Pango II
last modified October 18, 2023
In this part of the PyGTK programming tutorial, we continue exploring the Pango library.
Animated text
The following example shows animated text on window.
animation.py
#!/usr/bin/python
ZetCode PyGTK tutorial
This example shows animated text
author: jan bodnar
website: zetcode.com
last edited: February 2009
import gtk import glib import pango import math
class PyApp(gtk.Window): def init(self): super(PyApp, self).init()
self.connect("destroy", gtk.main_quit)
glib.timeout_add(160, self.on_timer)
self.count = 1
self.set_border_width(10)
self.set_title("ZetCode")
self.label = gtk.Label("ZetCode")
fontdesc = pango.FontDescription("Serif Bold 30")
self.label.modify_font(fontdesc)
vbox = gtk.VBox(False, 0)
vbox.add(self.label)
self.add(vbox)
self.set_size_request(300, 250)
self.set_position(gtk.WIN_POS_CENTER)
self.show_all()
def on_timer(self):
attr = pango.AttrList()
self.count = self.count + 1
for i in range(7):
r = pango.AttrRise(int(math.sin(self.count+i)*20)*pango.SCALE, i, i+1)
attr.insert(r)
self.label.set_attributes(attr)
return True
PyApp() gtk.main()
In the above code example, we have a text in a label widget. By continuously changing its pango attributes, the text is being animated.
self.label = gtk.Label(“ZetCode”)
fontdesc = pango.FontDescription(“Serif Bold 30”) self.label.modify_font(fontdesc)
We create a label widget and modify its font. We choose a bit larger text for better visibility.
vbox = gtk.VBox(False, 0) vbox.add(self.label)
We put the label into the vertical box. This centers the label on the window.
The animation is performed inside the on_timer method.
for i in range(7): r = pango.AttrRise(int(math.sin(self.count+i)*20)*pango.SCALE, i, i+1) attr.insert(r)
We have seven characters in our text. We periodically change the pango AttrRise attribute for each character. The rise is based on the trigonometric sine function. The text movement follows the sine function graphed on the cartesian graph.
Also notice the pango.SCALE constant. The pango library has its own units. They differ from what is used by the widgets to draw graphics or text. We must multiply our numbers by this constant.
Figure: Animated text
Using markup language
We can change the attributes of the text using the built-in markup language.
markup.py
#!/usr/bin/python
ZetCode PyGTK tutorial
This example uses markup language
to change attributes of the text
author: jan bodnar
website: zetcode.com
last edited: February 2009
import gtk import pango
quote = “<span foreground=‘blue’ size=‘19000’>The only victory over love is flight</span>”
class PyApp(gtk.Window): def init(self): super(PyApp, self).init()
self.set_title("Markup")
self.set_border_width(5)
self.connect("destroy", gtk.main_quit)
label = gtk.Label()
label.set_markup(quote)
vbox = gtk.VBox(False, 0)
vbox.add(label)
self.add(vbox)
self.set_position(gtk.WIN_POS_CENTER)
self.show_all()
PyApp() gtk.main()
In the code example, we have a label. We change the its text attributes with the markup language.
quote = “<span foreground=‘blue’ size=‘19000’>The only victory over love is flight</span>”
This is the text with the markup language.
label = gtk.Label() label.set_markup(quote)
We create a label widget and set a markup text for it.
Figure: Using markup
Pango layout
Pango layout is an object representing a paragraph of text with attributes.
layout.py
#!/usr/bin/python
ZetCode PyGTK tutorial
This example shows pango Layout
in action
author: jan bodnar
website: zetcode.com
last edited: February 2009
import gtk import pango
lyrics = “““Meet you downstairs in the bar and heard your rolled up sleeves and your skull t-shirt You say why did you do it with him today? and sniff me out like I was Tanqueray
cause you’re my fella, my guy hand me your stella and fly by the time I’m out the door you tear men down like Roger Moore
I cheated myself like I knew I would I told ya, I was trouble you know that I’m no good”””
class Area(gtk.DrawingArea): def init(self): super(Area, self).init() self.modify_bg(gtk.STATE_NORMAL, gtk.gdk.Color(16400, 16400, 16440)) self.connect(“expose_event”, self.expose)
def expose(self, widget, event):
gc = self.get_style().fg_gc[gtk.STATE_NORMAL]
font_desc = pango.FontDescription('Sans 10')
layout = self.create_pango_layout(lyrics)
width, height = self.get_size_request()
attr = pango.AttrList()
fg_color = pango.AttrForeground(60535, 60535, 60535, 0, -1)
attr.insert(fg_color)
layout.set_width(pango.SCALE * self.allocation.width)
layout.set_spacing(pango.SCALE * 3)
layout.set_alignment(pango.ALIGN_CENTER)
layout.set_font_description(font_desc)
layout.set_attributes(attr)
self.window.draw_layout(gc, 0, 5, layout)
class PyApp(gtk.Window): def init(self): super(PyApp, self).init()
self.connect("destroy", gtk.main_quit)
self.set_title("You know I'm no Good")
self.add(Area())
self.set_size_request(300, 300)
self.set_position(gtk.WIN_POS_CENTER)
self.show_all()
PyApp() gtk.main()
In the previous examples, we were modifying text in existing widgets. Now we are going to draw the text using the pango layout on the DrawingArea widget. We be drawing using the Gdk drawing tools.
gc = self.get_style().fg_gc[gtk.STATE_NORMAL]
We get the graphics contex of the drawing area widget.
layout = self.create_pango_layout(lyrics)
Here create the pango layout object.
layout.set_width(pango.SCALE * self.allocation.width) layout.set_spacing(pango.SCALE * 3) layout.set_alignment(pango.ALIGN_CENTER) layout.set_font_description(font_desc) layout.set_attributes(attr)
We modify layout’s width, spacing, alignment, font and set text attributes.
self.window.draw_layout(gc, 0, 5, layout)
The layout is being drawn on the window.
Figure: Layout
In this chapter of the PyGTK programming library, we further worked with pango library.
