wxWidgets/docs/latex/wx/richtextoverview.tex

\section{wxRichTextCtrl overview}\label{wxrichtextctrloverview}

Classes: \helpref{wxRichTextCtrl}{wxrichtextctrl}, \helpref{wxRichTextBuffer}{wxrichtextbuffer}, 
\helpref{wxRichTextAttr}{wxrichtextattr}, \helpref{wxTextAttrEx}{wxtextattrex}, 
\helpref{wxRichTextCharacterStyleDefinition}{wxrichtextcharacterstyledefinition}, 
\helpref{wxRichTextParagraphStyleDefinition}{wxrichtextparagraphstyledefinition}, 
\helpref{wxRichTextStyleSheet}{wxrichtextstylesheet}, 
\helpref{wxRichTextStyleListBox}{wxrichtextstylelistbox}, 
\helpref{wxRichTextEvent}{wxrichtextevent}, \helpref{wxRichTextRange}{wxrichtextrange}, 
\helpref{wxRichTextFileHandler}{wxrichtextfilehandler}, \helpref{wxRichTextHTMLHandler}{wxrichtexthtmlhandler}, 
\helpref{wxRichTextXMLHandler}{wxrichtextxmlhandler}

wxRichTextCtrl provides a generic implementation of a rich text editor that can handle different character
styles, paragraph formatting, and images. It's aimed at editing 'natural' language text - if you need an editor that supports code editing,
wxStyledTextCtrl is a better choice.

Despite its name, it cannot currently read or write RTF (rich text format) files. Instead, it
uses its own XML format, and can also read and write plain text. In future we expect to provide
RTF file capabilities. Custom file formats can be supported by creating additional
file handlers and registering them with the control.

wxRichTextCtrl is largely compatible with the wxTextCtrl API, but extends it where necessary.
The control can be used where the native rich text capabilities of wxTextCtrl are not
adequate (this is particularly true on Windows) and where more direct access to
the content representation is required. It is difficult and inefficient to read
the style information in a wxTextCtrl, whereas this information is readily
available in wxRichTextCtrl. Since it's written in pure wxWidgets, any customizations
you make to wxRichTextCtrl will be reflected on all platforms.

There are of course a few disadvantages to using wxRichTextCtrl. It is not native,
so does not behave exactly as a native wxTextCtrl, although common editing conventions
are followed. Users may miss the built-in spelling correction on Mac OS X, or any
special character input that may be provided by the native control. It would also
be a bad choice if intended users rely on screen readers that would be unhappy
with non-native text input implementation. You might mitigate this by providing
the choice between wxTextCtrl and wxRichTextCtrl, with fewer features in the
former case.

wxRichTextCtrl does not yet support printing directly, but content can be converted
to HTML which can then be used with \helpref{wxHtmlEasyPrinting}{wxhtmleasyprinting}.

The following screenshot shows the wxRichTextCtrl sample in action:

$$\image{8cm;0cm}{richtextctrl.gif}$$

\wxheading{Example}\label{wxrichtextctrlexample}

The following code is taken from the sample, and adds text and styles to a rich text control programmatically.

{\small
\begin{verbatim}
    wxRichTextCtrl* richTextCtrl = new wxRichTextCtrl(splitter, wxID_ANY, wxEmptyString, wxDefaultPosition, wxSize(200, 200), wxVSCROLL|wxHSCROLL|wxNO_BORDER|wxWANTS_CHARS);

    wxFont textFont = wxFont(12, wxROMAN, wxNORMAL, wxNORMAL);
    wxFont boldFont = wxFont(12, wxROMAN, wxNORMAL, wxBOLD);
    wxFont italicFont = wxFont(12, wxROMAN, wxITALIC, wxNORMAL);

    wxFont font(12, wxROMAN, wxNORMAL, wxNORMAL);

    m_richTextCtrl->SetFont(font);

    wxRichTextCtrl& r = richTextCtrl;

