Added text node.

README.md

@@ -116,7 +116,7 @@ For example, draw 10 circles:
 
 ```
 c = circle(x=-100, y=0, r=50)
-shape = c | Repeat(10, Translate(x=10, y=0)
+shape = c | repeat(10, translate(x=10, y=0)
 show(shape)
 ```
 

joy.py

@@ -249,8 +249,7 @@ def render(self):
         svg_header = render_tag(**attrs)+ "\n"
         svg_footer = "</svg>\n"
 
-        # flip the y axis so that y grows upwards
-        node = Group(self.nodes) | Scale(sx=1, sy=-1)
+        node = Group(self.nodes)
 
         return svg_header + node._svg() + svg_footer
 
@@ -490,6 +489,61 @@ class Group(Shape):
     def __init__(self, shapes, **kwargs):
         super().__init__("g", children=shapes, **kwargs)
 
+class Text(Shape):
+    """Creates a text node.
+
+    Parameters:
+        position:
+            The position of the text node.
+            Defaults to (0, 0) when not specified from the lower
+            left corner.
+
+    Examples:
+
+    Draw a text node:
+
+        >>> t = text("Hello!")
+        >>> show(t)
+
+    Draw a text node centered at (50, 50).
+
+        >>> t = text("Hello!", center=Point(x=100, y=100), alignment_baseline="middle", text_anchor="middle")
+        >>> show(t)
+    """
+    def __init__(self, content, anchor=Point(0, 0), **kwargs):
+        self.anchor = anchor
+        # self.width = needs to be determined dynamically
+        # self.height = needs to be determined dynamically
+
+        cx, cy = self.anchor.x, self.anchor.y
+        x = cx 
+        y = cy 
+        super().__init__(
+            tag="text",
+            children=[Content(content)],
+            x=x,
+            y=y,
+            **kwargs)
+
+class Content():
+    """Content is the holds actual character data for a text node. 
+
+    This uses a minimal subset of the Shape interface but cannot be used alone.
+    """
+    def __init__(self, content, **attrs):
+        """Creates a new character data object.
+        """
+        self.content = content
+
+    def _svg(self, indent="") -> str:
+        """Returns the svg representation of this node.
+
+        As this object is a leaf and does not have children we only
+        return its content directly. 
+        """
+        return self.content
+
+
 def render_tag(tag, *, close=False, **attrs):
     """Renders a html/svg tag.
 
@@ -793,7 +847,7 @@ def circle(x=0, y=0, r=100, **kwargs):
         c = circle(x=10, y=20, r=50)
         show(c)
     """
-    return Circle(center=Point(x=x, y=y), radius=r, **kwargs)
+    return Circle(center=Point(x=x, y=-y), radius=r, **kwargs)
 
 def rectangle(x=0, y=0, w=200, h=100, **kwargs):
     """Creates a rectangle with center at (x, y), a width of w and a height of h.
@@ -815,7 +869,7 @@ def rectangle(x=0, y=0, w=200, h=100, **kwargs):
         r = rectangle(x=10, y=20, w=100, h=50)
         show(r)
     """
-    return Rectangle(center=Point(x=x, y=y), width=w, height=h, **kwargs)
+    return Rectangle(center=Point(x=x, y=-y), width=w, height=h, **kwargs)
 
 def ellipse(x=0, y=0, w=200, h=100, **kwargs):
     """Creates an ellipse with center at (x, y), a width of w and a height of h.
@@ -837,7 +891,7 @@ def ellipse(x=0, y=0, w=200, h=100, **kwargs):
         r = ellipse(x=10, y=20, w=100, h=50)
         show(r)
     """
-    return Ellipse(center=Point(x=x, y=y), width=w, height=h, **kwargs)
+    return Ellipse(center=Point(x=x, y=-y), width=w, height=h, **kwargs)
 
 def line(x1=None, y1=None, x2=None, y2=None, **kwargs):
     """Creates a line from point (x1, y1) to point (x2, y2).
@@ -856,7 +910,7 @@ def line(x1=None, y1=None, x2=None, y2=None, **kwargs):
         x1, y1 = -100, 0
         x2, y2 = 100, 0
     else:
-        pairs = dict(x1=x1, y1=y1, x2=x2, y2=y2)
+        pairs = dict(x1=x1, y1=-y1, x2=x2, y2=-y2)
         missing = [name for name, value in pairs.items() if value is None]
         if missing:
             raise Exception("missing arguments for line: ", ", ".join(missing))
@@ -866,7 +920,7 @@ def line(x1=None, y1=None, x2=None, y2=None, **kwargs):
 def point(x, y):
     """Creates a Point with x and y coordinates.
     """
-    return Point(x, y)
+    return Point(x, -y)
 
 def polygon(points, **kwargs):
     """Creates a polygon with given list points.
@@ -879,7 +933,7 @@ def polygon(points, **kwargs):
         triangle = polygon([p1, p2, p3])
         show(triangle)
     """
-    points_str = " ".join(f"{p.x},{p.y}" for p in points)
+    points_str = " ".join(f"{p.x},{-p.y}" for p in points)
     return Shape(tag="polygon", points=points_str, **kwargs)
 
 def polyline(points, **kwargs):
@@ -894,9 +948,28 @@ def polyline(points, **kwargs):
         line = polyline([p1, p2, p3, p4])
         show(line)
     """
-    points_str = " ".join(f"{p.x},{p.y}" for p in points)
+    points_str = " ".join(f"{p.x},{-p.y}" for p in points)
     return Shape(tag="polyline", points=points_str, **kwargs)
 
+def text(content, x=0, y=0, fill="black", **kwargs):
+    """Creates a text node using the given content with anchor point at (x, y).
+
+    Examples:
+
+    Draw a text node.
+
+        t = text("Hello!")
+        show(t)
+
+    Draw a text node centered at (0, 0) with specific font features.
+        t = text("Hello!", x=0, y=0, font_family="Arial", 
+                 font_size="20", fill="black", 
+                 alignment_baseline="middle", text_anchor="left")
+        show(t)
+
+    """
+    return Text(content, anchor=Point(x=x, y=-y), **kwargs)
+
 def translate(x=0, y=0):
     """Translates a shape.
 
@@ -914,7 +987,7 @@ def translate(x=0, y=0):
 
         shape = circle() | translate(x=10, y=20)
     """
-    return Translate(x=x, y=y)
+    return Translate(x=x, y=-y)
 
 def scale(s=None, x=1, y=1):
     """Scales a shape.