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"""
This is a fully functional do nothing backend to provide a template to
backend writers. It is fully functional in that you can select it as
a backend with
import matplotlib
matplotlib.use('Template')
and your matplotlib scripts will (should!) run without error, though
no output is produced. This provides a nice starting point for
backend writers because you can selectively implement methods
(draw_rectangle, draw_lines, etc...) and slowly see your figure come
to life w/o having to have a full blown implementation before getting
any results.
Copy this to backend_xxx.py and replace all instances of 'template'
with 'xxx'. Then implement the class methods and functions below, and
add 'xxx' to the switchyard in matplotlib/backends/__init__.py and
'xxx' to the backends list in the validate_backend methon in
matplotlib/__init__.py and you're off. You can use your backend with::
import matplotlib
matplotlib.use('xxx')
from pylab import *
plot([1,2,3])
show()
matplotlib also supports external backends, so you can place you can
use any module in your PYTHONPATH with the syntax::
import matplotlib
matplotlib.use('module://my_backend')
where my_backend.py is your module name. Thus syntax is also
recognized in the rc file and in the -d argument in pylab, eg::
python simple_plot.py -dmodule://my_backend
The files that are most relevant to backend_writers are
matplotlib/backends/backend_your_backend.py
matplotlib/backend_bases.py
matplotlib/backends/__init__.py
matplotlib/__init__.py
matplotlib/_pylab_helpers.py
Naming Conventions
* classes Upper or MixedUpperCase
* varables lower or lowerUpper
* functions lower or underscore_separated
"""
from __future__ import division, print_function
import matplotlib
from matplotlib._pylab_helpers import Gcf
from matplotlib.backend_bases import RendererBase, GraphicsContextBase,\
FigureManagerBase, FigureCanvasBase
from matplotlib.figure import Figure
from matplotlib.transforms import Bbox
class RendererTemplate(RendererBase):
"""
The renderer handles drawing/rendering operations.
This is a minimal do-nothing class that can be used to get started when
writing a new backend. Refer to backend_bases.RendererBase for
documentation of the classes methods.
"""
def __init__(self, dpi):
self.dpi = dpi
def draw_path(self, gc, path, transform, rgbFace=None):
pass
# draw_markers is optional, and we get more correct relative
# timings by leaving it out. backend implementers concerned with
# performance will probably want to implement it
# def draw_markers(self, gc, marker_path, marker_trans, path, trans, rgbFace=None):
# pass
# draw_path_collection is optional, and we get more correct
# relative timings by leaving it out. backend implementers concerned with
# performance will probably want to implement it
# def draw_path_collection(self, gc, master_transform, paths,
# all_transforms, offsets, offsetTrans, facecolors,
# edgecolors, linewidths, linestyles,
# antialiaseds):
# pass
# draw_quad_mesh is optional, and we get more correct
# relative timings by leaving it out. backend implementers concerned with
# performance will probably want to implement it
# def draw_quad_mesh(self, gc, master_transform, meshWidth, meshHeight,
# coordinates, offsets, offsetTrans, facecolors,
# antialiased, edgecolors):
# pass
def draw_image(self, gc, x, y, im):
pass
def draw_text(self, gc, x, y, s, prop, angle, ismath=False):
pass
def flipy(self):
return True
def get_canvas_width_height(self):
return 100, 100
def get_text_width_height_descent(self, s, prop, ismath):
return 1, 1, 1
def new_gc(self):
return GraphicsContextTemplate()
def points_to_pixels(self, points):
# if backend doesn't have dpi, eg, postscript or svg
return points
# elif backend assumes a value for pixels_per_inch
#return points/72.0 * self.dpi.get() * pixels_per_inch/72.0
# else
#return points/72.0 * self.dpi.get()
class GraphicsContextTemplate(GraphicsContextBase):
"""
The graphics context provides the color, line styles, etc... See the gtk
and postscript backends for examples of mapping the graphics context
attributes (cap styles, join styles, line widths, colors) to a particular
backend. In GTK this is done by wrapping a gtk.gdk.GC object and
forwarding the appropriate calls to it using a dictionary mapping styles
to gdk constants. In Postscript, all the work is done by the renderer,
mapping line styles to postscript calls.
If it's more appropriate to do the mapping at the renderer level (as in
the postscript backend), you don't need to override any of the GC methods.
If it's more appropriate to wrap an instance (as in the GTK backend) and
do the mapping here, you'll need to override several of the setter
methods.
The base GraphicsContext stores colors as a RGB tuple on the unit
interval, eg, (0.5, 0.0, 1.0). You may need to map this to colors
appropriate for your backend.
"""
pass
########################################################################
#
# The following functions and classes are for pylab and implement
# window/figure managers, etc...
#
########################################################################
def draw_if_interactive():
"""
For image backends - is not required
For GUI backends - this should be overriden if drawing should be done in
interactive python mode
"""
pass
def show():
"""
For image backends - is not required
For GUI backends - show() is usually the last line of a pylab script and
tells the backend that it is time to draw. In interactive mode, this may
be a do nothing func. See the GTK backend for an example of how to handle
interactive versus batch mode
"""
for manager in Gcf.get_all_fig_managers():
# do something to display the GUI
pass
def new_figure_manager(num, *args, **kwargs):
"""
Create a new figure manager instance
"""
# if a main-level app must be created, this (and
# new_figure_manager_given_figure) is the usual place to
# do it -- see backend_wx, backend_wxagg and backend_tkagg for
# examples. Not all GUIs require explicit instantiation of a
# main-level app (egg backend_gtk, backend_gtkagg) for pylab
FigureClass = kwargs.pop('FigureClass', Figure)
thisFig = FigureClass(*args, **kwargs)
return new_figure_manager_given_figure(num, thisFig)
def new_figure_manager_given_figure(num, figure):
"""
Create a new figure manager instance for the given figure.
"""
canvas = FigureCanvasTemplate(figure)
manager = FigureManagerTemplate(canvas, num)
return manager
class FigureCanvasTemplate(FigureCanvasBase):
"""
The canvas the figure renders into. Calls the draw and print fig
methods, creates the renderers, etc...
Public attribute
figure - A Figure instance
Note GUI templates will want to connect events for button presses,
mouse movements and key presses to functions that call the base
class methods button_press_event, button_release_event,
motion_notify_event, key_press_event, and key_release_event. See,
eg backend_gtk.py, backend_wx.py and backend_tkagg.py
"""
def draw(self):
"""
Draw the figure using the renderer
"""
renderer = RendererTemplate(self.figure.dpi)
self.figure.draw(renderer)
# You should provide a print_xxx function for every file format
# you can write.
# If the file type is not in the base set of filetypes,
# you should add it to the class-scope filetypes dictionary as follows:
filetypes = FigureCanvasBase.filetypes.copy()
filetypes['foo'] = 'My magic Foo format'
def print_foo(self, filename, *args, **kwargs):
"""
Write out format foo. The dpi, facecolor and edgecolor are restored
to their original values after this call, so you don't need to
save and restore them.
"""
pass
def get_default_filetype(self):
return 'foo'
FigureCanvas = FigureCanvasTemplate
class FigureManagerTemplate(FigureManagerBase):
"""
Wrap everything up into a window for the pylab interface
For non interactive backends, the base class does all the work
"""
pass
########################################################################
#
# Now just provide the standard names that backend.__init__ is expecting
#
########################################################################
FigureManager = FigureManagerTemplate
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