From 95a7b27ff85de298de413db17753324721c7fec2 Mon Sep 17 00:00:00 2001
From: surdeus <surdeus@gmail.com>
Date: Sat, 18 Feb 2023 05:51:43 +0500
Subject: [PATCH] Started implementing the camera.

---
 src/cmd/test/main.go |  5 ++++-
 src/gx/camera.go     | 37 +++++++++++++++++++++++++++++++++++++
 src/gx/main.go       | 12 ++++++++++++
 src/gx/sprite.go     |  8 +++++++-
 4 files changed, 60 insertions(+), 2 deletions(-)
 create mode 100644 src/gx/camera.go

diff --git a/src/cmd/test/main.go b/src/cmd/test/main.go
index 2b370c8..af9c23e 100644
--- a/src/cmd/test/main.go
+++ b/src/cmd/test/main.go
@@ -31,7 +31,10 @@ func NewPlayer() *Player {
 }
 
 func (p *Player) Update(e *gx.Engine) {
-	p.Sprite.Object.T.P.Y += 40 * e.DT()
+	//p.Sprite.Object.T.P.Y += 40 * e.DT()
+	dt := e.DT()
+	c := e.Camera()
+	c.Object.T.P.X += 40 * dt
 }
 
 func main() {
diff --git a/src/gx/camera.go b/src/gx/camera.go
new file mode 100644
index 0000000..3e83153
--- /dev/null
+++ b/src/gx/camera.go
@@ -0,0 +1,37 @@
+package gx
+
+// Implements the camera component
+// for the main window.
+type Camera struct {
+	*Object
+}
+
+// Returns the matrix satysfying camera
+// position, scale and rotation to apply
+// it to the objects to get the real
+// transform to display on the screen.
+func (c *Camera)Matrix(scale bool) Matrix {
+	g := &Matrix{}
+
+	g.Translate(
+		c.Object.T.RA.X,
+		c.Object.T.RA.Y,
+	)
+
+	g.Rotate(c.Object.T.R)
+
+	g.Translate(
+		-c.Object.T.P.X,
+		-c.Object.T.P.Y,
+	)
+
+	if scale {
+		g.Scale(
+			c.Object.T.S.X,
+			c.Object.T.S.Y,
+		)
+	}
+
+	return *g
+}
+
diff --git a/src/gx/main.go b/src/gx/main.go
index db83b08..eb43c6b 100644
--- a/src/gx/main.go
+++ b/src/gx/main.go
@@ -22,10 +22,15 @@ type Engine struct {
 	behavers []Behaver
 	lastTime time.Time
 	dt Float
+	camera *Camera
 }
 
 type engine Engine
 
+func (e *Engine) Camera() *Camera {
+	return e.camera
+}
+
 func New(
 	cfg *WindowConfig,
 ) *Engine {
@@ -35,6 +40,13 @@ func New(
 			Layer,
 			*[]Drawer,
 		](true),
+		camera: &Camera{
+			Object: &Object{
+				T: Transform{
+					S: Vector{0.1, 1},
+				},
+			},
+		},
 	}
 }
 
diff --git a/src/gx/sprite.go b/src/gx/sprite.go
index 12a6519..62c4651 100644
--- a/src/gx/sprite.go
+++ b/src/gx/sprite.go
@@ -7,6 +7,7 @@ import (
 type Sprite struct {
 	*Object
 	*Image
+	Floating bool
 }
 
 func (s *Sprite) Draw(
@@ -14,8 +15,13 @@ func (s *Sprite) Draw(
 	i *Image,
 ) {
 	op := &ebiten.DrawImageOptions{}
-	op.GeoM = s.Object.T.Matrix()
+	m := s.Object.T.Matrix()
 
+	if e.camera != nil {
+		m.Concat(e.camera.Matrix(true))
+	}
+
+	op.GeoM = m
 	i.DrawImage(s.Image, op)
 }