# RichTextCtrl Overview¶

## Introduction¶

RichTextCtrl 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, wx.stc.StyledTextCtrl 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 or OpenDocument file capabilities. Custom file formats can be supported by creating additional file handlers and registering them with the control.

RichTextCtrl is largely compatible with the wx.TextCtrl API, but extends it where necessary. The control can be used where the native rich text capabilities of wx.TextCtrl 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 wx.TextCtrl, whereas this information is readily available in RichTextCtrl. Since it’s written in pure wxWidgets, any customizations you make to RichTextCtrl will be reflected on all platforms.

RichTextCtrl supports basic printing via the easy-to-use RichTextPrinting class. Creating applications with simple word processing features is simplified with the inclusion of RichTextFormattingDialog, a tabbed dialog allowing interactive tailoring of paragraph and character styling. Also provided is the multi-purpose dialog RichTextStyleOrganiserDialog 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 RichTextCtrl. It is not native, so does not behave exactly as a native wx.TextCtrl, 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 wx.TextCtrl and RichTextCtrl, with fewer features in the former case.

A good way to understand RichTextCtrl’s capabilities is to run the sample in the wxPython demo, and browse the code.

### Code Example¶

This is taken from the wxPython demo:

import wx
import wx.richtext as rt
import images

#----------------------------------------------------------------------

class RichTextFrame(wx.Frame):

def __init__(self, *args, **kw):

wx.Frame.__init__(self, *args, **kw)

self.MakeToolBar()
self.CreateStatusBar()
self.SetStatusText("Welcome to wx.richtext.RichTextCtrl!")

self.rtc = rt.RichTextCtrl(self, style=wx.VSCROLL|wx.HSCROLL|wx.NO_BORDER);
wx.CallAfter(self.rtc.SetFocus)

self.rtc.Freeze()
self.rtc.BeginSuppressUndo()

self.rtc.BeginParagraphSpacing(0, 20)

self.rtc.BeginAlignment(rt.TEXT_ALIGNMENT_CENTRE)
self.rtc.BeginBold()

self.rtc.BeginFontSize(14)
self.rtc.WriteText("Welcome to wxRichTextCtrl, a wxWidgets control for editing and presenting " \
"styled text and images")
self.rtc.EndFontSize()
self.rtc.Newline()

self.rtc.BeginItalic()
self.rtc.WriteText("by Julian Smart")
self.rtc.EndItalic()

self.rtc.EndBold()

self.rtc.Newline()
self.rtc.WriteImage(images._rt_zebra.GetImage())

self.rtc.EndAlignment()

self.rtc.Newline()
self.rtc.Newline()

self.rtc.WriteText("What can you do with this thing? ")
self.rtc.WriteImage(images._rt_smiley.GetImage())
self.rtc.WriteText(" Well, you can change text ")

self.rtc.BeginTextColour((255, 0, 0))
self.rtc.WriteText("colour, like this red bit.")
self.rtc.EndTextColour()

self.rtc.BeginTextColour((0, 0, 255))
self.rtc.WriteText(" And this blue bit.")
self.rtc.EndTextColour()

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

self.rtc.BeginFontSize(14)
self.rtc.WriteText(" Different font sizes on the same line is allowed, too.")
self.rtc.EndFontSize()

self.rtc.WriteText(" Next we'll show an indented paragraph.")

self.rtc.BeginLeftIndent(60)
self.rtc.Newline()

self.rtc.WriteText("It was in January, the most down-trodden month of an Edinburgh winter. " \
"An attractive woman came into the cafe, which is nothing remarkable.")
self.rtc.EndLeftIndent()

self.rtc.Newline()

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

self.rtc.BeginLeftIndent(100, -40)
self.rtc.Newline()

self.rtc.WriteText("It was in January, the most down-trodden month of an Edinburgh winter. " \
"An attractive woman came into the cafe, which is nothing remarkable.")
self.rtc.EndLeftIndent()

self.rtc.Newline()

self.rtc.WriteText("Numbered bullets are possible, again using sub-indents:")

self.rtc.BeginNumberedBullet(1, 100, 60)
self.rtc.Newline()

self.rtc.WriteText("This is my first item. Note that wxRichTextCtrl doesn't automatically do numbering, " \
"but this will be added later.")

