Get rid of QGlyphLayout::advances_y

...and thus consume 4 bytes less per glyph and increase the performance a bit.
It seems, the only CTFontGetAdvancesForGlyphs() returns both x and y
advances, though y advances are always equal to 0 for horizontal
orientation and x advances are always equal to 0 for vertical orientation.

Also, rename `advances_x` to `advances` for consistency
and declare QGlyphLayout's data size in a single place.

Change-Id: I56b20f893f8a6feb7aa870e3edbca99dd93ba2e2
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@digia.com>
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>

1 files changed, 14 insertions, 23 deletions

diff --git a/src/gui/text/qtextengine_p.h b/src/gui/text/qtextengine_p.h
index f2e16cf546..fce2bd808d 100644
--- a/src/gui/text/qtextengine_p.h
+++ b/src/gui/text/qtextengine_p.h
@@ -190,11 +190,15 @@ Q_DECLARE_TYPEINFO(QGlyphJustification, Q_PRIMITIVE_TYPE);
 
 struct QGlyphLayout
 {
+    enum {
+        SpaceNeeded = sizeof(glyph_t) + sizeof(QFixed) + sizeof(QFixedPoint)
+                    + sizeof(QGlyphAttributes) + sizeof(QGlyphJustification)
+    };
+
     // init to 0 not needed, done when shaping
     QFixedPoint *offsets; // 8 bytes per element
     glyph_t *glyphs; // 4 bytes per element
-    QFixed *advances_x; // 4 bytes per element
-    QFixed *advances_y; // 4 bytes per element
+    QFixed *advances; // 4 bytes per element
     QGlyphJustification *justifications; // 4 bytes per element
     QGlyphAttributes *attributes; // 2 bytes per element
 
@@ -208,9 +212,7 @@ struct QGlyphLayout
         int offset = totalGlyphs * sizeof(QFixedPoint);
         glyphs = reinterpret_cast<glyph_t *>(address + offset);
         offset += totalGlyphs * sizeof(glyph_t);
-        advances_x = reinterpret_cast<QFixed *>(address + offset);
-        offset += totalGlyphs * sizeof(QFixed);
-        advances_y = reinterpret_cast<QFixed *>(address + offset);
+        advances = reinterpret_cast<QFixed *>(address + offset);
         offset += totalGlyphs * sizeof(QFixed);
         justifications = reinterpret_cast<QGlyphJustification *>(address + offset);
         offset += totalGlyphs * sizeof(QGlyphJustification);
@@ -221,8 +223,7 @@ struct QGlyphLayout
     inline QGlyphLayout mid(int position, int n = -1) const {
         QGlyphLayout copy = *this;
         copy.glyphs += position;
-        copy.advances_x += position;
-        copy.advances_y += position;
+        copy.advances += position;
         copy.offsets += position;
         copy.justifications += position;
         copy.attributes += position;
@@ -233,27 +234,20 @@ struct QGlyphLayout
         return copy;
     }
 
-    static inline int spaceNeededForGlyphLayout(int totalGlyphs) {
-        return totalGlyphs * (sizeof(glyph_t) + sizeof(QGlyphAttributes)
-                + sizeof(QFixed) + sizeof(QFixed) + sizeof(QFixedPoint)
-                + sizeof(QGlyphJustification));
-    }
-
     inline QFixed effectiveAdvance(int item) const
-    { return (advances_x[item] + QFixed::fromFixed(justifications[item].space_18d6)) * !attributes[item].dontPrint; }
+    { return (advances[item] + QFixed::fromFixed(justifications[item].space_18d6)) * !attributes[item].dontPrint; }
 
     inline void clear(int first = 0, int last = -1) {
         if (last == -1)
             last = numGlyphs;
         if (first == 0 && last == numGlyphs
             && reinterpret_cast<char *>(offsets + numGlyphs) == reinterpret_cast<char *>(glyphs)) {
-            memset(offsets, 0, spaceNeededForGlyphLayout(numGlyphs));
+            memset(offsets, 0, (numGlyphs * SpaceNeeded));
         } else {
             const int num = last - first;
             memset(offsets + first, 0, num * sizeof(QFixedPoint));
             memset(glyphs + first, 0, num * sizeof(glyph_t));
-            memset(advances_x + first, 0, num * sizeof(QFixed));
-            memset(advances_y + first, 0, num * sizeof(QFixed));
+            memset(advances + first, 0, num * sizeof(QFixed));
             memset(justifications + first, 0, num * sizeof(QGlyphJustification));
             memset(attributes + first, 0, num * sizeof(QGlyphAttributes));
         }
@@ -272,7 +266,7 @@ private:
     typedef QVarLengthArray<void *> Array;
 public:
     QVarLengthGlyphLayoutArray(int totalGlyphs)
-        : Array(spaceNeededForGlyphLayout(totalGlyphs) / sizeof(void *) + 1)
+        : Array((totalGlyphs * SpaceNeeded) / sizeof(void *) + 1)
         , QGlyphLayout(reinterpret_cast<char *>(Array::data()), totalGlyphs)
     {
         memset(Array::data(), 0, Array::size() * sizeof(void *));
@@ -280,7 +274,7 @@ public:
 
     void resize(int totalGlyphs)
     {
-        Array::resize(spaceNeededForGlyphLayout(totalGlyphs) / sizeof(void *) + 1);
+        Array::resize((totalGlyphs * SpaceNeeded) / sizeof(void *) + 1);
 
         *((QGlyphLayout *)this) = QGlyphLayout(reinterpret_cast<char *>(Array::data()), totalGlyphs);
         memset(Array::data(), 0, Array::size() * sizeof(void *));
@@ -297,10 +291,7 @@ public:
     }
 
 private:
-    void *buffer[(N * (sizeof(glyph_t) + sizeof(QGlyphAttributes)
-                + sizeof(QFixed) + sizeof(QFixed) + sizeof(QFixedPoint)
-                + sizeof(QGlyphJustification)))
-                    / sizeof(void *) + 1];
+    void *buffer[(N * SpaceNeeded) / sizeof(void *) + 1];
 };
 
 struct QScriptItem;