🐛 Fix problem with inconsistency with border-radius

CHANGES.md

@@ -11,6 +11,9 @@
 ## 1.13.0-beta
 
 ### :boom: Breaking changes
+
+- We've changed the behaviour of the border-radius so it works as CSS that [has some limits](https://www.w3.org/TR/css-backgrounds-3/#corner-overlap).
+
 ### :sparkles: New features
 
 - Exporting big files flow [Taiga #2218](https://tree.taiga.io/project/penpot/us/2218)
@@ -49,6 +52,7 @@
 - Fix problem when importing a SVG with text [#1532](https://github.com/penpot/penpot/issues/1532)
 - Fix problem when adding shadows to imported text [#Taiga 3057](https://tree.taiga.io/project/penpot/issue/3057)
 - Fix problem when importing SVG's with uses with overriding properties [#Taiga 2884](https://tree.taiga.io/project/penpot/issue/2884)
+- Fix inconsistency with radius in SVG an CSS [#1587](https://github.com/penpot/penpot/issues/1587)
 
 ### :arrow_up: Deps updates
 ### :heart: Community contributions by (Thank you!)

common/src/app/common/geom/shapes.cljc

@@ -11,6 +11,7 @@
    [app.common.geom.shapes.bool :as gsb]
    [app.common.geom.shapes.common :as gco]
    [app.common.geom.shapes.constraints :as gct]
+   [app.common.geom.shapes.corners :as gsc]
    [app.common.geom.shapes.intersect :as gin]
    [app.common.geom.shapes.path :as gsp]
    [app.common.geom.shapes.rect :as gpr]
@@ -153,3 +154,7 @@
 ;; Constraints
 (dm/export gct/default-constraints-h)
 (dm/export gct/default-constraints-v)
+
+;; Corners
+(dm/export gsc/shape-corners-1)
+(dm/export gsc/shape-corners-4)

common/src/app/common/geom/shapes/corners.cljc

@@ -0,0 +1,46 @@
+;; This Source Code Form is subject to the terms of the Mozilla Public
+;; License, v. 2.0. If a copy of the MPL was not distributed with this
+;; file, You can obtain one at http://mozilla.org/MPL/2.0/.
+;;
+;; Copyright (c) UXBOX Labs SL
+
+(ns app.common.geom.shapes.corners)
+
+(defn fix-radius
+  ;; https://www.w3.org/TR/css-backgrounds-3/#corner-overlap
+  ;;
+  ;; > Corner curves must not overlap: When the sum of any two adjacent border radii exceeds the size of the border box,
+  ;; > UAs must proportionally reduce the used values of all border radii until none of them overlap.
+  ;;
+  ;; > The algorithm for reducing radii is as follows: Let f = min(Li/Si), where i ∈ {top, right, bottom, left}, Si is
+  ;; > the sum of the two corresponding radii of the corners on side i, and Ltop = Lbottom = the width of the box, and
+  ;; > Lleft = Lright = the height of the box. If f < 1, then all corner radii are reduced by multiplying them by f.
+  ([width height r]
+   (let [f (min (/ width  (* 2 r))
+                (/ height (* 2 r)))]
+     (if (< f 1)
+       (* r f)
+       r)))
+
+  ([width height r1 r2 r3 r4]
+   (let [f (min (/ width  (+ r1 r2))
+                (/ height (+ r2 r3))
+                (/ width  (+ r3 r4))
+                (/ height (+ r4 r1)))]
+     (if (< f 1)
+       [(* r1 f) (* r2 f) (* r3 f) (* r4 f)]
+       [r1 r2 r3 r4]))))
+
+(defn shape-corners-1
+  "Retrieve the effective value for the corner given a single value for corner."
+  [{:keys [width height rx] :as shape}]
+  (if (some? rx)
+    (fix-radius width height rx)
+    0))
+
+(defn shape-corners-4
+  "Retrieve the effective value for the corner given four values for the corners."
+  [{:keys [width height r1 r2 r3 r4]}]
+  (if (and (some? r1) (some? r2) (some? r3) (some? r4))
+    (fix-radius width height r1 r2 r3 r4)
+    [r1 r2 r3 r4]))

common/src/app/common/path/shapes_to_path.cljc

@@ -11,9 +11,11 @@
    [app.common.geom.matrix :as gmt]
    [app.common.geom.point :as gpt]
    [app.common.geom.shapes.common :as gsc]
+   [app.common.geom.shapes.corners :as gso]
    [app.common.geom.shapes.path :as gsp]
    [app.common.path.bool :as pb]
-   [app.common.path.commands :as pc]))
+   [app.common.path.commands :as pc]
+   [app.common.spec.radius :as ctr]))
 
 (def ^:const bezier-circle-c 0.551915024494)
 
@@ -93,7 +95,7 @@
 
 (defn circle->path
   "Creates the bezier curves to approximate a circle shape"
-  [x y width height]
+  [{:keys [x y width height]}]
   (let [mx (+ x (/ width 2))
         my (+ y (/ height 2))
         ex (+ x width)
@@ -116,11 +118,12 @@
      (pc/make-curve-to p4 (assoc p3 :x c1x) (assoc p4 :y c2y))
      (pc/make-curve-to p1 (assoc p4 :y c1y) (assoc p1 :x c1x))]))
 
