Support color font rendering for freetype engine

This patch mainly do two things:
1) Support color bitmap font for freetype fontengine. This partially
 based on Corentin Jabot's patch

2) Support ARGB opengl glyph cache when workaround_brokenFBOReadBack is
true (It is always true under Android). Some code refactor has been
done in QOpenGLTextureGlyphCache.

This patch also bump the minimal required freetype version to 2.2

[ChangeLog][General][Freetype] Support color font rendering

Task-number: QTBUG-35156
Change-Id: I35aae5f98ba9a27b70a48db3f2647fc070c39c33
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>

3 files changed, 285 insertions, 127 deletions

diff --git a/src/gui/opengl/qopengltextureglyphcache.cpp b/src/gui/opengl/qopengltextureglyphcache.cpp
index 8f69095464..9a7b1eb21d 100644
--- a/src/gui/opengl/qopengltextureglyphcache.cpp
+++ b/src/gui/opengl/qopengltextureglyphcache.cpp
@@ -181,6 +181,94 @@ void QOpenGLTextureGlyphCache::setupVertexAttribs()
     m_buffer.release();
 }
 
+static void load_glyph_image_to_texture(QOpenGLContext *ctx,
+                                        QImage &img,
+                                        GLuint texture,
+                                        int tx, int ty)
+{
+    QOpenGLFunctions *funcs = ctx->functions();
+
+    const int imgWidth = img.width();
+    const int imgHeight = img.height();
+
+    if (img.format() == QImage::Format_Mono) {
+        img = img.convertToFormat(QImage::Format_Grayscale8);
+    } else if (img.depth() == 32) {
+        if (img.format() == QImage::Format_RGB32
+            // We need to make the alpha component equal to the average of the RGB values.
+            // This is needed when drawing sub-pixel antialiased text on translucent targets.
+#if Q_BYTE_ORDER == Q_BIG_ENDIAN
+            || img.format() == QImage::Format_ARGB32_Premultiplied
+#else
+            || (img.format() == QImage::Format_ARGB32_Premultiplied
+                && ctx->isOpenGLES())
+#endif
+            ) {
+            for (int y = 0; y < imgHeight; ++y) {
+                QRgb *src = (QRgb *) img.scanLine(y);
+                for (int x = 0; x < imgWidth; ++x) {
+                    int r = qRed(src[x]);
+                    int g = qGreen(src[x]);
+                    int b = qBlue(src[x]);
+                    int avg;
+                    if (img.format() == QImage::Format_RGB32)
+                        avg = (r + g + b + 1) / 3; // "+1" for rounding.
+                    else // Format_ARGB_Premultiplied
+                        avg = qAlpha(src[x]);
+
+                    src[x] = qRgba(r, g, b, avg);
+                    // swizzle the bits to accommodate for the GL_RGBA upload.
+#if Q_BYTE_ORDER != Q_BIG_ENDIAN
+                    if (ctx->isOpenGLES())
+#endif
+                        src[x] = ARGB2RGBA(src[x]);
+                }
+            }
+        }
+    }
+
+    funcs->glBindTexture(GL_TEXTURE_2D, texture);
+    if (img.depth() == 32) {
+#ifdef QT_OPENGL_ES_2
+        GLenum fmt = GL_RGBA;
+#else
+        GLenum fmt = ctx->isOpenGLES() ? GL_RGBA : GL_BGRA;
+#endif // QT_OPENGL_ES_2
+
+#if Q_BYTE_ORDER == Q_BIG_ENDIAN
+        fmt = GL_RGBA;
+#endif
+        funcs->glTexSubImage2D(GL_TEXTURE_2D, 0, tx, ty, imgWidth, imgHeight, fmt, GL_UNSIGNED_BYTE, img.constBits());
+    } else {
+        // The scanlines in image are 32-bit aligned, even for mono or 8-bit formats. This
+        // is good because it matches the default of 4 bytes for GL_UNPACK_ALIGNMENT.
+#if !defined(QT_OPENGL_ES_2)
+        const GLenum format = isCoreProfile() ? GL_RED : GL_ALPHA;
+#else
+        const GLenum format = GL_ALPHA;
+#endif
+        funcs->glTexSubImage2D(GL_TEXTURE_2D, 0, tx, ty, imgWidth, imgHeight, format, GL_UNSIGNED_BYTE, img.constBits());
+    }
+}
+
+static void load_glyph_image_region_to_texture(QOpenGLContext *ctx,
+                                               const QImage &srcImg,
+                                               int x, int y,
+                                               int w, int h,
+                                               GLuint texture,
+                                               int tx, int ty)
+{
+    Q_ASSERT(x + w <= srcImg.width() && y + h <= srcImg.height());
+
+    QImage img;
+    if (x != 0 || y != 0 || w != srcImg.width() || h != srcImg.height())
+        img = srcImg.copy(x, y, w, h);
+    else
+        img = srcImg;
+
+    load_glyph_image_to_texture(ctx, img, texture, tx, ty);
+}
+
 void QOpenGLTextureGlyphCache::resizeTextureData(int width, int height)
 {
     QOpenGLContext *ctx = QOpenGLContext::currentContext();
@@ -207,9 +295,8 @@ void QOpenGLTextureGlyphCache::resizeTextureData(int width, int height)
 
