpFirst1);      // Set up IPs to scan match
        prip2->SetRange(cpFirst2, cpFirst2);      //  and trial ranges

        while(cch > 0 &&
            pf1->IsEqual(pf2, NULL) == NOERROR)   // Walk match & trial ranges
        {                                         //  together comparing font
            prip1->GetStart(&cch1);               //  properties
            prip1->Move(tomCharFormat, 1, NULL);
            prip1->GetStart(&cp);
            cch1 = cp - cch1;                     // cch of next match font run

            prip2->GetStart(&cch2);
            prip2->Move(tomCharFormat, 1, NULL);
            prip2->GetStart(&cp);
            cch2 = cp - cch2;                      // cch of next trial font run

            if(cch1 < cch)                         // There is more to compare
            {
                if(cch1 != cch2)                   // Different run lengths:
                    break;                         //  no formatting match
                cch = cch - cch1;                  // Matched format run
            }
            else if(cch2 < cch)                    // Trial range format run too
                break;                             //  short

            else                                   // Both match and trial runs
            {                                      //  reach at least to match
                pr2->GetEnd(&cp);                  //  text end: rich-text match
                (*ppr)->SetRange(cpFirst2, cp)     // Set input range to hit
                cchMatch = cp - cpFirst2;          //  coordinates and return
                break;                             //  length of matched string
            }
        }
    }
    pr2->Release();
    prip1->Release();
    prip2->Release();
    pf1->Release();
    pf2->Release();
    SysFreeString(bstr);

    return cchMatch;
}

TOM Accessibility

TOM provides accessibility support through the ITextSelection and ITextRange interfaces. This section describes methods that are useful for accessibility as well as how a program can determine the x, y screen position of an object.

Since UI-based accessibility programs typically work with the screen and the mouse, a common concern is to find the corresponding ITextDocument interface for the current mouse location (in screen coordinates). The following sections present two ways to determine the proper interface:

For more information, see the Microsoft Active Accessibility specification. After you obtain an object from a screen position, you can use for an ITextDocument interface and call the RangeFromPoint method to get an empty range object at the cp corresponding to the screen position.

Interface from Running Object Table

A running object table (ROT) tells what object instances are active. By querying this table, you can accelerate the process of connecting a client to an object when the object is already running. Before programs can access TOM interfaces through the running object table, a TOM instance with a window needs to register in the ROT using a moniker. You construct the moniker from a string containing the hexadecimal value of its HWND. The following code sample shows how to do this.

// This TOM implementation code is executed when a new windowed 
// instance starts up. 
// Variables with leading underscores are members of this class.

HRESULT hr;
OLECHAR szBuf[10];            // Place to put moniker
MONIKER *pmk;

hr = StringCchPrintf(szBuff, 10, "%x", _hwnd);
if (FAILED(hr))
{
    //
    // TODO: write error handler
    //
}
CreateFileMoniker(szBuf, &pmk);
OleStdRegisterAsRunning(this, pmk, &_dwROTcookie);
....................
 
// Accessibility Client: 
//    Find hwnd for window pointed to by mouse cursor.

GetCursorPos(&pt);
hwnd = WindowFromPoint(pt);

// Look in ROT (running object table) for an object attached to hwnd

hr = StringCchPrintf(szBuff, 10, "%x", hwnd);
if (FAILED(hr))
{
    //
    // TODO: write error handler
    //
}
CreateFileMoniker(szBuf, &pmk);
CreateBindContext(0, &pbc);
pmk->BindToObject(pbc, NULL, IID_ITextDocument, &pDoc);
pbc->Release();

if( pDoc )
{
    pDoc->RangeFromPoint(pt.x, pt.y, &pRange);
    // ...now do whatever with the range pRange
}

Interface from Window Messages

The EM_GETOLEINTERFACE message provides another way to obtain an IUnknown interface for an object at a given screen position. As described in Interface from Running Object Table, you get an HWND for the screen position and then send this message to that HWND. The EM_GETOLEINTERFACE message is rich edit-specific and returns a pointer to an IRichEditOle interface in the variable addressed by lParam.

Tip If a pointer is returned (be sure to set the object to which lParam points to null before sending the message), you can call its IUnknown::QueryInterface method to obtain an ITextDocument interface. The following code sample illustrates this approach.

