diff --git a/src/stage/timeline/body-canvas-widget.cpp b/src/stage/timeline/body-canvas-widget.cpp
index 62bb6dbb4..2230a50b1 100644
--- a/src/stage/timeline/body-canvas-widget.cpp
+++ b/src/stage/timeline/body-canvas-widget.cpp
@@ -72,6 +72,8 @@ namespace timeline {
   namespace { // details of track background painting
     
     const int INITIAL_TIMERULER_HEIGHT_px = 30;
+    const int INITIAL_CONTENT_HEIGHT_px = 100;
+    const int INITIAL_CONTENT_WIDTH_px = 200;
     
     /** request a pre-defined CSS style context for the track body */
     lumiera::advice::Request<PStyleContext> trackBodyStyle{"style(trackBody)"};
@@ -364,22 +366,19 @@ namespace timeline {
                           return profile_;
                         };
       
+      // initially set up some dummy space. Will be updated to match on first draw() call...
+      adjustCanvasHeight(INITIAL_CONTENT_WIDTH_px, INITIAL_CONTENT_HEIGHT_px, INITIAL_TIMERULER_HEIGHT_px);
+      
       this->set_border_width (0);
-      this->property_expand() = true;       // dynamically grab any available additional space
-      this->pack_start (rulerCanvas_);
-      this->pack_start (contentArea_);
+      this->property_expand() = true;   // dynamically grab any available additional space
+      this->pack_start (rulerCanvas_, Gtk::PACK_SHRINK);
+      this->pack_start (contentArea_, Gtk::PACK_EXPAND_WIDGET);
       
       contentArea_.set_shadow_type (Gtk::SHADOW_NONE);
       contentArea_.set_policy (Gtk::POLICY_ALWAYS, Gtk::POLICY_AUTOMATIC);  // always need a horizontal scrollbar
       contentArea_.property_expand() = true;                               //  dynamically grab additional space
       contentArea_.add (mainCanvas_);
       
-      { // for the initial empty canvas -- use all space the enclosing scrolled window got.
-        auto currSize = get_allocation();
-        int height = currSize.get_height();
-        adjustCanvasHeight(currSize.get_width(), height, INITIAL_TIMERULER_HEIGHT_px);
-      }
-      
       // realise all initially configured elements....
       this->show_all();
     }
@@ -420,9 +419,10 @@ namespace timeline {
     if (rootBody_ and isnil (profile_))
       {
         layout_.triggerDisplayEvaluation();
-        TODO("retrieve the vertical extension established by the triggerDisplayEvaluation() ");
-//      adjustCanvasHeight(currSize.get_width(), height, INITIAL_TIMERULER_HEIGHT_px); //////////////////////////TODO
         rootBody_->establishTrackSpace (profile_);
+        adjustCanvasHeight(layout_.getPixSpan().delta(),
+                           rootBody_->calcHeight(),
+                           rootBody_->calcRulerHeight());
       }
   }
   
@@ -437,8 +437,16 @@ namespace timeline {
   void
   BodyCanvasWidget::adjustCanvasHeight(int canvasWidth, int totalHeight, int rulerHeight)
   {
-    rulerCanvas_.set_size (canvasWidth, rulerHeight);
-    mainCanvas_.set_size (canvasWidth, max(0, totalHeight-rulerHeight));
+    auto adjust = [](Gtk::Layout& canvas, guint newWidth, guint newHeight) -> void
+                    {
+                      guint currWidth{0}, currHeight{0};
+                      canvas.get_size(currWidth, currHeight);
+                      if (currWidth != newWidth or currHeight != newHeight)
+                        canvas.set_size(newWidth, newHeight);
+                    };
+    
+    adjust (rulerCanvas_, canvasWidth, rulerHeight);
+    adjust (mainCanvas_, canvasWidth, max(0, totalHeight-rulerHeight));
   }
   
