Embedding matplotlib messes up GTK3 dpi - python-3.x

Question

I have an application that displays a GUI using GTK3 for python 3. It has a plot rendered by matplotlib. When the plot is included in the code the UI gets zoomed in (see pictures). This happens on a mac with retina display. On Ubuntu it works perfectly. Here is the code that draws the GUI:
import gi
gi.require_version('Gtk', '3.0')
from gi.repository import Gtk
from matplotlib.figure import Figure
import matplotlib.cm as cm
from matplotlib.backends.backend_gtk3cairo import FigureCanvasGTK3Cairo as FigureCanvas
from threading import Thread
import os
from instruction import *
from instructionwriter import *
class UI:
def __init__(self):
self.instructions = None
self.builder = Gtk.Builder()
self.builder.add_from_file(os.path.dirname(os.path.realpath(__file__)) + os.path.sep + "UI.glade")
self.builder.connect_signals(self)
scale = self.builder.get_object("scale")
scale.set_label("Välj skalfaktor")
scale.set_relief(Gtk.ReliefStyle.NORMAL)
# This part has to be commented out to make the GUI display correctly but is needed for the application.
#self.fig = Figure()
#self.fig.suptitle("Förhandsvisning")
#self.ax = self.fig.add_subplot(1, 1, 1)
#self.canvas = FigureCanvas(self.fig)
#self.builder.get_object("scrolledwindow1").add_with_viewport(self.canvas)
#self._preview()
self.buttons = [
self.builder.get_object("filechooser"),
self.builder.get_object("centerbutton"),
self.builder.get_object("scale"),
self.builder.get_object("autobutton"),
self.builder.get_object("preview"),
self.builder.get_object("save")
]
self.lastScale = 0.5
statusBar = self.builder.get_object("statusBar")
self.context_id = statusBar.get_context_id("id")
def show(self):
self.builder.get_object("window1").show_all()
def on_exit(self, *args):
Gtk.main_quit()
def on_file_select(self, *args):
filename = self.builder.get_object("filechooser").get_filename()
self.builder.get_object("snurrare").start()
self._disable_ui()
Thread(target=self._load, args=(filename,)).start()
def on_preview(self, *args):
self._preview()
self._display_time()
def on_center(self, *args):
self.instructions.center()
def on_fit(self, *args):
self.instructions.fit()
def on_save(self, *args):
dialog = Gtk.FileChooserDialog("Välj mapp", self.builder.get_object("window1"),
Gtk.FileChooserAction.SELECT_FOLDER,
(Gtk.STOCK_CANCEL, Gtk.ResponseType.CANCEL,
"Välj", Gtk.ResponseType.OK))
dialog.set_default_size(800, 400)
response = dialog.run()
if response == Gtk.ResponseType.OK:
self.builder.get_object("snurrare").start()
self._disable_ui()
Thread(target=self._save, args=(dialog.get_filename(),)).start()
dialog.destroy()
def _load(self, filename):
self.lastScale = 0.5
self.builder.get_object("scale").set_value(0.5)
ext = os.path.splitext(filename)[1]
if ext == ".svg":
self.instructions = InstructionList.from_svg(filename)
elif ext == ".py":
self.instructions = InstructionList.from_code(filename)
self.builder.get_object("snurrare").stop()
self._display_time()
self._enable_ui()
def _save(self, folder):
writer = InstructionWriter(self.instructions, 0)
writer.write(folder)
self.builder.get_object("snurrare").stop()
self._enable_ui()
def _disable_ui(self):
for button in self.buttons:
button.set_sensitive(False)
def _enable_ui(self):
for button in self.buttons:
button.set_sensitive(True)
def _preview(self):
if not self.instructions is None:
if self.builder.get_object("scale").get_value() != self.lastScale:
self.lastScale = self.builder.get_object("scale").get_value()
self.instructions.scale(2*self.lastScale)
self.ax.clear()
x = []
y = []
for inst in self.instructions.instructions:
if inst.type == Instruction.MOVE:
self.ax.plot(x, y, 'b')
x = [inst.dest.real]
y = [inst.dest.imag]
elif inst.type == Instruction.LINE:
x.append(inst.dest.real)
y.append(inst.dest.imag)
self.ax.plot(x, y, 'b')
self.ax.plot([-XLIM, XLIM, XLIM, -XLIM, -XLIM], [-YLIM, -YLIM, YLIM, YLIM, -YLIM], 'r')
self.ax.plot([-585, 585, 585, -585, -585], [-413.5, -413.5, 413.5, 413.5, -413.5], 'g:')
self.ax.axis("equal")
self.fig.canvas.draw()
def _display_time(self):
t = self.instructions.time()
self.builder.get_object("statusBar").push(self.context_id, "Uppskattad tid: %dmin %ds" % (t//60, t%60))
ui = UI()
ui.show()
Gtk.main()
GUI when plot is included
GUI when plot is excluded