self.rtc.EndNumberedBullet()

self.rtc.BeginNumberedBullet(2, 100, 60)
self.rtc.Newline()

self.rtc.WriteText("This is my second item.")
self.rtc.EndNumberedBullet()

self.rtc.Newline()

self.rtc.WriteText("The following paragraph is right-indented:")

self.rtc.BeginRightIndent(200)
self.rtc.Newline()

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

self.rtc.Newline()

self.rtc.WriteText("The following paragraph is right-aligned with 1.5 line spacing:")

self.rtc.BeginAlignment(rt.TEXT_ALIGNMENT_RIGHT)
self.rtc.BeginLineSpacing(rt.TEXT_ATTR_LINE_SPACING_HALF)
self.rtc.Newline()

self.rtc.WriteText("It was in January, the most down-trodden month of an Edinburgh winter. " \
"An attractive woman came into the cafe, which is nothing remarkable.")
self.rtc.EndLineSpacing()
self.rtc.EndAlignment()

self.rtc.Newline()
self.rtc.WriteText("Other notable features of wxRichTextCtrl include:")

self.rtc.BeginSymbolBullet('*', 100, 60)
self.rtc.Newline()
self.rtc.WriteText("Compatibility with wxTextCtrl API")
self.rtc.EndSymbolBullet()

self.rtc.BeginSymbolBullet('*', 100, 60)
self.rtc.Newline()
self.rtc.WriteText("Easy stack-based BeginXXX()...EndXXX() style setting in addition to SetStyle()")
self.rtc.EndSymbolBullet()

self.rtc.BeginSymbolBullet('*', 100, 60)
self.rtc.Newline()
self.rtc.EndSymbolBullet()

self.rtc.BeginSymbolBullet('*', 100, 60)
self.rtc.Newline()
self.rtc.WriteText("Undo/Redo, with batching option and Undo suppressing")
self.rtc.EndSymbolBullet()

self.rtc.BeginSymbolBullet('*', 100, 60)
self.rtc.Newline()
self.rtc.WriteText("Clipboard copy and paste")
self.rtc.EndSymbolBullet()

self.rtc.BeginSymbolBullet('*', 100, 60)
self.rtc.Newline()
self.rtc.WriteText("wxRichTextStyleSheet with named character and paragraph styles, and control for " \
"applying named styles")
self.rtc.EndSymbolBullet()

self.rtc.BeginSymbolBullet('*', 100, 60)
self.rtc.Newline()
self.rtc.WriteText("A design that can easily be extended to other content types, ultimately with text " \
"boxes, tables, controls, and so on")
self.rtc.EndSymbolBullet()

self.rtc.BeginSymbolBullet('*', 100, 60)
self.rtc.Newline()

# Make a style suitable for showing a URL
urlStyle = rt.TextAttrEx()
urlStyle.SetTextColour(wx.BLUE)
urlStyle.SetFontUnderlined(True)

self.rtc.WriteText("RichTextCtrl can also display URLs, such as this one: ")
self.rtc.BeginStyle(urlStyle)
self.rtc.BeginURL("http://wxPython.org/")
self.rtc.WriteText("The wxPython Web Site")
self.rtc.EndURL();
self.rtc.EndStyle();
self.rtc.WriteText(". Click on the URL to generate an event.")

self.rtc.Bind(wx.EVT_TEXT_URL, self.OnURL)

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

self.rtc.EndParagraphSpacing()

self.rtc.EndSuppressUndo()
self.rtc.Thaw()

def OnURL(self, evt):

wx.MessageBox(evt.GetString(), "URL Clicked")

def OnFileOpen(self, evt):

