Add support for more font weights internally

We should have more font weights in QFont::Weight to allow for
finer grained control.
For the time being, we can simply use intermediate weights to better
support the different font weights falling in between the ones
defined in QFont::Weight.
Also amend the documentation to clarify the fact that QFont supports
and can return weights falling outside the predefined values, which
is already the case (e.g. when using fontconfig).

Done-with: Gabriel de Dietrich
Change-Id: I693cdd48b8b77e7ed550cdf991227bcb819d8e7b
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@theqtcompany.com>
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@theqtcompany.com>

src/gui/text/qfont.cpp

@@ -1014,8 +1014,8 @@ void QFont::setStyle(Style style)
 }
 
 /*!
-    Returns the weight of the font which is one of the enumerated
-    values from \l{QFont::Weight}.
+    Returns the weight of the font, using the same scale as the
+    \l{QFont::Weight} enumeration.
 
     \sa setWeight(), Weight, QFontInfo
 */
@@ -1028,8 +1028,8 @@ int QFont::weight() const
     \enum QFont::Weight
 
     Qt uses a weighting scale from 0 to 99 similar to, but not the
-    same as, the scales used in Windows or CSS. A weight of 0 is
-    ultralight, whilst 99 will be extremely black.
+    same as, the scales used in Windows or CSS. A weight of 0 will be
+    thin, whilst 99 will be extremely black.
 
     This enum contains the predefined font weights:
 
@@ -1041,8 +1041,8 @@ int QFont::weight() const
 */
 
 /*!
-    Sets the weight the font to \a weight, which should be a value
-    from the \l QFont::Weight enumeration.
+    Sets the weight of the font to \a weight, using the scale defined by
+    \l QFont::Weight enumeration.
 
     \sa weight(), QFontInfo
 */

src/gui/text/qfontdatabase.cpp

@@ -85,10 +85,11 @@ static int getFontWeight(const QString &weightString)
     QString s = weightString.toLower();
 
     // Test in decreasing order of commonness
-    if (s == QLatin1String("medium") ||
-        s == QLatin1String("normal")
+    if (s == QLatin1String("normal")
         || s.compare(QCoreApplication::translate("QFontDatabase", "Normal"), Qt::CaseInsensitive) == 0)
         return QFont::Normal;
+    if (s == QLatin1String("medium"))
+        return qt_mediumFontWeight;
     if (s == QLatin1String("bold")
         || s.compare(QCoreApplication::translate("QFontDatabase", "Bold"), Qt::CaseInsensitive) == 0)
         return QFont::Bold;
@@ -100,6 +101,10 @@ static int getFontWeight(const QString &weightString)
         return QFont::Black;
     if (s == QLatin1String("light"))
         return QFont::Light;
+    if (s == QLatin1String("thin"))
+        return qt_thinFontWeight;
+    if (s == QLatin1String("extralight"))
+        return qt_extralightFontWeight;
 
     if (s.contains(QLatin1String("bold"))
         || s.contains(QCoreApplication::translate("QFontDatabase", "Bold"), Qt::CaseInsensitive)) {

src/gui/text/qfontengine_p.h

@@ -78,6 +78,10 @@ enum HB_Compat_Error {
 typedef void (*qt_destroy_func_t) (void *user_data);
 typedef bool (*qt_get_font_table_func_t) (void *user_data, uint tag, uchar *buffer, uint *length);
 
+const QFont::Weight qt_mediumFontWeight = static_cast<QFont::Weight>(57);
+const QFont::Weight qt_extralightFontWeight = static_cast<QFont::Weight>(12);
+const QFont::Weight qt_thinFontWeight = static_cast<QFont::Weight>(0);
+
 class Q_GUI_EXPORT QFontEngine
 {
 public:

src/platformsupport/fontdatabases/basic/qbasicfontdatabase.cpp

@@ -277,10 +277,16 @@ QStringList QBasicFontDatabase::addTTFile(const QByteArray &fontData, const QByt
 
             if (os2->usWeightClass == 0)
                 ;
+            else if (os2->usWeightClass < 150)
+                weight = qt_thinFontWeight;
+            else if (os2->usWeightClass < 250)
+                weight = qt_extralightFontWeight;
             else if (os2->usWeightClass < 350)
                 weight = QFont::Light;
             else if (os2->usWeightClass < 450)
                 weight = QFont::Normal;
+            else if (os2->usWeightClass < 550)
+                    weight = qt_mediumFontWeight;
             else if (os2->usWeightClass < 650)
                 weight = QFont::DemiBold;
             else if (os2->usWeightClass < 750)
@@ -290,10 +296,16 @@ QStringList QBasicFontDatabase::addTTFile(const QByteArray &fontData, const QByt
 
             if (os2->panose[2] >= 2) {
                 int w = os2->panose[2];
-                if (w <= 3)
+                if (w <= 1)
+                    weight = qt_thinFontWeight;
+                else if (w <= 2)
+                    weight = qt_extralightFontWeight;
+                else if (w <= 3)
                     weight = QFont::Light;
                 else if (w <= 5)
                     weight = QFont::Normal;
+                else if (w <= 6)
+                    weight = qt_mediumFontWeight;
                 else if (w <= 7)
                     weight = QFont::DemiBold;
                 else if (w <= 8)

src/platformsupport/fontdatabases/mac/qcoretextfontdatabase.mm

@@ -294,10 +294,16 @@ static void getFontDescription(CTFontDescriptorRef font, FontDescription *fd)
                     fd->weight = QFont::Bold;
                 else if (normalizedWeight >= 0.3)
                     fd->weight = QFont::DemiBold;
+                else if (normalizedWeight >= 0.2)
+                    fd->weight = qt_mediumFontWeight;
                 else if (normalizedWeight == 0.0)
                     fd->weight = QFont::Normal;
                 else if (normalizedWeight <= -0.4)
                     fd->weight = QFont::Light;
+                else if (normalizedWeight <= -0.6)
+                    fd->weight = qt_extralightFontWeight;
+                else if (normalizedWeight <= -0.8)
+                    fd->weight = qt_thinFontWeight;
             }
         }
         if (CFNumberRef italic = (CFNumberRef) CFDictionaryGetValue(styles, kCTFontSlantTrait)) {