wxWidgets/docs/doxygen/overviews/richtextctrl.h

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// Name:        richtextctrl
// Purpose:     topic overview
// Author:      wxWidgets team
// RCS-ID:      $Id$
// Licence:     wxWindows license
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/*!

 @page richtextctrl_overview wxRichTextCtrl overview

 @b Major classes: #wxRichTextCtrl, #wxRichTextBuffer, #wxRichTextEvent
 @b Helper classes: #wxTextAttr, #wxRichTextRange
 @b File handler classes: #wxRichTextFileHandler, #wxRichTextHTMLHandler,
 #wxRichTextXMLHandler
 @b Style classes: #wxRichTextCharacterStyleDefinition,
 #wxRichTextParagraphStyleDefinition,
 #wxRichTextListStyleDefinition,
 #wxRichTextStyleSheet
 @b Additional controls: #wxRichTextStyleComboCtrl,
 #wxRichTextStyleListBox,
 #wxRichTextStyleListCtrl
 @b Printing classes: #wxRichTextPrinting,
 #wxRichTextPrintout,
 #wxRichTextHeaderFooterData
 @b Dialog classes: #wxRichTextStyleOrganiserDialog,
 #wxRichTextFormattingDialog,
 #wxSymbolPickerDialog
 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.
 wxRichTextCtrl supports basic printing via the easy-to-use #wxRichTextPrinting class.
 Creating applications with simple word processing features is simplified with the inclusion of
 #wxRichTextFormattingDialog, a tabbed dialog allowing
 interactive tailoring of paragraph and character styling. Also provided is the multi-purpose dialog
 #wxRichTextStyleOrganiserDialog that can be used for
 managing style definitions, browsing styles and applying them, or selecting list styles with
 a renumber option.
 There are 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 poor choice if intended users rely on screen readers that would be not work well
 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.
 A good way to understand wxRichTextCtrl's capabilities is to compile and run the
 sample, @c samples/richtext, and browse the code. The following screenshot shows the sample in action:

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


 @code
 wxRichTextCtrl* richTextCtrl = new wxRichTextCtrl(splitter, wxID_ANY, wxEmptyString, wxDefaultPosition, wxSize(200, 200), wxVSCROLL|wxHSCROLL|wxBORDER_NONE|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);
     wxTextAttr 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();
 @endcode


 @ref topic19_overview
 @ref richtextctrldialogs_overview
 @ref topic22_overview
 @ref topic23_overview


 @section topic19 Programming with wxRichTextCtrl


 @section topic20 Starting to use wxRichTextCtrl

 You need to include @c wx/richtext/richtextctrl.h in your source, and link
 with the appropriate wxWidgets library with @c 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.

 @section topic21 wxRichTextCtrl and styles

 Styling attributes are represented by #wxTextAttr.
 When setting a style, the flags of the attribute object determine which
 attributes are applied. When querying a style, the passed flags are ignored
 except (optionally) to determine whether attributes should be retrieved from
 character content or from the paragraph object.
 wxRichTextCtrl takes a layered approach to styles, so that different parts of
 the content may be responsible for contributing different attributes to the final
 style you see on the screen.
 There are four main notions of style within a control:


  @b Basic style: the fundamental style of a control, onto which any other
 styles are layered. It provides default attributes, and changing the basic style
 may immediately change the look of the content depending on what other styles
 the content uses. Calling wxRichTextCtrl::SetFont changes the font for the basic style.
 The basic style is set with wxRichTextCtrl::SetBasicStyle.
  @b Paragraph style: each paragraph has attributes that are set independently
 from other paragraphs and independently from the content within the paragraph.
 Normally, these attributes are paragraph-related, such as alignment and indentation,
 but it is possible to set character attributes too.
 The paragraph style can be set independently of its content by passing wxRICHTEXT_SETSTYLE_PARAGRAPHS_ONLY
 to wxRichTextCtrl::SetStyleEx.
  @b Character style: characters within each paragraph can have attributes.
 A single character, or a run of characters, can have a particular set of attributes.
 The character style can be with wxRichTextCtrl::SetStyle or
 wxRichTextCtrl::SetStyleEx.
  @b Default style: this is the 'current' style that determines the
 style of content that is subsequently typed, pasted or programmatically inserted.
 The default style is set with wxRichTextCtrl::SetDefaultStyle.


 What you see on the screen is the dynamically @e combined style, found by merging
 the first three of the above style types (the fourth is only a guide for future content
 insertion and therefore does not affect the currently displayed content).
 To make all this more concrete, here are examples of where you might set these different
 styles:


  You might set the @b basic style to have a Times Roman font in 12 point,
 left-aligned, with two millimetres of spacing after each paragraph.
  You might set the @b paragraph style (for one particular paragraph) to
 be centred.
  You might set the @b character style of one particular word to bold.
  You might set the @b default style to be underlined, for subsequent
 inserted text.


