LibWeb: Plumbing for lineCap, lineJoin, miterLimit, lineDashOffset

Not used for painting yet, but adds a FIXME for what's missing.

Also tweak some existing spec comments minorly.

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

@@ -31,10 +31,52 @@ public:
         return my_drawing_state().line_width;
     }
 
+    // https://html.spec.whatwg.org/multipage/canvas.html#dom-context-2d-linecap
+    void set_line_cap(Bindings::CanvasLineCap line_cap)
+    {
+        // On setting, the current value must be changed to the new value.
+        my_drawing_state().line_cap = line_cap;
+    }
+    Bindings::CanvasLineCap line_cap() const
+    {
+        // On getting, it must return the current value.
+        return my_drawing_state().line_cap;
+    }
+
+    // https://html.spec.whatwg.org/multipage/canvas.html#dom-context-2d-linejoin
+    void set_line_join(Bindings::CanvasLineJoin line_join)
+    {
+        // On setting, the current value must be changed to the new value.
+        my_drawing_state().line_join = line_join;
+    }
+    Bindings::CanvasLineJoin line_join() const
+    {
+        // On getting, it must return the current value.
+        return my_drawing_state().line_join;
+    }
+
+    // https://html.spec.whatwg.org/multipage/canvas.html#dom-context-2d-miterlimit
+    void set_miter_limit(float miter_limit)
+    {
+        // On setting, zero, negative, infinite, and NaN values must be ignored, leaving the value unchanged;
+        if (miter_limit <= 0 || !isfinite(miter_limit))
+            return;
+        // other values must change the current value to the new value.
+        my_drawing_state().miter_limit = miter_limit;
+    }
+    float miter_limit() const
+    {
+        // On getting, it must return the current value.
+        return my_drawing_state().miter_limit;
+    }
+
     // https://html.spec.whatwg.org/multipage/canvas.html#dom-context-2d-setlinedash
     void set_line_dash(Vector<double> segments)
     {
-        // 1. If any value in segments is not finite (e.g. an Infinity or a NaN value), or if any value is negative (less than zero), then return (without throwing an exception; user agents could show a message on a developer console, though, as that would be helpful for debugging).
+        // The setLineDash(segments) method, when invoked, must run these steps:
+
+        // 1. If any value in segments is not finite (e.g. an Infinity or a NaN value), or if any value is negative (less than zero), then return
+        //    (without throwing an exception; user agents could show a message on a developer console, though, as that would be helpful for debugging).
         for (auto const& segment : segments) {
             if (!isfinite(segment) || segment < 0)
                 return;
@@ -51,9 +93,25 @@ public:
     // https://html.spec.whatwg.org/multipage/canvas.html#dom-context-2d-getlinedash
     Vector<double> get_line_dash()
     {
+        // When the getLineDash() method is invoked, it must return a sequence whose values are the values of the object's dash list, in the same order.
         return my_drawing_state().dash_list;
     }
 
+    // https://html.spec.whatwg.org/multipage/canvas.html#dom-context-2d-linedashoffset
+    void set_line_dash_offset(float line_dash_offset)
+    {
+        // On setting, infinite and NaN values must be ignored, leaving the value unchanged;
+        if (!isfinite(line_dash_offset))
+            return;
+        // other values must change the current value to the new value.
+        my_drawing_state().line_dash_offset = line_dash_offset;
+    }
+    float line_dash_offset() const
+    {
+        // On getting, it must return the current value.
+        return my_drawing_state().line_dash_offset;
+    }
+
 protected:
     CanvasPathDrawingStyles() = default;
 

Userland/Libraries/LibWeb/HTML/Canvas/CanvasPathDrawingStyles.idl

@@ -1,15 +1,15 @@
 // https://html.spec.whatwg.org/multipage/canvas.html#canvaslinecap
-enum CanvasLineCap { "butt", "round", "square" };
-enum CanvasLineJoin { "round", "bevel", "miter" };
+// enum CanvasLineCap { "butt", "round", "square" };
+// enum CanvasLineJoin { "round", "bevel", "miter" };
 
 // https://html.spec.whatwg.org/multipage/canvas.html#canvaspathdrawingstyles
 interface mixin CanvasPathDrawingStyles {
     attribute unrestricted double lineWidth;
-    [FIXME] attribute CanvasLineCap lineCap;
-    [FIXME] attribute CanvasLineJoin lineJoin;
-    [FIXME] attribute unrestricted double miterLimit;
+    attribute CanvasLineCap lineCap;
+    attribute CanvasLineJoin lineJoin;
+    attribute unrestricted double miterLimit;
 
     undefined setLineDash(sequence<unrestricted double> segments);
     sequence<unrestricted double> getLineDash();
-    [FIXME] attribute unrestricted double lineDashOffset;
+    attribute unrestricted double lineDashOffset;
 };

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

@@ -84,7 +84,11 @@ public:
         float shadow_offset_y { 0.0f };
         Gfx::Color shadow_color { Gfx::Color::Transparent };
         float line_width { 1 };
+        Bindings::CanvasLineCap line_cap { Bindings::CanvasLineCap::Butt };
+        Bindings::CanvasLineJoin line_join { Bindings::CanvasLineJoin::Miter };
+        float miter_limit { 10 };
         Vector<double> dash_list;
+        float line_dash_offset { 0 };
         bool image_smoothing_enabled { true };
         Bindings::ImageSmoothingQuality image_smoothing_quality { Bindings::ImageSmoothingQuality::Low };
         float global_alpha = { 1 };

Userland/Libraries/LibWeb/HTML/CanvasRenderingContext2D.cpp

@@ -272,6 +272,8 @@ void CanvasRenderingContext2D::stroke_internal(Gfx::Path const& path)
 
     auto& state = drawing_state();
 
+    // FIXME: Honor state's line_cap, line_join, miter_limit, dash_list, and line_dash_offset.
+
     if (auto color = state.stroke_style.as_color(); color.has_value()) {
         painter->stroke_path(path, color->with_opacity(state.global_alpha), state.line_width);
     } else {

Userland/Libraries/LibWeb/HTML/CanvasRenderingContext2D.idl

@@ -27,6 +27,10 @@ dictionary CanvasRenderingContext2DSettings {
 
 enum ImageSmoothingQuality { "low", "medium", "high" };
 
+// FIXME: This should be in CanvasPathDrawingStyles.idl but then it is not exported
+enum CanvasLineCap { "butt", "round", "square" };
+enum CanvasLineJoin { "round", "bevel", "miter" };
+
 // FIXME: This should be in CanvasTextDrawingStyles.idl but then it is not exported
 enum CanvasTextAlign { "start", "end", "left", "right", "center" };
 enum CanvasTextBaseline { "top", "hanging", "middle", "alphabetic", "ideographic", "bottom" };