assert/SAL_WARN in BlendWith

instead of just silently doing nothing, so we get some indication of
error

Change-Id: Iac7e21d42b45ebc97cfb95552d98c186b9eb05ac
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/145655
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

1 files changed, 4 insertions, 0 deletions

diff --git a/vcl/source/bitmap/alpha.cxx b/vcl/source/bitmap/alpha.cxx
index 196ba30d5f57..8618c052ab03 100644
--- a/vcl/source/bitmap/alpha.cxx
+++ b/vcl/source/bitmap/alpha.cxx
@@ -91,8 +91,12 @@ void AlphaMask::BlendWith(const Bitmap& rOther)
     AlphaMask aOther(rOther); // to 8 bits
     Bitmap::ScopedReadAccess pOtherAcc(aOther);
     AlphaScopedWriteAccess pAcc(*this);
+    assert (pOtherAcc && pAcc && pOtherAcc->GetBitCount() == 8 && pAcc->GetBitCount() == 8 && "cannot BlendWith this combination");
     if (!(pOtherAcc && pAcc && pOtherAcc->GetBitCount() == 8 && pAcc->GetBitCount() == 8))
+    {
+        SAL_WARN("vcl", "cannot BlendWith this combination");
         return;
+    }
 
     const tools::Long nHeight = std::min(pOtherAcc->Height(), pAcc->Height());
     const tools::Long nWidth = std::min(pOtherAcc->Width(), pAcc->Width());