Fix text rendering on windows (font size was incorrect throwing off intra-glyph spacing and line spacing)

src/calibre/ebooks/pdf/render/engine.py

@@ -19,7 +19,7 @@ from calibre.constants import plugins
 from calibre.ebooks.pdf.render.serialize import (PDFStream, Path)
 from calibre.ebooks.pdf.render.common import inch, A4, fmtnum
 from calibre.ebooks.pdf.render.graphics import convert_path, Graphics
-from calibre.utils.fonts.sfnt.container import Sfnt
+from calibre.utils.fonts.sfnt.container import Sfnt, UnsupportedFont
 from calibre.utils.fonts.sfnt.metrics import FontMetrics
 
 Point = namedtuple('Point', 'x y')
@@ -224,7 +224,11 @@ class PdfEngine(QPaintEngine):
 
     def create_sfnt(self, text_item):
         get_table = partial(self.qt_hack.get_sfnt_table, text_item)
-        ans = Font(Sfnt(get_table))
+        try:
+            ans = Font(Sfnt(get_table))
+        except UnsupportedFont as e:
+            raise UnsupportedFont('The font %s is not a valid sfnt. Error: %s'%(
+                text_item.font().family(), e))
         glyph_map = self.qt_hack.get_glyph_map(text_item)
         gm = {}
         for uc, glyph_id in enumerate(glyph_map):
@@ -251,18 +255,14 @@ class PdfEngine(QPaintEngine):
             except (KeyError, ValueError):
                 pass
         glyphs = []
-        pdf_pos = point
-        first_baseline = None
+        last_x = last_y = 0
         for i, pos in enumerate(gi.positions):
-            if first_baseline is None:
-                first_baseline = pos.y()
-            glyph_pos = pos
-            delta = glyph_pos - pdf_pos
-            glyphs.append((delta.x(), pos.y()-first_baseline, gi.indices[i]))
-            pdf_pos = glyph_pos
+            x, y = pos.x(), pos.y()
+            glyphs.append((x-last_x, last_y - y, gi.indices[i]))
+            last_x, last_y = x, y
 
-        self.pdf.draw_glyph_run([1, 0, 0, -1, point.x(),
-            point.y()], gi.size, metrics, glyphs)
+        self.pdf.draw_glyph_run([gi.stretch, 0, 0, -1, 0, 0], gi.size, metrics,
+                                glyphs)
         sip.delete(gi)
 
     @store_error

src/calibre/ebooks/pdf/render/qt_hack.cpp

@@ -17,18 +17,23 @@ GlyphInfo* get_glyphs(QPointF &p, const QTextItem &text_item) {
     QFontEngine *fe = ti.fontEngine;
     qreal size = ti.fontEngine->fontDef.pixelSize;
 #ifdef Q_WS_WIN
-    if (ti.fontEngine->type() == QFontEngine::Win) {
+    if (false && ti.fontEngine->type() == QFontEngine::Win) {
+        // This is used in the Qt sourcecode, but it gives incorrect results,
+        // so I have disabled it. I dont understand how it works in qpdf.cpp
         QFontEngineWin *fe = static_cast<QFontEngineWin *>(ti.fontEngine);
         size = fe->tm.tmHeight;
     }
 #endif
+    int synthesized = ti.fontEngine->synthesized();
+    qreal stretch = synthesized & QFontEngine::SynthesizedStretch ? ti.fontEngine->fontDef.stretch/100. : 1.;
+
     QVarLengthArray<glyph_t> glyphs;
     QVarLengthArray<QFixedPoint> positions;
     QTransform m = QTransform::fromTranslate(p.x(), p.y());
     fe->getGlyphPositions(ti.glyphs, m, ti.flags, glyphs, positions);
     QVector<QPointF> points = QVector<QPointF>(positions.count());
     for (int i = 0; i < positions.count(); i++) {
-        points[i].setX(positions[i].x.toReal());
+        points[i].setX(positions[i].x.toReal()/stretch);
         points[i].setY(positions[i].y.toReal());
     }
 
@@ -38,10 +43,10 @@ GlyphInfo* get_glyphs(QPointF &p, const QTextItem &text_item) {
 
     const quint32 *tag = reinterpret_cast<const quint32 *>("name");
 
-    return new GlyphInfo(fe->getSfntTable(qToBigEndian(*tag)), size, points, indices);
+    return new GlyphInfo(fe->getSfntTable(qToBigEndian(*tag)), size, stretch, points, indices);
 }
 
-GlyphInfo::GlyphInfo(const QByteArray& name, qreal size, const QVector<QPointF> &positions, const QVector<unsigned int> &indices) :name(name), positions(positions), size(size), indices(indices) {
+GlyphInfo::GlyphInfo(const QByteArray& name, qreal size, qreal stretch, const QVector<QPointF> &positions, const QVector<unsigned int> &indices) :name(name), positions(positions), size(size), stretch(stretch), indices(indices) {
 }
 
 QByteArray get_sfnt_table(const QTextItem &text_item, const char* tag_name) {

src/calibre/ebooks/pdf/render/qt_hack.h

@@ -17,9 +17,10 @@ class GlyphInfo {
         QByteArray name;
         QVector<QPointF> positions;
         qreal size;
+        qreal stretch;
         QVector<unsigned int> indices;
 
-        GlyphInfo(const QByteArray &name, qreal size, const QVector<QPointF> &positions, const QVector<unsigned int> &indices);
+        GlyphInfo(const QByteArray &name, qreal size, qreal stretch, const QVector<QPointF> &positions, const QVector<unsigned int> &indices);
 
     private:
         GlyphInfo(const GlyphInfo&);

src/calibre/ebooks/pdf/render/qt_hack.sip

@@ -13,9 +13,10 @@ class GlyphInfo {
 public:
     QByteArray name;
     qreal size;
+    qreal stretch;
     QVector<QPointF> &positions;
     QVector<unsigned int> indices;
-    GlyphInfo(const QByteArray &name, qreal size, const QVector<QPointF> &positions, const QVector<unsigned int> &indices);
+    GlyphInfo(const QByteArray &name, qreal size, qreal stretch, const QVector<QPointF> &positions, const QVector<unsigned int> &indices);
 private:
     GlyphInfo(const GlyphInfo& g);
 

src/calibre/ebooks/pdf/render/test.py

@@ -8,7 +8,6 @@ __copyright__ = '2012, Kovid Goyal <kovid at kovidgoyal.net>'
 __docformat__ = 'restructuredtext en'
 
 import os
-from tempfile import gettempdir
 
 from PyQt4.Qt import (QBrush, QColor, QPoint, QPixmap, QPainterPath, QRectF,
                       QApplication, QPainter, Qt, QImage, QLinearGradient,
@@ -99,14 +98,19 @@ def pen(p, xmax, ymax):
     p.drawRect(0, xmax/3, xmax/3, xmax/2)
 
 def text(p, xmax, ymax):
-    p.drawText(QPoint(0, ymax/3), 'Text')
+    f = p.font()
+    f.setPixelSize(24)
+    f.setFamily('Candara')
+    p.setFont(f)
+    p.drawText(QPoint(0, 100),
+        'Test intra glyph spacing ffagain imceo')
 
 def main():
     app = QApplication([])
     app
-    tdir = gettempdir()
+    tdir = os.path.abspath('.')
     pdf = os.path.join(tdir, 'painter.pdf')
-    func = full
+    func = text
     dpi = 100
     with open(pdf, 'wb') as f:
         dev = PdfDevice(f, xdpi=dpi, ydpi=dpi, compress=False)