# This gives us a string suitable for the file dialog based on
# the file handlers that are loaded
wildcard, types = rt.RichTextBuffer.GetExtWildcard(save=False)
dlg = wx.FileDialog(self, "Choose a filename",
wildcard=wildcard,
style=wx.OPEN)
if dlg.ShowModal() == wx.ID_OK:
path = dlg.GetPath()
if path:
fileType = types[dlg.GetFilterIndex()]
dlg.Destroy()

def OnFileSave(self, evt):

if not self.rtc.GetFilename():
self.OnFileSaveAs(evt)
return

self.rtc.SaveFile()

def OnFileSaveAs(self, evt):

wildcard, types = rt.RichTextBuffer.GetExtWildcard(save=True)

dlg = wx.FileDialog(self, "Choose a filename",
wildcard=wildcard,
style=wx.SAVE)

if dlg.ShowModal() == wx.ID_OK:
path = dlg.GetPath()
if path:
fileType = types[dlg.GetFilterIndex()]
ext = rt.RichTextBuffer.FindHandlerByType(fileType).GetExtension()
if not path.endswith(ext):
path += '.' + ext
self.rtc.SaveFile(path, fileType)

dlg.Destroy()

def OnFileViewHTML(self, evt):

# Get an instance of the html file handler, use it to save the
# document to a StringIO stream, and then display the
# resulting html text in a dialog with a HtmlWindow.
handler = rt.RichTextHTMLHandler()
handler.SetFlags(rt.RICHTEXT_HANDLER_SAVE_IMAGES_TO_MEMORY)
handler.SetFontSizeMapping([7,9,11,12,14,22,100])

import cStringIO
stream = cStringIO.StringIO()
if not handler.SaveStream(self.rtc.GetBuffer(), stream):
return

import wx.html
dlg = wx.Dialog(self, title="HTML", style=wx.DEFAULT_DIALOG_STYLE|wx.RESIZE_BORDER)
html = wx.html.HtmlWindow(dlg, size=(500,400), style=wx.BORDER_SUNKEN)
html.SetPage(stream.getvalue())
btn = wx.Button(dlg, wx.ID_CANCEL)
sizer = wx.BoxSizer(wx.VERTICAL)
dlg.SetSizer(sizer)
sizer.Fit(dlg)

dlg.ShowModal()

handler.DeleteTemporaryImages()

def OnFileExit(self, evt):

self.Close(True)

def OnBold(self, evt):

self.rtc.ApplyBoldToSelection()

def OnItalic(self, evt):

self.rtc.ApplyItalicToSelection()

def OnUnderline(self, evt):

self.rtc.ApplyUnderlineToSelection()

def OnAlignLeft(self, evt):

self.rtc.ApplyAlignmentToSelection(rt.TEXT_ALIGNMENT_LEFT)

def OnAlignRight(self, evt):

self.rtc.ApplyAlignmentToSelection(rt.TEXT_ALIGNMENT_RIGHT)

def OnAlignCenter(self, evt):

self.rtc.ApplyAlignmentToSelection(rt.TEXT_ALIGNMENT_CENTRE)

def OnIndentMore(self, evt):

attr = rt.TextAttrEx()
attr.SetFlags(rt.TEXT_ATTR_LEFT_INDENT)
ip = self.rtc.GetInsertionPoint()
if self.rtc.GetStyle(ip, attr):
r = rt.RichTextRange(ip, ip)
if self.rtc.HasSelection():
r = self.rtc.GetSelectionRange()

attr.SetLeftIndent(attr.GetLeftIndent() + 100)
attr.SetFlags(rt.TEXT_ATTR_LEFT_INDENT)
self.rtc.SetStyle(r, attr)

def OnIndentLess(self, evt):

attr = rt.TextAttrEx()
attr.SetFlags(rt.TEXT_ATTR_LEFT_INDENT)
ip = self.rtc.GetInsertionPoint()
if self.rtc.GetStyle(ip, attr):
r = rt.RichTextRange(ip, ip)
if self.rtc.HasSelection():
r = self.rtc.GetSelectionRange()

if attr.GetLeftIndent() >= 100:
attr.SetLeftIndent(attr.GetLeftIndent() - 100)
attr.SetFlags(rt.TEXT_ATTR_LEFT_INDENT)
self.rtc.SetStyle(r, attr)

def OnParagraphSpacingMore(self, evt):

attr = rt.TextAttrEx()
attr.SetFlags(rt.TEXT_ATTR_PARA_SPACING_AFTER)
ip = self.rtc.GetInsertionPoint()
if self.rtc.GetStyle(ip, attr):
r = rt.RichTextRange(ip, ip)
if self.rtc.HasSelection():
r = self.rtc.GetSelectionRange()

attr.SetParagraphSpacingAfter(attr.GetParagraphSpacingAfter() + 20);
attr.SetFlags(rt.TEXT_ATTR_PARA_SPACING_AFTER)
self.rtc.SetStyle(r, attr)

def OnParagraphSpacingLess(self, evt):

attr = rt.TextAttrEx()
attr.SetFlags(rt.TEXT_ATTR_PARA_SPACING_AFTER)
ip = self.rtc.GetInsertionPoint()
if self.rtc.GetStyle(ip, attr):
r = rt.RichTextRange(ip, ip)
if self.rtc.HasSelection():
r = self.rtc.GetSelectionRange()

if attr.GetParagraphSpacingAfter() >= 20:
attr.SetParagraphSpacingAfter(attr.GetParagraphSpacingAfter() - 20);
attr.SetFlags(rt.TEXT_ATTR_PARA_SPACING_AFTER)
self.rtc.SetStyle(r, attr)

def OnLineSpacingSingle(self, evt):

attr = rt.TextAttrEx()
attr.SetFlags(rt.TEXT_ATTR_LINE_SPACING)
ip = self.rtc.GetInsertionPoint()
if self.rtc.GetStyle(ip, attr):
r = rt.RichTextRange(ip, ip)
if self.rtc.HasSelection():
r = self.rtc.GetSelectionRange()

attr.SetFlags(rt.TEXT_ATTR_LINE_SPACING)
attr.SetLineSpacing(10)
self.rtc.SetStyle(r, attr)

def OnLineSpacingHalf(self, evt):

attr = rt.TextAttrEx()
attr.SetFlags(rt.TEXT_ATTR_LINE_SPACING)
ip = self.rtc.GetInsertionPoint()
if self.rtc.GetStyle(ip, attr):
r = rt.RichTextRange(ip, ip)
if self.rtc.HasSelection():
r = self.rtc.GetSelectionRange()

attr.SetFlags(rt.TEXT_ATTR_LINE_SPACING)
attr.SetLineSpacing(15)
self.rtc.SetStyle(r, attr)

def OnLineSpacingDouble(self, evt):

attr = rt.TextAttrEx()
attr.SetFlags(rt.TEXT_ATTR_LINE_SPACING)
ip = self.rtc.GetInsertionPoint()
if self.rtc.GetStyle(ip, attr):
r = rt.RichTextRange(ip, ip)
if self.rtc.HasSelection():
r = self.rtc.GetSelectionRange()

attr.SetFlags(rt.TEXT_ATTR_LINE_SPACING)
attr.SetLineSpacing(20)
self.rtc.SetStyle(r, attr)

def OnFont(self, evt):

if not self.rtc.HasSelection():
return

r = self.rtc.GetSelectionRange()
fontData = wx.FontData()
fontData.EnableEffects(False)
attr = rt.TextAttrEx()
attr.SetFlags(rt.TEXT_ATTR_FONT)
if self.rtc.GetStyle(self.rtc.GetInsertionPoint(), attr):
fontData.SetInitialFont(attr.GetFont())

dlg = wx.FontDialog(self, fontData)
if dlg.ShowModal() == wx.ID_OK:
fontData = dlg.GetFontData()
font = fontData.GetChosenFont()
if font:
attr.SetFlags(rt.TEXT_ATTR_FONT)
attr.SetFont(font)
self.rtc.SetStyle(r, attr)
dlg.Destroy()

def OnColour(self, evt):

colourData = wx.ColourData()
attr = rt.TextAttrEx()
attr.SetFlags(rt.TEXT_ATTR_TEXT_COLOUR)
if self.rtc.GetStyle(self.rtc.GetInsertionPoint(), attr):
colourData.SetColour(attr.GetTextColour())

dlg = wx.ColourDialog(self, colourData)
if dlg.ShowModal() == wx.ID_OK:
colourData = dlg.GetColourData()
colour = colourData.GetColour()
if colour:
if not self.rtc.HasSelection():
self.rtc.BeginTextColour(colour)
else:
r = self.rtc.GetSelectionRange()
attr.SetFlags(rt.TEXT_ATTR_TEXT_COLOUR)
attr.SetTextColour(colour)
self.rtc.SetStyle(r, attr)
dlg.Destroy()

def OnUpdateBold(self, evt):

evt.Check(self.rtc.IsSelectionBold())

def OnUpdateItalic(self, evt):

evt.Check(self.rtc.IsSelectionItalics())

def OnUpdateUnderline(self, evt):

evt.Check(self.rtc.IsSelectionUnderlined())

def OnUpdateAlignLeft(self, evt):

evt.Check(self.rtc.IsSelectionAligned(rt.TEXT_ALIGNMENT_LEFT))

def OnUpdateAlignCenter(self, evt):

evt.Check(self.rtc.IsSelectionAligned(rt.TEXT_ALIGNMENT_CENTRE))

def OnUpdateAlignRight(self, evt):

evt.Check(self.rtc.IsSelectionAligned(rt.TEXT_ALIGNMENT_RIGHT))

def ForwardEvent(self, evt):

# The RichTextCtrl can handle menu and update events for undo,
# redo, cut, copy, paste, delete, and select all, so just
# forward the event to it.
self.rtc.ProcessEvent(evt)

def doBind(item, handler, updateUI=None):

if updateUI is not None:
self.Bind(wx.EVT_UPDATE_UI, updateUI, item)

doBind( fileMenu.Append(-1, "&Open\tCtrl+O", "Open a file"),
self.OnFileOpen )
doBind( fileMenu.Append(-1, "&Save\tCtrl+S", "Save a file"),
self.OnFileSave )
doBind( fileMenu.Append(-1, "&Save As...\tF12", "Save to a new file"),
self.OnFileSaveAs )
doBind( fileMenu.Append(-1, "&View as HTML", "View HTML"),
self.OnFileViewHTML)
doBind( fileMenu.Append(-1, "E&xit\tCtrl+Q", "Quit this program"),
self.OnFileExit )

self.ForwardEvent, self.ForwardEvent)
self.ForwardEvent, self.ForwardEvent )
self.ForwardEvent, self.ForwardEvent )
self.ForwardEvent, self.ForwardEvent)
self.ForwardEvent, self.ForwardEvent)
self.ForwardEvent, self.ForwardEvent)
self.ForwardEvent, self.ForwardEvent )

self.OnBold, self.OnUpdateBold)
self.OnItalic, self.OnUpdateItalic)
self.OnUnderline, self.OnUpdateUnderline)
self.OnAlignLeft, self.OnUpdateAlignLeft)
self.OnAlignCenter, self.OnUpdateAlignCenter)
self.OnAlignRight, self.OnUpdateAlignRight)
doBind( formatMenu.Append(-1, "Increase Paragraph &Spacing"), self.OnParagraphSpacingMore)
doBind( formatMenu.Append(-1, "Decrease &Paragraph Spacing"), self.OnParagraphSpacingLess)
doBind( formatMenu.Append(-1, "Normal Line Spacing"), self.OnLineSpacingSingle)
doBind( formatMenu.Append(-1, "1.5 Line Spacing"), self.OnLineSpacingHalf)
doBind( formatMenu.Append(-1, "Double Line Spacing"), self.OnLineSpacingDouble)

def MakeToolBar(self):

def doBind(item, handler, updateUI=None):

self.Bind(wx.EVT_TOOL, handler, item)
if updateUI is not None:
self.Bind(wx.EVT_UPDATE_UI, updateUI, item)

