Source code for enaml.widgets.image_view

# Copyright (c) 2013, Nucleic Development Team.
# Distributed under the terms of the Modified BSD License.
# The full license is in the file LICENSE, distributed with this software.
from atom.api import Bool, Typed, ForwardTyped, set_default

from enaml.core.declarative import d_, observe
from enaml.image import Image

from .control import Control, ProxyControl

class ProxyImageView(ProxyControl):
    """ The abstract definition of a proxy ImageView object.

    #: A reference to the ImageView declaration.
    declaration = ForwardTyped(lambda: ImageView)

    def set_image(self, image):
        raise NotImplementedError

    def set_scale_to_fit(self, scale):
        raise NotImplementedError

    def set_allow_upscaling(self, allow):
        raise NotImplementedError

    def set_preserve_aspect_ratio(self, preserve):
        raise NotImplementedError

    def get_aspect_ratio(self):
        raise NotImplementedError

[docs] class ImageView(Control): """ A widget which can display an Image with optional scaling. """ #: The image to display in the viewer. image = d_(Typed(Image)) #: Whether or not to scale the image with the size of the component. scale_to_fit = d_(Bool(False)) #: Whether to allow upscaling of an image if scale_to_fit is True. allow_upscaling = d_(Bool(True)) #: Whether or not to preserve the aspect ratio if scaling the image. preserve_aspect_ratio = d_(Bool(True)) #: An image view hugs its width weakly by default. hug_width = set_default('weak') #: An image view hugs its height weakly by default. hug_height = set_default('weak') #: A reference to the ProxyImageView object. proxy = Typed(ProxyImageView)
[docs] def layout_constraints(self): """Add constraints to preserve the aspect ratio. """ if self.proxy_is_active and self.preserve_aspect_ratio: ratio = self.proxy.get_aspect_ratio() return self.constraints + [self.width == ratio*self.height] return self.constraints
#-------------------------------------------------------------------------- # Observers #-------------------------------------------------------------------------- @observe('image', 'scale_to_fit', 'allow_upscaling', 'preserve_aspect_ratio') def _update_proxy(self, change): """ An observer which sends state change to the proxy. """ # The superclass handler implementation is sufficient. super(ImageView, self)._update_proxy(change)