    HWND    hwnd;
    ITextDocument *pDoc;
    ITextRange *pRange;
    POINT    pt;
    IUnknown *pUnk = NULL;
    
    GetCursorPos(&pt);
    hwnd = WindowFromPoint(pt);
    SendMessage(hwnd, EM_GETOLEINTERFACE, 0, (LPARAM)&pUnk);
    if(pUnk && 
        pUnk->QueryInterface(IID_ITextDocument, &pDoc) == NOERROR)
    {
        pDoc->RangeFromPoint(pt.x, pt.y, &pRange);
        //  ... continue with rest of program
    }

Accessibility Oriented Methods

Some TOM methods are particularly useful for navigating around the screen, while other TOM methods enhance what you can do when you arrive at places of interest. The following table describes the most useful methods.

Method How it promotes accessibility
GetSelection This method gets the active selection that can be used for a variety of view-oriented purposes, such as highlighting text and scrolling.
RangeFromPoint When used on an active selection, this method is guaranteed to get a range associated with a particular view.
Expand Enlarges a text range so that any partial units it contains are completely contained. For example, Expand(tomWindow) expands the range to include the visible portion of the range's story.
GetDuplicate When used on an active selection, this method is guaranteed to get a range associated with a particular view. See the description of RangeFromPoint.
GetPoint Gets the screen coordinates for the start or end character position in the text range.
ScrollIntoView Scrolls a text range into view.
SetPoint Selects text at or up through a specified point.

 

Character Match Sets

The variant parameter of the various Move* methods in ITextRange, such as MoveWhile and MoveUntil, can take an explicit string or a character-match set 32-bit index. The indexes are defined by either Unicode ranges or GetStringTypeEx character sets. The Unicode range starting at n and of length l (< 32768) is given by the index n + (l << 16) + 0x80000000. For example, basic Greek letters are defined by CR_Greek = 0x805f0370 and printable ASCII characters are defined by CR_ASCIIPrint = 0x805e0020. In addition, the MoveWhile and MoveUntil methods let you rapidly bypass a span of characters in any GetStringTypeEx character set, or in a span of characters that is not in any one of these character sets.

The GetStringTypeEx sets are specified by the values for Ctype1, Ctype2, and Ctype3, and are defined as follows.

Cset Meaning
Ctype1 Combination of CT_CTYPE1 types.
Ctype2 + tomCType2 Any CT_CTYPE2 type.
Ctype3 + tomCType3 Combination of CT_CTYPE3 types.

 

Specifically, Ctype1 can be any combination of the following.

Ctype1 name Value Meaning
C1_UPPER 0x0001 Uppercase.
C1_LOWER 0x0002 Lowercase.
C1_DIGIT 0x0004 Decimal digits.
C1_SPACE 0x0008 Space characters.
C1_PUNCT 0x0010 Punctuation.
C1_CNTRL 0x0020 Control characters.
C1_BLANK 0x0040 Blank characters.
C1_XDIGIT 0x0080 Hexadecimal digits.
C1_ALPHA 0x0100 Any linguistic character (alphabetic, syllabary, or ideographic).
C1_DEFINED 0x0200 A defined character, but not one of the other C1_* types.

 

The Ctype2 types support proper layout of Unicode text. The direction attributes are assigned so that the bidirectional layout algorithm standardized by Unicode produces accurate results. These types are mutually exclusive. For more information about the use of these attributes, see The Unicode Standard: Worldwide Character Encoding, Volumes 1 and 2, Addison-Wesley Publishing Company: 1991, 1992.

CType2 name Value Meaning
Strong:
C2_LEFTTORIGHT 0x1 Left to right.
C2_RIGHTTOLEFT 0x2 Right to left.
Weak:
C2_EUROPENUMBER 0x3 European number, European digit.
C2_EUROPESEPARATOR 0x4 European numeric separator.
C2_EUROPETERMINATOR 0x5 European numeric terminator.
C2_ARABICNUMBER 0x6 Arabic number.
C2_COMMONSEPARATOR 0x7 Common numeric separator.
Neutral:
C2_BLOCKSEPARATOR 0x8 Block separator.
C2_SEGMENTSEPARATOR 0x9 Segment separator.
C2_WHITESPACE 0xA White space.
C2_OTHERNEUTRAL 0xB Other neutrals.
Not applicable:
C2_NOTAPPLICABLE 0x0 No implicit direction.

