# Source code for enaml.widgets.image_view

    #------------------------------------------------------------------------------
    # Copyright (c) 2013-2025, 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

    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)

        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)