   
diff --git a/src/stage/timeline/track-body.cpp b/src/stage/timeline/track-body.cpp
index 2f749ffee..5c6e60f61 100644
--- a/src/stage/timeline/track-body.cpp
+++ b/src/stage/timeline/track-body.cpp
@@ -103,6 +103,20 @@ namespace timeline {
    */
   uint
   TrackBody::calcHeight()
+  {
+    uint heightSum = calcRulerHeight() + contentHeight_;
+    for (TrackBody* subTrack : subTracks_)
+      heightSum += subTrack->calcHeight();
+    return heightSum;
+  }
+  
+  
+  /**
+   * sum up the vertical extension required by all overview rulers.
+   * @return height in pixels, including all gap space
+   */
+  uint
+  TrackBody::calcRulerHeight()
   {
     uint overviewHeight = 0;
     for (auto& ruler : rulers_)
@@ -110,10 +124,7 @@ namespace timeline {
         overviewHeight += ruler->calcHeight()
                         + ruler->getGapHeight();
       }
-    uint heightSum = overviewHeight + contentHeight_;
-    for (TrackBody* subTrack : subTracks_)
-      heightSum += subTrack->calcHeight();
-    return heightSum;
+    return overviewHeight;
   }
   
   
diff --git a/src/stage/timeline/track-body.hpp b/src/stage/timeline/track-body.hpp
index 0345218c7..325bc39f7 100644
--- a/src/stage/timeline/track-body.hpp
+++ b/src/stage/timeline/track-body.hpp
@@ -89,6 +89,7 @@ namespace timeline {
       void setTrackName (cuString&);
       void establishTrackSpace (TrackProfile&);
       void attachSubTrack (TrackBody*);
+      uint calcRulerHeight();
       uint calcHeight();
       