     if (ctx->d_func()->workaround_brokenFBOReadBack) {
         QImageTextureGlyphCache::resizeTextureData(width, height);
-        Q_ASSERT(image().depth() == 8);
-        funcs->glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, width, oldHeight, GL_ALPHA, GL_UNSIGNED_BYTE, image().constBits());
-        funcs->glDeleteTextures(1, &oldTexture);
+        load_glyph_image_region_to_texture(ctx, image(), 0, 0, qMin(oldWidth, width), qMin(oldHeight, height),
+                                           m_textureResource->m_texture, 0, 0);
         return;
     }
 
@@ -336,88 +423,14 @@ void QOpenGLTextureGlyphCache::fillTexture(const Coord &c, glyph_t glyph, QFixed
         return;
     }
 
-    QOpenGLFunctions *funcs = ctx->functions();
     if (ctx->d_func()->workaround_brokenFBOReadBack) {
         QImageTextureGlyphCache::fillTexture(c, glyph, subPixelPosition);
-
-        funcs->glBindTexture(GL_TEXTURE_2D, m_textureResource->m_texture);
-        const QImage &texture = image();
-        const uchar *bits = texture.constBits();
-        bits += c.y * texture.bytesPerLine() + c.x;
-        for (int i=0; i<c.h; ++i) {
-            funcs->glTexSubImage2D(GL_TEXTURE_2D, 0, c.x, c.y + i, c.w, 1, GL_ALPHA, GL_UNSIGNED_BYTE, bits);
-            bits += texture.bytesPerLine();
-        }
+        load_glyph_image_region_to_texture(ctx, image(), c.x, c.y, c.w, c.h, m_textureResource->m_texture, c.x, c.y);
         return;
     }
 
