From 81df0f1c8c7f6053aa0708753426a8fa604fc8a3 Mon Sep 17 00:00:00 2001
From: Tyge Løvset <tylo@norceresearch.no>
Date: Fri, 20 May 2022 10:36:53 +0200
Subject: Changed example shape.c

---
 examples/shape.c | 82 +++++++++++++++++++++++++++++++-------------------------
 1 file changed, 45 insertions(+), 37 deletions(-)

diff --git a/examples/shape.c b/examples/shape.c
index 69c8ca70..db42adf3 100644
--- a/examples/shape.c
+++ b/examples/shape.c
@@ -4,13 +4,13 @@
 #include <stdio.h>
 #include <stc/ccommon.h>
 
-#define c_self(s, T, api) \
-    T* self = (T *)s; \
-    assert(*s == &T##_##api)
+#define c_self(s, T) \
+    T* self = c_container_of(s, T, base); \
+    assert(s->api == &T##_api)
 
-#define c_vtable(Interface, T, api) \
-    c_static_assert(offsetof(T, api) == 0); \
-    static Interface T##_##api
+#define c_vtable(Api, T) \
+    c_static_assert(offsetof(T, base) == 0); \
+    static Api T##_api
 
 
 // Shape definition
@@ -18,19 +18,27 @@
 
 typedef struct { float x, y; } Point;
 
-typedef struct Shape {
-    void (*drop)(struct Shape**);
-    void (*draw)(struct Shape**);
+typedef struct {
+    struct ShapeAPI* api;
+    uint32_t color;
+    uint16_t style;
+    uint8_t thickness;
+    uint8_t hardness;
 } Shape;
 
-void Shape_drop(Shape** shape)
+struct ShapeAPI {
+    void (*drop)(Shape*);
+    void (*draw)(const Shape*);
+};
+
+void Shape_drop(Shape* shape)
 {
 }
 
-void Shape_delete(Shape** shape)
+void Shape_delete(Shape* shape)
 {
     if (shape) {
-        (*shape)->drop(shape);
+        shape->api->drop(shape);
         c_free(shape);
     }
 }
@@ -39,31 +47,31 @@ void Shape_delete(Shape** shape)
 // ============================================================
 
 typedef struct {
-    Shape* api;
+    Shape base;
     Point p[3];
 } Triangle;
 
-c_vtable(Shape, Triangle, api);
+c_vtable(struct ShapeAPI, Triangle);
 
 
-static void Triangle_draw(Shape** shape)
+static void Triangle_draw(const Shape* shape)
 {
-    const c_self(shape, Triangle, api);
+    const c_self(shape, Triangle);
     printf("Triangle: (%g,%g), (%g,%g), (%g,%g)\n",
            self->p[0].x, self->p[0].y,
            self->p[1].x, self->p[1].y,
            self->p[2].x, self->p[2].y);
 }
 
-static Shape Triangle_api = {
+static struct ShapeAPI Triangle_api = {
     .drop = Shape_drop,
     .draw = Triangle_draw,
 };
 
-Shape** Triangle_new(Point a, Point b, Point c)
+Shape* Triangle_new(Point a, Point b, Point c)
 {
-    Triangle* s = c_new(Triangle, {&Triangle_api, .p={a, b, c}});
-    return &s->api;
+    Triangle* s = c_new(Triangle, {{.api=&Triangle_api}, .p={a, b, c}});
+    return &s->base;
 }
 
 // Polygon implementation
@@ -74,43 +82,43 @@ Shape** Triangle_new(Point a, Point b, Point c)
 #include <stc/cstack.h>
 
 typedef struct {
-    Shape* api;
+    Shape base;
     PVec points;
 } Polygon;
 
-c_vtable(Shape, Polygon, api);
+c_vtable(struct ShapeAPI, Polygon);
 
 
-static void Polygon_drop(Shape** shape)
+static void Polygon_drop(Shape* shape)
 {
-    c_self(shape, Polygon, api);
+    c_self(shape, Polygon);
     puts("drop poly");
     PVec_drop(&self->points);
 }
 
-static void Polygon_draw(Shape** shape)
+static void Polygon_draw(const Shape* shape)
 {
-    const c_self(shape, Polygon, api);
+    const c_self(shape, Polygon);
     printf("Polygon:");
     c_foreach (i, PVec, self->points)
         printf(" (%g,%g)", i.ref->x, i.ref->y);
     puts("");
 }
 
-static Shape Polygon_api = {
+static struct ShapeAPI Polygon_api = {
     .drop = Polygon_drop,
     .draw = Polygon_draw,
 };
 
-Shape** Polygon_new(void)
+Shape* Polygon_new(void)
 {
-    Polygon* s = c_new(Polygon, {&Polygon_api, .points=PVec_init()});
-    return &s->api;
+    Polygon* s = c_new(Polygon, {{.api=&Polygon_api}, .points=PVec_init()});
+    return &s->base;
 }
 
-void Polygon_addPoint(Shape** shape, Point p)
+void Polygon_addPoint(Shape* shape, Point p)
 {
-    c_self(shape, Polygon, api);
+    c_self(shape, Polygon);
     PVec_push(&self->points, p);
 }
 
@@ -118,13 +126,13 @@ void Polygon_addPoint(Shape** shape, Point p)
 // Test
 // ============================================================
 
-void testShape(Shape** shape)
+void testShape(Shape* shape)
 {
-    (*shape)->draw(shape);
+    shape->api->draw(shape);
 }
 
 #define i_type Shapes
-#define i_val Shape**
+#define i_val Shape*
 #define i_opt c_no_clone
 #define i_valdrop(x) Shape_delete(*x)
 #include <stc/cstack.h>
@@ -133,8 +141,8 @@ int main(void)
 {
     c_auto (Shapes, shapes)
     {
-        Shape** tria = Triangle_new((Point){5, 7}, (Point){12, 7}, (Point){12, 20});
-        Shape** poly = Polygon_new();
+        Shape* tria = Triangle_new((Point){5, 7}, (Point){12, 7}, (Point){12, 20});
+        Shape* poly = Polygon_new();
 
         c_apply(p, Polygon_addPoint(poly, p), Point, {
             {5, 7}, {12, 7}, {12, 20}, {82, 33}, {17, 56},
-- 
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