From cd2c8e61bed1921543ae0df05ab2a4b78dbd9740 Mon Sep 17 00:00:00 2001
From: Nick Thomas <me@ur.gs>
Date: Tue, 31 Dec 2019 01:38:39 +0000
Subject: [PATCH] WIP: bounds checking

---
 Makefile             |  4 ++--
 cmd/view-map/main.go | 40 ++++++++++++++++++++++++----------------
 2 files changed, 26 insertions(+), 18 deletions(-)

diff --git a/Makefile b/Makefile
index 192e289..715f64c 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,6 @@
-srcfiles = Makefile $(shell find . -iname *.go)
+srcfiles = Makefile go.mod $(shell find . -iname *.go)
 
-GOBUILD ?= go build
+GOBUILD ?= go build -tags ebitengl
 
 all: loader palette-idx view-obj view-map view-menu view-minimap view-set wh40k
 
diff --git a/cmd/view-map/main.go b/cmd/view-map/main.go
index 959ae26..3394636 100644
--- a/cmd/view-map/main.go
+++ b/cmd/view-map/main.go
@@ -79,8 +79,8 @@ func main() {
 	}
 
 	state := state{
-		zoom:   1.0,
-		origin: image.Point{0, -3000}, // FIXME: haxxx
+		zoom:   0.5,
+		origin: image.Point{0, 3000}, // FIXME: haxxx
 	}
 	env := &env{
 		gameMap:   gameMap,
@@ -97,10 +97,10 @@ func main() {
 
 	// TODO: click to view cell data
 
-	win.OnKeyUp(ebiten.KeyLeft, env.changeOrigin(+64, +0))
-	win.OnKeyUp(ebiten.KeyRight, env.changeOrigin(-64, +0))
-	win.OnKeyUp(ebiten.KeyUp, env.changeOrigin(+0, +64))
-	win.OnKeyUp(ebiten.KeyDown, env.changeOrigin(+0, -64))
+	win.OnKeyUp(ebiten.KeyLeft, env.changeOrigin(-64, +0))
+	win.OnKeyUp(ebiten.KeyRight, env.changeOrigin(+64, +0))
+	win.OnKeyUp(ebiten.KeyUp, env.changeOrigin(+0, -64))
+	win.OnKeyUp(ebiten.KeyDown, env.changeOrigin(+0, +64))
 	win.OnMouseWheel(env.changeZoom)
 
 	for i := 0; i <= 6; i++ {
@@ -171,7 +171,6 @@ func (e *env) Draw(screen *ebiten.Image) error {
 
 func (e *env) renderCell(x, y, z int, screen *ebiten.Image) error {
 	var sprites []*conv.Sprite
-
 	cell := e.gameMap.Cells.At(x, y, z)
 
 	if spr, err := e.getSprite(e.set.Palette, cell.Surface); err != nil {
@@ -198,17 +197,26 @@ func (e *env) renderCell(x, y, z int, screen *ebiten.Image) error {
 		sprites = append(sprites, spr)
 	}
 
+	iso := ebiten.GeoM{}
+	iso.Translate(cellToPix(float64(x), float64(y)))
+	iso.Translate(float64(-e.state.origin.X), float64(-e.state.origin.Y))
 	// Taking the Z index away *seems* to draw the object in the correct place.
 	// FIXME: There are some artifacts, investigate more
-	fx, fy := cellToPix(float64(x), float64(y))
-	fx += float64(e.state.origin.X)
-	fy += float64(e.state.origin.Y)
-
-	iso := ebiten.GeoM{}
-	iso.Translate(fx, fy)
 	iso.Translate(0.0, -float64(z*48.0))  // offset for Z index
 	iso.Scale(e.state.zoom, e.state.zoom) // apply current zoom factor
 
+	// Check if we're going to draw far outside the viewport, cancel if so
+	minX, minY := iso.Apply(cellWidth, cellHeight)
+	if minX < 0.0 || minY < 0.0 {
+		return nil
+	}
+
+	screenW, screenL := screen.Size()
+	maxX, maxY := iso.Apply(float64(screenW), float64(screenL))
+	if int(maxX*e.state.zoom) > screenW || int(maxY*e.state.zoom) > screenL {
+		return nil
+	}
+
 	for _, sprite := range sprites {
 		if err := screen.DrawImage(sprite.Image, &ebiten.DrawImageOptions{GeoM: iso}); err != nil {
 			return err
@@ -236,9 +244,9 @@ func (e *env) setZIdx(to int) func() {
 	}
 }
 
-var (
-	cellWidth  = 64.0
-	cellHeight = 64.0
+const (
+	cellWidth  = 64
+	cellHeight = 64
 )
 
 // Doesn't take the camera or Z level into account