     QImage mask = textureMapForGlyph(glyph, subPixelPosition);
-    const int maskWidth = mask.width();
-    const int maskHeight = mask.height();
-
-    if (mask.format() == QImage::Format_Mono) {
-        mask = mask.convertToFormat(QImage::Format_Indexed8);
-        for (int y = 0; y < maskHeight; ++y) {
-            uchar *src = (uchar *) mask.scanLine(y);
-            for (int x = 0; x < maskWidth; ++x)
-                src[x] = -src[x]; // convert 0 and 1 into 0 and 255
-        }
-    } else if (mask.depth() == 32) {
-        if (mask.format() == QImage::Format_RGB32
-            // We need to make the alpha component equal to the average of the RGB values.
-            // This is needed when drawing sub-pixel antialiased text on translucent targets.
-#if Q_BYTE_ORDER == Q_BIG_ENDIAN
-            || mask.format() == QImage::Format_ARGB32_Premultiplied
-#else
-            || (mask.format() == QImage::Format_ARGB32_Premultiplied
-                && ctx->isOpenGLES())
-#endif
-            ) {
-            for (int y = 0; y < maskHeight; ++y) {
-                QRgb *src = (QRgb *) mask.scanLine(y);
-                for (int x = 0; x < maskWidth; ++x) {
-                    int r = qRed(src[x]);
-                    int g = qGreen(src[x]);
-                    int b = qBlue(src[x]);
-                    int avg;
-                    if (mask.format() == QImage::Format_RGB32)
-                        avg = (r + g + b + 1) / 3; // "+1" for rounding.
-                    else // Format_ARGB_Premultiplied
-                        avg = qAlpha(src[x]);
-
-                    src[x] = qRgba(r, g, b, avg);
-                    // swizzle the bits to accommodate for the GL_RGBA upload.
-#if Q_BYTE_ORDER != Q_BIG_ENDIAN
-                    if (ctx->isOpenGLES())
-#endif
-                        src[x] = ARGB2RGBA(src[x]);
-                }
-            }
-        }
-    }
-
-    funcs->glBindTexture(GL_TEXTURE_2D, m_textureResource->m_texture);
-    if (mask.depth() == 32) {
-#ifdef QT_OPENGL_ES_2
-        GLenum fmt = GL_RGBA;
-#else
-        GLenum fmt = ctx->isOpenGLES() ? GL_RGBA : GL_BGRA;
-#endif // QT_OPENGL_ES_2
-
-#if Q_BYTE_ORDER == Q_BIG_ENDIAN
-        fmt = GL_RGBA;
-#endif
-        funcs->glTexSubImage2D(GL_TEXTURE_2D, 0, c.x, c.y, maskWidth, maskHeight, fmt, GL_UNSIGNED_BYTE, mask.bits());
-    } else {
-        // The scanlines in mask are 32-bit aligned, even for mono or 8-bit formats. This
-        // is good because it matches the default of 4 bytes for GL_UNPACK_ALIGNMENT.
-#if !defined(QT_OPENGL_ES_2)
-        const GLenum format = isCoreProfile() ? GL_RED : GL_ALPHA;
-#else
-        const GLenum format = GL_ALPHA;
-#endif
-        funcs->glTexSubImage2D(GL_TEXTURE_2D, 0, c.x, c.y, maskWidth, maskHeight, format, GL_UNSIGNED_BYTE, mask.bits());
-    }
+    load_glyph_image_to_texture(ctx, mask, m_textureResource->m_texture, c.x, c.y);
 }
 
 int QOpenGLTextureGlyphCache::glyphPadding() const
diff --git a/src/gui/text/qfontengine_ft.cpp b/src/gui/text/qfontengine_ft.cpp
index ec995d5cc6..e89522f5af 100644
--- a/src/gui/text/qfontengine_ft.cpp
+++ b/src/gui/text/qfontengine_ft.cpp
@@ -52,6 +52,7 @@
 #include <qscopedvaluerollback.h>
 #include "qthreadstorage.h"
 #include <qmath.h>
+#include <qendian.h>
 
 #include <ft2build.h>
 #include FT_FREETYPE_H
@@ -192,6 +193,15 @@ int QFreetypeFace::getPointInOutline(glyph_t glyph, int flags, quint32 point, QF
     return Err_Ok;
 }
 
+bool QFreetypeFace::isScalableBitmap() const
+{
+#ifdef FT_HAS_COLOR
+    return !FT_IS_SCALABLE(face) && FT_HAS_COLOR(face);
+#else
+    return false;
+#endif
+}
+
 extern QByteArray qt_fontdata_from_index(int);
 
 /*
@@ -249,6 +259,7 @@ QFreetypeFace *QFreetypeFace::getFace(const QFontEngine::FaceId &face_id,
         newFreetype->ref.store(1);
         newFreetype->xsize = 0;
         newFreetype->ysize = 0;
+        newFreetype->scalableBitmapScaleFactor = 1;
         newFreetype->matrix.xx = 0x10000;
         newFreetype->matrix.yy = 0x10000;
         newFreetype->matrix.xy = 0;
@@ -330,36 +341,46 @@ void QFreetypeFace::computeSize(const QFontDef &fontDef, int *xsize, int *ysize,
     *xsize = *ysize * fontDef.stretch / 100;
     *outline_drawing = false;
 