 Naturally you can do any of these things either using your own UI, or programmatically.
 The basic wxTextCtrl doesn't make the same distinctions as wxRichTextCtrl regarding
 attribute storage. So we need finer control when setting and retrieving
 attributes. wxRichTextCtrl::SetStyleEx takes a @e flags parameter:


  wxRICHTEXT_SETSTYLE_OPTIMIZE specifies that the style should be changed only if
 the combined attributes are different from the attributes for the current object. This is important when
 applying styling that has been edited by the user, because he has just edited the @e combined (visible)
 style, and wxRichTextCtrl wants to leave unchanged attributes associated with their original objects
 instead of applying them to both paragraph and content objects.
  wxRICHTEXT_SETSTYLE_PARAGRAPHS_ONLY specifies that only paragraph objects within the given range
 should take on the attributes.
  wxRICHTEXT_SETSTYLE_CHARACTERS_ONLY specifies that only content objects (text or images) within the given range
 should take on the attributes.
  wxRICHTEXT_SETSTYLE_WITH_UNDO specifies that the operation should be undoable.


 It's great to be able to change arbitrary attributes in a wxRichTextCtrl, but
 it can be unwieldy for the user or programmer to set attributes separately. Word processors have collections
 of styles that you can tailor or use as-is, and this means that you can set a heading with one click
 instead of marking text in bold, specifying a large font size, and applying a certain
 paragraph spacing and alignment for every such heading. Similarly,
 wxWidgets provides a class called #wxRichTextStyleSheet which manages style definitions
 (#wxRichTextParagraphStyleDefinition, #wxRichTextListStyleDefinition and #wxRichTextCharacterStyleDefinition).
 Once you have added definitions to a style sheet and associated it with a wxRichTextCtrl,
 you can apply a named definition to a range of text. The classes #wxRichTextStyleComboCtrl
 and #wxRichTextStyleListBox can be used to present the user with a list
 of styles in a sheet, and apply them to the selected text.
 You can reapply a style sheet to the contents of the control, by calling wxRichTextCtrl::ApplyStyleSheet.
 This is useful if the style definitions have changed, and you want the content to reflect this.
 It relies on the fact that when you apply a named style, the style definition name is recorded in the
 content. So ApplyStyleSheet works by finding the paragraph attributes with style names and re-applying the definition's
 attributes to the paragraph. Currently, this works with paragraph and list style definitions only.

 @section wxrichtextctrldialogs wxRichTextCtrl dialogs

 wxRichTextCtrl comes with standard dialogs to make it easier to implement
 text editing functionality.
 #wxRichTextFormattingDialog can be used
 for character or paragraph formatting, or a combination of both. It's a wxPropertySheetDialog
 with the following available tabs: Font, Indents  Spacing, Tabs, Bullets, Style, and List Style.
 You can select which pages will be shown by supplying flags to the dialog constructor.
 In a character formatting dialog, typically only the Font page will be shown.
 In a paragraph formatting dialog, you'll show the Indents  Spacing, Tabs and Bullets
 pages. The Style tab is useful when editing a style definition.
 You can customize this dialog by providing your own wxRichTextFormattingDialogFactory
 object, which tells the formatting dialog how many pages are supported, what their identifiers
 are, and how to creates the pages.
 #wxRichTextStyleOrganiserDialog is a multi-purpose dialog
 that can be used for managing style definitions, browsing styles and applying them, or selecting list styles with
 a renumber option. See the sample for usage - it is used for the "Manage Styles" and "Bullets and Numbering"
 menu commands.
 #wxSymbolPickerDialog lets the user insert a symbol from
 a specified font. It has no wxRichTextCtrl dependencies besides being included in
 the rich text library.

 @section topic22 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 wxTextAttr containing style information;
 a paragraph object can contain both paragraph and character information, but
 content objects such as text can only store character information. The final
 style displayed in the control or in a printout is a combination of base
 style, paragraph style and content (character) style.
 The top of the hierarchy is the buffer, a kind of wxRichTextParagraphLayoutBox.
 containing further wxRichTextParagraph objects, each of which can include text,
 images and potentially other types of object.
 Each object maintains a range (start and end position) measured
 from the start of the main parent object.
 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 centred 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 wxTextAttr 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.

 @section topic23 wxRichTextCtrl roadmap

 @b Bugs
 This is an incomplete list of bugs.


  Moving the caret up at the beginning of a line sometimes incorrectly positions the
 caret.
  As the selection is expanded, the text jumps slightly due to kerning differences between
 drawing a single text string versus drawing several fragments separately. This could
 be improved by using wxDC::GetPartialTextExtents to calculate exactly where the separate fragments
 should be drawn. Note that this problem also applies to separation of text fragments due to difference in their attributes.


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


  RTF input and output
  Conversion from HTML
  Open Office input and output
  Floating images, with content wrapping around them
  A ruler control
  Standard editing toolbars
  Tables
  Bitmap bullets
  Borders
  Text frames
  Justified text, in print/preview at least


 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.

 */