 

The Ctype3 types are intended to be placeholders for extensions to the POSIX types required for general text processing or for the standard C library functions.

CType3 name Value Meaning
C3_NONSPACING 0x1 Nonspacing mark.
C3_DIACRITIC 0x2 Diacritic nonspacing mark.
C3_VOWELMARK 0x4 Vowel nonspacing mark.
C3_SYMBOL 0x8 Symbol.
C3_KATAKANA 0x10 Katakana character.
C3_HIRAGANA 0x20 Hiragana character.
C3_HALFWIDTH 0x40 Half-width character.
C3_FULLWIDTH 0x80 Full-width character.
C3_IDEOGRAPH 0x100 Ideographic character.
C3_KASHIDA 0x200 Arabic Kashida character.
C3_ALPHA 0x8000 All linguistic characters (alphabetic, syllabary, and ideographic).
C3_NOTAPPLICABLE 0x0 Not applicable.

 

An Edit Development Kit (EDK) could include pVar index definitions for the following ranges described in the Unicode Standard.

Character set Unicode Range Character set Unicode Range
ASCII 0x0—0x7f ANSI 0x0—0xff
ASCIIPrint 0x20—0x7e Latin1 0x20—0xff
Latin1Supp 0xa0—0xff LatinXA 0x100—0x17f
LatinXB 0x180—0x24f IPAX 0x250—0x2af
SpaceMod 0x2b0—0x2ff Combining 0x300—0x36f
Greek 0x370—0x3ff BasicGreek 0x370—0x3cf
GreekSymbols 0x3d0—0x3ff Cyrillic 0x400—0x4ff
Armenian 0x530—0x58f Hebrew 0x590—0x5ff
BasicHebrew 0x5d0—0x5ea HebrewXA 0x590—0x5cf
HebrewXB 0x5eb—0x5ff Arabic 0x600—0x6ff
BasicArabic 0x600—0x652 ArabicX 0x653—0x6ff
Devangari 0x900—0x97f Bangla (formerly Bengali) 0x980—0x9ff
Gurmukhi 0xa00—0xa7f Gujarati 0xa80—0xaff
Odia (formerly Oriya) 0xb00—0xb7f Tamil 0xb80—0xbff
Teluga 0xc00—0xc7f Kannada 0xc80—0xcff
Malayalam 0xd00—0xd7f Thai 0xe00—0xe7f
Lao 0xe80—0xeff GeorgianX 0x10a0—0xa0cf
BascGeorgian 0x10d0—0x10ff Jamo 0x1100—0x11ff
LatinXAdd 0x1e00—0x1eff GreekX 0x1f00—0x1fff
GenPunct 0x2000—0x206f Superscript 0x2070—0x207f
Subscript 0x2080—0x208f SuperSubscript 0x2070—0x209f
Currency 0x20a0—0x20cf CombMarkSym 0x20d0—0x20ff
LetterLike 0x2100—0x214f NumberForms 0x2150—0x218f
Arrows 0x2190—0x21ff MathOps 0x2200—0x22ff
MiscTech 0x2300—0x23ff CtrlPictures 0x2400—0x243f
OptCharRecog 0x2440—0x245f EnclAlphaNum 0x2460—x24ff
BoxDrawing 0x2500—0x257f BlockElement 0x2580—0x259f
GeometShapes 0x25a0—0x25ff MiscSymbols 0x2600—0x26ff
Dingbats 0x2700—0x27bf CJKSymPunct 0x3000—0x303f
Hiragana 0x3040—0x309f Katakana 0x30a0—0x30ff
Bopomofo 0x3100—0x312f HangulJamo 0x3130—0x318f
CJLMisc 0x3190—0x319f EnclCJK 0x3200—0x32ff
CJKCompatibl 0x3300—0x33ff Han 0x3400—0xabff
Hangul 0xac00—0xd7ff UTF16Lead 0xd800—0xdbff
UTF16Trail 0xdc00—0xdfff PrivateUse 0xe000—0xf800
CJKCompIdeog 0xf900—0xfaff AlphaPres 0xfb00—0xfb4f
ArabicPresA 0xfb50—0xfdff CombHalfMark 0xfe20—0xfe2f
CJKCompForm 0xfe30—0xfe4f SmallFormVar 0xfe50—0xfe6f
ArabicPresB 0xfe70—0xfefe HalfFullForm 0xff00—0xffef
Specials 0xfff0—0xfffd