How to reference Canvas elements in VueJS components from a different file

Question

How to reference Canvas elements in VueJS components from a different file

In my @vue3/cli project, I am facing a straightforward problem that I can't seem to find a solution for.

I have two components within the same view hierarchy. One component displays webcam video in a video tag, while the other component contains an HTML5 canvas. My goal is to render a portion of the video on the canvas component, but I'm unsure how to send the video image from one component to the other.

Home -->
        WebCam.vue  
        Canvas.vue

I attempted to send the video data from the WebCam component to the Canvas component using:

this.emitter.emit('cam-image', {
                   id:'video',
                    image: this.video 
                })

Despite using mitt for event emitting, this approach did not work as expected. The entire video tag is being logged in my console.

this.emitter.on("cam-image", data => { 
                     console.log(data.image)
                        this.canvasContext.drawImage(
                          data.image,
                         0, 0,
                         300, 150,
                        0, 0, this.canvasWidth, this.canvasHeight
                    );
                })

As an alternative, I considered accessing the refs from the Canvas component within the WebCam component to directly render the image from there.

javascript vue.js canvas vuejs3

Answer 1

Answer №1

If you're looking to share a variable between components, there are a few options available. One simple way is to use a global variable. This can be achieved by creating a global reactive instance, like the example below:

// global.js
import { ref } from "vue";
export const sharedVariable = ref(null);

Once you have defined the global variable, you can import and use it in your components like this:

<template>
  ...
  <div v-if="$sharedVariable.value">Shared Content</div>
  ...
</template>

<script>
  import { sharedVariable } from "global.js";

  export default {
    setup() {
      // make the variable available to the template
      return {
        sharedVariable 
      }
    }
  }
</script>

You can repeat the same process for other components that need access to the shared variable.

Another approach is using provide/inject to pass data down to child components only when needed. This method ensures that the shared data is scoped properly and doesn't require a global instance:

In the parent component:

<script>
provide() {
  return {
    sharedVariable: sharedVariable
  };
}
</script>

And in the child component:

<script>
inject: ['sharedVariable']
// now you can use sharedVariable within this component
</script>

This approach mimics the functionality of the context API in React and provides a clean separation of concerns for your components.

For a practical example and live code demonstration, check out the jsfiddle link.

Answer 2

If you're looking to share a variable between components, there are a few options available. One simple way is to use a global variable. This can be achieved by creating a global reactive instance, like the example below:

// global.js
import { ref } from "vue";
export const sharedVariable = ref(null);

Once you have defined the global variable, you can import and use it in your components like this:

<template>
  ...
  <div v-if="$sharedVariable.value">Shared Content</div>
  ...
</template>

<script>
  import { sharedVariable } from "global.js";

  export default {
    setup() {
      // make the variable available to the template
      return {
        sharedVariable 
      }
    }
  }
</script>

You can repeat the same process for other components that need access to the shared variable.

Another approach is using provide/inject to pass data down to child components only when needed. This method ensures that the shared data is scoped properly and doesn't require a global instance:

In the parent component:

<script>
provide() {
  return {
    sharedVariable: sharedVariable
  };
}
</script>

And in the child component:

<script>
inject: ['sharedVariable']
// now you can use sharedVariable within this component
</script>

This approach mimics the functionality of the context API in React and provides a clean separation of concerns for your components.

For a practical example and live code demonstration, check out the jsfiddle link.

How to reference Canvas elements in VueJS components from a different file

Answer №1

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