       DisplayManager::SignalStructureChange signalStructureChange_;
diff --git a/wiki/thinkPad.ichthyo.mm b/wiki/thinkPad.ichthyo.mm
index a95646635..893b8ecc5 100644
--- a/wiki/thinkPad.ichthyo.mm
+++ b/wiki/thinkPad.ichthyo.mm
@@ -16598,7 +16598,7 @@
 <icon BUILTIN="button_ok"/>
 </node>
 <node CREATED="1489777837120" ID="ID_466927949" MODIFIED="1557498707220" TEXT="Ort f&#xfc;r Command-Definitionen"/>
-<node COLOR="#338800" CREATED="1489777846095" ID="ID_1401258681" MODIFIED="1562236719536" TEXT="Design Proc-Command-Framework vorantreiben">
+<node COLOR="#338800" CREATED="1489777846095" ID="ID_1401258681" MODIFIED="1566407169479" TEXT="Design Proc-Command-Framework vorantreiben">
 <arrowlink COLOR="#352c7d" DESTINATION="ID_1622574347" ENDARROW="Default" ENDINCLINATION="-240;-3336;" ID="Arrow_ID_1512127407" STARTARROW="None" STARTINCLINATION="1848;0;"/>
 <font NAME="SansSerif" SIZE="14"/>
 <icon BUILTIN="button_ok"/>
@@ -19390,9 +19390,9 @@
 <icon BUILTIN="button_ok"/>
 <node COLOR="#338800" CREATED="1561036914961" ID="ID_318008470" MODIFIED="1561042586692" TEXT="der DisplayManager tr&#xe4;gt das &quot;Anker&quot;-Signal">
 <icon BUILTIN="button_ok"/>
-<node COLOR="#435e98" CREATED="1561036987264" ID="ID_1799554074" MODIFIED="1565283189044" TEXT="signalStructureChange">
+<node COLOR="#435e98" CREATED="1561036987264" ID="ID_1799554074" MODIFIED="1566407048588" TEXT="signalStructureChange">
 <linktarget COLOR="#a9b4c1" DESTINATION="ID_1799554074" ENDARROW="Default" ENDINCLINATION="93;0;" ID="Arrow_ID_576839005" SOURCE="ID_1490359824" STARTARROW="None" STARTINCLINATION="169;0;"/>
-<linktarget COLOR="#8db7cd" DESTINATION="ID_1799554074" ENDARROW="Default" ENDINCLINATION="816;264;" ID="Arrow_ID_1531606207" SOURCE="ID_833580972" STARTARROW="None" STARTINCLINATION="627;37;"/>
+<linktarget COLOR="#8db7cd" DESTINATION="ID_1799554074" ENDARROW="Default" ENDINCLINATION="816;264;" ID="Arrow_ID_1531606207" SOURCE="ID_833580972" STARTARROW="None" STARTINCLINATION="629;34;"/>
 <linktarget COLOR="#89adc8" DESTINATION="ID_1799554074" ENDARROW="Default" ENDINCLINATION="340;0;" ID="Arrow_ID_19787354" SOURCE="ID_1865072728" STARTARROW="None" STARTINCLINATION="1589;0;"/>
 <icon BUILTIN="info"/>
 </node>
@@ -20213,7 +20213,9 @@
 </node>
 </node>
 </node>
-<node CREATED="1563457226008" ID="ID_104997878" MODIFIED="1563457229476" TEXT="rulerKind"/>
+<node CREATED="1563457226008" ID="ID_104997878" MODIFIED="1566406624648" TEXT="rulerKind">
+<arrowlink COLOR="#c178a8" DESTINATION="ID_1177786099" ENDARROW="Default" ENDINCLINATION="-1830;0;" ID="Arrow_ID_829837415" STARTARROW="None" STARTINCLINATION="576;-53;"/>
+</node>
 <node CREATED="1563456345999" ID="ID_411877946" MODIFIED="1563456383198" TEXT="presentationBinding">
 <node CREATED="1563456386610" ID="ID_1590625879" MODIFIED="1563456393668" TEXT="wie erscheint der Ruler">
 <node CREATED="1563456477213" ID="ID_214170046" MODIFIED="1563456480985" TEXT="sichtbar?"/>
@@ -21430,11 +21432,25 @@
 </node>
 <node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1565282697992" ID="ID_1761874542" MODIFIED="1565282702979" TEXT="vertikal belegter Raum">
 <icon BUILTIN="flag-yellow"/>
-<node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1565283074170" ID="ID_1990551085" MODIFIED="1565283084014" TEXT="Trigger/Berechnungsfunktion">
+<node COLOR="#338800" CREATED="1565283074170" ID="ID_1990551085" MODIFIED="1566407001705" TEXT="Trigger/Berechnungsfunktion">
+<icon BUILTIN="button_ok"/>
+</node>
+<node COLOR="#435e98" CREATED="1565283089529" ID="ID_833580972" MODIFIED="1566407048588" TEXT="ausgel&#xf6;st durch allgemeine Struktur-&#xc4;nderungen">
+<arrowlink COLOR="#8db7cd" DESTINATION="ID_1799554074" ENDARROW="Default" ENDINCLINATION="816;264;" ID="Arrow_ID_1531606207" STARTARROW="None" STARTINCLINATION="629;34;"/>
+<icon BUILTIN="info"/>
+</node>
+<node COLOR="#338800" CREATED="1566407025586" ID="ID_1467953135" MODIFIED="1566407042985" TEXT="sicherstellen, da&#xdf; vorher der DisplayEvaluationPass gelaufen ist">
+<icon BUILTIN="button_ok"/>
+</node>
+<node COLOR="#338800" CREATED="1566407006341" ID="ID_375041651" MODIFIED="1566407015727" TEXT="H&#xf6;he vom TrackBody beziehen">
+<icon BUILTIN="button_ok"/>
