# Displayables

A displayable is an object that can be shown to the user. Ren'Py displayables can be used in many ways.

- Assignment to an image name using the `image` statement.

- Added to a screen using the screen language `add` statement.

- Assignment to certain config variables.

- Assignment to certain style properties.

When a Ren'Py function or variable expects a displayable, there are five things that can be provided:

- An object of type Displayable, created by calling one of the functions given below.

- A string with a colon `:` in it. These are rare, but see the section on displayable prefixes below.

- A string with a dot `.` in it. Such a string is interpreted as a filename by `Image()`.

- A color. A color may either be given as a hexadecimal color string in "#rgb", "#rgba", "#rrggbb", or "#rrggbbaa" form, a `Color`, or an (r, g, b, a) tuple, where each component is an integer between 0 and 255. Colors are passed to `Solid()`.

- An image name. Any other string is interpreted as a reference to an image, either defined with the image statement or auto-defined from the images directory.

- A list. If a list is provided, each item is expanded as described below, and checked to see if it matches a filename or image name. If so, expansion stops and the matched thing is then processed as described above.

Strings may have one or more square-bracket substitutions in them, such as "eileen [mood]" or "eileen_[outfit]_[mood].png". When such a string is given, a dynamic image is created. A dynamic image has text interpolation performed at the start of each interaction (such as say statements and menus). The resulting string is processed according to the rules above.

When a string has "[prefix_]" in it, that substitution is replaced with each of the style prefixes associated with the current displayable.

## Images

The most commonly used displayable is Image, which loads a file from disk and displays it. Since Image is so commonly used, when a string giving a filename is used in a context that expects a displayable, an Image is automatically created. The only time it's necessary to use Image directly is when you want to create an image with style properties.

    # These two lines are equivalent.
    image logo = "logo.png"
    image logo = Image("logo.png")

    # Using Image allows us to specify a default position as part of
    # an image.
    image logo right = Image("logo.png", xalign=1.0)

There are four image file formats we recommend you use:

- AVIF

- WEBP

- PNG

- JPG

And one vector image file format we recommend:

- SVG

Non-animated GIF and BMP files are also supported, but should not be used in modern games.

Loading an Image from a file on disk and decoding it so it can be drawn to the screen takes a long amount of time. While measured in the tenths or hundreds of seconds, the duration of the loading process is long enough that it can prevent an acceptable framerate, and become annoying to the user.

Since an Image is of a fixed size, and doesn't change in response to input, game state, or the size of the area available to it, an Image can be loaded before it is needed and placed into an area of memory known as the image cache. Once an Image is decoded and in the cache, it can be quickly drawn to the screen.

Ren'Py attempts to predict the images that will be used in the future, and loads them into the image cache before they are used. When space in the cache is needed for other images, Ren'Py will remove images that are no longer being used.

By default, Ren'Py will predictively cache up to 8 screens worth of image data. (If your screen is 800x600, then a screen's worth of data is one 800x600 image, two 400x600 images, and so on.) This can be changed with the `config.image_cache_size` configuration variable.

Although the precise amount is dependent on implementation details and there is significant overhead, as a rule of thumb, each pixel in the image cache consumes 4 bytes of main memory and 4 bytes of video memory.

## SVG Images

Ren'Py supports many SVG 1.0 images, using the NanoSVG library. Some unsupported features include:

- Text elements are ignored. If the text is converted into a path, it will be rendered.

- Embedded bitmaps are ignored.

- Scripts are ignored.

- Animations are ignored.

A list of features NanoSVG supports may be found here.

It's recommended to convert everything in an SVG image that will not render properly into paths.

Ren'Py will render SVG images as if the virtual screen was 96dpi. If the window is enlarged or shrunk, the SVG image will be scaled up or down, respectively, and oversampling will be used to ensture the image is rendered at the correct virtual size.

This ensures the SVG will be rendered sharp if it is not scaled.

## Image-Like Displayables

We call these displayables image-like because they take up a rectangular area of the screen, and do not react to input. These differ from normal images by varying their size to fill an area (Frame, Tile, and Solid), or by allowing the user to specify their size (Composite, Crop, Null). They are not image manipulators.

Image-like displayables take Position Style Properties.

## Text Displayables

See Text Displayables.

## Dynamic Displayables

Dynamic displayables display a child displayable based on the state of the game.

