How can I prevent buttons from interfering with an onPaste event?

Question

How can I prevent buttons from interfering with an onPaste event?

I've created an image modal that allows users to upload or paste an image. Everything is working well, except for the fact that the buttons on the modal are capturing the focus. This means that pasting only works if the user manually clicks outside the buttons. I want to enable pasting anytime the component or anything inside the component has focus.

<div onPaste="onPaste()">
  <button class="__cancel" aria-label="Close" onClick="onClickCancel()">
  <button ... upload .../>
</div>

Is there a way to allow the paste action to flow through the buttons?

Since this is an Angular application, below is code that resembles what I am working with:

<div (paste)="onPaste($event)" cdkTrapFocusAutoCapture cdkTrapFocus>
  <button class="__cancel" aria-label="Close" (onClick)="onClickCancel()">
  <button ... upload .../>
</div>

I have attempted to add the paste method to the buttons, but it seems that they do not fire.

<div (paste)="onPaste($event)" cdkTrapFocusAutoCapture cdkTrapFocus>
  <button class="__cancel" aria-label="Close" (onClick)="onClickCancel()" (paste)="onPaste($event)">
  <button ... upload (paste)="onPaste($event)".../>
</div>

Thank you

javascript angular typescript dom-events onpaste

Answer 1

Answer №1

When the Paste event takes place, it is detected by all HTML elements. However, its impact is only felt on editable elements like <input> fields and <textarea> boxes.
Other elements such as <div> and <p> can only respond to the (paste) event if they have content. This can be achieved by enabling contenteditable:

<div onPaste="onPaste()" contenteditable="true">
  <button class="__cancel" aria-label="Close" (click)="onClickCancel()">
                                              //^-here also
  <button ... upload .../>
</div>

An excerpt from the API documentation explains more about this:

If the cursor is within an editable context, the pasted data will be inserted in the most suitable format supported for that context, if any.

Pasting has no effect in a non-editable context, but the paste event will still trigger.

Furthermore, to adhere to privacy restrictions, the element must be in focus:

In order to prevent misuse, this API should only be accessible when the script is running within a focused document.

While different browsers may exhibit varying behaviors, following these guidelines can help ensure functionality across all platforms.

--- EDITS ---

Making buttons contenteditable can create complications.

Allowing the user to focus on the button area may show a cursor. This can be resolved by applying the following style

[contenteditable] { caret-color: transparent; }
This also grants users the ability to alter button content, which may not be desired. To prevent this, add a keydown handler:

<button class="__cancel" aria-label="Close" mat-icon-button onClick="onClickCancel()" onPaste="onPaste($event)" contenteditable="true" onKeydown="preventKey($event)">

For example:

  preventKey(event: KeyboardEvent) {
    // Buttons require contenteditable to receive (paste) events,
    // but we don't want the buttons to be editable, hence this function blocks that.
    if (
      !(
        event.key === 'Tab' ||
        event.keyCode == 9 ||
        ((event.ctrlKey || event.metaKey) &&
          (event.key === 'v' || event.keyCode == 86))
      )
    ) {
      event.preventDefault();
    }
  }

Pasting into a contenteditable element doesn't function in Safari unless we apply

user-select: auto;

If you're working on an Angular project (as in the original question), this may disrupt cdkTrapFocus. According to the author's knowledge, this is a known bug in Angular. Check https://github.com/angular/components/issues/23846

Answer 2

When the Paste event takes place, it is detected by all HTML elements. However, its impact is only felt on editable elements like <input> fields and <textarea> boxes.
Other elements such as <div> and <p> can only respond to the (paste) event if they have content. This can be achieved by enabling contenteditable:

<div onPaste="onPaste()" contenteditable="true">
  <button class="__cancel" aria-label="Close" (click)="onClickCancel()">
                                              //^-here also
  <button ... upload .../>
</div>

An excerpt from the API documentation explains more about this:

If the cursor is within an editable context, the pasted data will be inserted in the most suitable format supported for that context, if any.

Pasting has no effect in a non-editable context, but the paste event will still trigger.

Furthermore, to adhere to privacy restrictions, the element must be in focus:

In order to prevent misuse, this API should only be accessible when the script is running within a focused document.

While different browsers may exhibit varying behaviors, following these guidelines can help ensure functionality across all platforms.

--- EDITS ---

Making buttons contenteditable can create complications.

Allowing the user to focus on the button area may show a cursor. This can be resolved by applying the following style

[contenteditable] { caret-color: transparent; }
This also grants users the ability to alter button content, which may not be desired. To prevent this, add a keydown handler:

<button class="__cancel" aria-label="Close" mat-icon-button onClick="onClickCancel()" onPaste="onPaste($event)" contenteditable="true" onKeydown="preventKey($event)">

For example:

  preventKey(event: KeyboardEvent) {
    // Buttons require contenteditable to receive (paste) events,
    // but we don't want the buttons to be editable, hence this function blocks that.
    if (
      !(
        event.key === 'Tab' ||
        event.keyCode == 9 ||
        ((event.ctrlKey || event.metaKey) &&
          (event.key === 'v' || event.keyCode == 86))
      )
    ) {
      event.preventDefault();
    }
  }

Pasting into a contenteditable element doesn't function in Safari unless we apply

user-select: auto;

If you're working on an Angular project (as in the original question), this may disrupt cdkTrapFocus. According to the author's knowledge, this is a known bug in Angular. Check https://github.com/angular/components/issues/23846

How can I prevent buttons from interfering with an onPaste event?

Answer №1

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