Fallback to using the family when doing an exact match

If the difference between the families sizes is just 1 where one of them
is 0 in size then we can fallback to the family in that case.

Fixes: QTBUG-87267
Change-Id: I62b25b06c88000b4d7defe91871c07873b1fc792
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>
(cherry picked from commit bdc9d272eebff66827b566b1b24b6697c797807a)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

2 files changed, 38 insertions, 6 deletions

diff --git a/src/gui/text/qfont.cpp b/src/gui/text/qfont.cpp
index 2bea0e9a07..94020dc665 100644
--- a/src/gui/text/qfont.cpp
+++ b/src/gui/text/qfont.cpp
@@ -116,19 +116,36 @@ bool QFontDef::exactMatch(const QFontDef &other) const
     if (stretch != 0 && other.stretch != 0 && stretch != other.stretch)
         return false;
 
-    if (families.size() != other.families.size())
+    // If either families or other.families just has 1 entry and the other has 0 then
+    // we will fall back to using the family in that case
+    const int sizeDiff = qAbs(families.size() - other.families.size());
+    if (sizeDiff > 1)
+        return false;
+    if (sizeDiff == 1 && (families.size() > 1 || other.families.size() > 1))
         return false;
 
+    QStringList origFamilies = families;
+    QStringList otherFamilies = other.families;
+    if (sizeDiff != 0) {
+        if (origFamilies.size() != 1)
+            origFamilies << family;
+        else
+            otherFamilies << other.family;
+    }
+
     QString this_family, this_foundry, other_family, other_foundry;
-    for (int i = 0; i < families.size(); ++i) {
-        QFontDatabase::parseFontName(families.at(i), this_foundry, this_family);
-        QFontDatabase::parseFontName(other.families.at(i), other_foundry, other_family);
+    for (int i = 0; i < origFamilies.size(); ++i) {
+        QFontDatabase::parseFontName(origFamilies.at(i), this_foundry, this_family);
+        QFontDatabase::parseFontName(otherFamilies.at(i), other_foundry, other_family);
         if (this_family != other_family || this_foundry != other_foundry)
             return false;
     }
 
-    QFontDatabase::parseFontName(family, this_foundry, this_family);
-    QFontDatabase::parseFontName(other.family, other_foundry, other_family);
+    // Check family only if families is not set
+    if (origFamilies.size() == 0) {
+        QFontDatabase::parseFontName(family, this_foundry, this_family);
+        QFontDatabase::parseFontName(other.family, other_foundry, other_family);
+    }
 
     return (styleHint     == other.styleHint
             && styleStrategy == other.styleStrategy
diff --git a/tests/auto/gui/text/qfont/tst_qfont.cpp b/tests/auto/gui/text/qfont/tst_qfont.cpp
index 2d72eef459..9b70308092 100644
--- a/tests/auto/gui/text/qfont/tst_qfont.cpp
+++ b/tests/auto/gui/text/qfont/tst_qfont.cpp
@@ -134,6 +134,21 @@ void tst_QFont::exactMatch()
     QVERIFY(!QFont("serif").exactMatch());
     QVERIFY(!QFont("monospace").exactMatch());
 
+    // Confirm that exactMatch is true for a valid font
+    QFontDatabase db;
+    const QString family = db.families().first();
+    const QString style = db.styles(family).first();
+    const int pointSize = db.pointSizes(family, style).first();
+    font = db.font(family, style, pointSize);
+    QVERIFY(font.exactMatch());
+
+    if (db.families().contains("Arial")) {
+        font = QFont("Arial");
+        QVERIFY(font.exactMatch());
+        font = QFont(QString());
+        font.setFamilies({"Arial"});
+        QVERIFY(font.exactMatch());
+    }
 }
 
 void tst_QFont::italicOblique()