tdf#94004 Wrap Exponential trendline equation

Wrap equation trendline if it is longer than chart width
Continue https://gerrit.libreoffice.org/18397/

Change-Id: I3938aaeec6c56582ecfe50dbfc54ec711f1b963d
Reviewed-on: https://gerrit.libreoffice.org/25393
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: jan iversen <jani@documentfoundation.org>
(cherry picked from commit 9a9c778d81e8ae54dcc42290241a5fc72be29bf2)
Reviewed-on: https://gerrit.libreoffice.org/26117
Reviewed-by: Laurent BP <laurent.balland-poirier@laposte.net>

2 files changed, 52 insertions, 19 deletions

diff --git a/chart2/qa/extras/chart2_trendcalculators.cxx b/chart2/qa/extras/chart2_trendcalculators.cxx
index 0c3b972c3031..04af84869237 100644
--- a/chart2/qa/extras/chart2_trendcalculators.cxx
+++ b/chart2/qa/extras/chart2_trendcalculators.cxx
@@ -199,7 +199,7 @@ void Chart2TrendCalculators::testExponentialRegression2()
         xValues[i] = d;
         yValues[i] = -2.0 * exp ( 0.3 * d );
     }
-    checkCalculator( xValues, yValues, "f(x) = -2 exp( 0.3 x )");
+    checkCalculator( xValues, yValues, "f(x) = "+ aMinusSign + " 2 exp( 0.3 x )");
 }
 
 
diff --git a/chart2/source/tools/ExponentialRegressionCurveCalculator.cxx b/chart2/source/tools/ExponentialRegressionCurveCalculator.cxx
index 75e92aa79536..f6a75716eb80 100644
--- a/chart2/source/tools/ExponentialRegressionCurveCalculator.cxx
+++ b/chart2/source/tools/ExponentialRegressionCurveCalculator.cxx
@@ -20,6 +20,7 @@
 #include "ExponentialRegressionCurveCalculator.hxx"
 #include "macros.hxx"
 #include "RegressionCalculationHelper.hxx"
+#include <SpecialUnicodes.hxx>
 
 #include <rtl/math.hxx>
 #include <rtl/ustrbuf.hxx>
@@ -154,40 +155,72 @@ uno::Sequence< geometry::RealPoint2D > SAL_CALL ExponentialRegressionCurveCalcul
 
 OUString ExponentialRegressionCurveCalculator::ImplGetRepresentation(
     const uno::Reference< util::XNumberFormatter >& xNumFormatter,
-    sal_Int32 nNumberFormatKey, sal_Int32* /*pFormulaLength = nullptr */ ) const
+    sal_Int32 nNumberFormatKey, sal_Int32* pFormulaMaxWidth /* = nullptr */ ) const
 {
-    double fIntercept = m_fSign * exp(m_fLogIntercept);
+    double fIntercept = exp(m_fLogIntercept);
     bool bHasSlope = !rtl::math::approxEqual( exp(m_fLogSlope), 1.0 );
     bool bHasLogSlope = !rtl::math::approxEqual( fabs(m_fLogSlope), 1.0 );
-    bool bHasIntercept = !rtl::math::approxEqual( m_fSign*fIntercept, 1.0 ) && fIntercept != 0.0;
+    bool bHasIntercept = !rtl::math::approxEqual( fIntercept, 1.0 ) && fIntercept != 0.0;
 
     OUStringBuffer aBuf( "f(x) = " );
-
+    sal_Int32 nLineLength = aBuf.getLength();
+    sal_Int32 nValueLength=0;
+    if ( pFormulaMaxWidth && *pFormulaMaxWidth > 0 )
+    {          // count characters different from coefficients
+        sal_Int32 nCharMin = nLineLength + 11;  // 11 = "exp( ", " x )" + 2 extra characters
+        if ( m_fSign < 0.0 )
+            nCharMin += 2;
+        if ( fIntercept == 0.0 || ( !bHasSlope && m_fLogIntercept != 0.0 ) )
+            nCharMin += 3; // " + " special case where equation is writen exp( a + b x )
+        if ( ( bHasIntercept || fIntercept == 0.0 || ( !bHasSlope && m_fLogIntercept != 0.0 ) ) &&
+               bHasLogSlope )
+            nValueLength = ( *pFormulaMaxWidth - nCharMin ) / 2;
+        else
+            nValueLength = *pFormulaMaxWidth - nCharMin;
+        if ( nValueLength <= 0 )
+            nValueLength = 1;
+    }
+                    // temporary buffer
+    OUStringBuffer aTmpBuf("");
+        // if nValueLength not calculated then nullptr
+    sal_Int32* pValueLength = nValueLength ? &nValueLength : nullptr;
+    if ( m_fSign < 0.0 )
+        aTmpBuf.append( aMinusSign + " " );
     if ( bHasIntercept )
     {
-        aBuf.append( getFormattedString( xNumFormatter, nNumberFormatKey, fIntercept) );
-        aBuf.append( " exp( " );
+        OUString aValueString = getFormattedString( xNumFormatter, nNumberFormatKey, fIntercept, pValueLength );
+        if ( aValueString != "1" )  // aValueString may be rounded to 1 if nValueLength is small
+        {
+            aTmpBuf.append( aValueString + " " );
+            addStringToEquation( aBuf, nLineLength, aTmpBuf, pFormulaMaxWidth );
+            aTmpBuf.truncate();
+        }
     }
-    else
+    aTmpBuf.append( "exp( " );
+    if ( !bHasIntercept )
     {
-       if ( m_fSign < 0.0 )
-            aBuf.append( "- " );
-       aBuf.append( "exp( " );
-       if ( fIntercept == 0.0 ||  // underflow, a true zero is impossible
-          ( !bHasSlope && m_fLogIntercept != 0.0 ) )    // show logarithmic output, if intercept and slope both are near one
+        if ( fIntercept == 0.0 ||  // underflow, a true zero is impossible
+           ( !bHasSlope && m_fLogIntercept != 0.0 ) )   // show logarithmic output, if intercept and slope both are near one
         {                                               // otherwise drop output of intercept, which is 1 here
-            aBuf.append( getFormattedString( xNumFormatter, nNumberFormatKey, m_fLogIntercept) );
-            aBuf.append( (m_fLogSlope < 0.0) ? OUStringLiteral(" ") : OUStringLiteral(" + "));
+            OUString aValueString = getFormattedString( xNumFormatter, nNumberFormatKey, m_fLogIntercept, pValueLength );
+            if ( aValueString != "0" )  // aValueString may be rounded to 0 if nValueLength is small
+            {
+                aTmpBuf.append( aValueString + ( (m_fLogSlope < 0.0) ? OUStringBuffer(" ") : OUStringBuffer(" + ") ) );
+            }
         }
     }
     if ( m_fLogSlope < 0.0 )
-        aBuf.append( "- ");
+        aTmpBuf.append( aMinusSign + " " );
     if ( bHasLogSlope )
     {
-        aBuf.append( getFormattedString( xNumFormatter, nNumberFormatKey, fabs(m_fLogSlope)) );
-        aBuf.append( ' ' );
+        OUString aValueString = getFormattedString( xNumFormatter, nNumberFormatKey, fabs(m_fLogSlope), pValueLength );
+        if ( aValueString != "1" )  // aValueString may be rounded to 1 if nValueLength is small
+        {
+            aTmpBuf.append( aValueString + " " );
+        }
     }
-    aBuf.append( "x )");
+    aTmpBuf.append( "x )");
+    addStringToEquation( aBuf, nLineLength, aTmpBuf, pFormulaMaxWidth );
 
     return aBuf.makeStringAndClear();
 }