I'm trying to make some simple animations in python3 using the GTK3 libraries and pycairo.
I've been trying to find simple single file examples of this to no avail, but I'm sure it's do-able.
The closest I've found is: https://cairographics.org/cookbook/animationrotation/, but this is in python2 and the libraries/dependencies are completely different.
Would anyone be able to point me towards a decent source, or amendments to the above code?
Thanks!
There's some information on how to use cairo on a Python 3 + GTK+ 3 environnement in the PyGObject documentation:
https://pygobject.readthedocs.io/en/latest/guide/cairo_integration.html
I used that to adapt your example. Some changes from GTK+ 2 to GTK+ 3:
expose-event signal became drawself.window on a widget to access its GdkWindow, use self.get_window()I'll maintain the code there: https://github.com/liberforce/gtk-samples/blob/master/python/gtk3-rotating-square/rotating-square.py
Here it is in case the above link breaks:
#!/usr/bin/env python
## cairo demos
##
## Copyright (C) 2007 Donn.C.Ingle <[email protected]>
## Copyright (C) 2019 Luis Menina <[email protected]>
##
## This program is free software; you can redistribute it and/or modify
## it under the terms of the GNU General Public License as published by
## the Free Software Foundation; either version 2 of the License, or
## (at your option) any later version.
##
## This program is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with this program; if not, write to the Free Software
## Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
import cairo
import gi
gi.require_version("Gtk", "3.0")
from gi.repository import Gtk, Gdk, GObject
class Screen(Gtk.DrawingArea):
""" This class is a Drawing Area"""
def __init__(self):
super(Screen,self).__init__()
## Connect to the "draw" signal
self.connect("draw", self.on_draw)
## This is what gives the animation life!
GObject.timeout_add(50, self.tick) # Go call tick every 50 whatsits.
def tick(self):
## This invalidates the screen, causing the "draw" event to fire.
rect = self.get_allocation()
self.get_window().invalidate_rect(rect, True)
return True # Causes timeout to tick again.
## When the "draw" event fires, this is run
def on_draw(self, widget, event):
self.cr = self.get_window().cairo_create()
## Call our draw function to do stuff.
geom = self.get_window().get_geometry()
self.draw(geom.width, geom.height)
class MyStuff(Screen):
"""This class is also a Drawing Area, coming from Screen."""
def __init__(self):
Screen.__init__(self)
## x,y is where I'm at
self.x, self.y = 25, -25
## rx,ry is point of rotation
self.rx, self.ry = -10, -25
## rot is angle counter
self.rot = 0
## sx,sy is to mess with scale
self.sx, self.sy = 1, 1
def draw(self, width, height):
## A shortcut
cr = self.cr
## First, let's shift 0,0 to be in the center of page
## This means:
## -y | -y
## -x | +x
## ----0------
## -x | +x
## +y | +y
matrix = cairo.Matrix(1, 0, 0, 1, width/2, height/2)
cr.transform(matrix) # Make it so...
## Now save that situation so that we can mess with it.
## This preserves the last context(the one at 0,0)
## and let's us do new stuff.
cr.save()
## Now attempt to rotate something around a point
## Use a matrix to change the shape's position and rotation.
## First, make a matrix. Don't look at me, I only use this stuff :)
ThingMatrix = cairo.Matrix(1, 0, 0, 1, 0, 0)
## Next, move the drawing to it's x,y
cairo.Matrix.translate(ThingMatrix, self.x, self.y)
cr.transform(ThingMatrix) # Changes the context to reflect that
## Now, change the matrix again to:
cairo.Matrix.translate(ThingMatrix, self.rx, self.ry) # move it all to point of rotation
cairo.Matrix.rotate(ThingMatrix, self.rot) # Do the rotation
cairo.Matrix.translate(ThingMatrix, -self.rx, -self.ry) # move it back again
cairo.Matrix.scale(ThingMatrix, self.sx, self.sy) # Now scale it all
cr.transform(ThingMatrix) # and commit it to the context
## Now, whatever is draw is "under the influence" of the
## context and all that matrix magix we just did.
self.drawCairoStuff(cr)
## Let's inc the angle a little
self.rot += 0.1
## Now mess with scale too
self.sx += 0 # Change to 0 to see if rotation is working...
if self.sx > 4: self.sx=0.5
self.sy = self.sx
## We restore to a clean context, to undo all that hocus-pocus
cr.restore()
## Let's draw a crosshair so we can identify 0,0
## Drawn last to be above the red square.
self.drawcross(cr)
def drawCairoStuff(self, cr):
## Thrillingly, we draw a red rectangle.
## It's drawn such that 0,0 is in it's center.
cr.rectangle(-25, -25, 50, 50)
cr.set_source_rgb(1, 0, 0)
cr.fill()
## Now a visual indicator of the point of rotation
## I have no idea(yet) how to keep this as a
## tiny dot when the entire thing scales.
cr.set_source_rgb(1, 1, 1)
cr.move_to(self.rx, self.ry)
cr.line_to(self.rx+1, self.ry+1)
cr.stroke()
def drawcross(self, ctx):
## Also drawn around 0,0 in the center
ctx.set_source_rgb(0, 0, 0)
ctx.move_to(0,10)
ctx.line_to(0, -10)
ctx.move_to(-10, 0)
ctx.line_to(10, 0)
ctx.stroke()
def run(Widget):
window = Gtk.Window()
window.connect("destroy", Gtk.main_quit)
window.set_size_request(400, 400)
widget = Widget()
widget.show()
window.add(widget)
window.present()
Gtk.main()
run(MyStuff)