    r.BeginSuppressUndo();

    r.BeginParagraphSpacing(0, 20);

    r.BeginAlignment(wxTEXT_ALIGNMENT_CENTRE);
    r.BeginBold();

    r.BeginFontSize(14);
    r.WriteText(wxT("Welcome to wxRichTextCtrl, a wxWidgets control for editing and presenting styled text and images"));
    r.EndFontSize();
    r.Newline();

    r.BeginItalic();
    r.WriteText(wxT("by Julian Smart"));
    r.EndItalic();

    r.EndBold();

    r.Newline();
    r.WriteImage(wxBitmap(zebra_xpm));

    r.EndAlignment();

    r.Newline();
    r.Newline();

    r.WriteText(wxT("What can you do with this thing? "));
    r.WriteImage(wxBitmap(smiley_xpm));
    r.WriteText(wxT(" Well, you can change text "));

    r.BeginTextColour(wxColour(255, 0, 0));
    r.WriteText(wxT("colour, like this red bit."));
    r.EndTextColour();

    r.BeginTextColour(wxColour(0, 0, 255));
    r.WriteText(wxT(" And this blue bit."));
    r.EndTextColour();

    r.WriteText(wxT(" Naturally you can make things "));
    r.BeginBold();
    r.WriteText(wxT("bold "));
    r.EndBold();
    r.BeginItalic();
    r.WriteText(wxT("or italic "));
    r.EndItalic();
    r.BeginUnderline();
    r.WriteText(wxT("or underlined."));
    r.EndUnderline();

    r.BeginFontSize(14);
    r.WriteText(wxT(" Different font sizes on the same line is allowed, too."));
    r.EndFontSize();

    r.WriteText(wxT(" Next we'll show an indented paragraph."));

    r.BeginLeftIndent(60);
    r.Newline();

    r.WriteText(wxT("Indented paragraph."));
    r.EndLeftIndent();

    r.Newline();

    r.WriteText(wxT("Next, we'll show a first-line indent, achieved using BeginLeftIndent(100, -40)."));

    r.BeginLeftIndent(100, -40);
    r.Newline();

    r.WriteText(wxT("It was in January, the most down-trodden month of an Edinburgh winter."));
    r.EndLeftIndent();

    r.Newline();

    r.WriteText(wxT("Numbered bullets are possible, again using subindents:"));

    r.BeginNumberedBullet(1, 100, 60);
    r.Newline();

    r.WriteText(wxT("This is my first item. Note that wxRichTextCtrl doesn't automatically do numbering, but this will be added later."));
    r.EndNumberedBullet();

    r.BeginNumberedBullet(2, 100, 60);
    r.Newline();

    r.WriteText(wxT("This is my second item."));
    r.EndNumberedBullet();

    r.Newline();

    r.WriteText(wxT("The following paragraph is right-indented:"));

    r.BeginRightIndent(200);
    r.Newline();

    r.WriteText(wxT("It was in January, the most down-trodden month of an Edinburgh winter. An attractive woman came into the cafe, which is nothing remarkable."));
    r.EndRightIndent();

    r.Newline();

    wxArrayInt tabs;
    tabs.Add(400);
    tabs.Add(600);
    tabs.Add(800);
    tabs.Add(1000);
    wxTextAttrEx attr;
    attr.SetFlags(wxTEXT_ATTR_TABS);
    attr.SetTabs(tabs);
    r.SetDefaultStyle(attr);
    
    r.WriteText(wxT("This line contains tabs:\tFirst tab\tSecond tab\tThird tab"));

    r.Newline();
    r.WriteText(wxT("Other notable features of wxRichTextCtrl include:"));

    r.BeginSymbolBullet(wxT('*'), 100, 60);
    r.Newline();
    r.WriteText(wxT("Compatibility with wxTextCtrl API"));
    r.EndSymbolBullet();

    r.WriteText(wxT("Note: this sample content was generated programmatically from within the MyFrame constructor in the demo. The images were loaded from inline XPMs. Enjoy wxRichTextCtrl!"));

    r.EndSuppressUndo();
\end{verbatim}
}

\subsection{Programming with wxRichTextCtrl}

You need to include {\tt <wx/richtext/richtextctrl.h>} in your source, and link
with the appropriate wxWidgets library with {\tt richtext} suffix. Put the rich text
library first in your link line to avoid unresolved symbols.

