Pixi’VN 2D game engine

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Manage game flow with labels ​

The game flow is managed by functions that call labels, jump labels, go back, close labels... These functions are in the narration object.

Run a label ​

There are two ways to run a label:

Call a label ​

To call a label you must use the narration.callLabel function. This function have 2 parameters:

  • label: the label that will be called
  • props: the properties that will be passed to the label. Its interface corresponds to StepLabelProps.

When you call a label, the first step of that label will be started. If before the call was running another label, the remaining steps of the another label will be executed after the steps of the called label.

For example if currently the game is running the step 5 of the label A and you call the label B, when all the steps of the label B are executed, the game will continue with the step 6 of the label A.

narration.callLabel returns a result of first step of the called label.

typescript
import { narration } from '@drincs/pixi-vn'

narration.callLabel(startLabel, {})

Remember that if you execute the narration.callLabel inside a step, you should return the result of first step of the called label and use await. The reason is that it might generate a wrong history.

typescript
import { narration, newLabel } from '@drincs/pixi-vn'

export const startLabel = newLabel("start_label",
    [
        async (props) => {
            return await narration.callLabel(TestLabel, props)
        },
        async (props) => await narration.callLabel(TestLabel, props),
    ]
)

Jump to a label ​

To jump to a label you must use the narration.jumpLabel function and pass the label. This function have 2 parameters:

  • label: the label that will be called
  • props: the properties that will be passed to the label. Its interface corresponds to StepLabelProps.

When you jump to a label, the steps of the current label will be stopped and the steps of the label passed as parameter will be started.

For example if currently the game is running the step 5 of the label A, and call the label B, and you jump to the label C, when all the steps of the label C are executed, the game will continue with the step 6 of the label A. Because when you jump to the label C, the label B is closed.

narration.jumpLabel returns a result of first step of the called label.

typescript
import { narration } from '@drincs/pixi-vn'

narration.jumpLabel(startLabel, {})

Remember that if you execute the narration.jumpLabel inside a step, you should return the result of first step of the called label and use await. The reason is that it might not await the first step of the new label.

typescript
import { narration } from '@drincs/pixi-vn'

export const startLabel = newLabel("start_label",
    [
        async (props) => {
            return await narration.jumpLabel(TestLabel, props)
        },
        async (props) => await narration.jumpLabel(TestLabel, props),
    ]
)

Next step and go back ​

Next step ​

To execute the next step you must execute the narration.goNext() function. This function have a parameter:

  • props: the properties that will be passed to the label. Its interface corresponds to StepLabelProps.
typescript
import { narration } from '@drincs/pixi-vn'

await narration.goNext({})

narration.goNext() is asynchronous, so, for example, you can use then for disabled a next button until the next step is executed.

typescript
import { narration } from '@drincs/pixi-vn'

// disable next button
narration.goNext({})
    .then((result) => {
        // enable next button
    })

Remember that if you execute the narration.goNext() inside a step, you should return the result of the step and use await. The reason is that it might generate a wrong history.

typescript
import { narration, newLabel } from '@drincs/pixi-vn'

export const startLabel = newLabel("start_label",
    [
        async (props) => {
            await narration.goNext(props)
        },
    ]
)

Go back ​

Every step the system saves the current state of the game. To go back to the previous step you must execute the narration.goBack() function.

In parameters you must pass a function navigate: (path: string) => void that will be called with the URL Path or Route of the previous step, so you can to navigate to the previous UI screen.

For exemple if you use a React Router Dom:

typescript
import { narration } from '@drincs/pixi-vn'
import { useNavigate } from 'react-router-dom';

const navigate = useNavigate();

if (narration.canGoBack) {
    narration.goBack(navigate).then(() => {
        // ...
    })
}

Close labels ​

Close current label ​

To close the current label you must execute the narration.closeCurrentLabel() function.

typescript
import { narration } from '@drincs/pixi-vn'

narration.closeCurrentLabel()

Close all labels ​

To close all labels you must execute the narration.closeAllLabels() function. If you call this function and after that you don't call any label, the game will end.

typescript
import { narration } from '@drincs/pixi-vn'

narration.closeAllLabels()

How to create the go back and go next buttons ​

For example:

( It's in basic html, you will need to replace the basic html elements with UI components from your favorite library to improve the graphics. )