make the Color constructors explicitly specify transparency

to reduce the churn, we leave the existing constructor in place,
and add a clang plugin to detect when the value passed to the
existing constructor may contain transparency/alpha data.

i.e. we leave expressions like Color(0xffffff) alone, but
warn about any non-constant expression, and any expression
like Color(0xff000000)

Change-Id: Id2ce58e08882d9b7bd0b9f88eca97359dcdbcc8c
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/109362
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

1 files changed, 4 insertions, 4 deletions

diff --git a/chart2/source/view/main/VDataSeries.cxx b/chart2/source/view/main/VDataSeries.cxx
index bb628a9419e3..d3c4dcd857e8 100644
--- a/chart2/source/view/main/VDataSeries.cxx
+++ b/chart2/source/view/main/VDataSeries.cxx
@@ -1125,13 +1125,13 @@ double VDataSeries::getValueByProperty( sal_Int32 nIndex, const OUString& rPropN
         if(rPropName.endsWith("Color"))
         {
             //optimized interpolation for color values
-            Color aColor(static_cast<sal_uInt32>(fValue));
-            Color aOldColor(static_cast<sal_uInt32>(fOldValue));
+            Color aColor(ColorTransparency, static_cast<sal_uInt32>(fValue));
+            Color aOldColor(ColorTransparency, static_cast<sal_uInt32>(fOldValue));
             sal_uInt8 r = aOldColor.GetRed() + (aColor.GetRed() - aOldColor.GetRed()) * mnPercent;
             sal_uInt8 g = aOldColor.GetGreen() + (aColor.GetGreen() - aOldColor.GetGreen()) * mnPercent;
             sal_uInt8 b = aOldColor.GetBlue() + (aColor.GetBlue() - aOldColor.GetBlue()) * mnPercent;
-            sal_uInt8 t = 255 - (aOldColor.GetAlpha() + (aColor.GetAlpha() - aOldColor.GetAlpha()) * mnPercent);
-            Color aRet(t, r, g, b);
+            sal_uInt8 a = aOldColor.GetAlpha() + (aColor.GetAlpha() - aOldColor.GetAlpha()) * mnPercent;
+            Color aRet(ColorAlpha, a, r, g, b);
             return sal_uInt32(aRet);
         }
         return fOldValue + (fValue - fOldValue) * mnPercent;