From 4bed73d9e34b7208c307201290759e64e832635e Mon Sep 17 00:00:00 2001
From: "Sascha L. Teichmann" <sascha.teichmann@intevation.de>
Date: Sun, 8 May 2016 15:13:40 +0200
Subject: [PATCH] Prepare tiles updater in webmapper to have unupdated base
 tiles.

---
 cmd/mtwebmapper/tilesupdater.go | 54 ++++++++++++++++++++++++++-------
 1 file changed, 43 insertions(+), 11 deletions(-)

diff --git a/cmd/mtwebmapper/tilesupdater.go b/cmd/mtwebmapper/tilesupdater.go
index 1e91a3a..5cd8cc1 100644
--- a/cmd/mtwebmapper/tilesupdater.go
+++ b/cmd/mtwebmapper/tilesupdater.go
@@ -48,6 +48,11 @@ type xz struct {
 	Z int16
 }
 
+type xzc struct {
+	xz
+	canceled bool
+}
+
 type xzm struct {
 	P    xz
 	Mask uint16
@@ -150,21 +155,40 @@ func (tu *tileUpdater) ServeHTTP(rw http.ResponseWriter, r *http.Request) {
 	rw.WriteHeader(http.StatusOK)
 }
 
+func extractChanges(changes map[xz]bool) []xzc {
+	chs := make([]xzc, len(changes))
+	var i int
+	for ch := range changes {
+		chs[i] = xzc{ch, false}
+		i++
+	}
+	return chs
+}
+
+func activeChanges(changes []xzc) map[xz]bool {
+	chs := make(map[xz]bool)
+	for i := range changes {
+		if !changes[i].canceled {
+			chs[changes[i].xz] = true
+		}
+	}
+	return chs
+}
+
 func (tu *tileUpdater) doUpdates() {
 
 	for {
-		var changes map[xz]bool
 		tu.cond.L.Lock()
 		for len(tu.changes) == 0 {
 			tu.cond.Wait()
 		}
-		changes = tu.changes
+		changes := extractChanges(tu.changes)
 		tu.changes = map[xz]bool{}
 		tu.cond.L.Unlock()
 
 		baseDir := filepath.Join(tu.mapDir, "8")
 
-		jobs := make(chan xz)
+		jobs := make(chan *xzc)
 		var done sync.WaitGroup
 
 		for i, n := 0, common.Min(tu.workers, len(changes)); i < n; i++ {
@@ -182,17 +206,25 @@ func (tu *tileUpdater) doUpdates() {
 			go tu.updateBaseTiles(jobs, btc, &done)
 		}
 
-		parentJobs := make(map[xz]uint16)
-
-		for c := range changes {
+		for i := range changes {
 			//log.Printf("job: %+v\n", c)
-			jobs <- c
-			pxz := c.parent()
-			parentJobs[pxz.P] |= pxz.Mask
+			jobs <- &changes[i]
 		}
 		close(jobs)
 		done.Wait()
 
+		actChs := activeChanges(changes)
+
+		if len(actChs) == 0 {
+			continue
+		}
+
+		parentJobs := make(map[xz]uint16)
+		for c := range actChs {
+			pxz := c.parent()
+			parentJobs[pxz.P] |= pxz.Mask
+		}
+
 		for level := 7; level >= 0; level-- {
 			pJobs := make(chan xzm)
 			for i, n := 0, common.Min(len(parentJobs), tu.workers); i < n; i++ {
@@ -211,7 +243,7 @@ func (tu *tileUpdater) doUpdates() {
 		}
 
 		if tu.btu != nil {
-			tu.btu.BaseTilesUpdated(changes)
+			tu.btu.BaseTilesUpdated(actChs)
 		}
 	}
 }
@@ -294,7 +326,7 @@ func (tu *tileUpdater) updatePyramidTile(scratch, resized *image.RGBA, level int
 }
 
 func (tu *tileUpdater) updateBaseTiles(
-	jobs chan xz,
+	jobs chan *xzc,
 	btc *common.BaseTileCreator, done *sync.WaitGroup) {
 
 	defer btc.Close()