LibWeb: Extract CanvasState class from CRC2D

As with CanvasPath, this is to better match the spec IDL.

Userland/Libraries/LibWeb/HTML/Canvas/CanvasState.h

@@ -0,0 +1,51 @@
+/*
+ * Copyright (c) 2022, Sam Atkins <atkinssj@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Vector.h>
+#include <LibGfx/AffineTransform.h>
+#include <LibGfx/Color.h>
+
+namespace Web::HTML {
+
+// https://html.spec.whatwg.org/multipage/canvas.html#canvasstate
+class CanvasState {
+public:
+    virtual ~CanvasState() = default;
+
+    void save();
+    void restore();
+    void reset();
+    bool is_context_lost();
+
+    // https://html.spec.whatwg.org/multipage/canvas.html#drawing-state
+    struct DrawingState {
+        Gfx::AffineTransform transform;
+        Gfx::Color fill_style { Gfx::Color::Black };
+        Gfx::Color stroke_style { Gfx::Color::Black };
+        float line_width { 1 };
+    };
+    DrawingState& drawing_state() { return m_drawing_state; }
+    DrawingState const& drawing_state() const { return m_drawing_state; }
+
+    void clear_drawing_state_stack() { m_drawing_state_stack.clear(); }
+    void reset_drawing_state() { m_drawing_state = {}; }
+
+    virtual void reset_to_default_state() = 0;
+
+protected:
+    CanvasState() = default;
+
+private:
+    DrawingState m_drawing_state;
+    Vector<DrawingState> m_drawing_state_stack;
+
+    // https://html.spec.whatwg.org/multipage/canvas.html#concept-canvas-context-lost
+    bool m_context_lost { false };
+};
+
+}