tbar = self.CreateToolBar()
shortHelpString="Open"), self.OnFileOpen)
shortHelpString="Save"), self.OnFileSave)
shortHelpString="Cut"), self.ForwardEvent, self.ForwardEvent)
shortHelpString="Copy"), self.ForwardEvent, self.ForwardEvent)
shortHelpString="Paste"), self.ForwardEvent, self.ForwardEvent)
shortHelpString="Undo"), self.ForwardEvent, self.ForwardEvent)
shortHelpString="Redo"), self.ForwardEvent, self.ForwardEvent)
shortHelpString="Bold"), self.OnBold, self.OnUpdateBold)
shortHelpString="Italic"), self.OnItalic, self.OnUpdateItalic)
shortHelpString="Underline"), self.OnUnderline, self.OnUpdateUnderline)
shortHelpString="Align Left"), self.OnAlignLeft, self.OnUpdateAlignLeft)
shortHelpString="Center"), self.OnAlignCenter, self.OnUpdateAlignCenter)
shortHelpString="Align Right"), self.OnAlignRight, self.OnUpdateAlignRight)
shortHelpString="Indent Less"), self.OnIndentLess)
shortHelpString="Indent More"), self.OnIndentMore)
shortHelpString="Font"), self.OnFont)
shortHelpString="Font Colour"), self.OnColour)

tbar.Realize()

#----------------------------------------------------------------------

class TestPanel(wx.Panel):

def __init__(self, parent):

wx.Panel.__init__(self, parent, -1)

b = wx.Button(self, -1, "Show the RichTextCtrl sample", (50,50))
self.Bind(wx.EVT_BUTTON, self.OnButton, b)

if rt.RichTextBuffer.FindHandlerByType(rt.RICHTEXT_TYPE_HTML) is not None:
return

# This would normally go in your app's OnInit method.  I'm
# not sure why these file handlers are not loaded by
# default by the C++ richtext code, I guess it's so you
# can change the name or extension if you wanted...

# ...like this
ext="ox",
type=99))

# This is needed for the view as HTML option since we tell it
# to store the images in the memory file system.

def OnButton(self, evt):

win = RichTextFrame(self, -1, "wx.richtext.RichTextCtrl",
size=(700, 500),
style = wx.DEFAULT_FRAME_STYLE)
win.Show(True)

self.rtfrm = win
self.rtc = win.rtc

app = wx.App(0)

frame = wx.Frame(None)
panel = TestPanel(frame)
frame.Show()

app.MainLoop()


### Text Styles¶

Styling attributes are represented by wx.TextAttr, or for more control over attributes such as margins and size, the derived class RichTextAttr.

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.

RichTextCtrl 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:

• 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 SetFont changes the font for the basic style. The basic style is set with SetBasicStyle.

• 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 RICHTEXT_SETSTYLE_PARAGRAPHS_ONLY to SetStyleEx.

• 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 SetStyle or SetStyleEx.

• 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 SetDefaultStyle.

What you see on the screen is the dynamically 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 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 paragraph style (for one particular paragraph) to be centred.

• You might set the character style of one particular word to bold.

• You might set the 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 wx.TextCtrl doesn’t make the same distinctions as RichTextCtrl regarding attribute storage. So we need finer control when setting and retrieving attributes. SetStyleEx takes a flags parameter:

• RICHTEXT_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 combined (visible) style, and RichTextCtrl wants to leave unchanged attributes associated with their original objects instead of applying them to both paragraph and content objects.

• RICHTEXT_SETSTYLE_PARAGRAPHS_ONLY specifies that only paragraph objects within the given range should take on the attributes.

• RICHTEXT_SETSTYLE_CHARACTERS_ONLY specifies that only content objects (text or images) within the given range should take on the attributes.

• RICHTEXT_SETSTYLE_WITH_UNDO specifies that the operation should be undoable.

It’s great to be able to change arbitrary attributes in a RichTextCtrl, 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, wxPython provides a class called RichTextStyleSheet which manages style definitions (RichTextParagraphStyleDefinition, RichTextListStyleDefinition and RichTextCharacterStyleDefinition). Once you have added definitions to a style sheet and associated it with a RichTextCtrl, you can apply a named definition to a range of text. The classes RichTextStyleComboCtrl and RichTextStyleListBox 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 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.

