Support fallback fonts in DirectWrite font engine

When selecting fallback fonts for a DirectWrite font, we would
cast the font engine to QWindowsFontEngine and get unpredictable
results and crashes. This change factors out getting the LOGFONT
data from the QFontDef struct and will use this to create a new
DirectWrite engine.

Task-number: QTBUG-22658

Change-Id: I743944d9a44d8742b47b1aa3354532493362cc4a
Reviewed-by: Jiang Jiang <jiang.jiang@nokia.com>

1 files changed, 96 insertions, 85 deletions

diff --git a/src/plugins/platforms/windows/qwindowsfontdatabase.cpp b/src/plugins/platforms/windows/qwindowsfontdatabase.cpp
index a27386c2ad..25f6c4aa21 100644
--- a/src/plugins/platforms/windows/qwindowsfontdatabase.cpp
+++ b/src/plugins/platforms/windows/qwindowsfontdatabase.cpp
@@ -1594,6 +1594,100 @@ static const char *kr_tryFonts[] = {
 
 static const char **tryFonts = 0;
 
+LOGFONT QWindowsFontDatabase::fontDefToLOGFONT(const QFontDef &request)
+{
+    LOGFONT lf;
+    memset(&lf, 0, sizeof(LOGFONT));
+
+    lf.lfHeight = -qRound(request.pixelSize);
+    lf.lfWidth                = 0;
+    lf.lfEscapement        = 0;
+    lf.lfOrientation        = 0;
+    if (request.weight == 50)
+        lf.lfWeight = FW_DONTCARE;
+    else
+        lf.lfWeight = (request.weight*900)/99;
+    lf.lfItalic         = request.style != QFont::StyleNormal;
+    lf.lfCharSet        = DEFAULT_CHARSET;
+
+    int strat = OUT_DEFAULT_PRECIS;
+    if (request.styleStrategy & QFont::PreferBitmap) {
+        strat = OUT_RASTER_PRECIS;
+#ifndef Q_OS_WINCE
+    } else if (request.styleStrategy & QFont::PreferDevice) {
+        strat = OUT_DEVICE_PRECIS;
+    } else if (request.styleStrategy & QFont::PreferOutline) {
+        strat = OUT_OUTLINE_PRECIS;
+    } else if (request.styleStrategy & QFont::ForceOutline) {
+        strat = OUT_TT_ONLY_PRECIS;
+#endif
+    }
+
+    lf.lfOutPrecision   = strat;
+
+    int qual = DEFAULT_QUALITY;
+
+    if (request.styleStrategy & QFont::PreferMatch)
+        qual = DRAFT_QUALITY;
+#ifndef Q_OS_WINCE
+    else if (request.styleStrategy & QFont::PreferQuality)
+        qual = PROOF_QUALITY;
+#endif
+
+    if (request.styleStrategy & QFont::PreferAntialias) {
+        if (QSysInfo::WindowsVersion >= QSysInfo::WV_XP) {
+            qual = CLEARTYPE_QUALITY;
+        } else {
+            qual = ANTIALIASED_QUALITY;
+        }
+    } else if (request.styleStrategy & QFont::NoAntialias) {
+        qual = NONANTIALIASED_QUALITY;
+    }
+
+    lf.lfQuality        = qual;
+
+    lf.lfClipPrecision  = CLIP_DEFAULT_PRECIS;
+
+    int hint = FF_DONTCARE;
+    switch (request.styleHint) {
+        case QFont::Helvetica:
+            hint = FF_SWISS;
+            break;
+        case QFont::Times:
+            hint = FF_ROMAN;
+            break;
+        case QFont::Courier:
+            hint = FF_MODERN;
+            break;
+        case QFont::OldEnglish:
+            hint = FF_DECORATIVE;
+            break;
+        case QFont::System:
+            hint = FF_MODERN;
+            break;
+        default:
+            break;
+    }
+
+    lf.lfPitchAndFamily = DEFAULT_PITCH | hint;
+
+    QString fam = request.family;
+
+    if (fam.isEmpty())
+        fam = QStringLiteral("MS Sans Serif");
+
+    if ((fam == QStringLiteral("MS Sans Serif"))
+        && (request.style == QFont::StyleItalic || (-lf.lfHeight > 18 && -lf.lfHeight != 24))) {
+        fam = QStringLiteral("Arial"); // MS Sans Serif has bearing problems in italic, and does not scale
+    }
+    if (fam == QStringLiteral("Courier") && !(request.styleStrategy & QFont::PreferBitmap))
+        fam = QStringLiteral("Courier New");
+
+    memcpy(lf.lfFaceName, fam.utf16(), sizeof(wchar_t) * qMin(fam.length() + 1, 32));  // 32 = Windows hard-coded
