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# Copyright (c) 2016 Ruby-GNOME2 Project Team
# This program is licenced under the same licence as Ruby-GNOME2.
#
=begin
= Text View/Automatic Scrolling
This example demonstrates how to use the gravity of
GtkTextMarks to keep a text view scrolled to the bottom
while appending text.
=end
class TextscrollDemo
def initialize(main_window)
@window = Gtk::Window.new(:toplevel)
@window.screen = main_window.screen
@window.set_default_size(600, 400)
hbox = Gtk::Box.new(:horizontal, 6)
hbox.homogeneous = true
@window.add(hbox)
create_text_view(hbox, true)
create_text_view(hbox, false)
end
def run
if !@window.visible?
@window.show_all
else
@window.destroy
end
@window
end
private
def create_text_view(hbox, to_end)
swindow = Gtk::ScrolledWindow.new
hbox.pack_start(swindow, :fill => true, :expand => true, :padding => 0)
textview = Gtk::TextView.new
swindow.add(textview)
timeout = setup_scroll(textview, to_end)
textview.signal_connect("destroy") { GLib::Source.remove(timeout) }
end
def setup_scroll(textview, to_end)
buffer = textview.buffer
end_iter = buffer.end_iter
count = 0
if 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 explicitly moved with
# gtk_text_buffer_move_mark.
buffer.create_mark("end", end_iter, false)
# add scrolling timeout
return GLib::Timeout.add(50) do # scroll to end
count += 1
# Get "end" mark. It's located at the end of buffer because
# of right gravity
mark = buffer.get_mark("end")
mark_iter = buffer.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
buffer.insert(mark_iter, "\n")
buffer.insert(mark_iter, " " * count)
buffer.insert(mark_iter, "Scroll to end scroll to end scroll" +
" to end scroll to end #{count}")
# 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.
count = 0 if count > 150
GLib::Source::CONTINUE
end
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
# explicitly when needed. Use left gravity so the mark stays where
# we put it after inserting new text.
buffer.create_mark("scroll", end_iter, true)
return GLib::Timeout.add(100) do # scroll to bottom
count += 1
# Get end iterator
end_iter = buffer.end_iter
# and insert some text at it, the iter will be revalidated
# after insertion to point to the end of inserted text
buffer.insert(end_iter, "\n")
buffer.insert(end_iter, " " * count)
buffer.insert(end_iter,"Scroll to bottom scroll to bottom scroll" +
" to bottom scroll to bottom #{count}")
# Move the iterator to the beginning of line, so we don't scroll
# in horizontal direction
end_iter.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 left gravity.
mark = buffer.get_mark("scroll")
buffer.move_mark(mark, end_iter)
# Scroll the mark onscreen.
textview.scroll_mark_onscreen(mark)
# Shift text back if we got enough to the right.
count = 0 if count > 40
GLib::Source::CONTINUE
end
end
end
end
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