Fix printing with unhinted fonts

On high-dpi displays or when you explicitly select an unhinted font,
we pick a DirectWrite font engine. This hit an uncovered code path
on Windows, because we relied on being able to get the HFONT from
the font engine.

To fix this, we introduce an alternative code path which gets the
HFONT based on the DirectWrite font when this font engine is active.

[ChangeLog][Windows] Fixed an issue where the characters in printed
text would look too small.

Pick-to: 6.1 6.2
Fixes: QTBUG-95720
Change-Id: Ifd609e92512e1f25f0ee2aace35cb5ccedf09030
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

src/gui/text/windows/qwindowsfontenginedirectwrite.cpp

@@ -337,6 +337,22 @@ QString QWindowsFontEngineDirectWrite::filenameFromFontFile(IDWriteFontFile *fon
     return ret;
 }
 
+HFONT QWindowsFontEngineDirectWrite::createHFONT() const
+{
+    if (m_fontEngineData == nullptr || m_directWriteFontFace == nullptr)
+        return NULL;
+
+    LOGFONT lf;
+    HRESULT hr = m_fontEngineData->directWriteGdiInterop->ConvertFontFaceToLOGFONT(m_directWriteFontFace,
+                                                                                   &lf);
+    if (SUCCEEDED(hr)) {
+        lf.lfHeight = -qRound(fontDef.pixelSize);
+        return CreateFontIndirect(&lf);
+    } else {
+        return NULL;
+    }
+}
+
 void QWindowsFontEngineDirectWrite::initializeHeightMetrics() const
 {
     DWRITE_FONT_METRICS metrics;

src/gui/text/windows/qwindowsfontenginedirectwrite_p.h

@@ -71,7 +71,7 @@ QT_BEGIN_NAMESPACE
 
 class QWindowsFontEngineData;
 
-class QWindowsFontEngineDirectWrite : public QFontEngine
+class Q_GUI_EXPORT QWindowsFontEngineDirectWrite : public QFontEngine
 {
     Q_DISABLE_COPY_MOVE(QWindowsFontEngineDirectWrite)
 public:
@@ -107,6 +107,8 @@ public:
 
     bool supportsHorizontalSubPixelPositions() const override;
 
+    HFONT createHFONT() const;
+
     QImage alphaMapForGlyph(glyph_t glyph, const QFixedPoint &subPixelPosition) override;
     QImage alphaMapForGlyph(glyph_t glyph,
                             const QFixedPoint &subPixelPosition,

src/printsupport/platform/windows/qprintengine_win.cpp

@@ -49,6 +49,9 @@
 #include <private/qfont_p.h>
 #include <private/qfontengine_p.h>
 #include <private/qpainter_p.h>
+#if QT_CONFIG(directwrite)
+#  include <private/qwindowsfontenginedirectwrite_p.h>
+#endif
 
 #include <qpa/qplatformprintplugin.h>
 #include <qpa/qplatformprintersupport.h>
@@ -290,8 +293,22 @@ void QWin32PrintEngine::drawTextItem(const QPointF &p, const QTextItem &textItem
                     || d->txop >= QTransform::TxProject
                     || !d->embed_fonts;
 
-    if (!fallBack && ti.fontEngine->type() == QFontEngine::Win) {
-        if (HFONT hfont = static_cast<HFONT>(ti.fontEngine->handle())) {
+    if (!fallBack) {
+        bool deleteFont = false;
+        HFONT hfont = NULL;
+        if (ti.fontEngine->type() == QFontEngine::Win) {
+            hfont = static_cast<HFONT>(ti.fontEngine->handle());
+        }
+#if QT_CONFIG(directwrite)
+        else if (ti.fontEngine->type() == QFontEngine::DirectWrite) {
+            QWindowsFontEngineDirectWrite *fedw = static_cast<QWindowsFontEngineDirectWrite *>(ti.fontEngine);
+            hfont = fedw->createHFONT();
+            if (hfont)
+                deleteFont = true;
+        }
+#endif
+
+        if (hfont) {
             // Try selecting the font to see if we get a substitution font
             SelectObject(d->hdc, hfont);
             if (GetDeviceCaps(d->hdc, TECHNOLOGY) != DT_CHARSTREAM) {
@@ -302,7 +319,12 @@ void QWin32PrintEngine::drawTextItem(const QPointF &p, const QTextItem &textItem
                 GetTextFace(d->hdc, 64, n);
                 fallBack = QString::fromWCharArray(n)
                     != QString::fromWCharArray(logFont.lfFaceName);
+
+                if (deleteFont)
+                    DeleteObject(hfont);
             }
+        } else {
+            fallBack = true;
         }
     }
 
@@ -1720,11 +1742,20 @@ static void draw_text_item_win(const QPointF &pos, const QTextItemInt &ti, HDC h
     const bool has_kerning = ti.f && ti.f->kerning();
 
     HFONT hfont = 0;
+    bool deleteFont = false;
 
     if (ti.fontEngine->type() == QFontEngine::Win) {
         if (ti.fontEngine->supportsTransformation(QTransform::fromScale(0.5, 0.5))) // is TrueType font?
             hfont = static_cast<HFONT>(ti.fontEngine->handle());
     }
+#if QT_CONFIG(directwrite)
+    else if (ti.fontEngine->type() == QFontEngine::DirectWrite) {
+        QWindowsFontEngineDirectWrite *fedw = static_cast<QWindowsFontEngineDirectWrite *>(ti.fontEngine);
+        hfont = fedw->createHFONT();
+        if (hfont)
+            deleteFont = true;
+    }
+#endif
 
     if (!hfont)
         hfont = (HFONT)GetStockObject(ANSI_VAR_FONT);
@@ -1797,6 +1828,9 @@ static void draw_text_item_win(const QPointF &pos, const QTextItemInt &ti, HDC h
         SetWorldTransform(hdc, &win_xform);
 
     SelectObject(hdc, old_font);
+
+    if (deleteFont)
+        DeleteObject(hfont);
 }
 
 QT_END_NAMESPACE