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|
package main
import (
"math"
"age_of_empires/physics"
"github.com/hajimehoshi/ebiten/v2"
"github.com/hajimehoshi/ebiten/v2/inpututil"
)
const (
ScreenWidth = 960
ScreenHeight = 640
WorldWidth = 3200
WorldHeight = 2400
cameraZoomMin = 0.25
cameraZoomMax = 3.0
cameraZoomStep = 0.10
cameraScrollSpeed = 400.0
cameraDrag = 8.0
)
type Camera struct {
X, Y float64
Zoom float64
vx, vy float64
dragActive bool
dragStartScreenX, dragStartScreenY int
dragStartCamX, dragStartCamY float64
}
func (c *Camera) WorldToScreen(p physics.Point) (float64, float64) {
sx := (float64(p.X)-c.X)*c.Zoom + ScreenWidth/2
sy := (float64(p.Y)-c.Y)*c.Zoom + ScreenHeight/2
return sx, sy
}
func (c *Camera) ScreenToWorld(sx, sy int) physics.Point {
zoom := c.Zoom
if zoom == 0 {
zoom = 1
}
wx := float64(sx-ScreenWidth/2)/zoom + c.X
wy := float64(sy-ScreenHeight/2)/zoom + c.Y
return physics.Point{X: int(math.Round(wx)), Y: int(math.Round(wy))}
}
func (c *Camera) GeoM() ebiten.GeoM {
var m ebiten.GeoM
m.Translate(-c.X, -c.Y)
m.Scale(c.Zoom, c.Zoom)
m.Translate(ScreenWidth/2, ScreenHeight/2)
return m
}
func (c *Camera) clampToBounds() {
halfW := (ScreenWidth / 2.0) / c.Zoom
halfH := (ScreenHeight / 2.0) / c.Zoom
minX, maxX := halfW, float64(WorldWidth)-halfW
if minX > maxX {
minX = WorldWidth / 2
maxX = WorldWidth / 2
}
minY, maxY := halfH, float64(WorldHeight)-halfH
if minY > maxY {
minY = WorldHeight / 2
maxY = WorldHeight / 2
}
if c.X < minX {
c.X = minX
if c.vx < 0 {
c.vx = 0
}
}
if c.X > maxX {
c.X = maxX
if c.vx > 0 {
c.vx = 0
}
}
if c.Y < minY {
c.Y = minY
if c.vy < 0 {
c.vy = 0
}
}
if c.Y > maxY {
c.Y = maxY
if c.vy > 0 {
c.vy = 0
}
}
}
func (c *Camera) Update(dt float64) {
zoom := c.Zoom
if zoom == 0 {
zoom = 1
}
// Scroll wheel zoom toward cursor
_, wy := ebiten.Wheel()
if wy != 0 {
mx, my := ebiten.CursorPosition()
// cursor world pos before zoom
wx0 := float64(mx-ScreenWidth/2)/zoom + c.X
wy0 := float64(my-ScreenHeight/2)/zoom + c.Y
newZoom := math.Max(cameraZoomMin, math.Min(cameraZoomMax, zoom+wy*cameraZoomStep))
c.Zoom = newZoom
zoom = newZoom
// translate so cursor stays fixed
wx1 := float64(mx-ScreenWidth/2)/zoom + c.X
wy1 := float64(my-ScreenHeight/2)/zoom + c.Y
c.X -= wx1 - wx0
c.Y -= wy1 - wy0
}
// Middle-mouse drag
mx, my := ebiten.CursorPosition()
if inpututil.IsMouseButtonJustPressed(ebiten.MouseButtonMiddle) {
c.dragActive = true
c.dragStartScreenX = mx
c.dragStartScreenY = my
c.dragStartCamX = c.X
c.dragStartCamY = c.Y
}
if c.dragActive {
if ebiten.IsMouseButtonPressed(ebiten.MouseButtonMiddle) {
c.X = c.dragStartCamX - float64(mx-c.dragStartScreenX)/zoom
c.Y = c.dragStartCamY - float64(my-c.dragStartScreenY)/zoom
} else {
c.dragActive = false
}
}
// Arrow key pan (velocity-based)
dx, dy := 0.0, 0.0
if ebiten.IsKeyPressed(ebiten.KeyArrowLeft) {
dx -= 1
}
if ebiten.IsKeyPressed(ebiten.KeyArrowRight) {
dx += 1
}
if ebiten.IsKeyPressed(ebiten.KeyArrowUp) {
dy -= 1
}
if ebiten.IsKeyPressed(ebiten.KeyArrowDown) {
dy += 1
}
if dx != 0 && dy != 0 {
inv := 1.0 / math.Sqrt2
dx *= inv
dy *= inv
}
c.vx += dx * cameraScrollSpeed
c.vy += dy * cameraScrollSpeed
// Apply velocity and exponential drag
c.X += c.vx * dt
c.Y += c.vy * dt
decay := math.Exp(-cameraDrag * dt)
c.vx *= decay
c.vy *= decay
c.clampToBounds()
}
|
