17. Multiline Text Editor

The Gtk.TextView widget can be used to display and edit large amounts of formatted text. Like the Gtk.TreeView, it has a model/view design. In this case the Gtk.TextBuffer is the model which represents the text being edited. This allows two or more Gtk.TextView widgets to share the same Gtk.TextBuffer, and allows those text buffers to be displayed slightly differently. Or you could maintain several text buffers and choose to display each one at different times in the same Gtk.TextView widget.

17.1. The View

The Gtk.TextView is the frontend with which the user can add, edit and delete textual data. They are commonly used to edit multiple lines of text. When creating a Gtk.TextView it contains its own default Gtk.TextBuffer, which you can access via the Gtk.TextView.get_buffer() method.

By default, text can be added, edited and removed from the Gtk.TextView. You can disable this by calling Gtk.TextView.set_editable(). If the text is not editable, you usually want to hide the text cursor with Gtk.TextView.set_cursor_visible() as well. In some cases it may be useful to set the justification of the text with Gtk.TextView.set_justification(). The text can be displayed at the left edge, (Gtk.Justification.LEFT), at the right edge (Gtk.Justification.RIGHT), centered (Gtk.Justification.CENTER), or distributed across the complete width (Gtk.Justification.FILL).

Another default setting of the Gtk.TextView widget is long lines of text will continue horizontally until a break is entered. To wrap the text and prevent it going off the edges of the screen call Gtk.TextView.set_wrap_mode().

17.2. Das Modell

The Gtk.TextBuffer is the core of the Gtk.TextView widget, and is used to hold whatever text is being displayed in the Gtk.TextView. Setting and retrieving the contents is possible with Gtk.TextBuffer.set_text() and Gtk.TextBuffer.get_text(). However, most text manipulation is accomplished with iterators, represented by a Gtk.TextIter. An iterator represents a position between two characters in the text buffer. Iterators are not valid indefinitely; whenever the buffer is modified in a way that affects the contents of the buffer, all outstanding iterators become invalid.

Because of this, iterators can’t be used to preserve positions across buffer modifications. To preserve a position, use Gtk.TextMark. A text buffer contains two built-in marks; an „insert“ mark (which is the position of the cursor) and the „selection_bound“ mark. Both of them can be retrieved using Gtk.TextBuffer.get_insert() and Gtk.TextBuffer.get_selection_bound(), respectively. By default, the location of a Gtk.TextMark is not shown. This can be changed by calling Gtk.TextMark.set_visible().

Many methods exist to retrieve a Gtk.TextIter. For instance, Gtk.TextBuffer.get_start_iter() returns an iterator pointing to the first position in the text buffer, whereas Gtk.TextBuffer.get_end_iter() returns an iterator pointing past the last valid character. Retrieving the bounds of the selected text can be achieved by calling Gtk.TextBuffer.get_selection_bounds().

To insert text at a specific position use Gtk.TextBuffer.insert(). Another useful method is Gtk.TextBuffer.insert_at_cursor() which inserts text wherever the cursor may be currently positioned. To remove portions of the text buffer use Gtk.TextBuffer.delete().

In addition, Gtk.TextIter can be used to locate textual matches in the buffer using Gtk.TextIter.forward_search() and Gtk.TextIter.backward_search(). The start and end iters are used as the starting point of the search and move forwards/backwards depending on requirements.

17.3. Tags

Text in a buffer can be marked with tags. A tag is an attribute that can be applied to some range of text. For example, a tag might be called „bold“ and make the text inside the tag bold. However, the tag concept is more general than that; tags don’t have to affect appearance. They can instead affect the behaviour of mouse and key presses, „lock“ a range of text so the user can’t edit it, or countless other things. A tag is represented by a Gtk.TextTag object. One Gtk.TextTag can be applied to any number of text ranges in any number of buffers.

Each tag is stored in a Gtk.TextTagTable. A tag table defines a set of tags that can be used together. Each buffer has one tag table associated with it; only tags from that tag table can be used with the buffer. A single tag table can be shared between multiple buffers, however.

To specify that some text in the buffer should have specific formatting, you must define a tag to hold that formatting information, and then apply that tag to the region of text using Gtk.TextBuffer.create_tag() and Gtk.TextBuffer.apply_tag():

tag = textbuffer.create_tag("orange_bg", background="orange")
textbuffer.apply_tag(tag, start_iter, end_iter)

The following are some of the common styles applied to text:

  • Background colour („background“ property)

  • Foreground colour („foreground“ property)

  • Underline („underline“ property)

  • Bold („weight“ property)

  • Italics („style“ property)

  • Strikethrough („strikethrough“ property)

  • Justification („justification“ property)

  • Size („size“ and „size-points“ properties)

  • Text wrapping („wrap-mode“ property)

You can also delete particular tags later using Gtk.TextBuffer.remove_tag() or delete all tags in a given region by calling Gtk.TextBuffer.remove_all_tags().

