Merge pull request #11727 from Snuffleupagus/issue-11713

Add a heuristic to scale even single-char text, when the horizontal/vertical scaling differs significantly (issue 11713)

src/display/text_layer.js

@@ -113,7 +113,22 @@ var renderTextLayer = (function renderTextLayerClosure() {
     // We don't bother scaling single-char text divs, because it has very
     // little effect on text highlighting. This makes scrolling on docs with
     // lots of such divs a lot faster.
+    let shouldScaleText = false;
     if (geom.str.length > 1) {
+      shouldScaleText = true;
+    } else if (geom.transform[0] !== geom.transform[3]) {
+      const absScaleX = Math.abs(geom.transform[0]),
+        absScaleY = Math.abs(geom.transform[3]);
+      // When the horizontal/vertical scaling differs significantly, also scale
+      // even single-char text to improve highlighting (fixes issue11713.pdf).
+      if (
+        absScaleX !== absScaleY &&
+        Math.max(absScaleX, absScaleY) / Math.min(absScaleX, absScaleY) > 1.5
+      ) {
+        shouldScaleText = true;
+      }
+    }
+    if (shouldScaleText) {
       if (style.vertical) {
         textDivProperties.canvasWidth = geom.height * task._viewport.scale;
       } else {

test/pdfs/.gitignore

@@ -143,6 +143,7 @@
 !issue6621.pdf
 !issue6286.pdf
 !issue1055r.pdf
+!issue11713.pdf
 !issue1293r.pdf
 !issue1655r.pdf
 !issue6541.pdf

test/test_manifest.json

@@ -1107,6 +1107,12 @@
        "link": false,
        "type": "text"
     },
+    {  "id": "issue11713",
+       "file": "pdfs/issue11713.pdf",
+       "md5": "bafe5801234feeb95969da106f2ce6d8",
+       "rounds": 1,
+       "type": "text"
+    },
     {  "id": "bug1250079",
        "file": "pdfs/bug1250079.pdf",
        "md5": "a1dd21a70ae7097d96273e85a80b26ef",