From 9204252d029aee871da23861e971ac25e488cbaf Mon Sep 17 00:00:00 2001
From: Nico Weber <thakis@chromium.org>
Date: Fri, 3 Nov 2023 06:18:37 -0400
Subject: [PATCH] LibPDF: Add scaffolding for function objects

See PDF 1.7 Spec, "3.9 Functions".
---
 Userland/Libraries/LibPDF/CMakeLists.txt |  1 +
 Userland/Libraries/LibPDF/Function.cpp   | 58 ++++++++++++++++++++++++
 Userland/Libraries/LibPDF/Function.h     | 21 +++++++++
 3 files changed, 80 insertions(+)
 create mode 100644 Userland/Libraries/LibPDF/Function.cpp
 create mode 100644 Userland/Libraries/LibPDF/Function.h

diff --git a/Userland/Libraries/LibPDF/CMakeLists.txt b/Userland/Libraries/LibPDF/CMakeLists.txt
index 0f58e65b8e..e16c5a30bf 100644
--- a/Userland/Libraries/LibPDF/CMakeLists.txt
+++ b/Userland/Libraries/LibPDF/CMakeLists.txt
@@ -14,6 +14,7 @@ set(SOURCES
     Fonts/Type0Font.cpp
     Fonts/Type1Font.cpp
     Fonts/Type1FontProgram.cpp
+    Function.cpp
     Interpolation.cpp
     ObjectDerivatives.cpp
     Page.cpp
diff --git a/Userland/Libraries/LibPDF/Function.cpp b/Userland/Libraries/LibPDF/Function.cpp
new file mode 100644
index 0000000000..7262839eda
--- /dev/null
+++ b/Userland/Libraries/LibPDF/Function.cpp
@@ -0,0 +1,58 @@
+/*
+ * Copyright (c) 2023, Nico Weber <thakis@chromium.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibPDF/Function.h>
+
+// PDF 1.7 spec, 3.9 Functions
+
+namespace PDF {
+
+class SampledFunction final : public Function {
+public:
+    virtual PDFErrorOr<ReadonlySpan<float>> evaluate(ReadonlySpan<float>) const override;
+};
+
+PDFErrorOr<ReadonlySpan<float>> SampledFunction::evaluate(ReadonlySpan<float>) const
+{
+    return Error(Error::Type::RenderingUnsupported, "SampledFunction not yet implemented"_string);
+}
+
+class ExponentialInterpolationFunction final : public Function {
+public:
+    virtual PDFErrorOr<ReadonlySpan<float>> evaluate(ReadonlySpan<float>) const override;
+};
+
+PDFErrorOr<ReadonlySpan<float>> ExponentialInterpolationFunction::evaluate(ReadonlySpan<float>) const
+{
+    return Error(Error::Type::RenderingUnsupported, "ExponentialInterpolationFunction not yet implemented"_string);
+}
+
+class StitchingFunction final : public Function {
+public:
+    virtual PDFErrorOr<ReadonlySpan<float>> evaluate(ReadonlySpan<float>) const override;
+};
+
+PDFErrorOr<ReadonlySpan<float>> StitchingFunction::evaluate(ReadonlySpan<float>) const
+{
+    return Error(Error::Type::RenderingUnsupported, "StitchingFunction not yet implemented"_string);
+}
+
+class PostScriptCalculatorFunction final : public Function {
+public:
+    virtual PDFErrorOr<ReadonlySpan<float>> evaluate(ReadonlySpan<float>) const override;
+};
+
+PDFErrorOr<ReadonlySpan<float>> PostScriptCalculatorFunction::evaluate(ReadonlySpan<float>) const
+{
+    return Error(Error::Type::RenderingUnsupported, "PostScriptCalculatorFunction not yet implemented"_string);
+}
+
+PDFErrorOr<NonnullRefPtr<Function>> Function::create(Document*, NonnullRefPtr<Object>)
+{
+    return Error(Error::Type::RenderingUnsupported, "Function creation not yet implemented"_string);
+}
+
+}
diff --git a/Userland/Libraries/LibPDF/Function.h b/Userland/Libraries/LibPDF/Function.h
new file mode 100644
index 0000000000..9b51ffef92
--- /dev/null
+++ b/Userland/Libraries/LibPDF/Function.h
@@ -0,0 +1,21 @@
+/*
+ * Copyright (c) 2023, Nico Weber <thakis@chromium.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Forward.h>
+#include <LibPDF/Value.h>
+
+namespace PDF {
+
+class Function : public RefCounted<Function> {
+public:
+    static PDFErrorOr<NonnullRefPtr<Function>> create(Document*, NonnullRefPtr<Object>);
+    virtual ~Function() = default;
+    virtual PDFErrorOr<ReadonlySpan<float>> evaluate(ReadonlySpan<float>) const = 0;
+};
+
+}