-    /*
-     * Bitmap only faces must match exactly, so find the closest
-     * one (height dominant search)
-     */
     if (!(face->face_flags & FT_FACE_FLAG_SCALABLE)) {
         int best = 0;
-        for (int i = 1; i < face->num_fixed_sizes; i++) {
-            if (qAbs(*ysize -  face->available_sizes[i].y_ppem) <
-                qAbs(*ysize - face->available_sizes[best].y_ppem) ||
-                (qAbs(*ysize - face->available_sizes[i].y_ppem) ==
-                 qAbs(*ysize - face->available_sizes[best].y_ppem) &&
-                 qAbs(*xsize - face->available_sizes[i].x_ppem) <
-                 qAbs(*xsize - face->available_sizes[best].x_ppem))) {
-                best = i;
+        if (!isScalableBitmap()) {
+            /*
+             * Bitmap only faces must match exactly, so find the closest
+             * one (height dominant search)
+             */
+            for (int i = 1; i < face->num_fixed_sizes; i++) {
+                if (qAbs(*ysize -  face->available_sizes[i].y_ppem) <
+                    qAbs(*ysize - face->available_sizes[best].y_ppem) ||
+                    (qAbs(*ysize - face->available_sizes[i].y_ppem) ==
+                     qAbs(*ysize - face->available_sizes[best].y_ppem) &&
+                     qAbs(*xsize - face->available_sizes[i].x_ppem) <
+                     qAbs(*xsize - face->available_sizes[best].x_ppem))) {
+                    best = i;
+                }
+            }
+        } else {
+            // Select the shortest bitmap strike whose height is larger than the desired height
+            for (int i = 1; i < face->num_fixed_sizes; i++) {
+                if (face->available_sizes[i].y_ppem < *ysize) {
+                    if (face->available_sizes[i].y_ppem > face->available_sizes[best].y_ppem)
+                        best = i;
+                } else if (face->available_sizes[best].y_ppem < *ysize) {
+                    best = i;
+                } else if (face->available_sizes[i].y_ppem < face->available_sizes[best].y_ppem) {
+                    best = i;
+                }
             }
         }
-        if (FT_Set_Char_Size(face, face->available_sizes[best].x_ppem, face->available_sizes[best].y_ppem, 0, 0) == 0) {
+
+        // According to freetype documentation we must use FT_Select_Size
+        // to make sure we can select the desired bitmap strike index
+        if (FT_Select_Size(face, best) == 0) {
+            if (isScalableBitmap())
+                scalableBitmapScaleFactor = QFixed::fromReal((qreal)fontDef.pixelSize / face->available_sizes[best].height);
             *xsize = face->available_sizes[best].x_ppem;
             *ysize = face->available_sizes[best].y_ppem;
         } else {
-            int err = 1;
-            if (!(face->face_flags & FT_FACE_FLAG_SCALABLE) && ysize == 0 && face->num_fixed_sizes >= 1) {
-                // work around FT 2.1.10 problem with BDF without PIXEL_SIZE property
-                err = FT_Set_Pixel_Sizes(face, face->available_sizes[0].width, face->available_sizes[0].height);
-                if (err && face->num_fixed_sizes == 1)
-                    err = 0; //even more of a workaround...
-            }
-
-            if (err)
-                *xsize = *ysize = 0;
+            *xsize = *ysize = 0;
         }
     } else {
         *outline_drawing = (*xsize > (QT_MAX_CACHED_GLYPH_SIZE<<6) || *ysize > (QT_MAX_CACHED_GLYPH_SIZE<<6));
@@ -736,6 +757,11 @@ bool QFontEngineFT::init(FaceId faceId, bool antialias, GlyphFormat format,
         if (line_thickness < 2 && score >= 1050)
             line_thickness = 2;
         underline_position =  ((line_thickness * 2) + 3) / 6;
+
+        if (isScalableBitmap()) {
+            glyphFormat = defaultFormat = GlyphFormat::Format_ARGB;
+            cacheEnabled = false;
+        }
     }
     if (line_thickness < 1)
         line_thickness = 1;
@@ -829,6 +855,10 @@ int QFontEngineFT::loadFlags(QGlyphSet *set, GlyphFormat format, int flags,
                 load_target = FT_LOAD_TARGET_LCD_V;
             vfactor = 3;
         }
+    } else if (format == Format_ARGB) {
+#ifdef FT_LOAD_COLOR
+        load_flags |= FT_LOAD_COLOR;
+#endif
     }
 