Note that these dynamic displayables always display their current state. Because of this, a dynamic displayable will not participate in a transition. (Or more precisely, it will display the same thing in both the old and new states of the transition.)

By design, dynamic displayables are intended to be used for things that change rarely and when an image defined this way is off screen (Such as a character customization system). It is not designed for things that change frequently, such as character emotions.

## Layer Displayables

Layer displayables display the contents of a layer based on the state of the game. They are intended for use with `config.detached_layers`.

Note that similar to dynamic displayables, the layers shown within always display their current state. Because of this, the contents of a layer displayable will not participate in a transition, unless that transition is targeted at the layer being displayed.

    # A new detached layer to hold the contents of a broadcast.
    define config.detached_layers += [ "broadcast" ]

    # A layer displayable to represent a TV and watch the broadcast layer.
    image tv = Window(Layer("broadcast"), background='#000', padding=(10, 10))

    image living_room = Placeholder('bg', text='living_room')
    image studio = Solid('7c7')
    image eileen = Placeholder('girl')

    label example:
        pause

        # Set up the broadcast scene.
        scene studio onlayer broadcast
        with None

        # Begin a new scene in the living room.
        scene living_room

        # Show the TV in the lower right corner of ths screen.
        show tv:
          align (.75, .75) zoom .3

        # Show Eileen in the broadcast.
        show eileen onlayer broadcast

        # Dissolve into the living room, as Eileen enters the TV from the right.
        with {'master': dissolve, 'broadcast': moveinright}
        pause

## Applying Transforms to Displayables

The At function produces a displayable from a displayable and one or more transforms.

## Layout Boxes and Grids

Layout boxes are displayables that lay out their children on the screen. They can lay out the children in a horizontal or vertical manner, or lay them out using the standard positioning algorithm.

The box displayables take any number of positional and keyword arguments. Positional arguments should be displayables that are added to the box as children. Keyword arguments are style properties that are applied to the box.

Boxes take Position Style Properties and Box Style Properties.

    # Display two logos, to the left and right of each other.
    image logo hbox = HBox("logo.png", "logo.png")

    # Display two logos, one on top of the other.
    image logo vbox = VBox("logo.png", "logo.png")

    # Display two logos. Since both default to the upper-left
    # corner of the screen, we need to use Image to place
    # those logos on the screen.
    image logo fixed = Fixed(
        Image("logo.png", xalign=0.0, yalign=0.0),
        Image("logo.png", xalign=1.0, yalign=1.0))

The Grid layout displays its children in a grid on the screen. It takes Position Style Properties and the `spacing` style property.

## Effects

These displayables are used to create certain visual effects.

## Image Manipulators

An image manipulator is a displayable that takes an image or image manipulator, and either loads it or performs an operation on it. Image manipulators can only take images or other image manipulators as input.

An image manipulator can be used any place a displayable can, but not vice-versa. An `Image()` is a kind of image manipulator, so an Image can be used whenever an image manipulator is required.

The use of image manipulators is historic. A number of image manipulators that had been documented in the past should no longer be used, as they suffer from inherent problems. In any case except for `im.Data()`, the `Transform()` displayable provides similar functionality in a more general manner, while fixing the problems.

For the list of image manipulators, see the image manipulator documentation.

## Placeholders

The Placeholder displayable is used to display background or character images as appropriate. Placeholders are used automatically when an undefined image is used in developer mode. Placeholder displayables can also be used manually when the defaults are inappropriate.

    # By default, the girl placeholder will be used.
    image sue = Placeholder("boy")

    label start:
         show sue angry
         "Sue" "How do you do? Now you gonna die!"

## Displayable Prefixes

Displayable prefixes make it possible for a creator to define their own displayables, and refer to them anywhere a displayable can be used in Ren'Py. A prefixed displayable is a string with a colon in it. The prefix is to the left of the colon, and the argument is anything to the right of it. The `config.displayable_prefix` variable maps a prefix to a function. The function takes the argument, and either returns a displayable or None.

For example, this makes the big prefix return an image that is twice as big as the original.

    init -10 python:
        def embiggen(s):
            return Transform(s, zoom=2)

        config.displayable_prefix["big"] = embiggen

The `init -10` makes sure the prefix is defined before any images that use it. The prefix can then be used to define images:

    image eileen big = "big:eileen happy"

or in any other place where a displayable is required.

## See also

Displaying Images : the basics of how to make all these displayables appear on the screen.