How to resize text on canvas?

Remember, that Konva.Transformer is changing scaleX and scaleY properties of a node. If you want to change width of the text, without changing its size, you should reset scale of a text back to 1 and adjust width accordingly.

You can use transform event to update text's properties as you need it.

Instructions: Try to resize a text.

Vanilla

import Konva from 'konva';

const width = window.innerWidth;
const height = window.innerHeight;

const stage = new Konva.Stage({
container: 'container',
width: width,
height: height,
});

const layer = new Konva.Layer();
stage.add(layer);

const text = new Konva.Text({
x: 50,
y: 50,
text: 'Hello from Konva! Try to resize me.',
fontSize: 24,
draggable: true,
width: 200,
});
layer.add(text);

const tr = new Konva.Transformer({
nodes: [text],
// enable only one anchor to see better what is happening
// we are changing width only
enabledAnchors: ['middle-left', 'middle-right'],
});
layer.add(tr);

text.on('transform', function () {
// reset scale on transform
text.setAttrs({
width: text.width() * text.scaleX(),
scaleX: 1,
});
});

React

import { Stage, Layer, Text, Transformer } from 'react-konva';
import { useRef, useEffect, useState } from 'react';

const App = () => {
  const [textAttrs, setTextAttrs] = useState({
    x: 50,
    y: 50,
    width: 200,
  });
  const textRef = useRef();
  const trRef = useRef();

  useEffect(() => {
    trRef.current.nodes([textRef.current]);
  }, []);

  return (
    <Stage width={window.innerWidth} height={window.innerHeight}>
      <Layer>
        <Text
          x={textAttrs.x}
          y={textAttrs.y}
          text="Hello from Konva! Try to resize me."
          fontSize={24}
          draggable
          width={textAttrs.width}
          ref={textRef}
          onDragEnd={(e) => {
            setTextAttrs((attrs) => ({
              ...attrs,
              ...e.target.position(),
            }));
          }}
          onTransform={() => {
            const node = textRef.current;
            const nextWidth = node.width() * node.scaleX();
            node.scaleX(1);
            setTextAttrs({
              x: node.x(),
              y: node.y(),
              width: nextWidth,
            });
          }}
        />
        <Transformer
          ref={trRef}
          enabledAnchors={['middle-left', 'middle-right']}
        />
      </Layer>
    </Stage>
  );
};

export default App;

Vue

<template>
  <v-stage :config="stageSize">
    <v-layer>
      <v-text
        :config="textConfig"
        @transform="handleTransform"
        ref="textRef"
      />
      <v-transformer
        :config="transformerConfig"
        ref="transformerRef"
      />
    </v-layer>
  </v-stage>
</template>

<script setup>
import { ref, computed, onMounted } from 'vue';

const stageSize = {
  width: window.innerWidth,
  height: window.innerHeight
};

const textWidth = ref(200);

const textConfig = computed(() => ({
  x: 50,
  y: 50,
  text: 'Hello from Konva! Try to resize me.',
  fontSize: 24,
  draggable: true,
  width: textWidth.value
}));

const transformerConfig = {
  enabledAnchors: ['middle-left', 'middle-right']
};

const textRef = ref(null);
const transformerRef = ref(null);

const handleTransform = () => {
  const node = textRef.value.getNode();
  textWidth.value = node.width() * node.scaleX();
  node.scaleX(1);
};

onMounted(() => {
  transformerRef.value.getNode().nodes([textRef.value.getNode()]);
});
</script>