### Included Dialogs¶

RichTextCtrl comes with standard dialogs to make it easier to implement text editing functionality.

RichTextFormattingDialog can be used for character or paragraph formatting, or a combination of both. It’s a PropertySheetDialog with the following available tabs: Font, Indents & Spacing, Tabs, Bullets, Style, Borders, Margins, Background, Size, 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 RichTextFormattingDialogFactory object, which tells the formatting dialog how many pages are supported, what their identifiers are, and how to creates the pages.

RichTextStyleOrganiserDialog 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.

SymbolPickerDialog lets the user insert a symbol from a specified font. It has no RichTextCtrl dependencies besides being included in the rich text library.

### How RichTextCtrl is Implemented¶

Data representation is handled by RichTextBuffer, and a RichTextCtrl always has one such buffer.

The content is represented by a hierarchy of objects, all derived from RichTextObject. An object might be an image, a fragment of text, a paragraph, or a further composite object. Objects store a RichTextAttr 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 RichTextParagraphLayoutBox, containing further RichTextParagraph 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 RichTextPlainText 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 wx.TextAttr 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.

### Nested Objects¶

RichTextCtrl supports nested objects such as text boxes and tables. To achieve compatibility with the existing API, there is the concept of object focus. When the user clicks on a nested text box, the object focus is set to that container object so all keyboard input and API functions apply to that container. The application can change the focus using SetObjectFocus. Call this function with a None parameter to set the focus back to the top-level object.

An event will be sent to the control when the focus changes.

When the user clicks on the control, RichTextCtrl determines which container to set as the current object focus by calling the found container’s overrided AcceptsFocus function. For example, although a table is a container, it must not itself be the object focus because there is no text editing at the table level. Instead, a cell within the table must accept the focus.

Since with nested objects it is not possible to represent a section with merely a start position and an end position, the class RichTextSelection is provided which stores multiple ranges (for non-contiguous selections such as table cells) and a pointer to the container object in question. You can pass RichTextSelection to SetSelection or get an instance of it from GetSelection.

When selecting multiple objects, such as cell tables, the RichTextCtrl dragging handler code calls the function HandlesChildSelections to determine whether the children can be individual selections. Currently only table cells can be multiply-selected in this way.

### Context Menus and Property Dialogs¶

There are three ways you can make use of context menus: you can let RichTextCtrl handle everything and provide a basic menu; you can set your own context menu using SetContextMenu but let RichTextCtrl handle showing it and adding property items; or you can override the default context menu behaviour by adding a context menu event handler to your class in the normal way.

If you right-click over a text box in cell in a table, you may want to edit the properties of one of these objects - but which properties will you be editing?

Well, the default behaviour allows up to three property-editing menu items simultaneously - for the object clicked on, the container of that object, and the container’s parent (depending on whether any of these objects return true from their CanEditProperties functions). If you supply a context menu, add a property command item using the ID_RICHTEXT_PROPERTIES1 identifier, so that RichTextCtrl can find the position to add command items. The object should tell the control what label to use by returning a string from GetPropertiesMenuLabel.

Since there may be several property-editing commands showing, it is recommended that you don’t include the word Properties - just the name of the object, such as Text Box or Table.

## 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 wx.DC.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.

## Features¶

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

• Support for composite objects in some functions where it’s not yet implemented, for example ApplyStyleSheet

• Table API enhancements and dialogs; improved table layout especially row spans and fitting

• Conversion from HTML, and a rewrite of the HTML output handler that includes CSS, tables, text boxes, and floating images, in addition to a simplified-HTML mode for wxHTML compatibility

• Open Office input and output

• RTF input and output

• A ruler control

• Standard editing toolbars

• Bitmap bullets

• Justified text, in print/preview at least

• Scaling: either everything scaled, or rendering using a custom reference point size and an optional dimension scale

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 wx.DC API is unnecessary. However this would require additions to the wxPython API.