Then you can create a wxRichTextCtrl, with the wxWANT\_CHARS style if you want tabs to
be processed by the control rather than being used for navigation between controls.

It's helpful to have a model of how styling works. Any piece of text can have its
style changed, but there also two global notions of style. The control's {\it basic} style
is the fundamental style for the whole control, to which other character and paragraph styles are
applied. For example, you can change the control's overall font by either calling SetBasicStyle with
the appropriate font style, or by calling SetFont.

The {\it default} style, on the other hand, is applied to subsequently inserted
content. You might click on a Bold formatting tool, which sets bold as one of the default
attributes, and typing will appear in bold. Then when you select Italic, both
bold and italic attributes are applied as you type. The default attribute
is set with \helpref{SetDefaultStyle}{wxrichtextctrlsetdefaultstyle}.

(To be finished.)

\subsection{How wxRichTextCtrl is implemented}

Data representation is handled by wxRichTextBuffer, and a wxRichTextCtrl
always has one such buffer.

The content is represented by a hierarchy of objects, all derived from
wxRichTextObject. An object might be an image, a fragment of text, a paragraph,
or a whole buffer. Objects store a wxRichTextAttr containing style information;
although it contains both paragraph formatting and character style, the
paragraph style information is ignored by children of a paragraph (only
character style is relevant to these objects).

The top of the hierarchy is the buffer, a kind of wxRichTextParagraphLayoutBox.
containing further wxRichTextParagraph objects, each of which can include text and
images.

Each object maintains a range (start and end position) measured
from the start of the main parent box.

When Layout is called on an object, it is given a size which the object
must limit itself to, or one or more flexible directions (vertical
or horizontal). So, for example, a centered paragraph is given the page
width to play with (minus any margins), but can extend indefinitely
in the vertical direction. The implementation of Layout caches the calculated
size and position.

When the buffer is modified, a range is invalidated (marked as requiring
layout), so that only the minimum amount of layout is performed.

A paragraph of pure text with the same style contains just one further
object, a wxRichTextPlainText object. When styling is applied to part of
this object, the object is decomposed into separate objects, one object
for each different character style. So each object within a paragraph always has
just one wxRichTextAttr object to denote its character style. Of course, this can
lead to fragmentation after a lot of edit operations, potentially leading
to several objects with the same style where just one would do. So
a Defragment function is called when updating the control's display, to ensure that
the minimum number of objects is used.

(To be finished.)

\subsection{wxRichTextCtrl roadmap}

\wxheading{Bugs}

This is an incomplete list of bugs.

\begin{itemize}
\item Moving the caret up at the beginning of a line sometimes incorrectly positions the
caret.
\end{itemize}

\wxheading{Features}

This is a list of some of the features that have yet to be implemented. Help with them will be appreciated.

\begin{itemize}
\item Printing
\item RTF input and output
\item Floating images, with content wrapping around them
\item A ruler control
\item Standard editing toolbars
\item Automatic list numbering
\item Standard dialogs for paragraph/character formatting
\item Tables
\item Text frames
\item Add ability to show images in wxHTML output (currently uses
\item More complete stylesheet viewer, plus style sheet editing dialogs
\item Ability to store style sheets with documents
embedded images suitable only for browsers).
\end{itemize}

There are also things that could be done to take advantage of the underlying text capabilities of the platform;
higher-level text formatting APIs are available on some platforms, such as Mac OS X, and some of translation from
high level to low level wxDC API is unnecessary. However this would require additions to the wxWidgets API.