     if (set && set->outline_drawing)
@@ -890,7 +920,7 @@ QFontEngineFT::Glyph *QFontEngineFT::loadGlyph(QGlyphSet *set, uint glyph,
                      || matrix.xy != 0
                      || matrix.yx != 0;
 
-    if (transform || (format != Format_Mono && !embeddedbitmap))
+    if (transform || (format != Format_Mono && !isScalableBitmap()))
         load_flags |= FT_LOAD_NO_BITMAP;
 
     FT_Error err = FT_Load_Glyph(face, glyph, load_flags);
@@ -1121,7 +1151,11 @@ QFontEngineFT::Glyph *QFontEngineFT::loadGlyph(QGlyphSet *set, uint glyph,
         if (bitmap.buffer != glyph_buffer.data())
             delete [] bitmap.buffer;
     } else if (slot->format == FT_GLYPH_FORMAT_BITMAP) {
+#if ((FREETYPE_MAJOR*10000 + FREETYPE_MINOR*100) >= 20500)
+        Q_ASSERT(slot->bitmap.pixel_mode == FT_PIXEL_MODE_MONO || slot->bitmap.pixel_mode == FT_PIXEL_MODE_BGRA);
+#else
         Q_ASSERT(slot->bitmap.pixel_mode == FT_PIXEL_MODE_MONO);
+#endif
         uchar *src = slot->bitmap.buffer;
         uchar *dst = glyph_buffer.data();
         int h = slot->bitmap.rows;
@@ -1132,7 +1166,7 @@ QFontEngineFT::Glyph *QFontEngineFT::loadGlyph(QGlyphSet *set, uint glyph,
                 dst += pitch;
                 src += slot->bitmap.pitch;
             }
-        } else {
+        } else if (slot->bitmap.pixel_mode == FT_PIXEL_MODE_MONO) {
             if (hsubpixel) {
                 while (h--) {
                     uint *dd = (uint *)dst;
@@ -1166,6 +1200,29 @@ QFontEngineFT::Glyph *QFontEngineFT::loadGlyph(QGlyphSet *set, uint glyph,
                 }
             }
         }
+#if ((FREETYPE_MAJOR*10000 + FREETYPE_MINOR*100) >= 20500)
+        else if (slot->bitmap.pixel_mode == FT_PIXEL_MODE_BGRA)
+        {
+            while (h--) {
+#if Q_BYTE_ORDER == Q_BIG_ENDIAN
+                const quint32 *srcPixel = (const quint32 *)src;
+                quint32 *dstPixel = (quint32 *)dst;
+                for (int x = 0; x < static_cast<int>(slot->bitmap.width); x++, srcPixel++, dstPixel++) {
+                    const quint32 pixel = *srcPixel;
+                    *dstPixel = qbswap(pixel);
+                }
+#else
+                memcpy(dst, src, slot->bitmap.width * 4);
+#endif
+                dst += slot->bitmap.pitch;
+                src += slot->bitmap.pitch;
+            }
+            info.width = info.linearAdvance = info.xOff = slot->bitmap.width;
+            info.height = slot->bitmap.rows;
+            info.x = slot->bitmap_left;
+            info.y = slot->bitmap_top;
+        }
+#endif
     } else {
         qWarning("QFontEngine: Glyph neither outline nor bitmap format=%d", slot->format);
         return 0;
@@ -1236,46 +1293,68 @@ int QFontEngineFT::synthesized() const
 
 QFixed QFontEngineFT::ascent() const
 {
-    return QFixed::fromFixed(metrics.ascender);
+    QFixed v = QFixed::fromFixed(metrics.ascender);
+    if (freetype->scalableBitmapScaleFactor != 1)
+        v *= freetype->scalableBitmapScaleFactor;
+    return v;
 }
 
