[PDF Ink Signatures] Introduce PdfInkBrush

Introduce chrome_pdf::PdfInkBrush, which is a wrapper class for
chrome_pdf::InkBrush. The purpose of PdfInkBrush is to provide an easy
way to quickly create certain brushes used only for PDF annotation mode.

For example, PDF annotation mode currently only needs a pen,
highlighter, and eraser. The pen and highlighter should have a certain
tip, transparency, etc. PdfInkBrush uses the brush type and relevant
parameters to quickly create preset InkBrushes.

PdfInkBrush::CreateInkBrush() will be implemented and used in
https://crrev.com/c/5550545.

Low-Coverage-Reason: TESTS_IN_SEPARATE_CL. Class is unused in current
CL, and is used in https://crrev.com/c/5550545.

Bug: 335524382
Change-Id: I200c994d0d903fe745ec9ecd9f8ad3cd15d98474
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5550544
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Andy Phan <andyphan@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1304484}

pdf/BUILD.gn

@@ -196,6 +196,8 @@ if (enable_pdf) {
       sources += [
         "ink_module.cc",
         "ink_module.h",
+        "pdf_ink_brush.cc",
+        "pdf_ink_brush.h",
       ]
 
       public_deps += [ "//pdf/ink" ]

pdf/pdf_ink_brush.cc

@@ -0,0 +1,37 @@
+// Copyright 2024 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "pdf/pdf_ink_brush.h"
+
+#include <optional>
+
+#include "base/check_op.h"
+
+namespace chrome_pdf {
+
+// static
+std::optional<PdfInkBrush::Type> PdfInkBrush::StringToType(
+    const std::string& brush_type) {
+  if (brush_type == "highlighter") {
+    return Type::kHighlighter;
+  }
+  if (brush_type == "pen") {
+    return Type::kPen;
+  }
+  return std::nullopt;
+}
+
+PdfInkBrush::PdfInkBrush(Type brush_type, Params brush_params)
+    : type_(brush_type), params_(brush_params) {
+  CHECK_GT(brush_params.size, 0);
+}
+
+PdfInkBrush::~PdfInkBrush() = default;
+
+std::unique_ptr<InkBrush> PdfInkBrush::CreateInkBrush() {
+  // TODO(crbug.com/335524382): Implement this.
+  return nullptr;
+}
+
+}  // namespace chrome_pdf

pdf/pdf_ink_brush.h

@@ -0,0 +1,61 @@
+// Copyright 2024 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef PDF_PDF_INK_BRUSH_H_
+#define PDF_PDF_INK_BRUSH_H_
+
+#include <memory>
+#include <optional>
+#include <string>
+
+#include "third_party/skia/include/core/SkColor.h"
+
+namespace chrome_pdf {
+
+class InkBrush;
+
+// A wrapper class used to create ink brushes specifically for PDF annotation
+// mode.
+// TODO(crbug.com/335524382): Add unit tests that check that `PdfInkBrush`
+// properly creates `InkBrush` instances.
+class PdfInkBrush {
+ public:
+  // The types of brushes supported in PDF annotation mode.
+  enum class Type {
+    kHighlighter,
+    kPen,
+  };
+
+  // Converts `brush_type` to a `Type`, returning `std::nullopt` if `brush_type`
+  // does not correspond to any `Type`.
+  static std::optional<Type> StringToType(const std::string& brush_type);
+
+  // Parameters for the brush.
+  struct Params {
+    SkColor color;
+    float size;
+  };
+
+  PdfInkBrush(Type brush_type, Params brush_params);
+
+  PdfInkBrush(const PdfInkBrush&) = delete;
+  PdfInkBrush& operator=(const PdfInkBrush&) = delete;
+  ~PdfInkBrush();
+
+  Type type() const { return type_; }
+
+  const Params& params() const { return params_; }
+
+  // Returns a new ink brush of `type_` with `params_` Returns nullptr if failed
+  // to create an ink brush.
+  std::unique_ptr<InkBrush> CreateInkBrush();
+
+ private:
+  Type type_;
+  Params params_;
+};
+
+}  // namespace chrome_pdf
+
+#endif  // PDF_PDF_INK_BRUSH_H_