17.4. Beispiel

_images/textview_example.png 
  1import gi
  2
  3gi.require_version("Gtk", "3.0")
  4from gi.repository import Gtk, Pango
  5
  6
  7class SearchDialog(Gtk.Dialog):
  8    def __init__(self, parent):
  9        Gtk.Dialog.__init__(
 10            self, title="Search", transient_for=parent, modal=True,
 11        )
 12        self.add_buttons(
 13            Gtk.STOCK_FIND,
 14            Gtk.ResponseType.OK,
 15            Gtk.STOCK_CANCEL,
 16            Gtk.ResponseType.CANCEL,
 17        )
 18
 19        box = self.get_content_area()
 20
 21        label = Gtk.Label(label="Insert text you want to search for:")
 22        box.add(label)
 23
 24        self.entry = Gtk.Entry()
 25        box.add(self.entry)
 26
 27        self.show_all()
 28
 29
 30class TextViewWindow(Gtk.Window):
 31    def __init__(self):
 32        Gtk.Window.__init__(self, title="TextView Example")
 33
 34        self.set_default_size(-1, 350)
 35
 36        self.grid = Gtk.Grid()
 37        self.add(self.grid)
 38
 39        self.create_textview()
 40        self.create_toolbar()
 41        self.create_buttons()
 42
 43    def create_toolbar(self):
 44        toolbar = Gtk.Toolbar()
 45        self.grid.attach(toolbar, 0, 0, 3, 1)
 46
 47        button_bold = Gtk.ToolButton()
 48        button_bold.set_icon_name("format-text-bold-symbolic")
 49        toolbar.insert(button_bold, 0)
 50
 51        button_italic = Gtk.ToolButton()
 52        button_italic.set_icon_name("format-text-italic-symbolic")
 53        toolbar.insert(button_italic, 1)
 54
 55        button_underline = Gtk.ToolButton()
 56        button_underline.set_icon_name("format-text-underline-symbolic")
 57        toolbar.insert(button_underline, 2)
 58
 59        button_bold.connect("clicked", self.on_button_clicked, self.tag_bold)
 60        button_italic.connect("clicked", self.on_button_clicked, self.tag_italic)
 61        button_underline.connect("clicked", self.on_button_clicked, self.tag_underline)
 62
 63        toolbar.insert(Gtk.SeparatorToolItem(), 3)
 64
 65        radio_justifyleft = Gtk.RadioToolButton()
 66        radio_justifyleft.set_icon_name("format-justify-left-symbolic")
 67        toolbar.insert(radio_justifyleft, 4)
 68
 69        radio_justifycenter = Gtk.RadioToolButton.new_from_widget(radio_justifyleft)
 70        radio_justifycenter.set_icon_name("format-justify-center-symbolic")
 71        toolbar.insert(radio_justifycenter, 5)
 72
 73        radio_justifyright = Gtk.RadioToolButton.new_from_widget(radio_justifyleft)
 74        radio_justifyright.set_icon_name("format-justify-right-symbolic")
 75        toolbar.insert(radio_justifyright, 6)
 76
 77        radio_justifyfill = Gtk.RadioToolButton.new_from_widget(radio_justifyleft)
 78        radio_justifyfill.set_icon_name("format-justify-fill-symbolic")
 79        toolbar.insert(radio_justifyfill, 7)
 80
 81        radio_justifyleft.connect(
 82            "toggled", self.on_justify_toggled, Gtk.Justification.LEFT
 83        )
 84        radio_justifycenter.connect(
 85            "toggled", self.on_justify_toggled, Gtk.Justification.CENTER
 86        )
 87        radio_justifyright.connect(
 88            "toggled", self.on_justify_toggled, Gtk.Justification.RIGHT
 89        )
 90        radio_justifyfill.connect(
 91            "toggled", self.on_justify_toggled, Gtk.Justification.FILL
 92        )
 93
 94        toolbar.insert(Gtk.SeparatorToolItem(), 8)
 95
 96        button_clear = Gtk.ToolButton()
 97        button_clear.set_icon_name("edit-clear-symbolic")
 98        button_clear.connect("clicked", self.on_clear_clicked)
 99        toolbar.insert(button_clear, 9)
100
101        toolbar.insert(Gtk.SeparatorToolItem(), 10)
102
103        button_search = Gtk.ToolButton()
104        button_search.set_icon_name("system-search-symbolic")
105        button_search.connect("clicked", self.on_search_clicked)
106        toolbar.insert(button_search, 11)
107
108    def create_textview(self):
109        scrolledwindow = Gtk.ScrolledWindow()
110        scrolledwindow.set_hexpand(True)
111        scrolledwindow.set_vexpand(True)
112        self.grid.attach(scrolledwindow, 0, 1, 3, 1)
113