 QFixed QFontEngineFT::descent() const
 {
-    return QFixed::fromFixed(-metrics.descender);
+    QFixed v = QFixed::fromFixed(-metrics.descender);
+    if (freetype->scalableBitmapScaleFactor != 1)
+        v *= freetype->scalableBitmapScaleFactor;
+    return v;
 }
 
 QFixed QFontEngineFT::leading() const
 {
-    return QFixed::fromFixed(metrics.height - metrics.ascender + metrics.descender);
+    QFixed v = QFixed::fromFixed(metrics.height - metrics.ascender + metrics.descender);
+    if (freetype->scalableBitmapScaleFactor != 1)
+        v *= freetype->scalableBitmapScaleFactor;
+    return v;
 }
 
 QFixed QFontEngineFT::xHeight() const
 {
-    TT_OS2 *os2 = (TT_OS2 *)FT_Get_Sfnt_Table(freetype->face, ft_sfnt_os2);
-    if (os2 && os2->sxHeight) {
-        lockFace();
-        QFixed answer = QFixed(os2->sxHeight * freetype->face->size->metrics.y_ppem) / emSquareSize();
-        unlockFace();
-        return answer;
+    if (!isScalableBitmap()) {
+        TT_OS2 *os2 = (TT_OS2 *)FT_Get_Sfnt_Table(freetype->face, ft_sfnt_os2);
+        if (os2 && os2->sxHeight) {
+            lockFace();
+            QFixed answer = QFixed(os2->sxHeight * freetype->face->size->metrics.y_ppem) / emSquareSize();
+            unlockFace();
+            return answer;
+        }
+    } else {
+        return QFixed(freetype->face->size->metrics.y_ppem) * freetype->scalableBitmapScaleFactor;
     }
     return QFontEngine::xHeight();
 }
 
 QFixed QFontEngineFT::averageCharWidth() const
 {
-    TT_OS2 *os2 = (TT_OS2 *)FT_Get_Sfnt_Table(freetype->face, ft_sfnt_os2);
-    if (os2 && os2->xAvgCharWidth) {
-        lockFace();
-        QFixed answer = QFixed(os2->xAvgCharWidth * freetype->face->size->metrics.x_ppem) / emSquareSize();
-        unlockFace();
-        return answer;
-    }
-    return QFontEngine::averageCharWidth();
+     if (!isScalableBitmap()) {
+         TT_OS2 *os2 = (TT_OS2 *)FT_Get_Sfnt_Table(freetype->face, ft_sfnt_os2);
+         if (os2 && os2->xAvgCharWidth) {
+             lockFace();
+             QFixed answer = QFixed(os2->xAvgCharWidth * freetype->face->size->metrics.x_ppem) / emSquareSize();
+             unlockFace();
+             return answer;
+         }
+     } else {
+         const qreal aspectRatio = (qreal)xsize / ysize;
+         return QFixed::fromReal(fontDef.pixelSize * aspectRatio);
+     }
+
+     return QFontEngine::averageCharWidth();
 }
 
 qreal QFontEngineFT::maxCharWidth() const
 {
-    return metrics.max_advance >> 6;
+    QFixed max_advance = QFixed::fromFixed(metrics.max_advance);
+    if (freetype->scalableBitmapScaleFactor != 1)
+        max_advance *= freetype->scalableBitmapScaleFactor;
+    return max_advance.toReal();
 }
 
 QFixed QFontEngineFT::lineThickness() const
@@ -1558,6 +1637,23 @@ bool QFontEngineFT::shouldUseDesignMetrics(QFontEngine::ShaperFlags flags) const
     return default_hint_style == HintNone || default_hint_style == HintLight || (flags & DesignMetrics);
 }
 
