Fix missing glyphs when changing distance field parameters

When altering the environment variables that decide how distance
fields are generated, you could get into the situation where
the QT_DISTANCEFIELD_RADIUS / QT_DISTANCEFIELD_SCALE would not
be an integer. This caused an issue where the distance field cache
was too small to contain glyphs that happened at the end of the
rows.

The effect of this would depend on the backend. On some backends,
it was not detectable, whereas on others it would cause missing
glyphs or even crashes.

The reason was that the logic to calculate the necessary size of
the cache would always truncate the fraction, whereas we would
use floats when storing the margin of the glyph. To consolidate,
we use floats also in the calculation of the required size of the
cache.

Cherry-pick adapted to Qt 5.15 by including OpenGL implementation
of glyph cache.

[ChangeLog][Text] Fixed an issue where glyphs would sometimes be
missing when changing the environment variables that define how
distance fields are generated to certain values.

Task-number: QTBUG-86633
Change-Id: I3c390737e0eaf1391d82cf1f9b3896eff25a5a8c
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
(cherry picked from commit 063c5c7fae28972ac1302774d08bbfc5851a0682)

3 files changed, 11 insertions, 11 deletions

diff --git a/src/quick/scenegraph/qsgadaptationlayer_p.h b/src/quick/scenegraph/qsgadaptationlayer_p.h
index f4f1e1bf2b..f2d684e43c 100644
--- a/src/quick/scenegraph/qsgadaptationlayer_p.h
+++ b/src/quick/scenegraph/qsgadaptationlayer_p.h
@@ -465,9 +465,9 @@ public:
     {
         return pixelSize / QT_DISTANCEFIELD_BASEFONTSIZE(m_doubleGlyphResolution);
     }
-    int distanceFieldRadius() const
+    qreal distanceFieldRadius() const
     {
-        return QT_DISTANCEFIELD_RADIUS(m_doubleGlyphResolution) / QT_DISTANCEFIELD_SCALE(m_doubleGlyphResolution);
+        return QT_DISTANCEFIELD_RADIUS(m_doubleGlyphResolution) / qreal(QT_DISTANCEFIELD_SCALE(m_doubleGlyphResolution));
     }
     int glyphCount() const { return m_glyphCount; }
     bool doubleGlyphResolution() const { return m_doubleGlyphResolution; }
diff --git a/src/quick/scenegraph/qsgopengldistancefieldglyphcache.cpp b/src/quick/scenegraph/qsgopengldistancefieldglyphcache.cpp
index 65c1afb724..971b4eee93 100644
--- a/src/quick/scenegraph/qsgopengldistancefieldglyphcache.cpp
+++ b/src/quick/scenegraph/qsgopengldistancefieldglyphcache.cpp
@@ -122,7 +122,7 @@ void QSGOpenGLDistanceFieldGlyphCache::requestGlyphs(const QSet<glyph_t> &glyphs
 
         // We need to add a buffer to avoid glyphs that overlap the border between two
         // textures causing the height of the textures to extend beyond the limit.
-        m_maxTextureHeight = m_maxTextureWidth - (qCeil(m_referenceFont.pixelSize() * scaleFactor) + distanceFieldRadius() * 2 + padding * 2);
+        m_maxTextureHeight = m_maxTextureWidth - (qCeil(m_referenceFont.pixelSize() * scaleFactor + distanceFieldRadius() * 2) + padding * 2);
     }
 
     if (m_areaAllocator == nullptr)
@@ -132,8 +132,8 @@ void QSGOpenGLDistanceFieldGlyphCache::requestGlyphs(const QSet<glyph_t> &glyphs
         glyph_t glyphIndex = *it;
 
         QRectF boundingRect = glyphData(glyphIndex).boundingRect;
-        int glyphWidth = qCeil(boundingRect.width()) + distanceFieldRadius() * 2;
-        int glyphHeight = qCeil(boundingRect.height()) + distanceFieldRadius() * 2;
+        int glyphWidth = qCeil(boundingRect.width() + distanceFieldRadius()) * 2;
+        int glyphHeight = qCeil(boundingRect.height() + distanceFieldRadius()) * 2;
         QSize glyphSize(glyphWidth + padding * 2, glyphHeight + padding * 2);
         QRect alloc = m_areaAllocator->allocate(glyphSize);
 
@@ -144,8 +144,8 @@ void QSGOpenGLDistanceFieldGlyphCache::requestGlyphs(const QSet<glyph_t> &glyphs
 
                 TexCoord unusedCoord = glyphTexCoord(unusedGlyph);
                 QRectF unusedGlyphBoundingRect = glyphData(unusedGlyph).boundingRect;
-                int unusedGlyphWidth = qCeil(unusedGlyphBoundingRect.width()) + distanceFieldRadius() * 2;
-                int unusedGlyphHeight = qCeil(unusedGlyphBoundingRect.height())  + distanceFieldRadius() * 2;
+                int unusedGlyphWidth = qCeil(unusedGlyphBoundingRect.width() + distanceFieldRadius()) * 2;
+                int unusedGlyphHeight = qCeil(unusedGlyphBoundingRect.height()  + distanceFieldRadius()) * 2;
                 m_areaAllocator->deallocate(QRect(unusedCoord.x - padding,
                                                   unusedCoord.y - padding,
                                                   padding * 2 + unusedGlyphWidth,
diff --git a/src/quick/scenegraph/qsgrhidistancefieldglyphcache.cpp b/src/quick/scenegraph/qsgrhidistancefieldglyphcache.cpp
index 6463b8c137..63319389fe 100644
--- a/src/quick/scenegraph/qsgrhidistancefieldglyphcache.cpp
+++ b/src/quick/scenegraph/qsgrhidistancefieldglyphcache.cpp
@@ -86,8 +86,8 @@ void QSGRhiDistanceFieldGlyphCache::requestGlyphs(const QSet<glyph_t> &glyphs)
 
         int padding = QSG_RHI_DISTANCEFIELD_GLYPH_CACHE_PADDING;
         QRectF boundingRect = glyphData(glyphIndex).boundingRect;
-        int glyphWidth = qCeil(boundingRect.width()) + distanceFieldRadius() * 2;
-        int glyphHeight = qCeil(boundingRect.height()) + distanceFieldRadius() * 2;
+        int glyphWidth = qCeil(boundingRect.width() + distanceFieldRadius() * 2);
+        int glyphHeight = qCeil(boundingRect.height() + distanceFieldRadius() * 2);
         QSize glyphSize(glyphWidth + padding * 2, glyphHeight + padding * 2);
         QRect alloc = m_areaAllocator->allocate(glyphSize);
 
@@ -98,8 +98,8 @@ void QSGRhiDistanceFieldGlyphCache::requestGlyphs(const QSet<glyph_t> &glyphs)
 
                 TexCoord unusedCoord = glyphTexCoord(unusedGlyph);
                 QRectF unusedGlyphBoundingRect = glyphData(unusedGlyph).boundingRect;
-                int unusedGlyphWidth = qCeil(unusedGlyphBoundingRect.width()) + distanceFieldRadius() * 2;
-                int unusedGlyphHeight = qCeil(unusedGlyphBoundingRect.height())  + distanceFieldRadius() * 2;
+                int unusedGlyphWidth = qCeil(unusedGlyphBoundingRect.width() + distanceFieldRadius() * 2);
+                int unusedGlyphHeight = qCeil(unusedGlyphBoundingRect.height() + distanceFieldRadius() * 2);
                 m_areaAllocator->deallocate(QRect(unusedCoord.x - padding,
                                                   unusedCoord.y - padding,
                                                   padding * 2 + unusedGlyphWidth,