Clamp camera zoom and position

game/game.go

@@ -3,6 +3,7 @@ package game
 import (
 	"image/color"
 	"log"
+	"math"
 	"os"
 
 	"code.rocketnine.space/tslocum/commandeuropa/component"
@@ -44,6 +45,11 @@ func (g *Game) Layout(outsideWidth, outsideHeight int) (screenWidth, screenHeigh
 	// Handle window resize.
 	if outsideWidth != world.ScreenWidth || outsideHeight != world.ScreenHeight {
 		world.ScreenWidth, world.ScreenHeight = outsideWidth, outsideHeight
+
+		mapSize := float64(16 * 128)
+		minZoomWidth := float64(world.ScreenWidth) / mapSize
+		minZoomHeight := float64(world.ScreenHeight) / mapSize
+		world.MinCamScale = int(math.Ceil(math.Max(minZoomWidth, minZoomHeight)))
 	}
 
 	return outsideWidth, outsideHeight

system/handleinput.go

@@ -12,7 +12,20 @@ type HandleInput struct {
 }
 
 func (r *HandleInput) Update(e gohan.Entity) error {
-	const panDistance = 3
+	// Zoom with mouse.
+	_, scroll := ebiten.Wheel()
+	if scroll < 0 {
+		world.CamScale -= 1
+	} else if scroll > 0 {
+		world.CamScale += 1
+	}
+
+	// Clamp camera zoom.
+	if world.CamScale < world.MinCamScale {
+		world.CamScale = world.MinCamScale
+	}
+
+	panDistance := 4
 
 	// Pan with keyboard.
 	if ebiten.IsKeyPressed(ebiten.KeyLeft) {
@@ -28,22 +41,6 @@ func (r *HandleInput) Update(e gohan.Entity) error {
 		world.CamY += panDistance
 	}
 
-	// Zoom with mouse.
-	const minZoom = 1
-	const maxZoom = 7
-	_, scroll := ebiten.Wheel()
-	if scroll < 0 {
-		world.CamScale -= 1
-		if world.CamScale < minZoom {
-			world.CamScale = minZoom
-		}
-	} else if scroll > 0 {
-		world.CamScale += 1
-		if world.CamScale > maxZoom {
-			world.CamScale = maxZoom
-		}
-	}
-
 	// Pan with mouse.
 	const panArea = 7
 	x, y := ebiten.CursorPosition()
@@ -57,6 +54,20 @@ func (r *HandleInput) Update(e gohan.Entity) error {
 	} else if y >= world.ScreenHeight-panArea {
 		world.CamY += panDistance
 	}
+
+	// Clamp camera position.
+	halfWidth := (world.ScreenWidth / 2) / world.CamScale
+	halfHeight := (world.ScreenHeight / 2) / world.CamScale
+	if world.CamX < halfWidth {
+		world.CamX = halfWidth
+	} else if world.CamX > (16*128)-halfWidth {
+		world.CamX = (16 * 128) - halfWidth
+	}
+	if world.CamY < halfHeight {
+		world.CamY = halfHeight
+	} else if world.CamY > (16*128)-halfHeight {
+		world.CamY = (16 * 128) - halfHeight
+	}
 	return nil
 }
 

world/world.go

@@ -17,6 +17,8 @@ var (
 
 	CamScale = 1
 
+	MinCamScale = 1
+
 	Map []MapTile
 
 	Debug int