Worlds are now opened by their level.dat and are centered properly.

The world spawn will be read from the level.dat and the view will be
centered to that position.

4 files changed, 77 insertions, 6 deletions

diff --git a/leveldat.go b/leveldat.go
new file mode 100644
index 0000000..51344a8
--- /dev/null
+++ b/leveldat.go
@@ -0,0 +1,41 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	"github.com/kch42/gonbt/nbt"
+	"io"
+)
+
+func invalidLevelDat(err error) error {
+	return fmt.Errorf("Invalid level.dat: %s", err)
+}
+
+func getMapCenter(leveldat io.Reader) (int, int, error) {
+	lvl, _, err := nbt.ReadGzipdNamedTag(leveldat)
+	if err != nil {
+		return 0, 0, err
+	}
+
+	if lvl.Type != nbt.TAG_Compound {
+		return 0, 0, invalidLevelDat(errors.New("Root tag has wrong type"))
+	}
+	root := lvl.Payload.(nbt.TagCompound)
+
+	data, err := root.GetCompound("Data")
+	if err != nil {
+		return 0, 0, invalidLevelDat(err)
+	}
+
+	x, err := data.GetInt("SpawnX")
+	if err != nil {
+		return 0, 0, invalidLevelDat(err)
+	}
+
+	z, err := data.GetInt("SpawnZ")
+	if err != nil {
+		return 0, 0, invalidLevelDat(err)
+	}
+
+	return int(x), int(z), nil
+}
diff --git a/listmaps.go b/listmaps.go
index ad8a0cc..8a1c088 100644
--- a/listmaps.go
+++ b/listmaps.go
@@ -42,12 +42,13 @@ func allMaps() map[string]string {
 		}
 		p := path.Join(savesDir, info.Name())
 
-		fi, err := os.Stat(path.Join(p, "level.dat"))
+		leveldat := path.Join(p, "level.dat")
+		fi, err := os.Stat(leveldat)
 		if (err != nil) || (!fi.Mode().IsRegular()) {
 			continue
 		}
 
-		maps[info.Name()] = path.Join(p, "region")
+		maps[info.Name()] = leveldat
 	}
 
 	return maps
diff --git a/main.go b/main.go
index 50a975d..37f1a1e 100644
--- a/main.go
+++ b/main.go
@@ -7,6 +7,7 @@ import (
 	"github.com/mattn/go-gtk/glib"
 	"github.com/mattn/go-gtk/gtk"
 	"os"
+	"path"
 )
 
 type GUI struct {
@@ -31,23 +32,45 @@ type GUI struct {
 }
 
 func (g *GUI) openWorldDlg() {
-	dlg := gtk.NewFileChooserDialog("Open World (region directory)", g.window, gtk.FILE_CHOOSER_ACTION_SELECT_FOLDER, "Open Region dir", gtk.RESPONSE_OK, "Cancel", gtk.RESPONSE_CANCEL)
+	dlg := gtk.NewFileChooserDialog("Open World (level.dat)", g.window, gtk.FILE_CHOOSER_ACTION_OPEN, "Open", gtk.RESPONSE_OK, "Cancel", gtk.RESPONSE_CANCEL)
+	filter := gtk.NewFileFilter()
+	filter.AddPattern("level.dat")
+	filter.SetName("level.dat")
+	dlg.AddFilter(filter)
 	if dlg.Run() == gtk.RESPONSE_OK {
 		g.openWorld(dlg.GetFilename())
 	}
 	dlg.Destroy()
 }
 
-func (g *GUI) openWorld(path string) {
-	region, err := mcmap.OpenRegion(path, false)
+func readWorld(p string) (*mcmap.Region, int, int, error) {
+	f, err := os.Open(p)
 	if err != nil {
-		dlg := gtk.NewMessageDialog(g.window, gtk.DIALOG_MODAL|gtk.DIALOG_DESTROY_WITH_PARENT, gtk.MESSAGE_WARNING, gtk.BUTTONS_OK, "Could not load world %s:\n%s", path, err.Error())
+		return nil, 0, 0, err
+	}
+	defer f.Close()
+
+	x, z, err := getMapCenter(f)
+	if err != nil {
+		return nil, 0, 0, err
+	}
+
+	dir, _ := path.Split(p)
+	region, err := mcmap.OpenRegion(path.Join(dir, "region"), false)
+	return region, x, z, err
+}
+
+func (g *GUI) openWorld(p string) {
+	region, centerX, centerZ, err := readWorld(p)
+	if err != nil {
+		dlg := gtk.NewMessageDialog(g.window, gtk.DIALOG_MODAL|gtk.DIALOG_DESTROY_WITH_PARENT, gtk.MESSAGE_WARNING, gtk.BUTTONS_OK, "Could not load world %s:\n%s", p, err.Error())
 		dlg.Run()
 		dlg.Destroy()
 	}
 
 	g.menuitemSave.SetSensitive(true)
 
+	g.mapw.SetCenter(centerX, centerZ)
 	g.mapw.SetRegion(region)
 }
 
diff --git a/mapwidget.go b/mapwidget.go
index e04b5eb..8fc2b71 100644
--- a/mapwidget.go
+++ b/mapwidget.go
@@ -63,6 +63,12 @@ func (mw *MapWidget) SetTool(t Tool)                 { mw.regWrap.SetTool(t) }
 
 func (mw *MapWidget) Save() { mw.regWrap.Save() }
 
+func (mw *MapWidget) SetCenter(x, z int) {
+	mw.offX = x*zoom - mw.w/2
+	mw.offZ = z*zoom - mw.h/2
+	mw.updateChunkBounds()
+}
+
 func (mw *MapWidget) updateChunkBounds() {
 	startX := int(math.Floor(float64(mw.offX) / tileSize))
 	startZ := int(math.Floor(float64(mw.offZ) / tileSize))