gg: add draw_ellipse_thick and draw_ellipse_thick_rotate (#26327)

Author: Linklancien

vlib/gg/draw.c.v

@@ -1009,6 +1009,32 @@ pub fn (ctx &Context) draw_ellipse_empty(x f32, y f32, rw f32, rh f32, c Color)
 	sgl.end()
 }
 
+// draw_ellipse_empty draws the outline of an ellipse.
+// `x`,`y` defines the center of the ellipse.
+// `rw` defines the *width* radius of the ellipse.
+// `rh` defines the *height* radius of the ellipse.
+// `th` defines the *thickness* of the ellipse.
+// `c` is the color of the outline.
+pub fn (ctx &Context) draw_ellipse_thick(x f32, y f32, rw f32, rh f32, th f32, c Color) {
+	if c.a != 255 {
+		sgl.load_pipeline(ctx.pipeline.alpha)
+	}
+	sgl.c4b(c.r, c.g, c.b, c.a)
+
+	sgl.begin_quads()
+	for i := 0; i < 360; i += 10 {
+		sgl.v2f(x + math.sinf(f32(math.radians(i + 10))) * (rw - th / 2), y +
+			math.cosf(f32(math.radians(i + 10))) * (rh - th / 2))
+		sgl.v2f(x + math.sinf(f32(math.radians(i))) * (rw - th / 2), y +
+			math.cosf(f32(math.radians(i))) * (rh - th / 2))
+		sgl.v2f(x + math.sinf(f32(math.radians(i))) * (rw + th / 2), y +
+			math.cosf(f32(math.radians(i))) * (rh + th / 2))
+		sgl.v2f(x + math.sinf(f32(math.radians(i + 10))) * (rw + th / 2), y +
+			math.cosf(f32(math.radians(i + 10))) * (rh + th / 2))
+	}
+	sgl.end()
+}
+
 // draw_ellipse_filled draws an opaque ellipse.
 // `x`,`y` defines the center of the ellipse.
 // `rw` defines the *width* radius of the ellipse.
@@ -1057,6 +1083,42 @@ pub fn (ctx &Context) draw_ellipse_empty_rotate(x f32, y f32, rw f32, rh f32, ro
 	sgl.end()
 }
 
+// draw_ellipse_empty draws the outline of an ellipse.
+// `x`,`y` defines the center of the ellipse.
+// `rw` defines the *width* radius of the ellipse.
+// `rh` defines the *height* radius of the ellipse.
+// `th` defines the *thickness* of the ellipse.
+// `rota` defines the *rotation* angle of the ellipse, in radians.
+// `c` is the color of the outline.
+pub fn (ctx &Context) draw_ellipse_thick_rotate(x f32, y f32, rw f32, rh f32, th f32, rota f32, c Color) {
+	if c.a != 255 {
+		sgl.load_pipeline(ctx.pipeline.alpha)
+	}
+	sgl.c4b(c.r, c.g, c.b, c.a)
+
+	cos_rot := math.cosf(rota)
+	sin_rot := math.sinf(rota)
+	sgl.begin_quads()
+	for i := 0; i < 360; i += 10 {
+		xfactor_current := math.sinf(f32(math.radians(i)))
+		xfactor_next := math.sinf(f32(math.radians(i + 10)))
+		yfactor_current := math.cosf(f32(math.radians(i)))
+		yfactor_next := math.cosf(f32(math.radians(i + 10)))
+
+		sgl.v2f(x + xfactor_next * (rw - th / 2) * cos_rot - yfactor_next * (rh - th / 2) * sin_rot,
+			y + yfactor_next * (rh - th / 2) * cos_rot + xfactor_next * (rw - th / 2) * sin_rot)
+		sgl.v2f(x + xfactor_current * (rw - th / 2) * cos_rot - yfactor_current * (rh - th / 2) * sin_rot,
+			y + yfactor_current * (rh - th / 2) * cos_rot +
+			xfactor_current * (rw - th / 2) * sin_rot)
+		sgl.v2f(x + xfactor_current * (rw + th / 2) * cos_rot - yfactor_current * (rh + th / 2) * sin_rot,
+			y + yfactor_current * (rh + th / 2) * cos_rot + xfactor_current * (rw +
+			th / 2) * sin_rot)
+		sgl.v2f(x + xfactor_next * (rw + th / 2) * cos_rot - yfactor_next * (rh + th / 2) * sin_rot,
+			y + yfactor_next * (rh + th / 2) * cos_rot + xfactor_next * (rw + th / 2) * sin_rot)
+	}
+	sgl.end()
+}
+
 // draw_ellipse_filled draws an opaque ellipse.
 // `x`,`y` defines the center of the ellipse.
 // `rw` defines the *width* radius of the ellipse.

vlib/gg/testdata/draw_elipses.vv

@@ -1,9 +1,11 @@
 import gg
 
+const thickness = f32(5)
+
 gg.start(
 	window_title: 'Ellipses'
 	width:        600
-	height:       200
+	height:       400
 	frame_fn:     fn (mut ctx gg.Context) {
 		ctx.begin()
 		drot := f32(ctx.frame) / 60
@@ -13,6 +15,9 @@ gg.start(
 		ctx.draw_ellipse_empty_rotate(300, 100, 50, 25, -drot, gg.black)
 		ctx.draw_ellipse_filled_rotate(500, 100, 100, 50, drot, gg.yellow)
 		ctx.draw_ellipse_empty_rotate(500, 100, 50, 25, drot, gg.black)
+		ctx.draw_ellipse_thick(100, 300, 100, 50, thickness, gg.green)
+		ctx.draw_ellipse_thick_rotate(300, 300, 100, 50, thickness, drot, gg.purple)
+		ctx.draw_ellipse_thick_rotate(500, 300, 100, 50, thickness, -drot, gg.indigo)
 		ctx.end()
 	}
 )