LibWeb: Extract CanvasTransform class from CRC2D

The implementation of this got a little funky, because it has to access
methods from CanvasState.

5 files changed, 101 insertions, 69 deletions

diff --git a/Userland/Libraries/LibWeb/HTML/Canvas/CanvasTransform.h b/Userland/Libraries/LibWeb/HTML/Canvas/CanvasTransform.h
new file mode 100644
index 0000000000..6a73a5939b
--- /dev/null
+++ b/Userland/Libraries/LibWeb/HTML/Canvas/CanvasTransform.h
@@ -0,0 +1,84 @@
+/*
+ * Copyright (c) 2020-2022, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2021-2022, Linus Groh <linusg@serenityos.org>
+ * Copyright (c) 2022, Sam Atkins <atkinssj@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Debug.h>
+#include <LibWeb/HTML/Canvas/CanvasState.h>
+
+namespace Web::HTML {
+
+// https://html.spec.whatwg.org/multipage/canvas.html#canvastransform
+template<typename IncludingClass>
+class CanvasTransform {
+public:
+    ~CanvasTransform() = default;
+
+    void scale(float sx, float sy)
+    {
+        dbgln_if(CANVAS_RENDERING_CONTEXT_2D_DEBUG, "CanvasTransform::scale({}, {})", sx, sy);
+
+        my_drawing_state().transform.scale(sx, sy);
+    }
+
+    void translate(float tx, float ty)
+    {
+        dbgln_if(CANVAS_RENDERING_CONTEXT_2D_DEBUG, "CanvasTransform::translate({}, {})", tx, ty);
+        my_drawing_state().transform.translate(tx, ty);
+    }
+
+    void rotate(float radians)
+    {
+        dbgln_if(CANVAS_RENDERING_CONTEXT_2D_DEBUG, "CanvasTransform::rotate({})", radians);
+        my_drawing_state().transform.rotate_radians(radians);
+    }
+
+    // https://html.spec.whatwg.org/multipage/canvas.html#dom-context-2d-transform
+    void transform(double a, double b, double c, double d, double e, double f)
+    {
+        // 1. If any of the arguments are infinite or NaN, then return.
+        if (!isfinite(a) || !isfinite(b) || !isfinite(c) || !isfinite(d) || !isfinite(e) || !isfinite(f))
+            return;
+
+        // 2. Replace the current transformation matrix with the result of multiplying the current transformation matrix with the matrix described by:
+        //    a c e
+        //    b d f
+        //    0 0 1
+        my_drawing_state().transform.multiply({ static_cast<float>(a), static_cast<float>(b), static_cast<float>(c), static_cast<float>(d), static_cast<float>(e), static_cast<float>(f) });
+    }
+
+    // https://html.spec.whatwg.org/multipage/canvas.html#dom-context-2d-settransform
+    void set_transform(double a, double b, double c, double d, double e, double f)
+    {
+        // 1. If any of the arguments are infinite or NaN, then return.
+        if (!isfinite(a) || !isfinite(b) || !isfinite(c) || !isfinite(d) || !isfinite(e) || !isfinite(f))
+            return;
+
+        // 2. Reset the current transformation matrix to the identity matrix.
+        my_drawing_state().transform = {};
+
+        // 3. Invoke the transform(a, b, c, d, e, f) method with the same arguments.
+        transform(a, b, c, d, e, f);
+    }
+
+    // https://html.spec.whatwg.org/multipage/canvas.html#dom-context-2d-resettransform
+    void reset_transform()
+    {
+        // The resetTransform() method, when invoked, must reset the current transformation matrix to the identity matrix.
+        my_drawing_state().transform = {};
+    }
+
+protected:
+    CanvasTransform() = default;
+
+private:
+    CanvasState::DrawingState& my_drawing_state() { return reinterpret_cast<IncludingClass&>(*this).drawing_state(); }
+    CanvasState::DrawingState const& my_drawing_state() const { return reinterpret_cast<IncludingClass const&>(*this).drawing_state(); }
+};
+
+}
diff --git a/Userland/Libraries/LibWeb/HTML/Canvas/CanvasTransform.idl b/Userland/Libraries/LibWeb/HTML/Canvas/CanvasTransform.idl
new file mode 100644
index 0000000000..423b10ba86
--- /dev/null
+++ b/Userland/Libraries/LibWeb/HTML/Canvas/CanvasTransform.idl
@@ -0,0 +1,12 @@
+// https://html.spec.whatwg.org/multipage/canvas.html#canvastransform
+interface mixin CanvasTransform {
+    undefined scale(unrestricted double x, unrestricted double y);
+    undefined rotate(unrestricted double radians);
+    undefined translate(unrestricted double x, unrestricted double y);
+    undefined transform(unrestricted double a, unrestricted double b, unrestricted double c, unrestricted double d, unrestricted double e, unrestricted double f);
+
+    // FIXME: [NewObject] DOMMatrix getTransform();
+    undefined setTransform(unrestricted double a, unrestricted double b, unrestricted double c, unrestricted double d, unrestricted double e, unrestricted double f);
+    // FIXME: undefined setTransform(optional DOMMatrix2DInit transform = {});
+    undefined resetTransform();
+};
diff --git a/Userland/Libraries/LibWeb/HTML/CanvasRenderingContext2D.cpp b/Userland/Libraries/LibWeb/HTML/CanvasRenderingContext2D.cpp
index 08d42cb396..d20449d17e 100644
--- a/Userland/Libraries/LibWeb/HTML/CanvasRenderingContext2D.cpp
+++ b/Userland/Libraries/LibWeb/HTML/CanvasRenderingContext2D.cpp
@@ -263,24 +263,6 @@ DOM::ExceptionOr<void> CanvasRenderingContext2D::draw_image(CanvasImageSource co
     return {};
 }
 
-void CanvasRenderingContext2D::scale(float sx, float sy)
-{
-    dbgln_if(CANVAS_RENDERING_CONTEXT_2D_DEBUG, "CanvasRenderingContext2D::scale({}, {})", sx, sy);
-    drawing_state().transform.scale(sx, sy);
-}
-
-void CanvasRenderingContext2D::translate(float tx, float ty)
-{
-    dbgln_if(CANVAS_RENDERING_CONTEXT_2D_DEBUG, "CanvasRenderingContext2D::translate({}, {})", tx, ty);
-    drawing_state().transform.translate(tx, ty);
-}
-
-void CanvasRenderingContext2D::rotate(float radians)
-{
-    dbgln_if(CANVAS_RENDERING_CONTEXT_2D_DEBUG, "CanvasRenderingContext2D::rotate({})", radians);
-    drawing_state().transform.rotate_radians(radians);
-}
-
 void CanvasRenderingContext2D::did_draw(Gfx::FloatRect const&)
 {
     // FIXME: Make use of the rect to reduce the invalidated area when possible.
@@ -601,41 +583,6 @@ NonnullRefPtr<CanvasGradient> CanvasRenderingContext2D::create_conic_gradient(do
     return CanvasGradient::create_conic(start_angle, x, y);
 }
 
-// https://html.spec.whatwg.org/multipage/canvas.html#dom-context-2d-transform
-void CanvasRenderingContext2D::transform(double a, double b, double c, double d, double e, double f)
-{
-    // 1. If any of the arguments are infinite or NaN, then return.
-    if (!isfinite(a) || !isfinite(b) || !isfinite(c) || !isfinite(d) || !isfinite(e) || !isfinite(f))
-        return;
-
-    // 2. Replace the current transformation matrix with the result of multiplying the current transformation matrix with the matrix described by:
-    //    a c e
-    //    b d f
-    //    0 0 1
-    drawing_state().transform.multiply({ static_cast<float>(a), static_cast<float>(b), static_cast<float>(c), static_cast<float>(d), static_cast<float>(e), static_cast<float>(f) });
-}
-
-// https://html.spec.whatwg.org/multipage/canvas.html#dom-context-2d-settransform
-void CanvasRenderingContext2D::set_transform(double a, double b, double c, double d, double e, double f)
-{
-    // 1. If any of the arguments are infinite or NaN, then return.
-    if (!isfinite(a) || !isfinite(b) || !isfinite(c) || !isfinite(d) || !isfinite(e) || !isfinite(f))
-        return;
-
-    // 2. Reset the current transformation matrix to the identity matrix.
-    drawing_state().transform = {};
-
-    // 3. Invoke the transform(a, b, c, d, e, f) method with the same arguments.
-    transform(a, b, c, d, e, f);
-}
-
-// https://html.spec.whatwg.org/multipage/canvas.html#dom-context-2d-resettransform
-void CanvasRenderingContext2D::reset_transform()
-{
-    // The resetTransform() method, when invoked, must reset the current transformation matrix to the identity matrix.
-    drawing_state().transform = {};
-}
-
 void CanvasRenderingContext2D::clip()
 {
     // FIXME: Implement.
diff --git a/Userland/Libraries/LibWeb/HTML/CanvasRenderingContext2D.h b/Userland/Libraries/LibWeb/HTML/CanvasRenderingContext2D.h
index 9951dd5973..ee4c1f2b9c 100644
--- a/Userland/Libraries/LibWeb/HTML/CanvasRenderingContext2D.h
+++ b/Userland/Libraries/LibWeb/HTML/CanvasRenderingContext2D.h
@@ -18,6 +18,7 @@
 #include <LibWeb/DOM/ExceptionOr.h>
 #include <LibWeb/HTML/Canvas/CanvasPath.h>
 #include <LibWeb/HTML/Canvas/CanvasState.h>
+#include <LibWeb/HTML/Canvas/CanvasTransform.h>
 #include <LibWeb/HTML/CanvasGradient.h>
 #include <LibWeb/Layout/InlineNode.h>
 #include <LibWeb/Layout/LineBox.h>
@@ -32,7 +33,8 @@ class CanvasRenderingContext2D
     : public RefCountForwarder<HTMLCanvasElement>
     , public Bindings::Wrappable
     , public CanvasPath
-    , public CanvasState {
+    , public CanvasState
+    , public CanvasTransform<CanvasRenderingContext2D> {
 
     AK_MAKE_NONCOPYABLE(CanvasRenderingContext2D);
     AK_MAKE_NONMOVABLE(CanvasRenderingContext2D);
@@ -57,10 +59,6 @@ public:
     DOM::ExceptionOr<void> draw_image(CanvasImageSource const&, float destination_x, float destination_y, float destination_width, float destination_height);
     DOM::ExceptionOr<void> draw_image(CanvasImageSource const&, float source_x, float source_y, float source_width, float source_height, float destination_x, float destination_y, float destination_width, float destination_height);
 
-    void scale(float sx, float sy);
-    void translate(float x, float y);
-    void rotate(float degrees);
-
     void set_line_width(float line_width) { drawing_state().line_width = line_width; }
     float line_width() const { return drawing_state().line_width; }
 
@@ -88,9 +86,6 @@ public:
     NonnullRefPtr<CanvasGradient> create_linear_gradient(double x0, double y0, double x1, double y1);
     NonnullRefPtr<CanvasGradient> create_conic_gradient(double start_angle, double x, double y);
 
-    void transform(double a, double b, double c, double d, double e, double f);
-    void set_transform(double a, double b, double c, double d, double e, double f);
-    void reset_transform();
     void clip();
 
 private:
diff --git a/Userland/Libraries/LibWeb/HTML/CanvasRenderingContext2D.idl b/Userland/Libraries/LibWeb/HTML/CanvasRenderingContext2D.idl
index 041c00b770..8191f524ae 100644
--- a/Userland/Libraries/LibWeb/HTML/CanvasRenderingContext2D.idl
+++ b/Userland/Libraries/LibWeb/HTML/CanvasRenderingContext2D.idl
@@ -5,6 +5,7 @@
 #import <HTML/CanvasGradient.idl>
 #import <HTML/Canvas/CanvasPath.idl>
 #import <HTML/Canvas/CanvasState.idl>
+#import <HTML/Canvas/CanvasTransform.idl>
 #import <HTML/Path2D.idl>
 
 // https://html.spec.whatwg.org/multipage/canvas.html#canvasrenderingcontext2d
@@ -15,10 +16,6 @@ interface CanvasRenderingContext2D {
     undefined strokeRect(double x, double y, double w, double h);
     undefined clearRect(double x, double y, double w, double h);
 
-    undefined scale(double x, double y);
-    undefined translate(double x, double y);
-    undefined rotate(double radians);
-
     undefined beginPath();
     // FIXME: `DOMString` should be `CanvasFillRule`
     undefined fill(optional DOMString fillRule = "nonzero");
@@ -50,10 +47,6 @@ interface CanvasRenderingContext2D {
     CanvasGradient createLinearGradient(double x0, double y0, double x1, double y1);
     CanvasGradient createConicGradient(double startAngle, double x, double y);
 
-    undefined transform(unrestricted double a, unrestricted double b, unrestricted double c, unrestricted double d, unrestricted double e, unrestricted double f);
-    undefined setTransform(unrestricted double a, unrestricted double b, unrestricted double c, unrestricted double d, unrestricted double e, unrestricted double f);
-    undefined resetTransform();
-
     // undefined clip(optional CanvasFillRule fillRule = "nonzero");
     // undefined clip(Path2D path, optional CanvasFillRule fillRule = "nonzero");
     // FIXME: Replace this with the two definitions above.
@@ -62,4 +55,5 @@ interface CanvasRenderingContext2D {
 };
 
 CanvasRenderingContext2D includes CanvasState;
+CanvasRenderingContext2D includes CanvasTransform;
 CanvasRenderingContext2D includes CanvasPath;