Fix printing bitmap fonts on X11 with FontConfig enabled

When FontConfig was enabled, bitmap fonts would often get a different
pixel size than the one we requested. Usually the size would only be
a pixel off, but this was especially visible when printing in highres
with bitmap fonts, because in those cases we would request a pixel size
which was computed based on the printer's high dpi.

The result was that all printed text with bitmap fonts would be really
really tiny. The fix falls back to using the XLFD font engine when
using bitmap fonts (when the returned pixel size is different from the
requested), because this engine scales the fonts for us. This will
cause bitmap fonts to be rendered without antialiasing.

Task-number: QTBUG-3620
Reviewed-by: Simon Hausmann

3 files changed, 24 insertions, 11 deletions

diff --git a/src/gui/text/qfontdatabase.cpp b/src/gui/text/qfontdatabase.cpp
index 0aed71a..d0f4d2e 100644
--- a/src/gui/text/qfontdatabase.cpp
+++ b/src/gui/text/qfontdatabase.cpp
@@ -949,7 +949,7 @@ struct QtFontDesc
 #if !defined(Q_WS_MAC)
 static void match(int script, const QFontDef &request,
                   const QString &family_name, const QString &foundry_name, int force_encoding_id,
-                  QtFontDesc *desc, const QList<int> &blacklistedFamilies = QList<int>());
+                  QtFontDesc *desc, const QList<int> &blacklistedFamilies = QList<int>(), bool forceXLFD=false);
 
 #if defined(Q_WS_X11) || defined(Q_WS_QWS)
 static void initFontDef(const QtFontDesc &desc, const QFontDef &request, QFontDef *fontDef)
@@ -1316,7 +1316,7 @@ unsigned int bestFoundry(int script, unsigned int score, int styleStrategy,
 */
 static void match(int script, const QFontDef &request,
                   const QString &family_name, const QString &foundry_name, int force_encoding_id,
-                  QtFontDesc *desc, const QList<int> &blacklistedFamilies)
+                  QtFontDesc *desc, const QList<int> &blacklistedFamilies, bool forceXLFD)
 {
     Q_UNUSED(force_encoding_id);
 
@@ -1351,7 +1351,7 @@ static void match(int script, const QFontDef &request,
 
     unsigned int score = ~0u;
 
-    load(family_name, script);
+    load(family_name, script, forceXLFD);
 
     QFontDatabasePrivate *db = privateDb();
     for (int x = 0; x < db->count; ++x) {
diff --git a/src/gui/text/qfontdatabase_x11.cpp b/src/gui/text/qfontdatabase_x11.cpp
index ae93f90..382c4fe 100644
--- a/src/gui/text/qfontdatabase_x11.cpp
+++ b/src/gui/text/qfontdatabase_x11.cpp
@@ -1204,9 +1204,9 @@ static void loadFontConfig()
 
 static void initializeDb();
 
-static void load(const QString &family = QString(), int script = -1)
+static void load(const QString &family = QString(), int script = -1, bool forceXLFD = false)
 {
-    if (X11->has_fontconfig) {
+    if (X11->has_fontconfig && !forceXLFD) {
         initializeDb();
         return;
     }
@@ -1784,7 +1784,7 @@ QFontEngine *QFontDatabase::loadXlfd(int screen, int script, const QFontDef &req
         QString family, foundry;
         QT_PREPEND_NAMESPACE(parseFontName)(families_and_foundries.at(i), foundry, family);
         FM_DEBUG("loadXlfd: >>>>>>>>>>>>>>trying to match '%s' encoding=%d", family.toLatin1().data(), force_encoding_id);
-        QT_PREPEND_NAMESPACE(match)(script, request, family, foundry, force_encoding_id, &desc);
+        QT_PREPEND_NAMESPACE(match)(script, request, family, foundry, force_encoding_id, &desc, QList<int>(), true);
         if (desc.family)
             break;
     }
@@ -1847,23 +1847,26 @@ QFontEngine *QFontDatabase::loadXlfd(int screen, int script, const QFontDef &req
         }
     } else {
         QList<int> encodings;
-        if (desc.encoding)
-            encodings.append(int(desc.encoding->encoding));
+        if (desc.encoding) {
+            if (desc.encoding->encoding >= 0)
+                encodings.append(int(desc.encoding->encoding));
+        }
 
         if (desc.size) {
             // append all other encodings for the matched font
             for (int i = 0; i < desc.size->count; ++i) {
                 QtFontEncoding *e = desc.size->encodings + i;
-                if (e == desc.encoding)
-                    continue;
+                if (e == desc.encoding || e->encoding < 0)
+                    continue;                
                 encodings.append(int(e->encoding));
             }
         }
         // fill in the missing encodings
         const XlfdEncoding *enc = xlfd_encoding;
         for (; enc->name; ++enc) {
-            if (!encodings.contains(enc->id))
+            if (!encodings.contains(enc->id) && enc->id >= 0) {
                 encodings.append(enc->id);
+            }
         }
 
 #if defined(FONT_MATCH_DEBUG)
@@ -1925,6 +1928,13 @@ void QFontDatabase::load(const QFontPrivate *d, int script)
 #ifndef QT_NO_FONTCONFIG
         } else if (X11->has_fontconfig) {
             fe = loadFc(d, script, req);
+
+            if (fe != 0 && fe->fontDef.pixelSize != req.pixelSize) {
+                delete fe;
+                fe = loadXlfd(d->screen, script, req);
+            }
+
+
 #endif
         } else if (mainThread) {
             fe = loadXlfd(d->screen, script, req);
diff --git a/src/gui/text/qfontengine_x11.cpp b/src/gui/text/qfontengine_x11.cpp
index 5ea4554..ffc0eb4 100644
--- a/src/gui/text/qfontengine_x11.cpp
+++ b/src/gui/text/qfontengine_x11.cpp
@@ -488,6 +488,7 @@ glyph_metrics_t QFontEngineXLFD::boundingBox(const QGlyphLayout &glyphs)
             QFixed y = overall.yoff + glyphs.offsets[i].y - xcs->ascent;
             overall.x = qMin(overall.x, x);
             overall.y = qMin(overall.y, y);
+            // XCharStruct::rbearing is defined as distance from left edge to rightmost pixel
             xmax = qMax(xmax, overall.xoff + glyphs.offsets[i].x + xcs->rbearing);
             ymax = qMax(ymax, y + xcs->ascent + xcs->descent);
             overall.xoff += glyphs.advances_x[i];
@@ -511,6 +512,8 @@ glyph_metrics_t QFontEngineXLFD::boundingBox(glyph_t glyph)
     glyph_metrics_t gm;
     XCharStruct *xcs = charStruct(_fs, glyph);
     if (xcs) {
+        // XCharStruct::rbearing is defined as distance from left edge to rightmost pixel
+        // XCharStruct::width is defined as the advance
         gm = glyph_metrics_t(xcs->lbearing, -xcs->ascent, xcs->rbearing- xcs->lbearing, xcs->ascent + xcs->descent,
                               xcs->width, 0);
     } else {