While you can use the UI features provided by the Platform API without modification, there are a few ways you can change the way they look or behave.

Change the look and behavior of OpenFin windows.
Changing keyboard shortcuts
Changing the look of Layouts via CSS

Using keyboard shortcuts

OpenFin defines and implements a set of optional commands and behaviors specific to UI objects created with the Platform API. You can configure keyboard shortcuts for the commands in the commands property of the platform object in your manifest. For details about the properties of command items, see the hotkeys option on Window.

{
    "platform": {
        "uuid": "example_platform",
        "defaultWindowOptions": {
            ...
        },
        "commands": [
            {
                "command": "stack.nextTab",
                "keys": "Ctrl+T"
            }
        ]
    },
    "snapshot": {
        ...
    }
}

Available commands for keyboard shortcuts

Some of the commands are enabled by default. The following table shows the list of commands enabled by default and their keyboard shortcuts:

Command name	Default shortcut	Description
`stack.closeTab`	None	Closes the currently focused tab.
`stack.nextTab`	`Ctrl+Tab`	Switches to the next tab in the stack.
`stack.nth-tab`	`Ctrl+1` through `Ctrl+9`	Switches to the nth tab in the current stack.
`stack.previousTab`	`Ctrl`+`Shift`+`Tab`	Switches to the previous tab in the current stack.
`view.detach`	`Ctrl`+`Shift`+`D`	Pops the current view out of the window.
`view.focusDown`	`Ctrl`+`Shift`+`Down`	Moves the focus to the view below currently focused one.
`view.focusLeft`	`Ctrl`+`Shift`+`Left`	Moves the focus to the view to the left of currently focused one.
`view.focusRight`	`Ctrl`+`Shift`+`Right`	Moves the focus to the view to the right of currently focused one.
`view.focusUp`	`Ctrl`+`Shift`+`Up`	Moves the focus to the view above currently focused one.
`view.zoomIn`	`Ctrl`+`=`	Zooms in on the contents of the current view
`view.zoomInSecondary` (v24+)	`Ctrl`+`Shift`+`=`	Zooms in on the contents of the current view
`view.zoomOut`	`Ctrl`+`-`	Zooms out on the contents of the current view.
`view.zoomOutSecondary` (v24+)	`Ctrl`+`Shift`+`=`	Zooms out on the contents of the current view.
`view.zoomReset`	`Ctrl`+`0`	Resets zoom level of the current view contents.

Keyboard command example

{
    "command": "view.detach",
    "keys": "Ctrl+D"
}

/*
To disable a command you can simply omit its 'keys' property
*/

{
    "command": "stack.zoomIn"
}

/*
You can disable all default commands using the 'disableDefaultCommands' 
property on your 'platform' object. Once you do that, you can enable 
only the ones you need individually:
*/

{
    "platform": {
        ...,
        "disableDefaultCommands": true,
        "commands": [
            {
                "command": "stack.nextTab",
                "keys": "Ctrl+T"
            }
        ]
    }
    ...
}

Layout CSS classes

When using a custom CSS file to modify the layout's appearance, you can extend or overwrite the internal CSS classes used by the layout to achieve a customized layout look and feel.

The following are the main classes used by the Layout components:

.lm_root: The top-level container of all other containers
.lm_row: Represents a row of layout containers
.lm_column: Represents a column of layout containers
.lm_stack: Represents a pile of tabs stacked on top of each other
- .lm_header: Contains lm_tabs, lm_controls, lm_tabdropdown_list
  - .lm_tabs: Contains all tabs in the current stack
    - .lm_tab: Contains the tab cap title and buttons
  - .lm_controls: Unused
  - .lm_tabdropdown_list: Contains all dropdown tabs in the current stack
    - .lm_tab: Contains the tab cap title and buttons
- .lm_items: Contains all item containers in the stack
  - .lm_item_container: A placeholder div on top of which views are drawn. Show an error message if a view fails to render.

Customizing platform behavior

The Platform Provider is the communication hub that coordinates among all windows in a Platform. This Provider runs in a hidden window. By creating a custom Provider, you can overwrite or extend default Platform behavior.

Provide custom HTML for the Provider window

Because the Provider runs in a normal (hidden) OpenFin window, it needs an HTML document. To provide your own document, add a providerUrl property to your Platform's manifest:

// app.json
{
    "platform": {
        "uuid": "my-uuid",
        ...,
        "providerUrl": "https://my.server.com/platform-provider.html"
    },
    "snapshot": {
        ...
    }
}
```

Overriding default behavior in custom HTML

The custom HTML document must call fin.Platform.init() to initialize the platform and open the manifest-defined snapshot.

Minimal custom Provider HTML

<html>
    <head>
        <script>
            fin.Platform.init();
        </script>
    </head>
    <body></body>
</html>

The fin.Platform.init() method takes an options argument which may contain an overrideCallback property. The class that implements default Platform behavior is provided as an argument to this callback, and OpenFin uses the callback's return value to handle Platform functionality.

Using overrideCallback allows you to extend or replace default functionality in order to customize Platform behavior. To implement your own handlers for Platform behavior, extend the provided class and override any methods you'd like to alter.

Example: Overriding default `getSnapshot` behavior

const saveSnapshotToServer = async (snapshot) => {
    // async code here.
    // Send a snapshot to the server, store it locally somewhere, etc.
}

const overrideCallback = (Provider) => {
    // Extend default behavior
    class MyOverride extends Provider {
        async getSnapshot() {
            // Call super to access vanilla platform behavior
            const snapshot = await super.getSnapshot();
            // Perform any additional logic needed
            const modifiedSnapshot = { ...snapshot, answer: 42 }
            await saveSnapshotToServer(modifiedSnapshot);
            return modifiedSnapshot;
        }
    }
    // Return instance with methods to be consumed by Platform
    return new MyOverride();
};
fin.Platform.init({ overrideCallback });

You can perform any custom initialization before calling fin.Platform.init()

const overrideCallback = async (Provider) => {
    // Do async stuff here
    const userInfo = await loginUser();

    // Extend default behavior
    class MyOverride extends Provider {
        async getSnapshot() {
            const snapshot = await super.getSnapshot();
            return { ...snapshot, userInfo };
        }
    }
    // Return instance with methods to be consumed by Platform
    return new MyOverride();
};
fin.Platform.init({ overrideCallback });