114        self.textview = Gtk.TextView()
115        self.textbuffer = self.textview.get_buffer()
116        self.textbuffer.set_text(
117            "This is some text inside of a Gtk.TextView. "
118            + "Select text and click one of the buttons 'bold', 'italic', "
119            + "or 'underline' to modify the text accordingly."
120        )
121        scrolledwindow.add(self.textview)
122
123        self.tag_bold = self.textbuffer.create_tag("bold", weight=Pango.Weight.BOLD)
124        self.tag_italic = self.textbuffer.create_tag("italic", style=Pango.Style.ITALIC)
125        self.tag_underline = self.textbuffer.create_tag(
126            "underline", underline=Pango.Underline.SINGLE
127        )
128        self.tag_found = self.textbuffer.create_tag("found", background="yellow")
129
130    def create_buttons(self):
131        check_editable = Gtk.CheckButton(label="Editable")
132        check_editable.set_active(True)
133        check_editable.connect("toggled", self.on_editable_toggled)
134        self.grid.attach(check_editable, 0, 2, 1, 1)
135
136        check_cursor = Gtk.CheckButton(label="Cursor Visible")
137        check_cursor.set_active(True)
138        check_editable.connect("toggled", self.on_cursor_toggled)
139        self.grid.attach_next_to(
140            check_cursor, check_editable, Gtk.PositionType.RIGHT, 1, 1
141        )
142
143        radio_wrapnone = Gtk.RadioButton.new_with_label_from_widget(None, "No Wrapping")
144        self.grid.attach(radio_wrapnone, 0, 3, 1, 1)
145
146        radio_wrapchar = Gtk.RadioButton.new_with_label_from_widget(
147            radio_wrapnone, "Character Wrapping"
148        )
149        self.grid.attach_next_to(
150            radio_wrapchar, radio_wrapnone, Gtk.PositionType.RIGHT, 1, 1
151        )
152
153        radio_wrapword = Gtk.RadioButton.new_with_label_from_widget(
154            radio_wrapnone, "Word Wrapping"
155        )
156        self.grid.attach_next_to(
157            radio_wrapword, radio_wrapchar, Gtk.PositionType.RIGHT, 1, 1
158        )
159
160        radio_wrapnone.connect("toggled", self.on_wrap_toggled, Gtk.WrapMode.NONE)
161        radio_wrapchar.connect("toggled", self.on_wrap_toggled, Gtk.WrapMode.CHAR)
162        radio_wrapword.connect("toggled", self.on_wrap_toggled, Gtk.WrapMode.WORD)
163
164    def on_button_clicked(self, widget, tag):
165        bounds = self.textbuffer.get_selection_bounds()
166        if len(bounds) != 0:
167            start, end = bounds
168            self.textbuffer.apply_tag(tag, start, end)
169
170    def on_clear_clicked(self, widget):
171        start = self.textbuffer.get_start_iter()
172        end = self.textbuffer.get_end_iter()
173        self.textbuffer.remove_all_tags(start, end)
174
175    def on_editable_toggled(self, widget):
176        self.textview.set_editable(widget.get_active())
177
178    def on_cursor_toggled(self, widget):
179        self.textview.set_cursor_visible(widget.get_active())
180
181    def on_wrap_toggled(self, widget, mode):
182        self.textview.set_wrap_mode(mode)
183
184    def on_justify_toggled(self, widget, justification):
185        self.textview.set_justification(justification)
186
187    def on_search_clicked(self, widget):
188        dialog = SearchDialog(self)
189        response = dialog.run()
190        if response == Gtk.ResponseType.OK:
191            cursor_mark = self.textbuffer.get_insert()
192            start = self.textbuffer.get_iter_at_mark(cursor_mark)
193            if start.get_offset() == self.textbuffer.get_char_count():
194                start = self.textbuffer.get_start_iter()
195
196            self.search_and_mark(dialog.entry.get_text(), start)
197
198        dialog.destroy()
199
200    def search_and_mark(self, text, start):
201        end = self.textbuffer.get_end_iter()
202        match = start.forward_search(text, 0, end)
203
204        if match is not None:
205            match_start, match_end = match
206            self.textbuffer.apply_tag(self.tag_found, match_start, match_end)
207            self.search_and_mark(text, match_end)
208
209
210win = TextViewWindow()
211win.connect("destroy", Gtk.main_quit)
212win.show_all()
213Gtk.main()