Scenic v0.7.0 Scenic.Components

About Components

Components are small scenes that are referenced, and managed, by another scene. They are useful for reusing bits of UI and containing the logic that runs them.

Helper Functions

This module contains a set of helper functions to make it easy to add, or modify, the standard components in a graph.

In general, each helper function is of the form

def name_of_component( graph, data, options \\ [] )

Unlike primitives, components are scenes in themselves. Each component is is run by a GenServer and adding a basic component does two things.

1) A new component GenServer is started and supervised by the owning scene’s dynamic scene supervisor. 2) A reference to the new scene is added to the graph.

This doesn’t happen all at once. These helper functions simply add a reference to a to-be-started component to your graph. When you call push_graph/1 to the ViewPort then manages the lifecycle of the components.

You can also supervise components yourself, but then you should add the scene reference yourself via the scene_ref/3 function, which is in the Scenice.Primitives module.

When adding components to a graph, each helper function accepts a graph as the first parameter and returns the transformed graph. This makes is very easy to buid a complex graph by piping helper functions together.

@graph Graph.build()
|> button( "Press Me", id: :sample_button )

When modifying a graph, you can again use the helpers by passing in the component to be modified. The transformed component will be returned.

Graph.modify(graph, :sample_button, fn(p) ->
  button( p, "Continue" )
end)

# or, more compactly...

Graph.modify(graph, :sample_button, &button(&1, "Continue") )

In each case, the second parameter is a data term that is specific to the component being acted on. See the documentation below. If you pass in invalid data for the second parameter an error will be thrown along with some explanation of what it expected.

The third parameter is a keyword list of options that are to be applied to the component. This includes setting the id, styles, transforms and such.

@graph Graph.build()
|> button( "Press Me", id: :sample_button, rotate: 0.4)

Event messages

Most basic or input components exist to collect data and/or send messages to the host scene that references.

For example, when a button scene decides that it has been “clicked”, the generic button component doesn’t know how to do anything with that information. So it sends a {:click, id} to the host scene that referenced it.

That scene can intercept the message, act on it, transform it, and/or send it up to the host scene that references it. (Components can be nested many layers deep)

To do this, the host scene should implement the filter_event callback.

examples:

  def filter_event( {:click, :sample_button}, _, state ) do
    {:stop, state }
  end

  def filter_event( {:click, :sample_button}, _, state ) do
    {:continue, {:click, :transformed}, state }
  end

Inside a filter_event callback you can modify a graph, change state, send messages, transform the event, stop the event, and much more.

Link to this section Summary

Functions

button(graph, data, options \\ [])

Add a button to a graph

checkbox(graph, data, options \\ [])

Add a checkbox to a graph

dropdown(graph, data, options \\ [])

Add a dropdown to a graph

radio_group(graph, data, options \\ [])

Add a radio group to a graph

slider(graph, data, options \\ [])

Add a slider to a graph

text_field(graph, data, options \\ [])

Add a text field input to a graph

Link to this section Functions

button(graph, data, options \\ [])

Add a button to a graph

A button is a small scene that is pretty much just some text drawn over a rounded rectangle. The button scene contains logic to detect when the button is pressed, tracks it as the pointer moves around, and when it is released.

Data:

text

text must be a bitstring

Messages

If a button press is successful, it sends an event message to the host scene in the form of:

{:click, id}

Styles

Buttons honor the following standard styles

:hidden - If false the component is rendered. If true, it is skipped. The default is false.
:theme - The color set used to draw. See below. The default is :primary

Additional Styles

Buttons honor the following list of additional styles.

:width - pass in a number to set the width of the button.
:height - pass in a number to set the height of the button.
:radius - pass in a number to set the radius of the button’s rounded rectangle.
:alignment - set the aligment of the text inside the button. Can be one of :left, :right, :center. The default is :center.
:button_font_size - the size of the font in the button

Buttons do not use the inherited :font_size style as the should look consistent regardless of what size the surrounding text is.

Theme

Buttons work well with the follwing predefined themes: :primary, :secondary, :success, :danger, :warning, :info, :text, :light, :dark

To pass in a custom theme, supply a map with at least the following entries:

:text - the color of the text in the button
:background - the normal background of the button
:active - the background while the button is pressed

Examples

The following example creates a simple button and positions it on the screen.

graph
|> button( "Example", id: :button_id, translate: {20, 20} )

The next example makes the same button as before, but colors it as a warning button. See the options list above for more details.

graph
|> button( "Example", id: :button_id, translate: {20, 20}, theme: :warning )

checkbox(graph, data, options \\ [])

Add a checkbox to a graph

Data:

{text, checked?}

text must be a bitstring
checked? must be a boolean and indicates if the checkbox is set.

Messages

When the state of the checkbox, it sends an event message to the host scene in the form of:

{:value_changed, id, checked?}

Styles

Buttons honor the following standard styles

:hidden - If false the component is rendered. If true, it is skipped. The default is false.
:theme - The color set used to draw. See below. The default is :dark

Theme

Checkboxes work well with the follwing predefined themes: :light, :dark

To pass in a custom theme, supply a map with at least the following entries:

:text - the color of the text in the button
:background - the background of the box
:border - the border of the box
:active - the border of the box while the button is pressed
:thumb - the color of the checkmark itself

Examples

The following example creates a checkbox and positions it on the screen.

graph
|> checkbox( {"Example", :checkbox_id, true}, translate: {20, 20} )

dropdown(graph, data, options \\ [])

Add a dropdown to a graph

Data:

{items, initial_item}

items must be a list of items, each of which is: {text, id}. See below…
initial_item is the id of the initial selected item. It can be any term you want, however it must be an item_id in the items list. See below.

