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# -*- coding: utf-8 -*-
# Copyright (c) Vispy Development Team. All Rights Reserved.
# Distributed under the (new) BSD License. See LICENSE.txt for more info.
Functionality to deal with GL Contexts in vispy. This module is defined
in gloo, because gloo (and the layers that depend on it) need to be
context aware. The module "provides" a context, and therefore
depends on this module. Although the GLContext class is aimed for use
by (for practical reasons), it should be possible to use
GLContext without using by overloading it in an appropriate
An GLContext object acts as a placeholder on which different parts
of vispy (or other systems) can keep track of information related to
an OpenGL context.
from copy import deepcopy
import weakref
from .glir import GlirQueue, BaseGlirParser, GlirParser, glir_logger
from .wrappers import BaseGlooFunctions
from .. import config
_default_dict = dict(red_size=8, green_size=8, blue_size=8, alpha_size=8,
depth_size=24, stencil_size=0, double_buffer=True,
stereo=False, samples=0)
canvasses = []
def get_default_config():
"""Get the default OpenGL context configuration
config : dict
Dictionary of config values.
return deepcopy(_default_dict)
def get_current_canvas():
"""Get the currently active canvas
Returns None if there is no canvas available. A canvas is made
active on initialization and before the draw event is emitted.
When a gloo object is created, it is associated with the currently
active Canvas, or with the next Canvas to be created if there is
no current Canvas. Use Canvas.set_current() to manually activate a
cc = [c() for c in canvasses if c() is not None]
if cc:
return cc[-1]
return None
def set_current_canvas(canvas):
"""Make a canvas active. Used primarily by the canvas itself."""
# Notify glir
canvas.context._do_CURRENT_command = True
# Try to be quick
if canvasses and canvasses[-1]() is canvas:
# Make this the current
cc = [c() for c in canvasses if c() is not None]
while canvas in cc:
canvasses[:] = [weakref.ref(c) for c in cc]
def forget_canvas(canvas):
"""Forget about the given canvas. Used by the canvas when closed."""
cc = [c() for c in canvasses if c() is not None]
while canvas in cc:
canvasses[:] = [weakref.ref(c) for c in cc]
class GLContext(BaseGlooFunctions):
"""An object encapsulating data necessary for a OpenGL context
config : dict | None
The requested configuration.
shared : instance of GLContext | None
The shared context.
def __init__(self, config=None, shared=None):
self._shared = shared if (shared is not None) else GLShared()
assert isinstance(self._shared, GLShared)
self._glir = GlirQueue()
self._do_CURRENT_command = False # flag that CURRENT cmd must be given
self._last_viewport = None
def __repr__(self):
return "<GLContext at 0x%x>" % id(self)
def _set_config(self, config):
self._config = deepcopy(_default_dict)
self._config.update(config or {})
# Check the config dict
for key, val in self._config.items():
if key not in _default_dict:
raise KeyError('Key %r is not a valid GL config key.' % key)
if not isinstance(val, type(_default_dict[key])):
raise TypeError('Context value of %r has invalid type.' % key)
def create_shared(self, name, ref):
"""For the app backends to create the GLShared object.
name : str
The name.
ref : object
The reference.
if self._shared is not None:
raise RuntimeError('Can only set_shared once.')
self._shared = GLShared(name, ref)
def config(self):
"""A dictionary describing the configuration of this GL context."""
return self._config
def glir(self):
"""The glir queue for the context. This queue is for objects
that can be shared accross canvases (if they share a contex).
return self._glir
def shared(self):
"""Get the object that represents the namespace that can
potentially be shared between multiple contexts.
return self._shared
def capabilities(self):
"""The OpenGL capabilities"""
return deepcopy(self.shared.parser.capabilities)
def flush_commands(self, event=None):
event : instance of Event
The event.
if self._do_CURRENT_command:
self._do_CURRENT_command = False
canvas = get_current_canvas()
if canvas and hasattr(canvas, '_backend'):
fbo = canvas._backend._vispy_get_fb_bind_location()
fbo = 0
self.shared.parser.parse([('CURRENT', 0, fbo)])
def set_viewport(self, *args):
BaseGlooFunctions.set_viewport(self, *args)
self._last_viewport = args
def get_viewport(self):
return self._last_viewport
class GLShared(object):
"""Representation of a "namespace" that can be shared between
different contexts. App backends can associate themselves with this
object via add_ref().
This object can be used to establish whether two contexts/canvases
share objects, and can be used as a placeholder to store shared
information, such as glyph atlasses.
# We keep a (weak) ref of each backend that gets associated with
# this object. In theory, this means that multiple canvases can
# be created and also deleted; as long as there is at least one
# left, things should Just Work.
def __init__(self):
glir_file = config['glir_file']
parser_cls = GlirParser
if glir_file:
parser_cls = glir_logger(parser_cls, glir_file)
self._parser = parser_cls()
self._name = None
self._refs = []
def __repr__(self):
return "<GLShared of %s backend at 0x%x>" % (str(, id(self))
def parser(self):
"""The GLIR parser (shared between contexts)"""
return self._parser
def parser(self, parser):
assert isinstance(parser, BaseGlirParser) or parser is None
self._parser = parser
def add_ref(self, name, ref):
"""Add a reference for the backend object that gives access
to the low level context. Used in
The given name must match with that of previously added
if self._name is None:
self._name = name
elif name != self._name:
raise RuntimeError('Contexts can only share between backends of '
'the same type')
def name(self):
"""The name of the canvas backend that this shared namespace is
associated with. Can be None.
return self._name
def ref(self):
"""A reference (stored internally via a weakref) to an object
that the backend system can use to obtain the low-level
information of the "reference context". In Vispy this will
typically be the CanvasBackend object.
# Clean
self._refs = [r for r in self._refs if (r() is not None)]
# Get ref
ref = self._refs[0]() if self._refs else None
if ref is not None:
return ref
raise RuntimeError('No reference for available for GLShared')
class FakeCanvas(object):
"""Fake canvas to allow using gloo without
Instantiate this class to collect GLIR commands from gloo
interactions. Call flush() in your draw event handler to execute
the commands in the active contect.
def __init__(self):
self.context = GLContext()
def flush(self):
"""Flush commands. Call this after setting to context to current."""