What you'll learn

In this codelab you will learn how to:

What you'll build

A very simple Blockly workspace with customized themes.

What you'll need

This codelab is focused on Blockly's theme extension. Non-relevant concepts
are glossed over and provided for you to simple copy and paste.

Download the sample code

You can get the sample code for this code by either downloading the zip here:

Download zip

or by cloning this git repo:

git clone https://github.com/google/blockly-samples.git

If you downloaded the source as a zip, unpacking it should give you a root folder named blockly-samples-master.

The relevant files are in examples/theme-extension-codelab. There are two versions of the app:

Each folder contains:

To run the code, simple open starter-code/index.html in a browser. You should see a Blockly workspace with a flyout.

A web page with the text “Theme Extension Codelab” and a Blockly workspace.

In this section you will create a very basic halloween theme, then inject it to display in the workspace.

Themes

Themes are a way to customize the look and feel of Blockly. Currently, we support customizing block colours, category colours and certain components through the Themes class.

A theme can be created using the constructor or by using defineTheme. Using defineTheme makes it easy to extend a pre existing theme and set all values with a single object.

Add the below code in index.js right before function start()

Blockly.Themes.Halloween = Blockly.Theme.defineTheme('halloween', {
  'base': Blockly.Themes.Classic,
});

And then add a line to inject this theme in function start() in index.js

function start() {
    // Create main workspace.
    workspace = Blockly.inject('blocklyDiv',
      {
        toolbox: toolboxCategories,
        theme: Blockly.Themes.Halloween,
      });
 } 

Note: At this point, we have just created a new theme. But it does not have any customizations. We will do that next.

Within the Halloween theme definition, you can customize the colours of multiple components:

Blockly.Themes.Halloween = Blockly.Theme.defineTheme('halloween', {
  'base': Blockly.Themes.Classic,
  'componentStyles': {
    'workspaceBackgroundColour': '#ff7518',
    'toolboxBackgroundColour': '#F9C10E',
    'toolboxForegroundColour': '#fff',
    'flyoutBackgroundColour': '#252526',
    'flyoutForegroundColour': '#ccc',
    'flyoutOpacity': 1,
    'scrollbarColour': '#ff0000',
    'insertionMarkerColour': '#fff',
    'insertionMarkerOpacity': 0.3,
    'scrollbarOpacity': 0.4,
    'cursorColour': '#d0d0d0',
    'blackBackground': '#333'
  }
});

Test it

Reload your web page. You should see a themed workspace!

Fun with colours.

A category style currently only holds a colour property. It is the colour of the category on the toolbox.
This value can either be defined as a hex value or as a hue. Usually these colours should be the same as
the colourPrimary on the majority of blocks in the category making it easy for users to tell what blocks
belong in what category.

Update the Theme definition to have the category styles as below.

Blockly.Themes.Halloween = Blockly.Theme.defineTheme('halloween', {
  'base': Blockly.Themes.Classic,
  'categoryStyles': {
    'list_category': {
      'colour': "#4a148c"
    },
    'logic_category': {
      'colour': "#8b4513",
    },
    'loop_category': {
      'colour': "#85E21F",
    },
    'text_category': {
      'colour': "#FE9B13",
    }
  },
  'componentStyles': {
    'workspaceBackgroundColour': '#ff7518',
    'toolboxBackgroundColour': '#F9C10E',
    'toolboxForegroundColour': '#fff',
    'flyoutBackgroundColour': '#252526',
    'flyoutForegroundColour': '#ccc',
    'flyoutOpacity': 1,
    'scrollbarColour': '#ff0000',
    'insertionMarkerColour': '#fff',
    'insertionMarkerOpacity': 0.3,
    'scrollbarOpacity': 0.4,
    'cursorColour': '#d0d0d0',
    'blackBackground': '#333'
  }
});

Test it

The colour displayed next to the toolbox category should display your new colours.
Clicking on a category will highlight the row with your new colour.

Customized Block colors on the components

A block style currently only holds three different colour properties. They are ‘colourPrimary',
‘colourSecondary' and ‘colourTertiary'. This value can either be defined as a hex value or as a hue.
For more information on block styles visit our themes documentation

Update the Theme definition to have the block styles as below.

Blockly.Themes.Halloween = Blockly.Theme.defineTheme('halloween', {
  'base': Blockly.Themes.Classic,
  'categoryStyles': {
    'list_category': {
      'colour': "#4a148c"
    },
    'logic_category': {
      'colour': "#8b4513",
    },
    'loop_category': {
      'colour': "#85E21F",
    },
    'text_category': {
      'colour': "#FE9B13",
    },
  },
  'blockStyles': {
    'list_blocks': {
      'colourPrimary': "#4a148c",
      'colourSecondary':"#AD7BE9",
      'colourTertiary':"#CDB6E9",
    },
    'logic_blocks': {
      'colourPrimary': "#8b4513",
      'colourSecondary':"#ff0000",
      'colourTertiary':"#C5EAFF"
    },
    'loop_blocks': {
      'colourPrimary': "#85E21F",
      'colourSecondary':"#ff0000",
      'colourTertiary':"#C5EAFF"
    },
    'text_blocks': {
      'colourPrimary': "#FE9B13",
      'colourSecondary':"#ff0000",
      'colourTertiary':"#C5EAFF"
    },
  },
  'componentStyles': {
    'workspaceBackgroundColour': '#ff7518',
    'toolboxBackgroundColour': '#F9C10E',
    'toolboxForegroundColour': '#fff',
    'flyoutBackgroundColour': '#252526',
    'flyoutForegroundColour': '#ccc',
    'flyoutOpacity': 1,
    'scrollbarColour': '#ff0000',
    'insertionMarkerColour': '#fff',
    'insertionMarkerOpacity': 0.3,
    'scrollbarOpacity': 0.4,
    'cursorColour': '#d0d0d0',
    'blackBackground': '#333'
  }
});

Test it

Click on different blocks in the component and you should see the colours that you applied show up.

Customized Block colors on the components

In this codelab you have learned how to extend and customize themes for the blocks component.

Additional information