Auto-scrolling text box cursor movement

Question

Auto-scrolling text box cursor movement

My query is quite similar to the topic discussed in this thread on automatic newline in textarea. However, my situation involves multiple textareas with a 1-row attribute, making it seem like writing on air due to the absence of visible borders (I've set the CSS border property as border: 0;).

I am looking to use jQuery or JavaScript to determine when a user's text input reaches the end of a row in a textarea and automatically move to the next one below. One approach could be counting characters, but different characters have varying widths.

One idea I'm considering is placing a hidden element at the edge of the textareas to trigger the nexttextarea.focus() event, yet I’m unsure how to implement this.

I’ve experimented with various hacks but only one appears promising - storing each character in an array with its corresponding default width value in pixels e.g., 'a'=>0.7px,'b'=>0.9px . This method seems memory-intensive since I'd need to store values for uppercase letters, lowercase letters, and numerous other characters. Subsequently, calculations based on browser width might reveal when the textarea row aligns with the browser’s edge, assuming the current textarea has a width of 100% without a parent container.

If anyone can suggest a straightforward or advanced approach to tackle this issue, please assist me. A major concern is that IE and Mozilla display scroll bars upon resizing the browser window, which contradicts the desired seamless typing experience without these elements being visible.

Pardon my lengthy explanation; accuracy and detail were key objectives here.

javascript jquery css html

Answer 1

Answer №1

Trying to detect text overflow in a textarea can be quite challenging. One approach is to monitor the scrollHeight and scrollWidth of the textarea and transfer text accordingly between textareas when overflow occurs.

For example:

document.onkeyup = function(evt) {
    var event = evt || window.event;
    var target = event.target;
    var nextArea = target.nextSibling; // assuming no whitespace between textareas.
    var chars;
    if (target.tagName == 'TEXTAREA' && (target.scrollLeft || target.scrollTop)) {
        chars = 0;
        while (target.scrollLeft || target.scrollTop) {
            target.value = target.value.replace(/.$/, function(m0) {
                nextArea.value = m0 + nextArea.value;
                return '';
            })
            ++chars;
            target.selectionStart = target.value.length;
        }
        nextArea.focus();
        nextArea.selectionStart = chars;
    }

}

http://jsfiddle.net/L73RG/3/

It is important to note that a complete solution would require binding this functionality to more than just keyup events, as users may also paste text using the context menu. Consider incorporating mouse events or setting up a periodic timer to ensure the functionality works reliably even when user actions do not trigger events directly.

Answer 2

Trying to detect text overflow in a textarea can be quite challenging. One approach is to monitor the scrollHeight and scrollWidth of the textarea and transfer text accordingly between textareas when overflow occurs.

For example:

document.onkeyup = function(evt) {
    var event = evt || window.event;
    var target = event.target;
    var nextArea = target.nextSibling; // assuming no whitespace between textareas.
    var chars;
    if (target.tagName == 'TEXTAREA' && (target.scrollLeft || target.scrollTop)) {
        chars = 0;
        while (target.scrollLeft || target.scrollTop) {
            target.value = target.value.replace(/.$/, function(m0) {
                nextArea.value = m0 + nextArea.value;
                return '';
            })
            ++chars;
            target.selectionStart = target.value.length;
        }
        nextArea.focus();
        nextArea.selectionStart = chars;
    }

}

http://jsfiddle.net/L73RG/3/

It is important to note that a complete solution would require binding this functionality to more than just keyup events, as users may also paste text using the context menu. Consider incorporating mouse events or setting up a periodic timer to ensure the functionality works reliably even when user actions do not trigger events directly.

Answer 3

Answer №2

Make sure to constantly monitor your textarea for overflow by checking it after every keypress. Refer to this link for guidance on how to determine if an HTML element's content is overflowing: Check if HTML element has overflowing content

Once you detect overflow, remove the excess characters and transfer them to the next textarea. Take it step by step, using the overflow check function each time a character is moved to ensure that the textarea is no longer overflowing.

Answer 4

Make sure to constantly monitor your textarea for overflow by checking it after every keypress. Refer to this link for guidance on how to determine if an HTML element's content is overflowing: Check if HTML element has overflowing content

Once you detect overflow, remove the excess characters and transfer them to the next textarea. Take it step by step, using the overflow check function each time a character is moved to ensure that the textarea is no longer overflowing.

Answer 5

Answer №3

One way to solve this problem is by determining the size of the text. Ext-JS accomplishes this task by creating a hidden div with absolute positioning, applying specific font styles, and then measuring the dimensions of the div itself.

If you need guidance on how to implement this technique, refer to Ext-JS's example code at

Answer 6

One way to solve this problem is by determining the size of the text. Ext-JS accomplishes this task by creating a hidden div with absolute positioning, applying specific font styles, and then measuring the dimensions of the div itself.

If you need guidance on how to implement this technique, refer to Ext-JS's example code at

Auto-scrolling text box cursor movement

Answer №1

Answer №2

Answer №3

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