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, 63 insertions, 3 deletions

diff --git a/src/plugins/platforms/windows/qwindowsfontengine.cpp b/src/plugins/platforms/windows/qwindowsfontengine.cpp
index d7f48e59c5..a78b6f1620 100644
--- a/src/plugins/platforms/windows/qwindowsfontengine.cpp
+++ b/src/plugins/platforms/windows/qwindowsfontengine.cpp
@@ -50,6 +50,7 @@
 #include "qwindowscontext.h"
 #include "qwindowsfontdatabase.h"
 #include "qtwindows_additional.h"
+#include "qwindowsfontenginedirectwrite.h"
 
 #include <QtGui/private/qtextengine_p.h> // glyph_metrics_t
 #include <QtGui/private/qguiapplication_p.h>
@@ -74,6 +75,10 @@
 #  include "qplatformfunctions_wince.h"
 #endif
 
+#if !defined(QT_NO_DIRECTWRITE)
+#  include <dwrite.h>
+#endif
+
 QT_BEGIN_NAMESPACE
 
 //### mingw needed define
@@ -1318,10 +1323,65 @@ void QWindowsMultiFontEngine::loadEngine(int at)
     Q_ASSERT(at < engines.size());
     Q_ASSERT(engines.at(at) == 0);
 
+    QFontEngine *fontEngine = engines.at(0);
+    QSharedPointer<QWindowsFontEngineData> data;
+    LOGFONT lf;
+
+#ifndef QT_NO_DIRECTWRITE
+    if (fontEngine->type() == QFontEngine::DirectWrite) {
+        QWindowsFontEngineDirectWrite *fe = static_cast<QWindowsFontEngineDirectWrite *>(fontEngine);
+        lf = QWindowsFontDatabase::fontDefToLOGFONT(fe->fontDef);
+
+        data = fe->fontEngineData();
+    } else
+#endif
+    {
+        QWindowsFontEngine *fe = static_cast<QWindowsFontEngine*>(fontEngine);
+        lf = fe->logFont();
+
+        data = fe->fontEngineData();
+    }
+
     const QString fam = fallbacks.at(at-1);
-    QWindowsFontEngine *fe = static_cast<QWindowsFontEngine*>(engines.at(0));
-    LOGFONT lf = fe->logFont();
     memcpy(lf.lfFaceName, fam.utf16(), sizeof(wchar_t) * qMin(fam.length() + 1, 32));  // 32 = Windows hard-coded
+
+#ifndef QT_NO_DIRECTWRITE
+    if (fontEngine->type() == QFontEngine::DirectWrite) {
+        const QString nameSubstitute = QWindowsFontEngineDirectWrite::fontNameSubstitute(QString::fromWCharArray(lf.lfFaceName));
+        memcpy(lf.lfFaceName, nameSubstitute.utf16(),
+               sizeof(wchar_t) * qMin(nameSubstitute.length() + 1, LF_FACESIZE));
+
+        IDWriteFont *directWriteFont = 0;
+        HRESULT hr = data->directWriteGdiInterop->CreateFontFromLOGFONT(&lf, &directWriteFont);
+        if (FAILED(hr)) {
+            qErrnoWarning("%s: CreateFontFromLOGFONT failed", __FUNCTION__);
+        } else {
+            IDWriteFontFace *directWriteFontFace = NULL;
+            HRESULT hr = directWriteFont->CreateFontFace(&directWriteFontFace);
+            if (SUCCEEDED(hr)) {
+                QWindowsFontEngineDirectWrite *fedw = new QWindowsFontEngineDirectWrite(directWriteFontFace,
+                                                                                        fontEngine->fontDef.pixelSize,
+                                                                                        data);
+                fedw->setObjectName(QStringLiteral("QWindowsFontEngineDirectWrite_") + fontEngine->fontDef.family);
+
+                fedw->fontDef = fontDef;
+                fedw->ref.ref();
+                engines[at] = fedw;
+
+                if (QWindowsContext::verboseFonts)
+                    qDebug("%s %d %s", __FUNCTION__, at, qPrintable(fam));
+
+                return;
+            } else {
+                qErrnoWarning("%s: CreateFontFace failed", __FUNCTION__);
+            }
+
+        }
+    }
+#endif
+
+    // Get here if original font is not DirectWrite or DirectWrite creation failed for some
+    // reason
     HFONT hfont = CreateFontIndirect(&lf);
 
     bool stockFont = false;
@@ -1329,7 +1389,7 @@ void QWindowsMultiFontEngine::loadEngine(int at)
         hfont = (HFONT)GetStockObject(ANSI_VAR_FONT);
         stockFont = true;
     }
-    engines[at] = new QWindowsFontEngine(fam, hfont, stockFont, lf, fe->fontEngineData());
+    engines[at] = new QWindowsFontEngine(fam, hfont, stockFont, lf, data);
     engines[at]->ref.ref();
     engines[at]->fontDef = fontDef;
     if (QWindowsContext::verboseFonts)