feat: add p/demo/svg (gnolang#905)

* feat: add p/demo/svg

Signed-off-by: Manfred Touron <94029+moul@users.noreply.github.com>

* chore: fixup

* chore: fixup

* chore: fixup

* chore: add gno.mod

Signed-off-by: Manfred Touron <94029+moul@users.noreply.github.com>

---------

Signed-off-by: Manfred Touron <94029+moul@users.noreply.github.com>

examples/gno.land/p/demo/svg/doc.gno

@@ -0,0 +1,17 @@
+/*
+Package svg is a minimalist SVG generation library for Gno.
+
+The svg package provides a simple and lightweight solution for programmatically generating SVG (Scalable Vector Graphics) markup in Gno. It allows you to create basic shapes like rectangles and circles, and output the generated SVG to a
+
+Example:
+
+	import "gno.land/p/demo/svg""
+
+	func Foo() string {
+	    canvas := svg.Canvas{Width: 200, Height: 200}
+	    canvas.DrawRectangle(50, 50, 100, 100, "red")
+	    canvas.DrawCircle(100, 100, 50, "blue")
+	    return canvas.String()
+	}
+*/
+package svg // import "gno.land/p/demo/svg"

examples/gno.land/p/demo/svg/gno.mod

@@ -0,0 +1,5 @@
+module gno.land/p/demo/svg
+
+require (
+     "gno.land/p/demo/ufmt" v0.0.0-latest
+)

examples/gno.land/p/demo/svg/svg.gno

@@ -0,0 +1,82 @@
+package svg
+
+import "gno.land/p/demo/ufmt"
+
+type Canvas struct {
+	Width  int
+	Height int
+	Elems  []Elem
+}
+
+type Elem interface{ String() string }
+
+func (c Canvas) String() string {
+	output := ""
+	output += ufmt.Sprintf(`<svg xmlns="http://www.w3.org/2000/svg" width="%d" height="%d">`, c.Width, c.Height)
+	for _, elem := range c.Elems {
+		output += elem.String()
+	}
+	output += "</svg>"
+	return output
+}
+
+func (c *Canvas) Append(elem Elem) {
+	c.Elems = append(c.Elems, elem)
+}
+
+type Circle struct {
+	CX   int // center X
+	CY   int // center Y
+	R    int // radius
+	Fill string
+}
+
+func (c Circle) String() string {
+	return ufmt.Sprintf(`<circle cx="%d" cy="%d" r="%d" fill="%s" />`, c.CX, c.CY, c.R, c.Fill)
+}
+
+func (c *Canvas) DrawCircle(cx, cy, r int, fill string) {
+	c.Append(Circle{
+		CX:   cx,
+		CY:   cy,
+		R:    r,
+		Fill: fill,
+	})
+}
+
+type Rectangle struct {
+	X, Y, Width, Height int
+	Fill                string
+}
+
+func (c Rectangle) String() string {
+	return ufmt.Sprintf(`<rect x="%d" y="%d" width="%d" height="%d" fill="%s" />`, c.X, c.Y, c.Width, c.Height, c.Fill)
+}
+
+func (c *Canvas) DrawRectangle(x, y, width, height int, fill string) {
+	c.Append(Rectangle{
+		X:      x,
+		Y:      y,
+		Width:  width,
+		Height: height,
+		Fill:   fill,
+	})
+}
+
+type Text struct {
+	X, Y       int
+	Text, Fill string
+}
+
+func (c Text) String() string {
+	return ufmt.Sprintf(`<text x="%d" y="%d" fill="%s">%s</text>`, c.X, c.Y, c.Fill, c.Text)
+}
+
+func (c *Canvas) DrawText(x, y int, text, fill string) {
+	c.Append(Text{
+		X:    x,
+		Y:    y,
+		Text: text,
+		Fill: fill,
+	})
+}

examples/gno.land/p/demo/svg/z0_filetest.gno

@@ -0,0 +1,15 @@
+// PKGPATH: gno.land/p/demo/svg_test
+package svg_test
+
+import "gno.land/p/demo/svg"
+
+func main() {
+	canvas := svg.Canvas{Width: 500, Height: 500}
+	canvas.DrawRectangle(50, 50, 100, 100, "red")
+	canvas.DrawCircle(100, 100, 50, "blue")
+	canvas.DrawText(100, 100, "hello world!", "magenta")
+	println(canvas)
+}
+
+// Output:
+// <svg xmlns="http://www.w3.org/2000/svg" width="500" height="500"><rect x="50" y="50" width="100" height="100" fill="red" /><circle cx="100" cy="100" r="50" fill="blue" /><text x="100" y="100" fill="magenta">hello world!</text></svg>

examples/gno.land/p/demo/svg/z1_filetest.gno

@@ -0,0 +1,19 @@
+// PKGPATH: gno.land/p/demo/svg_test
+package svg_test
+
+import "gno.land/p/demo/svg"
+
+func main() {
+	canvas := svg.Canvas{
+		Width: 500, Height: 500,
+		Elems: []svg.Elem{
+			svg.Rectangle{50, 50, 100, 100, "red"},
+			svg.Circle{50, 50, 100, "red"},
+			svg.Text{100, 100, "hello world!", "magenta"},
+		},
+	}
+	println(canvas)
+}
+
+// Output:
+// <svg xmlns="http://www.w3.org/2000/svg" width="500" height="500"><rect x="50" y="50" width="100" height="100" fill="red" /><circle cx="50" cy="50" r="100" fill="red" /><text x="100" y="100" fill="magenta">hello world!</text></svg>