Make axis labels more accurate by using qreals for label values

Also refactor axis formatter sub grid array to be one dimensional.
There is no need to know which segment each sub grid line belongs
to.

Change-Id: Ie9813088650fcc0ca844f3c358ea1abae9258367
Reviewed-by: Tomi Korpipää <tomi.korpipaa@digia.com>

1 files changed, 17 insertions, 8 deletions

diff --git a/src/datavisualization/axis/qlogvalue3daxisformatter.cpp b/src/datavisualization/axis/qlogvalue3daxisformatter.cpp
index 36f27c02..17ae4476 100644
--- a/src/datavisualization/axis/qlogvalue3daxisformatter.cpp
+++ b/src/datavisualization/axis/qlogvalue3daxisformatter.cpp
@@ -293,6 +293,11 @@ QLogValue3DAxisFormatterPrivate::~QLogValue3DAxisFormatterPrivate()
 
 void QLogValue3DAxisFormatterPrivate::recalculate()
 {
+    // When doing position/value mappings, base doesn't matter, so just use natural logarithm
+    m_logMin = qLn(qreal(m_min));
+    m_logMax = qLn(qreal(m_max));
+    m_logRangeNormalizer = m_logMax - m_logMin;
+
     if (m_base > 0.0) {
         // Update parent axis segment counts
         qreal logMin = qLn(qreal(m_min)) / qLn(m_base);
@@ -309,17 +314,19 @@ void QLogValue3DAxisFormatterPrivate::recalculate()
             m_axis->setSubSegmentCount(subSegmentCount);
         }
 
-        resetPositionArrays();
+        resetArrays();
 
         // Calculate segment positions
         for (int i = 0; i < segmentCount; i++) {
-            float gridValue = float(qreal(i) / logRangeNormalizer);
+            float gridValue = float(i) / float(logRangeNormalizer);
             m_gridPositions[i] = gridValue;
             m_labelPositions[i] = gridValue;
+            m_labelValues[i] = qPow(m_base, qreal(i) + logMin);
         }
         // Ensure max value doesn't suffer from any rounding errors
         m_gridPositions[segmentCount] = 1.0f;
         m_labelPositions[segmentCount] = 1.0f;
+        m_labelValues[segmentCount] = qreal(m_max);
         float lastDiff = 1.0f - m_labelPositions.at(segmentCount - 1);
         float firstDiff = m_labelPositions.at(1) - m_labelPositions.at(0);
         m_evenSegments = qFuzzyCompare(lastDiff, firstDiff);
@@ -327,13 +334,15 @@ void QLogValue3DAxisFormatterPrivate::recalculate()
         // Grid lines and label positions are the same as the parent class, so call parent impl
         // first to populate those
         QValue3DAxisFormatterPrivate::doRecalculate();
+
+        // Label value array needs to be repopulated
+        qreal segmentStep = 1.0 / qreal(m_axis->segmentCount());
+        for (int i = 0; i < m_labelPositions.size(); i++)
+            m_labelValues[i] = qExp(segmentStep * qreal(i) * m_logRangeNormalizer + m_logMin);
+
         m_evenSegments = true;
     }
 
-    // When doing position/value mappings, base doesn't matter, so just use natural logarithm
-    m_logMin = qLn(qreal(m_min));
-    m_logMax = qLn(qreal(m_max));
-    m_logRangeNormalizer = m_logMax - m_logMin;
 
     // Subgrid line positions are logarithmically spaced
     int subGridCount = m_axis->subSegmentCount() - 1;
@@ -355,8 +364,8 @@ void QLogValue3DAxisFormatterPrivate::recalculate()
             for (int j = 0; j < subGridCount; j++) {
                 float position = m_gridPositions.at(i) + actualSubSegmentSteps.at(j);
                 if (position > 1.0f)
-                    position  = 1.0f;
-                m_subGridPositions[i][j] = position;
+                    position = 1.0f;
+                m_subGridPositions[i * subGridCount + j] = position;
             }
         }
     }