-(defn rect->path
-  "Creates a bezier curve that approximates a rounded corner rectangle"
-  [x y width height r1 r2 r3 r4 rx]
-  (let [[r1 r2 r3 r4] (->> [r1 r2 r3 r4] (mapv #(or % rx 0)))
-        p1 (gpt/point x (+ y r1))
+(defn draw-rounded-rect-path
+  ([x y width height r]
+   (draw-rounded-rect-path x y width height r r r r))
+
+  ([x y width height r1 r2 r3 r4]
+   (let [p1 (gpt/point x (+ y r1))
          p2 (gpt/point (+ x r1) y)
 
          p3 (gpt/point (+ width x (- r2)) y)
@@ -144,7 +147,21 @@
          (conj (pc/make-line-to p7))
          (cond-> (not= p7 p8)
            (conj (make-corner-arc p7 p8 :bottom-left r4)))
-        (conj (pc/make-line-to p1)))))
+         (conj (pc/make-line-to p1))))))
+
+(defn rect->path
+  "Creates a bezier curve that approximates a rounded corner rectangle"
+  [{:keys [x y width height] :as shape}]
+  (case (ctr/radius-mode shape)
+    :radius-1
+    (let [radius (gso/shape-corners-1 shape)]
+      (draw-rounded-rect-path x y width height radius))
+
+    :radius-4
+    (let [[r1 r2 r3 r4] (gso/shape-corners-4 shape)]
+      (draw-rounded-rect-path x y width height r1 r2 r3 r4))
+
+    []))
 
 (declare convert-to-path)
 
@@ -192,9 +209,9 @@
   "Transforms the given shape to a path"
   ([shape]
    (convert-to-path shape {}))
-  ([{:keys [type x y width height r1 r2 r3 r4 rx metadata] :as shape} objects]
+  ([{:keys [type metadata] :as shape} objects]
    (assert (map? objects))
-   (case (:type shape)
+   (case type
      :group
      (group-to-path shape objects)
 
@@ -204,8 +221,8 @@
      (:rect :circle :image :text)
      (let [new-content
            (case type
-             :circle (circle->path x y width height)
-             #_:else (rect->path x y width height r1 r2 r3 r4 rx))
+             :circle (circle->path shape)
+             #_:else (rect->path shape))
 
            ;; Apply the transforms that had the shape
            transform (:transform shape)

frontend/src/app/main/ui/shapes/attrs.cljs

@@ -7,6 +7,8 @@
 (ns app.main.ui.shapes.attrs
   (:require
    [app.common.data :as d]
+   [app.common.data.macros :as dm]
+   [app.common.geom.shapes :as gsh]
    [app.common.spec.radius :as ctr]
    [app.common.spec.shape :refer [stroke-caps-line stroke-caps-marker]]
    [app.main.ui.context :as muc]
@@ -26,49 +28,21 @@
 
     (->> values (map #(+ % width)) (str/join ","))))
 
-(defn- truncate-side
-  [shape ra-attr rb-attr dimension-attr]
-  (let [ra        (ra-attr shape)
-        rb        (rb-attr shape)
-        dimension (dimension-attr shape)]
-    (if (<= (+ ra rb) dimension)
-      [ra rb]
-      [(/ (* ra dimension) (+ ra rb))
-       (/ (* rb dimension) (+ ra rb))])))
 
-(defn- truncate-radius
-  [shape]
-  (let [[r-top-left r-top-right]
-        (truncate-side shape :r1 :r2 :width)
-
-        [r-right-top r-right-bottom]
-        (truncate-side shape :r2 :r3 :height)
-
-        [r-bottom-right r-bottom-left]
-        (truncate-side shape :r3 :r4 :width)
-
-        [r-left-bottom r-left-top]
-        (truncate-side shape :r4 :r1 :height)]
-
-    [(min r-top-left r-left-top)
-     (min r-top-right r-right-top)
-     (min r-right-bottom r-bottom-right)
-     (min r-bottom-left r-left-bottom)]))
-
-(defn add-border-radius [attrs shape]
+(defn add-border-radius [attrs {:keys [x y width height] :as shape}]
   (case (ctr/radius-mode shape)
-
     :radius-1
-    (obj/merge! attrs #js {:rx (:rx shape 0)
-                           :ry (:ry shape 0)})
+    (let [radius (gsh/shape-corners-1 shape)]
+      (obj/merge! attrs #js {:rx radius :ry radius}))
 
     :radius-4
-    (let [[r1 r2 r3 r4] (truncate-radius shape)
-          top    (- (:width shape) r1 r2)
-          right  (- (:height shape) r2 r3)
-          bottom (- (:width shape) r3 r4)
-          left   (- (:height shape) r4 r1)]
-      (obj/merge! attrs #js {:d (str "M" (+ (:x shape) r1) "," (:y shape) " "
+    (let [[r1 r2 r3 r4] (gsh/shape-corners-4 shape)
+          top    (- width r1 r2)
+          right  (- height r2 r3)
+          bottom (- width r3 r4)
+          left   (- height r4 r1)]
+      (obj/merge! attrs #js {:d (dm/str
+                                 "M" (+ x r1) "," y " "
                                  "h" top " "
                                  "a" r2 "," r2 " 0 0 1 " r2 "," r2 " "
                                  "v" right " "