+QFixed QFontEngineFT::scaledBitmapMetrics(QFixed m) const
+{
+    return m * freetype->scalableBitmapScaleFactor;
+}
+
+glyph_metrics_t QFontEngineFT::scaledBitmapMetrics(const glyph_metrics_t &m) const
+{
+    glyph_metrics_t metrics;
+    metrics.x = scaledBitmapMetrics(m.x);
+    metrics.y = scaledBitmapMetrics(m.y);
+    metrics.width = scaledBitmapMetrics(m.width);
+    metrics.height = scaledBitmapMetrics(m.height);
+    metrics.xoff = scaledBitmapMetrics(m.xoff);
+    metrics.yoff = scaledBitmapMetrics(m.yoff);
+    return metrics;
+}
+
 void QFontEngineFT::recalcAdvances(QGlyphLayout *glyphs, QFontEngine::ShaperFlags flags) const
 {
     FT_Face face = 0;
@@ -1580,6 +1676,9 @@ void QFontEngineFT::recalcAdvances(QGlyphLayout *glyphs, QFontEngine::ShaperFlag
             if (!cacheEnabled && g != &emptyGlyph)
                 delete g;
         }
+
+        if (freetype->scalableBitmapScaleFactor != 1)
+            glyphs->advances[i] *= freetype->scalableBitmapScaleFactor;
     }
     if (face)
         unlockFace();
@@ -1596,8 +1695,13 @@ glyph_metrics_t QFontEngineFT::boundingBox(const QGlyphLayout &glyphs)
 
     glyph_metrics_t overall;
     // initialize with line height, we get the same behaviour on all platforms
-    overall.y = -ascent();
-    overall.height = ascent() + descent();
+    if (!isScalableBitmap()) {
+        overall.y = -ascent();
+        overall.height = ascent() + descent();
+    } else {
+        overall.y = QFixed::fromFixed(-metrics.ascender);
+        overall.height = QFixed::fromFixed(metrics.ascender - metrics.descender);
+    }
 
     QFixed ymax = 0;
     QFixed xmax = 0;
@@ -1639,6 +1743,8 @@ glyph_metrics_t QFontEngineFT::boundingBox(const QGlyphLayout &glyphs)
     if (face)
         unlockFace();
 
+    if (isScalableBitmap())
+        overall = scaledBitmapMetrics(overall);
     return overall;
 }
 
@@ -1675,6 +1781,9 @@ glyph_metrics_t QFontEngineFT::boundingBox(glyph_t glyph)
     }
     if (face)
         unlockFace();
+
+    if (isScalableBitmap())
+        overall = scaledBitmapMetrics(overall);
     return overall;
 }
 
@@ -1710,6 +1819,9 @@ glyph_metrics_t QFontEngineFT::alphaMapBoundingBox(glyph_t glyph, QFixed subPixe
         overall.xoff = TRUNC(ROUND(face->glyph->advance.x));
         unlockFace();
     }
+
+    if (isScalableBitmap())
+        overall = scaledBitmapMetrics(overall);
     return overall;
 }
 
@@ -1857,6 +1969,31 @@ QImage QFontEngineFT::alphaRGBMapForGlyph(glyph_t g, QFixed subPixelPosition, co
     return QFontEngine::alphaRGBMapForGlyph(g, subPixelPosition, t);
 }
 
