Solid and gradients in high color accuracy

This patch updates the internal color precisions of solids and
gradients to 16bit per color. This makes it possible to render
at higher precision on non-premultiplied ARGB32, the RGB30
formats and any other hi-color formats if more are added.

[ChangeLog][QtGui][Painting] Internal precision of solids and gradients
is now up to 16bit per color.

Change-Id: Ieae5468bd6de1f56adfa4cb9fa966faf2ed824fd
Reviewed-by: Gunnar Sletta <gunnar@sletta.org>

1 files changed, 30 insertions, 13 deletions

diff --git a/src/gui/opengl/qopenglgradientcache.cpp b/src/gui/opengl/qopenglgradientcache.cpp
index ab493fa85c..6622d4805f 100644
--- a/src/gui/opengl/qopenglgradientcache.cpp
+++ b/src/gui/opengl/qopenglgradientcache.cpp
@@ -34,8 +34,18 @@
 #include "qopenglgradientcache_p.h"
 #include <private/qdrawhelper_p.h>
 #include <private/qopenglcontext_p.h>
+#include <private/qrgba64_p.h>
 #include <QtCore/qmutex.h>
-#include <QtGui/qopenglfunctions.h>
+#include "qopenglfunctions.h"
+#include "qopenglextensions_p.h"
+
+#ifndef GL_RGBA8
+#define GL_RGBA8    0x8058
+#endif
+
+#ifndef GL_RGBA16
+#define GL_RGBA16   0x805B
+#endif
 
 QT_BEGIN_NAMESPACE
 
@@ -137,33 +147,40 @@ GLuint QOpenGL2GradientCache::addCacheElement(quint64 hash_val, const QGradient
     }
 
     CacheInfo cache_entry(gradient.stops(), opacity, gradient.interpolationMode());
-    uint buffer[1024];
+    QRgba64 buffer[1024];
     generateGradientColorTable(gradient, buffer, paletteSize(), opacity);
     funcs->glGenTextures(1, &cache_entry.texId);
     funcs->glBindTexture(GL_TEXTURE_2D, cache_entry.texId);
-    funcs->glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, paletteSize(), 1,
-                        0, GL_RGBA, GL_UNSIGNED_BYTE, buffer);
+    GLenum internalFormat = GL_RGBA16;
+    if (QOpenGLContext::currentContext()->isOpenGLES()) {
+        if (static_cast<QOpenGLExtensions*>(funcs)->hasOpenGLExtension(QOpenGLExtensions::Sized8Formats))
+            internalFormat = GL_RGBA8;
+        else
+            internalFormat = GL_RGBA; // Let OpenGLES use whatever it prefers.
+    }
+    funcs->glTexImage2D(GL_TEXTURE_2D, 0, internalFormat, paletteSize(), 1,
+                        0, GL_RGBA, GL_UNSIGNED_SHORT, buffer);
     return cache.insert(hash_val, cache_entry).value().texId;
 }
 
 
 //TODO: Let GL generate the texture using an FBO
-void QOpenGL2GradientCache::generateGradientColorTable(const QGradient& gradient, uint *colorTable, int size, qreal opacity) const
+void QOpenGL2GradientCache::generateGradientColorTable(const QGradient& gradient, QRgba64 *colorTable, int size, qreal opacity) const
 {
     int pos = 0;
     QGradientStops s = gradient.stops();
-    QVector<uint> colors(s.size());
+    QVector<QRgba64> colors(s.size());
 
     for (int i = 0; i < s.size(); ++i)
-        colors[i] = s[i].second.rgba(); // Qt LIES! It returns ARGB (on little-endian AND on big-endian)
+        colors[i] = s[i].second.rgba64();
 
     bool colorInterpolation = (gradient.interpolationMode() == QGradient::ColorInterpolation);
 
     uint alpha = qRound(opacity * 256);
-    uint current_color = ARGB_COMBINE_ALPHA(colors[0], alpha);
+    QRgba64 current_color = combineAlpha256(colors[0], alpha);
     qreal incr = 1.0 / qreal(size);
     qreal fpos = 1.5 * incr;
-    colorTable[pos++] = ARGB2RGBA(qPremultiply(current_color));
+    colorTable[pos++] = qPremultiply(current_color);
 
     while (fpos <= s.first().first) {
         colorTable[pos] = colorTable[pos - 1];
@@ -176,7 +193,7 @@ void QOpenGL2GradientCache::generateGradientColorTable(const QGradient& gradient
 
     for (int i = 0; i < s.size() - 1; ++i) {
         qreal delta = 1/(s[i+1].first - s[i].first);
-        uint next_color = ARGB_COMBINE_ALPHA(colors[i+1], alpha);
+        QRgba64 next_color = combineAlpha256(colors[i+1], alpha);
         if (colorInterpolation)
             next_color = qPremultiply(next_color);
 
@@ -184,9 +201,9 @@ void QOpenGL2GradientCache::generateGradientColorTable(const QGradient& gradient
             int dist = int(256 * ((fpos - s[i].first) * delta));
             int idist = 256 - dist;
             if (colorInterpolation)
-                colorTable[pos] = ARGB2RGBA(INTERPOLATE_PIXEL_256(current_color, idist, next_color, dist));
+                colorTable[pos] = interpolate256(current_color, idist, next_color, dist);
             else
-                colorTable[pos] = ARGB2RGBA(qPremultiply(INTERPOLATE_PIXEL_256(current_color, idist, next_color, dist)));
+                colorTable[pos] = qPremultiply(interpolate256(current_color, idist, next_color, dist));
             ++pos;
             fpos += incr;
         }
@@ -195,7 +212,7 @@ void QOpenGL2GradientCache::generateGradientColorTable(const QGradient& gradient
 
     Q_ASSERT(s.size() > 0);
 
-    uint last_color = ARGB2RGBA(qPremultiply(ARGB_COMBINE_ALPHA(colors[s.size() - 1], alpha)));
+    QRgba64 last_color = qPremultiply(combineAlpha256(colors[s.size() - 1], alpha));
     for (;pos < size; ++pos)
         colorTable[pos] = last_color;