From 8986633624877fa9a4acc64460d5fba7471c3b7a Mon Sep 17 00:00:00 2001
From: Leah Lundqvist <hampus0505@gmail.com>
Date: Mon, 27 Jan 2020 20:42:32 +0100
Subject: [PATCH] gg: draw_arc()

---
 vlib/gg/gg.v | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/vlib/gg/gg.v b/vlib/gg/gg.v
index a0867f3405..191cf19f9c 100644
--- a/vlib/gg/gg.v
+++ b/vlib/gg/gg.v
@@ -11,6 +11,7 @@ import (
 	gx
 	os
 	glfw
+	math
 )
 
 pub struct Vec2 {
@@ -414,6 +415,32 @@ pub fn (ctx &GG) draw_line(x, y, x2, y2 f32, color gx.Color) {
 	gl.draw_arrays(C.GL_LINES, 0, 2)
 }
 
+pub fn (ctx &GG) draw_arc(x, y, r, start_angle, end_angle f32, segments int, color gx.Color) {
+	ctx.shader.set_int('has_texture', 0)
+	C.glDeleteBuffers(1, &ctx.vao)
+	C.glDeleteBuffers(1, &ctx.vbo)
+	ctx.shader.use()
+	ctx.shader.set_color('color', color)
+	start_rads := start_angle * 0.0174533 // deg -> rad approx
+	end_rads := end_angle * 0.0174533
+	rad_increment := end_rads / segments
+	mut vertices := []f32
+	mut i := 0
+	for i < segments {
+		theta := f32(i) * rad_increment - start_rads 
+		vertices << [x + f32(math.cos(theta)) * r, y + f32(math.sin(theta)) * r]
+		i++
+	}
+	// Add the last vertex at the final arc angle.
+	vertices << [x + f32(math.cos(end_rads)) * r, y + f32(math.sin(end_rads)) * r]
+	gl.bind_vao(ctx.vao)
+	gl.set_vbo(ctx.vbo, vertices, C.GL_STATIC_DRAW)
+	gl.vertex_attrib_pointer(0, 2, C.GL_FLOAT, false, 2, 0)
+	gl.enable_vertex_attrib_array(0)
+	gl.bind_vao(ctx.vao)
+	gl.draw_arrays(C.GL_LINE_STRIP, 0, segments + 1)
+}
+
 /*
 pub fn (c &GG) draw_gray_line(x, y, x2, y2 f32) {
 	c.draw_line(x, y, x2, y2, gx.Gray)