Merge pull request #12106 from IQGeo/issue-12101

improve text width calculation

src/ol/geom/flat/textpath.js

@@ -104,6 +104,9 @@ export function drawTextOnPath(
     return result;
   }
 
+  // rendering across line segments
+  text = text.replace(/\n/g, ' '); // ensure rendering in single-line as all calculations below don't handle multi-lines
+
   for (let i = 0, ii = text.length; i < ii; ) {
     advance();
     let angle = Math.atan2(y2 - y1, x2 - x1);

src/ol/render/canvas.js

@@ -362,7 +362,9 @@ export function measureAndCacheTextWidth(font, text, cache) {
   if (text in cache) {
     return cache[text];
   }
-  const width = measureTextWidth(font, text);
+  const width = text
+    .split('\n')
+    .reduce((prev, curr) => Math.max(prev, measureTextWidth(font, curr)), 0);
   cache[text] = width;
   return width;
 }