cfb: added API for drawing a circle

Added a new CFB API for drawing a circle. Using the Midpoint Circle
Algorithm for optimization.

Signed-off-by: Yishai Jaffe <yishai1999@gmail.com>

include/zephyr/display/cfb.h

@@ -136,6 +136,17 @@ int cfb_draw_line(const struct device *dev, const struct cfb_position *start,
 int cfb_draw_rect(const struct device *dev, const struct cfb_position *start,
 		  const struct cfb_position *end);
 
+/**
+ * @brief Draw a circle.
+ *
+ * @param dev Pointer to device structure for driver instance
+ * @param start Center position of the circle
+ * @param radius Radius of the circle
+ *
+ * @return 0 on success, negative value otherwise
+ */
+int cfb_draw_circle(const struct device *dev, const struct cfb_position *start, uint16_t radius);
+
 /**
  * @brief Clear framebuffer.
  *

subsys/fb/cfb.c

@@ -394,6 +394,36 @@ int cfb_draw_rect(const struct device *dev, const struct cfb_position *start,
 	return 0;
 }
 
+int cfb_draw_circle(const struct device *dev, const struct cfb_position *center, uint16_t radius)
+{
+	struct char_framebuffer *fb = &char_fb;
+	uint16_t x = 0;
+	int16_t y = -radius;
+	int16_t p = -radius;
+
+	/* Using the Midpoint Circle Algorithm */
+	while (x < -y) {
+		if (p > 0) {
+			p += 2 * (x + ++y) + 1;
+		} else {
+			p += 2 * x + 1;
+		}
+
+		draw_point(fb, center->x + x, center->y + y);
+		draw_point(fb, center->x - x, center->y + y);
+		draw_point(fb, center->x + x, center->y - y);
+		draw_point(fb, center->x - x, center->y - y);
+		draw_point(fb, center->x + y, center->y + x);
+		draw_point(fb, center->x + y, center->y - x);
+		draw_point(fb, center->x - y, center->y + x);
+		draw_point(fb, center->x - y, center->y - x);
+
+		x++;
+	}
+
+	return 0;
+}
+
 int cfb_draw_text(const struct device *dev, const char *const str, int16_t x, int16_t y)
 {
 	return draw_text(dev, str, x, y, false);

subsys/fb/cfb_shell.c

@@ -21,6 +21,7 @@
 #define HELP_DRAW_POINT "<x> <y>"
 #define HELP_DRAW_LINE "<x0> <y0> <x1> <y1>"
 #define HELP_DRAW_RECT "<x0> <y0> <x1> <y1>"
+#define HELP_DRAW_CIRCLE "<x> <y> <radius>"
 #define HELP_INVERT "[<x> <y> <width> <height>]"
 
 static const struct device *const dev =
@@ -187,6 +188,27 @@ static int cmd_draw_rect(const struct shell *sh, size_t argc, char *argv[])
 	return err;
 }
 
+static int cmd_draw_circle(const struct shell *sh, size_t argc, char *argv[])
+{
+	int err;
+	struct cfb_position center;
+	uint16_t radius;
+
+	center.x = strtol(argv[1], NULL, 10);
+	center.y = strtol(argv[2], NULL, 10);
+	radius = strtol(argv[3], NULL, 10);
+
+	err = cfb_draw_circle(dev, &center, radius);
+	if (err) {
+		shell_error(sh, "Failed circle drawing to Framebuffer error=%d", err);
+		return err;
+	}
+
+	err = cfb_framebuffer_finalize(dev);
+
+	return err;
+}
+
 static int cmd_scroll_vert(const struct shell *sh, size_t argc, char *argv[])
 {
 	int err = 0;
@@ -509,6 +531,7 @@ SHELL_STATIC_SUBCMD_SET_CREATE(sub_cmd_draw,
 	SHELL_CMD_ARG(point, NULL, HELP_DRAW_POINT, cmd_draw_point, 3, 0),
 	SHELL_CMD_ARG(line, NULL, HELP_DRAW_LINE, cmd_draw_line, 5, 0),
 	SHELL_CMD_ARG(rect, NULL, HELP_DRAW_RECT, cmd_draw_rect, 5, 0),
+	SHELL_CMD_ARG(circle, NULL, HELP_DRAW_RECT, cmd_draw_circle, 4, 0),
 	SHELL_SUBCMD_SET_END
 );