Author: Zhang Hao <zhanghao@uniontech.com>
Date:   Thu Jul 22 10:47:50 2021 +0800
Upstream: https://github.com/qt/qtbase/commit/fccd419dd632306a4bd85928223e0a56a59510ef
Subject: Assertion violation in text shaping on special string with EmojiOneColor font

Index: qtbase-opensource-src/src/gui/text/qtextengine.cpp
===================================================================
--- qtbase-opensource-src.orig/src/gui/text/qtextengine.cpp
+++ qtbase-opensource-src/src/gui/text/qtextengine.cpp
@@ -1496,7 +1496,14 @@ void QTextEngine::shapeText(int item) co
         si.num_glyphs = shapeTextWithHarfbuzz(si, string, itemLength, fontEngine, itemBoundaries, kerningEnabled);
     }
     if (Q_UNLIKELY(si.num_glyphs == 0)) {
-        Q_UNREACHABLE(); // ### report shaping errors somehow
+        if (Q_UNLIKELY(!ensureSpace(si.glyph_data_offset + 1))) {
+            qWarning() << "Unable to allocate space for place-holder glyph";
+            return;
+        }
+        si.num_glyphs = 1;
+        // Overwrite with 0 token to indicate failure
+        QGlyphLayout g = availableGlyphs(&si);
+        g.glyphs[0] = 0;
         return;
     }
 
Index: qtbase-opensource-src/tests/auto/gui/text/qglyphrun/tst_qglyphrun.cpp
===================================================================
--- qtbase-opensource-src.orig/tests/auto/gui/text/qglyphrun/tst_qglyphrun.cpp
+++ qtbase-opensource-src/tests/auto/gui/text/qglyphrun/tst_qglyphrun.cpp
@@ -66,6 +66,7 @@ private slots:
     void boundingRect();
     void mixedScripts();
     void multiLineBoundingRect();
+    void defaultIgnorables();
 
 private:
     int m_testFontId;
@@ -762,6 +763,20 @@ void tst_QGlyphRun::multiLineBoundingRec
     QVERIFY(firstLineGlyphRun.boundingRect().height() < allGlyphRun.boundingRect().height());
 }
 
+void tst_QGlyphRun::defaultIgnorables()
+{
+    QTextLayout layout;
+    layout.setFont(QFont("QtsSpecialTestFont"));
+    layout.setText(QChar(0x200D));
+    layout.beginLayout();
+    layout.createLine();
+    layout.endLayout();
+    QList<QGlyphRun> runs = layout.glyphRuns();
+    QCOMPARE(runs.size(), 1);
+    QCOMPARE(runs.at(0).glyphIndexes().size(), 1);
+    QCOMPARE(runs.at(0).glyphIndexes()[0], 0);
+}
+
 #endif // QT_NO_RAWFONT
 
 QTEST_MAIN(tst_QGlyphRun)