Per item data:

{text, item_id}

text is a string that will be shown in the dropdown.
item_id can be any term you want. It will identify the item that is currently selected in the dropdown and will be passed back to you during event messages.

When the state of the checkbox, it sends an event message to the host scene in the form of:

{:value_changed, id, selected_item_id}

Dropdowns honor the following list of options.

Buttons honor the following styles

:hidden - If false the component is rendered. If true, it is skipped. The default is false.
:theme - The color set used to draw. See below. The default is :dark

Buttons honor the following list of additional styles.

:width - pass in a number to set the width of the button.
:height - pass in a number to set the height of the button.

Dropdowns work well with the follwing predefined themes: :light, :dark

To pass in a custom theme, supply a map with at least the following entries:

:text - the color of the text
:background - the background of the component
:border - the border of the component
:active - the background of selecte item in the dropdown list
:thumb - the color of the item being hovered over

The following example creates a dropdown and positions it on the screen.

graph
|> dropdown({[
  {"Dashboard", :dashboard},
  {"Controls", :controls},
  {"Primitives", :primitives},
], :controls, :dropdown_id }, translate: {20, 20} )

radio_group(graph, data, options \\ [])

Add a radio group to a graph

Data:

radio_buttons

radio_buttons must be a list of radio button data. See below.

Radio button data:

{text, radio_id, checked? \\ false}

text must be a bitstring
button_id can be any term you want. It will be passed back to you as the group’s value.
checked? must be a boolean and indicates if the button is selected. checked? is not required and will default to false if not supplied.

Messages

When the state of the radio group changes, it sends an event message to the host scene in the form of:

{:value_changed, id, radio_id}

Options

Radio Buttons honor the following list of options.

:theme - This sets the color scheme of the button. This can be one of pre-defined button schemes :light, :dark, or it can be a completly custom scheme like this: {text_color, box_background, border_color, pressed_color, checkmark_color}.

Styles

Radio Buttons honor the following styles

:hidden - If false the component is rendered. If true, it is skipped. The default is false.
:theme - The color set used to draw. See below. The default is :dark

Theme

Dropdowns work well with the follwing predefined themes: :light, :dark

To pass in a custom theme, supply a map with at least the following entries:

:text - the color of the text
:background - the background of the component
:border - the border of the component
:active - the background of the circle while the button is pressed
:thumb - the color of inner selected-mark

Examples

The following example creates a radio group and positions it on the screen.

graph
|> radio_group({[
    {"Radio A", :radio_a},
    {"Radio B", :radio_b, true},
    {"Radio C", :radio_c},
  ], :radio_group_id },
  translate: {20, 20} )

slider(graph, data, options \\ [])

Add a slider to a graph

Data:

{ extents, initial_value}

extents gives the range of values. It can take several forms…
- {min,max} If min and max are integers, then the slider value will be an integer.
- {min,max} If min and max are floats, then the slider value will be an float.
- [a, b, c] A list of terms. The value will be one of the terms
initial_value Sets the intial value (and position) of the slider. It must make sense with the extents you passed in.

Messages

When the state of the slider changes, it sends an event message to the host scene in the form of:

{:value_changed, id, value}

Options

Sliders honor the following list of options.

Styles

Sliders honor the following styles

:hidden - If false the component is rendered. If true, it is skipped. The default is false.
:theme - The color set used to draw. See below. The default is :dark

Theme

Sliders work well with the follwing predefined themes: :light, :dark

To pass in a custom theme, supply a map with at least the following entries:

:border - the color of the slider line
:thumb - the color of slider thumb

Examples

The following example creates a numeric sliderand positions it on the screen.

graph
|> Component.Input.Slider.add_to_graph( {{0,100}, 0, :num_slider}, translate: {20,20} )

The following example creates a list slider and positions it on the screen.

graph
|> slider( {[
    :white,
    :cornflower_blue,
    :green,
    :chartreuse
  ], :cornflower_blue, :slider_id}, translate: {20,20} )

text_field(graph, data, options \\ [])

Add a text field input to a graph

Data: initial_value

initial_value is the string that will be the starting value

Messages

When the text in the field changes, it sends an event message to the host scene in the form of:

{:value_changed, id, value}

Styles

Text fields honor the following styles

:hidden - If false the component is rendered. If true, it is skipped. The default is false.
:theme - The color set used to draw. See below. The default is :dark

Additional Styles

Text fields honor the following list of additional styles.

:filter - Adding a filter option restricts which characters can be entered into the text_field component. The value of filter can be one of:
- :all - Accept all characters. This is the default
- :number - Any characters from “0123456789.,”
- "filter_string" - Pass in a string containing all the characters you will accept
- function/1 - Pass in an anonymous function. The single parameter will be the character to be filtered. Return true or false to keep or reject it.
:hint - A string that will be shown (greyed out) when the entered value of the componenet is empty.
:type - Can be one of the following options:
- :all - Show all characters. This is the default.
- :password - Display a string of ‘*’ characters instead of the value.
:width - set the width of the control.

Theme

Dropdowns work well with the follwing predefined themes: :light, :dark

To pass in a custom theme, supply a map with at least the following entries:

:text - the color of the text
:background - the background of the component
:border - the border of the component
:focus - the border while the component has focus

Examples

graph
|> text_field( {"Sample Text", :text_id}, translate: {20,20} )

graph
|> text_field(
  {"", :pass_id, [type: :password, hint: "Enter password"]},
  translate: {20,20}
)