214 lines
7.8 KiB
Python
214 lines
7.8 KiB
Python
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"""
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A fully functional, do-nothing backend intended as a template for backend
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writers. It is fully functional in that you can select it as a backend e.g.
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with ::
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import matplotlib
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matplotlib.use("template")
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and your program will (should!) run without error, though no output is
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produced. This provides a starting point for backend writers; you can
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selectively implement drawing methods (`~.RendererTemplate.draw_path`,
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`~.RendererTemplate.draw_image`, etc.) and slowly see your figure come to life
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instead having to have a full-blown implementation before getting any results.
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Copy this file to a directory outside the Matplotlib source tree, somewhere
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where Python can import it (by adding the directory to your ``sys.path`` or by
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packaging it as a normal Python package); if the backend is importable as
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``import my.backend`` you can then select it using ::
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import matplotlib
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matplotlib.use("module://my.backend")
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If your backend implements support for saving figures (i.e. has a `print_xyz`
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method), you can register it as the default handler for a given file type::
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from matplotlib.backend_bases import register_backend
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register_backend('xyz', 'my_backend', 'XYZ File Format')
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...
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plt.savefig("figure.xyz")
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"""
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from matplotlib import _api
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from matplotlib._pylab_helpers import Gcf
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from matplotlib.backend_bases import (
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FigureCanvasBase, FigureManagerBase, GraphicsContextBase, RendererBase)
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from matplotlib.figure import Figure
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class RendererTemplate(RendererBase):
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"""
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The renderer handles drawing/rendering operations.
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This is a minimal do-nothing class that can be used to get started when
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writing a new backend. Refer to `.backend_bases.RendererBase` for
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documentation of the methods.
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"""
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def __init__(self, dpi):
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super().__init__()
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self.dpi = dpi
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def draw_path(self, gc, path, transform, rgbFace=None):
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pass
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# draw_markers is optional, and we get more correct relative
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# timings by leaving it out. backend implementers concerned with
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# performance will probably want to implement it
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# def draw_markers(self, gc, marker_path, marker_trans, path, trans,
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# rgbFace=None):
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# pass
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# draw_path_collection is optional, and we get more correct
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# relative timings by leaving it out. backend implementers concerned with
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# performance will probably want to implement it
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# def draw_path_collection(self, gc, master_transform, paths,
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# all_transforms, offsets, offset_trans,
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# facecolors, edgecolors, linewidths, linestyles,
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# antialiaseds):
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# pass
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# draw_quad_mesh is optional, and we get more correct
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# relative timings by leaving it out. backend implementers concerned with
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# performance will probably want to implement it
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# def draw_quad_mesh(self, gc, master_transform, meshWidth, meshHeight,
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# coordinates, offsets, offsetTrans, facecolors,
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# antialiased, edgecolors):
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# pass
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def draw_image(self, gc, x, y, im):
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pass
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def draw_text(self, gc, x, y, s, prop, angle, ismath=False, mtext=None):
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pass
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def flipy(self):
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# docstring inherited
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return True
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def get_canvas_width_height(self):
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# docstring inherited
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return 100, 100
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def get_text_width_height_descent(self, s, prop, ismath):
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return 1, 1, 1
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def new_gc(self):
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# docstring inherited
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return GraphicsContextTemplate()
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def points_to_pixels(self, points):
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# if backend doesn't have dpi, e.g., postscript or svg
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return points
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# elif backend assumes a value for pixels_per_inch
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# return points/72.0 * self.dpi.get() * pixels_per_inch/72.0
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# else
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# return points/72.0 * self.dpi.get()
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class GraphicsContextTemplate(GraphicsContextBase):
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"""
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The graphics context provides the color, line styles, etc. See the cairo
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and postscript backends for examples of mapping the graphics context
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attributes (cap styles, join styles, line widths, colors) to a particular
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backend. In cairo this is done by wrapping a cairo.Context object and
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forwarding the appropriate calls to it using a dictionary mapping styles
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to gdk constants. In Postscript, all the work is done by the renderer,
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mapping line styles to postscript calls.
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If it's more appropriate to do the mapping at the renderer level (as in
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the postscript backend), you don't need to override any of the GC methods.
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If it's more appropriate to wrap an instance (as in the cairo backend) and
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do the mapping here, you'll need to override several of the setter
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methods.
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The base GraphicsContext stores colors as an RGB tuple on the unit
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interval, e.g., (0.5, 0.0, 1.0). You may need to map this to colors
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appropriate for your backend.
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"""
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########################################################################
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#
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# The following functions and classes are for pyplot and implement
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# window/figure managers, etc.
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#
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########################################################################
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class FigureManagerTemplate(FigureManagerBase):
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"""
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Helper class for pyplot mode, wraps everything up into a neat bundle.
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For non-interactive backends, the base class is sufficient. For
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interactive backends, see the documentation of the `.FigureManagerBase`
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class for the list of methods that can/should be overridden.
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"""
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class FigureCanvasTemplate(FigureCanvasBase):
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"""
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The canvas the figure renders into. Calls the draw and print fig
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methods, creates the renderers, etc.
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Note: GUI templates will want to connect events for button presses,
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mouse movements and key presses to functions that call the base
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class methods button_press_event, button_release_event,
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motion_notify_event, key_press_event, and key_release_event. See the
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implementations of the interactive backends for examples.
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Attributes
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----------
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figure : `~matplotlib.figure.Figure`
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A high-level Figure instance
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"""
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# The instantiated manager class. For further customization,
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# ``FigureManager.create_with_canvas`` can also be overridden; see the
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# wx-based backends for an example.
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manager_class = FigureManagerTemplate
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def draw(self):
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"""
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Draw the figure using the renderer.
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It is important that this method actually walk the artist tree
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even if not output is produced because this will trigger
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deferred work (like computing limits auto-limits and tick
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values) that users may want access to before saving to disk.
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"""
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renderer = RendererTemplate(self.figure.dpi)
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self.figure.draw(renderer)
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# You should provide a print_xxx function for every file format
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# you can write.
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# If the file type is not in the base set of filetypes,
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# you should add it to the class-scope filetypes dictionary as follows:
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filetypes = {**FigureCanvasBase.filetypes, 'foo': 'My magic Foo format'}
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def print_foo(self, filename, **kwargs):
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"""
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Write out format foo.
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This method is normally called via `.Figure.savefig` and
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`.FigureCanvasBase.print_figure`, which take care of setting the figure
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facecolor, edgecolor, and dpi to the desired output values, and will
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restore them to the original values. Therefore, `print_foo` does not
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need to handle these settings.
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"""
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self.draw()
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def get_default_filetype(self):
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return 'foo'
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########################################################################
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#
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# Now just provide the standard names that backend.__init__ is expecting
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#
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########################################################################
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FigureCanvas = FigureCanvasTemplate
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FigureManager = FigureManagerTemplate
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