+QImage QFontEngineFT::bitmapForGlyph(glyph_t g, QFixed subPixelPosition, const QTransform &t)
+{
+    Glyph *glyph = loadGlyphFor(g, subPixelPosition, defaultFormat, t);
+    if (glyph == Q_NULLPTR)
+        return QImage();
+
+    QImage img;
+    if (defaultFormat == GlyphFormat::Format_ARGB)
+        img = QImage(glyph->data, glyph->width, glyph->height, QImage::Format_ARGB32_Premultiplied).copy();
+    else if (defaultFormat == GlyphFormat::Format_Mono)
+        img = QImage(glyph->data, glyph->width, glyph->height, QImage::Format_Mono).copy();
+
+    if (!img.isNull() && (!t.isIdentity() || freetype->scalableBitmapScaleFactor != 1)) {
+        QTransform trans(t);
+        const qreal scaleFactor = freetype->scalableBitmapScaleFactor.toReal();
+        trans.scale(scaleFactor, scaleFactor);
+        img = img.transformed(trans, Qt::SmoothTransformation);
+    }
+
+    if (!cacheEnabled && glyph != &emptyGlyph)
+        delete glyph;
+
+    return img;
+}
+
 void QFontEngineFT::removeGlyphFromCache(glyph_t glyph)
 {
     defaultGlyphSet.removeGlyphFromCache(glyph, 0);
@@ -1878,9 +2015,10 @@ FT_Face QFontEngineFT::lockFace(Scaling scale) const
     freetype->lock();
     FT_Face face = freetype->face;
     if (scale == Unscaled) {
-        FT_Set_Char_Size(face, face->units_per_EM << 6, face->units_per_EM << 6, 0, 0);
-        freetype->xsize = face->units_per_EM << 6;
-        freetype->ysize = face->units_per_EM << 6;
+        if (FT_Set_Char_Size(face, face->units_per_EM << 6, face->units_per_EM << 6, 0, 0) == 0) {
+            freetype->xsize = face->units_per_EM << 6;
+            freetype->ysize = face->units_per_EM << 6;
+        }
     } else if (freetype->xsize != xsize || freetype->ysize != ysize) {
         FT_Set_Char_Size(face, xsize, ysize, 0, 0);
         freetype->xsize = xsize;
diff --git a/src/gui/text/qfontengine_ft_p.h b/src/gui/text/qfontengine_ft_p.h
index ee2df6f665..3f4bf84753 100644
--- a/src/gui/text/qfontengine_ft_p.h
+++ b/src/gui/text/qfontengine_ft_p.h
@@ -96,6 +96,7 @@ public:
     FT_Face face;
     int xsize; // 26.6
     int ysize; // 26.6
+    QFixed scalableBitmapScaleFactor;
     FT_Matrix matrix;
     FT_CharMap unicode_map;
     FT_CharMap symbol_map;
@@ -107,6 +108,8 @@ public:
 
     int getPointInOutline(glyph_t glyph, int flags, quint32 point, QFixed *xpos, QFixed *ypos, quint32 *nPoints);
 
+    bool isScalableBitmap() const;
+
     static void addGlyphToPath(FT_Face face, FT_GlyphSlot g, const QFixedPoint &point, QPainterPath *path, FT_Fixed x_scale, FT_Fixed y_scale);
     static void addBitmapToPath(FT_GlyphSlot slot, const QFixedPoint &point, QPainterPath *path);
 
@@ -239,6 +242,7 @@ private:
     QImage alphaMapForGlyph(glyph_t, QFixed) Q_DECL_OVERRIDE;
     QImage alphaMapForGlyph(glyph_t glyph, QFixed subPixelPosition, const QTransform &t) Q_DECL_OVERRIDE;
     QImage alphaRGBMapForGlyph(glyph_t, QFixed subPixelPosition, const QTransform &t) Q_DECL_OVERRIDE;
+    QImage bitmapForGlyph(glyph_t, QFixed subPixelPosition, const QTransform &t) Q_DECL_OVERRIDE;
     glyph_metrics_t alphaMapBoundingBox(glyph_t glyph,
                                         QFixed subPixelPosition,
                                         const QTransform &matrix,
@@ -266,6 +270,7 @@ private:
     inline bool drawAntialiased() const { return antialias; }
     inline bool invalid() const { return xsize == 0 && ysize == 0; }
     inline bool isBitmapFont() const { return defaultFormat == Format_Mono; }
+    inline bool isScalableBitmap() const { return freetype->isScalableBitmap(); }
 
     inline Glyph *loadGlyph(uint glyph, QFixed subPixelPosition, GlyphFormat format = Format_None, bool fetchMetricsOnly = false) const
     { return loadGlyph(cacheEnabled ? &defaultGlyphSet : 0, glyph, subPixelPosition, format, fetchMetricsOnly); }
@@ -316,6 +321,8 @@ private:
 
     int loadFlags(QGlyphSet *set, GlyphFormat format, int flags, bool &hsubpixel, int &vfactor) const;
     bool shouldUseDesignMetrics(ShaperFlags flags) const;
+    QFixed scaledBitmapMetrics(QFixed m) const;
+    glyph_metrics_t scaledBitmapMetrics(const glyph_metrics_t &m) const;
 
     GlyphFormat defaultFormat;
     FT_Matrix matrix;