From 4db1ed716b5c4f5cfbb2e15b9a8ca65284b11afb Mon Sep 17 00:00:00 2001
From: Christian Rocha <christian@rocha.is>
Date: Fri, 9 Jul 2021 13:19:05 -0400
Subject: [PATCH] Add 2D pixel-based demo

---
 examples/canvas/main.go | 88 +++++++++++++++++++++++++++++++++++++++++
 examples/go.mod         | 11 ++++++
 examples/go.sum         | 24 +++++++++++
 3 files changed, 123 insertions(+)
 create mode 100644 examples/canvas/main.go
 create mode 100644 examples/go.mod
 create mode 100644 examples/go.sum

diff --git a/examples/canvas/main.go b/examples/canvas/main.go
new file mode 100644
index 0000000..cafa15d
--- /dev/null
+++ b/examples/canvas/main.go
@@ -0,0 +1,88 @@
+package main
+
+import (
+	"time"
+
+	"github.com/charmbracelet/harmonica"
+	"github.com/h8gi/canvas"
+)
+
+const (
+	width   = 1024
+	height  = 768
+	fps     = 60
+	bgColor = "#111111"
+)
+
+func main() {
+	var (
+		circ       = newCircle()
+		clickedYet bool
+	)
+
+	c := canvas.NewCanvas(&canvas.CanvasConfig{
+		Width:     width,
+		Height:    height,
+		FrameRate: fps,
+		Title:     "Harmonica",
+	})
+
+	c.Draw(func(ctx *canvas.Context) {
+		ctx.SetHexColor(bgColor)
+		ctx.Clear()
+
+		if ctx.IsMouseDragged {
+			if !clickedYet {
+				// Set starting positions.
+				circ.x = ctx.Mouse.X
+				circ.y = ctx.Mouse.Y
+
+				circ.Radius = 100
+				clickedYet = true
+			}
+			circ.X = ctx.Mouse.X
+			circ.Y = ctx.Mouse.Y
+		}
+
+		if clickedYet {
+			circ.draw(ctx)
+		}
+	})
+}
+
+type circle struct {
+	// Target values. This is what the spring will seek.
+	X, Y, Radius float64
+
+	// Managed values. These are the initial
+	x, xVel     float64
+	y, yVel     float64
+	rad, radVel float64
+
+	spring harmonica.Spring
+}
+
+func newCircle() circle {
+	const (
+		frequency = 0.8
+		damping   = 0.99
+	)
+
+	return circle{
+		spring: harmonica.NewSpring(harmonica.TimeDelta(time.Second/fps), frequency, damping),
+	}
+}
+
+func (c *circle) draw(ctx *canvas.Context) {
+	// Update
+	c.spring.Update(&c.x, &c.xVel, c.X)
+	c.spring.Update(&c.y, &c.yVel, c.Y)
+	c.spring.Update(&c.rad, &c.radVel, c.Radius)
+
+	const color = "#f1f1f1"
+
+	ctx.Push()
+	ctx.DrawCircle(c.x, c.y, c.rad)
+	ctx.SetHexColor(color)
+	ctx.Fill()
+}
diff --git a/examples/go.mod b/examples/go.mod
new file mode 100644
index 0000000..f408763
--- /dev/null
+++ b/examples/go.mod
@@ -0,0 +1,11 @@
+module examples
+
+go 1.16
+
+replace github.com/charmbracelet/harmonica => ../
+
+require (
+	github.com/charmbracelet/harmonica v0.0.0-20210709144143-16876a63b30d // indirect
+	github.com/h8gi/canvas v0.0.0-20200710004640-a6361a06ab49
+	golang.org/x/image v0.0.0-20190523035834-f03afa92d3ff
