1 files changed, 90 insertions, 0 deletions
diff --git a/basegfx/source/tools/keystoplerp.cxx b/basegfx/source/tools/keystoplerp.cxx
new file mode 100644
index 0000000000..e5d0d76304
--- /dev/null
+++ b/basegfx/source/tools/keystoplerp.cxx
@@ -0,0 +1,90 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ * This file incorporates work covered by the following license notice:
+ *
+ *   Licensed to the Apache Software Foundation (ASF) under one or more
+ *   contributor license agreements. See the NOTICE file distributed
+ *   with this work for additional information regarding copyright
+ *   ownership. The ASF licenses this file to you under the Apache
+ *   License, Version 2.0 (the "License"); you may not use this file
+ *   except in compliance with the License. You may obtain a copy of
+ *   the License at http://www.apache.org/licenses/LICENSE-2.0 .
+ */
+
+#include <basegfx/utils/keystoplerp.hxx>
+#include <com/sun/star/uno/Sequence.hxx>
+#include <osl/diagnose.h>
+
+#include <algorithm>
+
+static void validateInput(const std::vector<double>& rKeyStops)
+{
+#ifdef DBG_UTIL
+    OSL_ENSURE( rKeyStops.size() > 1,
+                "KeyStopLerp::KeyStopLerp(): key stop vector must have two entries or more" );
+
+    // rKeyStops must be sorted in ascending order
+    for( std::size_t i=1, len=rKeyStops.size(); i<len; ++i )
+    {
+        if( rKeyStops[i-1] > rKeyStops[i] )
+            OSL_FAIL( "KeyStopLerp::KeyStopLerp(): time vector is not sorted in ascending order!" );
+    }
+#else
+    (void)rKeyStops;
+#endif
+}
+
+namespace basegfx::utils
+{
+        KeyStopLerp::KeyStopLerp( std::vector<double>&& rKeyStops ) :
+            maKeyStops(std::move(rKeyStops)),
+            mnLastIndex(0)
+        {
+            validateInput(maKeyStops);
+        }
+
+        KeyStopLerp::KeyStopLerp( const ::css::uno::Sequence<double>& rKeyStops ) :
+            maKeyStops(rKeyStops.begin(), rKeyStops.end()),
+            mnLastIndex(0)
+        {
+            validateInput(maKeyStops);
+        }
+
+        KeyStopLerp::ResultType KeyStopLerp::lerp(double fAlpha) const
+        {
+            // cached value still okay?
+            if( maKeyStops.at(mnLastIndex) < fAlpha ||
+                maKeyStops.at(mnLastIndex+1) >= fAlpha )
+            {
+                // nope, find new index
+                mnLastIndex = std::min<std::ptrdiff_t>(
+                    maKeyStops.size()-2,
+                    // range is ensured by max below
+                    std::max<std::ptrdiff_t>(
+                        0,
+                        std::distance( maKeyStops.begin(),
+                                       std::lower_bound( maKeyStops.begin(),
+                                                         maKeyStops.end(),
+                                                         fAlpha )) - 1 ));
+            }
+
+            // lerp between stop and stop+1
+            const double fRawLerp=
+                (fAlpha-maKeyStops.at(mnLastIndex)) /
+                (maKeyStops.at(mnLastIndex+1) - maKeyStops.at(mnLastIndex));
+
+            // clamp to permissible range (input fAlpha might be
+            // everything)
+            return ResultType(
+                mnLastIndex,
+                std::clamp(fRawLerp,0.0,1.0));
+        }
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */