LibWeb: Compensate for CRC2D transform in internal stored path

The CRC2D path should be unaffected by the CRC2D transform changing.
To achieve this, we transform the path to compensate whenever the
CRC2D transform is changed.

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

@@ -11,6 +11,7 @@
 #include <AK/Debug.h>
 #include <LibGfx/Painter.h>
 #include <LibWeb/Geometry/DOMMatrix.h>
+#include <LibWeb/HTML/Canvas/CanvasPath.h>
 #include <LibWeb/HTML/Canvas/CanvasState.h>
 
 namespace Web::HTML {
@@ -21,6 +22,8 @@ class CanvasTransform {
 public:
     ~CanvasTransform() = default;
 
+    Gfx::Path& mutable_path() { return static_cast<IncludingClass&>(*this).path(); }
+
     void scale(float sx, float sy)
     {
         dbgln_if(CANVAS_RENDERING_CONTEXT_2D_DEBUG, "CanvasTransform::scale({}, {})", sx, sy);
@@ -28,6 +31,7 @@ public:
             return;
         my_drawing_state().transform.scale(sx, sy);
         flush_transform();
+        mutable_path().transform(Gfx::AffineTransform().scale(1.0 / sx, 1.0 / sy));
     }
 
     void translate(float tx, float ty)
@@ -37,6 +41,7 @@ public:
             return;
         my_drawing_state().transform.translate(tx, ty);
         flush_transform();
+        mutable_path().transform(Gfx::AffineTransform().translate(-tx, -ty));
     }
 
     void rotate(float radians)
@@ -46,6 +51,7 @@ public:
             return;
         my_drawing_state().transform.rotate_radians(radians);
         flush_transform();
+        mutable_path().transform(Gfx::AffineTransform().rotate_radians(-radians));
     }
 
     // https://html.spec.whatwg.org/multipage/canvas.html#dom-context-2d-transform
@@ -59,7 +65,12 @@ public:
         //    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) });
+        auto transform = Gfx::AffineTransform(a, b, c, d, e, f);
+        my_drawing_state().transform.multiply(transform);
+
+        if (auto inverse = transform.inverse(); inverse.has_value()) {
+            mutable_path().transform(inverse.value());
+        }
         flush_transform();
     }
 
@@ -98,9 +109,14 @@ public:
         if (!isfinite(matrix->m11()) || !isfinite(matrix->m12()) || !isfinite(matrix->m21()) || !isfinite(matrix->m22()) || !isfinite(matrix->m41()) || !isfinite(matrix->m42()))
             return {};
 
+        auto original_transform = my_drawing_state().transform;
+
         // 3. Reset the current transformation matrix to matrix.
         auto transform = Gfx::AffineTransform { static_cast<float>(matrix->a()), static_cast<float>(matrix->b()), static_cast<float>(matrix->c()), static_cast<float>(matrix->d()), static_cast<float>(matrix->e()), static_cast<float>(matrix->f()) };
         my_drawing_state().transform = transform;
+
+        mutable_path().transform(original_transform);
+
         flush_transform();
         return {};
     }