+)
diff --git a/examples/go.sum b/examples/go.sum
new file mode 100644
index 0000000..62fd2f4
--- /dev/null
+++ b/examples/go.sum
@@ -0,0 +1,24 @@
+github.com/faiface/glhf v0.0.0-20181018222622-82a6317ac380 h1:FvZ0mIGh6b3kOITxUnxS3tLZMh7yEoHo75v3/AgUqg0=
+github.com/faiface/glhf v0.0.0-20181018222622-82a6317ac380/go.mod h1:zqnPFFIuYFFxl7uH2gYByJwIVKG7fRqlqQCbzAnHs9g=
+github.com/faiface/mainthread v0.0.0-20171120011319-8b78f0a41ae3 h1:baVdMKlASEHrj19iqjARrPbaRisD7EuZEVJj6ZMLl1Q=
+github.com/faiface/mainthread v0.0.0-20171120011319-8b78f0a41ae3/go.mod h1:VEPNJUlxl5KdWjDvz6Q1l+rJlxF2i6xqDeGuGAxa87M=
+github.com/faiface/pixel v0.8.0 h1:phOHW6ixfMAKRamjnvhI6FFI2VRyPEq7+LmmkDGXB/4=
+github.com/faiface/pixel v0.8.0/go.mod h1:CEUU/s9E82Kqp01Boj1O67KnBskqiLghANqvUJGgDAM=
+github.com/fogleman/gg v1.3.0 h1:/7zJX8F6AaYQc57WQCyN9cAIz+4bCJGO9B+dyW29am8=
+github.com/fogleman/gg v1.3.0/go.mod h1:R/bRT+9gY/C5z7JzPU0zXsXHKM4/ayA+zqcVNZzPa1k=
+github.com/go-gl/gl v0.0.0-20190320180904-bf2b1f2f34d7 h1:SCYMcCJ89LjRGwEa0tRluNRiMjZHalQZrVrvTbPh+qw=
+github.com/go-gl/gl v0.0.0-20190320180904-bf2b1f2f34d7/go.mod h1:482civXOzJJCPzJ4ZOX/pwvXBWSnzD4OKMdH4ClKGbk=
+github.com/go-gl/glfw v0.0.0-20190409004039-e6da0acd62b1 h1:QbL/5oDUmRBzO9/Z7Seo6zf912W/a6Sr4Eu0G/3Jho0=
+github.com/go-gl/glfw v0.0.0-20190409004039-e6da0acd62b1/go.mod h1:vR7hzQXu2zJy9AVAgeJqvqgH9Q5CA+iKCZ2gyEVpxRU=
+github.com/go-gl/mathgl v0.0.0-20190416160123-c4601bc793c7 h1:THttjeRn1iiz69E875U6gAik8KTWk/JYAHoSVpUxBBI=
+github.com/go-gl/mathgl v0.0.0-20190416160123-c4601bc793c7/go.mod h1:yhpkQzEiH9yPyxDUGzkmgScbaBVlhC06qodikEM0ZwQ=
+github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0 h1:DACJavvAHhabrF08vX0COfcOBJRhZ8lUbR+ZWIs0Y5g=
+github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0/go.mod h1:E/TSTwGwJL78qG/PmXZO1EjYhfJinVAhrmmHX6Z8B9k=
+github.com/h8gi/canvas v0.0.0-20200710004640-a6361a06ab49 h1:svddC2dRqy+Y1zGH4+AvvCFZLKuPhAfEvlgYSNP4lcg=
+github.com/h8gi/canvas v0.0.0-20200710004640-a6361a06ab49/go.mod h1:7iSUKfOcA+GiWc+LpxXggMogUFIo8pm1FZcYTUmL3YY=
+github.com/pkg/errors v0.8.1 h1:iURUrRGxPUNPdy5/HRSm+Yj6okJ6UtLINN0Q9M4+h3I=
+github.com/pkg/errors v0.8.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
+golang.org/x/image v0.0.0-20190321063152-3fc05d484e9f/go.mod h1:kZ7UVZpmo3dzQBMxlp+ypCbDeSB+sBbTgSJuh5dn5js=
+golang.org/x/image v0.0.0-20190523035834-f03afa92d3ff h1:+2zgJKVDVAz/BWSsuniCmU1kLCjL88Z8/kv39xCI9NQ=
+golang.org/x/image v0.0.0-20190523035834-f03afa92d3ff/go.mod h1:kZ7UVZpmo3dzQBMxlp+ypCbDeSB+sBbTgSJuh5dn5js=
+golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=