add new example textscroll.py by Muntyan, fixes #522047

svn path=/trunk/; revision=2982

2 files changed, 134 insertions, 0 deletions

diff --git a/examples/Makefile.am b/examples/Makefile.am
index 43f33103..9238b6e4 100644
--- a/examples/Makefile.am
+++ b/examples/Makefile.am
@@ -83,6 +83,7 @@ demo_PYTHON = \
 	pygtk-demo/demos/print_editor.py	\
 	pygtk-demo/demos/sizegroup.py		\
 	pygtk-demo/demos/stock_browser.py	\
+	pygtk-demo/demos/textscroll.py		\
 	pygtk-demo/demos/textview.py		\
 	pygtk-demo/demos/tree_store.py		\
 	pygtk-demo/demos/treemodel.py		\
diff --git a/examples/pygtk-demo/demos/textscroll.py b/examples/pygtk-demo/demos/textscroll.py
new file mode 100644
index 00000000..aa59ca2c
--- /dev/null
+++ b/examples/pygtk-demo/demos/textscroll.py
@@ -0,0 +1,133 @@
+#!/usr/bin/env python
+"""Text Widget/Automatic scrolling
+
+This example demonstrates how to use the gravity of
+GtkTextMarks to keep a text view scrolled to the bottom
+while appending text."""
+
+import gobject
+import gtk
+
+class AutomaticScrollingDemo(gtk.Window):
+    def __init__(self, parent=None):
+        # Create the toplevel window
+        gtk.Window.__init__(self)
+        try:
+            self.set_screen(parent.get_screen())
+        except AttributeError:
+            self.connect('destroy', lambda *w: gtk.main_quit())
+
+        self.set_title(self.__class__.__name__)
+        self.set_default_size(600, 400)
+        self.set_border_width(0)
+
+        hbox = gtk.HBox(True, 6)
+        self.add(hbox)
+
+        self.create_text_view(hbox, True)
+        self.create_text_view(hbox, False)
+        self.count_sb = 0
+        self.count_se = 0
+
+        self.show_all()
+
+    def create_text_view(self, hbox, scroll_to_end):
+        swindow = gtk.ScrolledWindow()
+        hbox.pack_start(swindow)
+        textview = gtk.TextView()
+        swindow.add(textview)
+
+        timeout = self.setup_scroll(textview, scroll_to_end)
+
+        # Remove the timeout in destroy handler, so we don't try to
+        # scroll destroyed widget.
+        textview.connect("destroy", lambda widget: gobject.source_remove(timeout))
+
+    def setup_scroll(self, textview, scroll_to_end):
+        buf = textview.get_buffer()
+        itr = buf.get_end_iter()
+
+        if scroll_to_end:
+            # If we want to scroll to the end, including horizontal scrolling,
+            # then we just create a mark with right gravity at the end of the
+            # buffer. It will stay at the end unless explicitely moved with
+            # gtk_text_buffer_move_mark.
+            buf.create_mark("end", itr, False)
+
+            # Add scrolling timeout.
+            return gobject.timeout_add(50, self.scroll_to_end, textview)
+        else:
+            # If we want to scroll to the bottom, but not scroll horizontally,
+            # then an end mark won't do the job. Just create a mark so we can
+            # use it with gtk_text_view_scroll_mark_onscreen, we'll position it
+            # explicitely when needed. Use left gravity so the mark stays where
+            # we put it after inserting new text.
+            buf.create_mark("scroll", itr, True)
+
+            # Add scrolling timeout.
+            return gobject.timeout_add(100, self.scroll_to_bottom, textview)
+
+    """ Scroll to the end of the buffer. """
+    def scroll_to_end(self, textview):
+        buf = textview.get_buffer()
+
+        # Get the "end" mark. It's located at the end of buffer because
+        # of right gravity
+        mark = buf.get_mark("end")
+        itr = buf.get_iter_at_mark(mark)
+
+        # and insert some text at its position, the iter will be
+        # revalidated after insertion to point to the end of inserted text
+        buf.insert(itr, "\n")
+        buf.insert(itr, " " * self.count_se)
+        buf.insert(itr, "Scroll to end scroll to end scroll to end scroll to end ")
+
+        # Now scroll the end mark onscreen.
+        textview.scroll_mark_onscreen(mark)
+
+        # Emulate typewriter behavior, shift to the left if we 
+        # are far enough to the right.
+        self.count_se += 1
+        if self.count_se > 150:
+            self.count_se = 0
+
+        return True
+
+    """ Scroll to the bottom of the buffer. """
+    def scroll_to_bottom(self, textview):
+        buf = textview.get_buffer()
+
+        # Get the end iterator
+        itr = buf.get_end_iter()
+
+        # and insert some text at it, the iter will be revalidated
+        # after insertion to point to the end of inserted text
+        buf.insert(itr, "\n")
+        buf.insert(itr, " " * self.count_sb)
+        buf.insert(itr, "Scroll to bottom scroll to bottom scroll to bottom scroll to bottom")
+
+        # Move the iterator to the beginning of line, so we don't scroll
+        # in horizontal direction
+        itr.set_line_offset(0)
+
+        # and place the mark at iter. the mark will stay there after we
+        # insert some text at the end because it has right gravity.
+        mark = buf.get_mark("scroll")
+        buf.move_mark(mark, itr)
+
+        # Scroll the mark onscreen.
+        textview.scroll_mark_onscreen(mark)
+
+        # Shift text back if we got enough to the right.
+        self.count_sb += 1
+        if self.count_sb > 40:
+            self.count_sb = 0
+
+        return True
+
+def main():
+    AutomaticScrollingDemo()
+    gtk.main()
+
+if __name__ == '__main__':
+    main()