+
+    return lf;
+}
+
 QFontEngine *QWindowsFontDatabase::createEngine(int script, const QFontDef &request,
                                                 HDC fontHdc, int dpi, bool rawMode,
                                                 const QStringList &family_list,
@@ -1645,91 +1739,8 @@ QFontEngine *QWindowsFontDatabase::createEngine(int script, const QFontDef &requ
         }
         stockFont = true;
     } else {
-        int hint = FF_DONTCARE;
-        switch (request.styleHint) {
-            case QFont::Helvetica:
-                hint = FF_SWISS;
-                break;
-            case QFont::Times:
-                hint = FF_ROMAN;
-                break;
-            case QFont::Courier:
-                hint = FF_MODERN;
-                break;
-            case QFont::OldEnglish:
-                hint = FF_DECORATIVE;
-                break;
-            case QFont::System:
-                hint = FF_MODERN;
-                break;
-            default:
-                break;
-        }
-
-        lf.lfHeight = -qRound(request.pixelSize);
-        lf.lfWidth                = 0;
-        lf.lfEscapement        = 0;
-        lf.lfOrientation        = 0;
-        if (request.weight == 50)
-            lf.lfWeight = FW_DONTCARE;
-        else
-            lf.lfWeight = (request.weight*900)/99;
-        lf.lfItalic         = request.style != QFont::StyleNormal;
-        lf.lfCharSet        = DEFAULT_CHARSET;
-
-        int strat = OUT_DEFAULT_PRECIS;
-        if (request.styleStrategy & QFont::PreferBitmap) {
-            strat = OUT_RASTER_PRECIS;
-#ifndef Q_OS_WINCE
-        } else if (request.styleStrategy & QFont::PreferDevice) {
-            strat = OUT_DEVICE_PRECIS;
-        } else if (request.styleStrategy & QFont::PreferOutline) {
-            strat = OUT_OUTLINE_PRECIS;
-        } else if (request.styleStrategy & QFont::ForceOutline) {
-            strat = OUT_TT_ONLY_PRECIS;
-#endif
-        }
-
-        lf.lfOutPrecision   = strat;
-
-        int qual = DEFAULT_QUALITY;
-
-        if (request.styleStrategy & QFont::PreferMatch)
-            qual = DRAFT_QUALITY;
-#ifndef Q_OS_WINCE
-        else if (request.styleStrategy & QFont::PreferQuality)
-            qual = PROOF_QUALITY;
-#endif
-
-        if (request.styleStrategy & QFont::PreferAntialias) {
-            if (QSysInfo::WindowsVersion >= QSysInfo::WV_XP) {
-                qual = CLEARTYPE_QUALITY;
-                preferClearTypeAA = true;
-            } else {
-                qual = ANTIALIASED_QUALITY;
-            }
-        } else if (request.styleStrategy & QFont::NoAntialias) {
-            qual = NONANTIALIASED_QUALITY;
-        }
-
-        lf.lfQuality        = qual;
-
-        lf.lfClipPrecision  = CLIP_DEFAULT_PRECIS;
-        lf.lfPitchAndFamily = DEFAULT_PITCH | hint;
-
-        QString fam = request.family;
-
-        if(fam.isEmpty())
-            fam = QStringLiteral("MS Sans Serif");
-
-        if ((fam == QStringLiteral("MS Sans Serif"))
-            && (request.style == QFont::StyleItalic || (-lf.lfHeight > 18 && -lf.lfHeight != 24))) {
-            fam = QStringLiteral("Arial"); // MS Sans Serif has bearing problems in italic, and does not scale
-        }
-        if (fam == QStringLiteral("Courier") && !(request.styleStrategy & QFont::PreferBitmap))
-            fam = QStringLiteral("Courier New");
-
-        memcpy(lf.lfFaceName, fam.utf16(), sizeof(wchar_t) * qMin(fam.length() + 1, 32));  // 32 = Windows hard-coded
+        lf = fontDefToLOGFONT(request);
+        preferClearTypeAA = lf.lfQuality == CLEARTYPE_QUALITY;
 
         hfont = CreateFontIndirect(&lf);
         if (!hfont)