textwidget.html

最新gtk中文资料集

</p>
<p>
Because of this, iterators can't be used to preserve positions across buffer
modifications. To preserve a position, the <a class="link" href="GtkTextMark.html" title="GtkTextMark"><span class="type">GtkTextMark</span></a> object is ideal. You
can think of a mark as an invisible cursor or insertion point; it floats in 
the buffer, saving a position. If the text surrounding the mark is deleted, 
the mark remains in the position the text once occupied; if text is inserted 
at the mark, the mark ends up either to the left or to the right of the new 
text, depending on its <em class="firstterm">gravity</em>. The standard text 
cursor in left-to-right languages is a mark with right gravity, because it 
stays to the right of inserted text.
</p>
<p>
Like tags, marks can be either named or anonymous. There are two marks built-in
to <a class="link" href="GtkTextBuffer.html" title="GtkTextBuffer"><span class="type">GtkTextBuffer</span></a>; these are named <code class="literal">"insert"</code> and 
<code class="literal">"selection_bound"</code> and refer to the insertion point and the 
boundary of the selection which is not the insertion point, respectively. If 
no text is selected, these two marks will be in the same position. You can 
manipulate what is selected and where the cursor appears by moving these 
marks around.
<sup>[<a name="id3561876" href="#ftn.id3561876" class="footnote">2</a>]</sup>
</p>
<p>
Text buffers always contain at least one line, but may be empty (that
is, buffers can contain zero characters). The last line in the text
buffer never ends in a line separator (such as newline); the other
lines in the buffer always end in a line separator. Line separators
count as characters when computing character counts and character
offsets. Note that some Unicode line separators are represented with 
multiple bytes in UTF-8, and the two-character sequence "\r\n" is also
considered a line separator.
</p>
</div>
<div class="refsect1" lang="en">
<a name="id3561913"></a><h2>Simple Example</h2>
<p>
The simplest usage of <a class="link" href="GtkTextView.html" title="GtkTextView"><span class="type">GtkTextView</span></a>  might look like this:
</p>
<div class="informalexample"><pre class="programlisting">
  GtkWidget *view;
  GtkTextBuffer *buffer;

  view = gtk_text_view_new ();

  buffer = gtk_text_view_get_buffer (GTK_TEXT_VIEW (view));

  gtk_text_buffer_set_text (buffer, "Hello, this is some text", -1);

  /* Now you might put the view in a container and display it on the
   * screen; when the user edits the text, signals on the buffer
   * will be emitted, such as "changed", "insert_text", and so on.
   */
</pre></div>
<p>
In many cases it's also convenient to first create the buffer with 
<a class="link" href="GtkTextBuffer.html#gtk-text-buffer-new"><code class="function">gtk_text_buffer_new()</code></a>, then create a widget for that buffer with 
<a class="link" href="GtkTextView.html#gtk-text-view-new-with-buffer"><code class="function">gtk_text_view_new_with_buffer()</code></a>. Or you can change the buffer the widget 
displays after the widget is created with <a class="link" href="GtkTextView.html#gtk-text-view-set-buffer"><code class="function">gtk_text_view_set_buffer()</code></a>.
</p>
</div>
<div class="refsect1" lang="en">
<a name="id3561988"></a><h2>Example of Changing Text Attributes</h2>
<p>

There are two ways to affect text attributes in <a class="link" href="GtkTextView.html" title="GtkTextView"><span class="type">GtkTextView</span></a>.
You can change the default attributes for a given <a class="link" href="GtkTextView.html" title="GtkTextView"><span class="type">GtkTextView</span></a>, and you can 
apply tags that change the attributes for a region of text.  For text features 
that come from the theme &#8212; such as font and foreground color &#8212; use 
standard <a class="link" href="GtkWidget.html" title="GtkWidget"><span class="type">GtkWidget</span></a> functions such as <a class="link" href="GtkWidget.html#gtk-widget-modify-font"><code class="function">gtk_widget_modify_font()</code></a> or 
<a class="link" href="GtkWidget.html#gtk-widget-modify-text"><code class="function">gtk_widget_modify_text()</code></a>. For other attributes there are dedicated methods on 
<a class="link" href="GtkTextView.html" title="GtkTextView"><span class="type">GtkTextView</span></a> such as <a class="link" href="GtkTextView.html#gtk-text-view-set-tabs"><code class="function">gtk_text_view_set_tabs()</code></a>.

</p>
<div class="informalexample"><pre class="programlisting">
  GtkWidget *view;
  GtkTextBuffer *buffer;
  GtkTextIter start, end;
  PangoFontDescription *font_desc;
  GdkColor color;
  GtkTextTag *tag;

  view = gtk_text_view_new ();

  buffer = gtk_text_view_get_buffer (GTK_TEXT_VIEW (view));

  gtk_text_buffer_set_text (buffer, "Hello, this is some text", -1);

  /* Change default font throughout the widget */
  font_desc = pango_font_description_from_string ("Serif 15");
  gtk_widget_modify_font (view, font_desc);
  pango_font_description_free (font_desc);

  /* Change default color throughout the widget */
  gdk_color_parse ("green", &amp;color);
  gtk_widget_modify_text (view, GTK_STATE_NORMAL, &amp;color);

  /* Change left margin throughout the widget */
  gtk_text_view_set_left_margin (GTK_TEXT_VIEW (view), 30);

  /* Use a tag to change the color for just one part of the widget */
  tag = gtk_text_buffer_create_tag (buffer, "blue_foreground",
	   		            "foreground", "blue", NULL);  
  gtk_text_buffer_get_iter_at_offset (buffer, &amp;start, 7);
  gtk_text_buffer_get_iter_at_offset (buffer, &amp;end, 12);
  gtk_text_buffer_apply_tag (buffer, tag, &amp;start, &amp;end);
</pre></div>
<p>

</p>
<p>
The <span class="application">gtk-demo</span> application that comes with
GTK+ contains more example code for <a class="link" href="GtkTextView.html" title="GtkTextView"><span class="type">GtkTextView</span></a>.
</p>
</div>
<div class="footnotes">
<br><hr width="100" align="left">
<div class="footnote"><p><sup>[<a name="ftn.id3561876" href="#id3561876" class="para">2</a>] </sup>
If you want to place the cursor in response to a user action, be sure to use
<a class="link" href="GtkTextBuffer.html#gtk-text-buffer-place-cursor"><code class="function">gtk_text_buffer_place_cursor()</code></a>, which moves both at once without causing a 
temporary selection (moving one then the other temporarily selects the range in 
between the old and new positions).
</p></div>
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