+</node>
+<node COLOR="#338800" CREATED="1566407055894" ID="ID_982642970" MODIFIED="1566407059861" TEXT="&#xc4;nderungen erkennen">
+<icon BUILTIN="button_ok"/>
+<node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1566407136811" ID="ID_832049284" MODIFIED="1566407183538" TEXT="ge&#xe4;nderte Gr&#xf6;&#xdf;e wird nicht sichtbar">
+<arrowlink COLOR="#df2014" DESTINATION="ID_1463503563" ENDARROW="Default" ENDINCLINATION="186;-101;" ID="Arrow_ID_29417298" STARTARROW="None" STARTINCLINATION="-60;173;"/>
 <icon BUILTIN="flag-yellow"/>
 </node>
-<node CREATED="1565283089529" ID="ID_833580972" MODIFIED="1565283189044" TEXT="ausgel&#xf6;st durch allgemeine Struktur-&#xc4;nderungen">
-<arrowlink COLOR="#8db7cd" DESTINATION="ID_1799554074" ENDARROW="Default" ENDINCLINATION="816;264;" ID="Arrow_ID_1531606207" STARTARROW="None" STARTINCLINATION="627;37;"/>
 </node>
 </node>
 <node COLOR="#435e98" CREATED="1555084648375" ID="ID_483631091" MODIFIED="1565283046031" TEXT="Thema: Struktur-Profil">
@@ -21444,6 +21460,20 @@
 </node>
 </node>
 </node>
+<node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1566406980688" ID="ID_196847136" MODIFIED="1566406988165" TEXT="Layout-Anpsassungen">
+<icon BUILTIN="flag-yellow"/>
+<node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1566407065037" ID="ID_548414744" MODIFIED="1566407093353" TEXT="Scrollbar anpassen nach Gr&#xf6;&#xdf;en&#xe4;nderung">
+<icon BUILTIN="flag-yellow"/>
+<node BACKGROUND_COLOR="#fdfdcf" COLOR="#ff0000" CREATED="1566407096905" ID="ID_1463503563" MODIFIED="1566407183538" TEXT="reagiert noch nicht">
+<linktarget COLOR="#df2014" DESTINATION="ID_1463503563" ENDARROW="Default" ENDINCLINATION="186;-101;" ID="Arrow_ID_29417298" SOURCE="ID_832049284" STARTARROW="None" STARTINCLINATION="-60;173;"/>
+<icon BUILTIN="flag-pink"/>
+<node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1566407104280" ID="ID_1989341591" MODIFIED="1566407127648" TEXT="was hab ich seinerzeit beim Gtk-Canvas-Experiment gemacht?">
+<icon BUILTIN="flag-yellow"/>
+<icon BUILTIN="help"/>
+</node>
+</node>
+</node>
+</node>
 <node CREATED="1560618609627" ID="ID_506564995" MODIFIED="1560618618079" TEXT="ben&#xf6;tigt ein Struktur-Profil der Spuren">
 <node CREATED="1565282840443" ID="ID_19246515" MODIFIED="1565283046031" TEXT="was ist dieses Struktur-Profil?">
 <arrowlink COLOR="#1b36ab" DESTINATION="ID_483631091" ENDARROW="Default" ENDINCLINATION="-88;6;" ID="Arrow_ID_1079857163" STARTARROW="None" STARTINCLINATION="-26;-28;"/>
@@ -21672,8 +21702,8 @@
 </node>
 </node>
 <node CREATED="1561151742029" ID="ID_857875045" MODIFIED="1561151755207" TEXT="repr&#xe4;sentiert als Ruler des top-level-Track"/>
-<node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1561151772593" ID="ID_1142063549" MODIFIED="1561151789167" TEXT="aber die Zahl der Pr&#xe4;fix-Elemente mu&#xdf; korrekt eingesetzt werden">
-<icon BUILTIN="flag-yellow"/>
+<node COLOR="#338800" CREATED="1561151772593" ID="ID_1142063549" MODIFIED="1566406715937" TEXT="aber die Zahl der Pr&#xe4;fix-Elemente mu&#xdf; korrekt eingesetzt werden">
+<icon BUILTIN="button_ok"/>
 </node>
 <node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1554995841966" ID="ID_1443277448" MODIFIED="1561151658998" TEXT="genaue Rolle der Session??">
 <linktarget COLOR="#ce7c94" DESTINATION="ID_1443277448" ENDARROW="Default" ENDINCLINATION="509;0;" ID="Arrow_ID_1589685813" SOURCE="ID_725781646" STARTARROW="None" STARTINCLINATION="296;0;"/>
@@ -21683,8 +21713,9 @@
 </node>
 </node>
 </node>
-<node CREATED="1544839288936" ID="ID_43593052" MODIFIED="1563143640658" TEXT="Ruler-Konfigs in das systematische UI-Modell">
+<node CREATED="1544839288936" ID="ID_43593052" MODIFIED="1566406817964" TEXT="Ruler-Konfigs in das systematische UI-Modell">
 <arrowlink COLOR="#5f84b0" DESTINATION="ID_1083901292" ENDARROW="Default" ENDINCLINATION="-746;-75;" ID="Arrow_ID_1167484185" STARTARROW="None" STARTINCLINATION="-981;0;"/>
+<linktarget COLOR="#5287c5" DESTINATION="ID_43593052" ENDARROW="Default" ENDINCLINATION="-197;439;" ID="Arrow_ID_350259030" SOURCE="ID_1516897126" STARTARROW="None" STARTINCLINATION="-244;0;"/>
 <node COLOR="#338800" CREATED="1544849869166" ID="ID_1025477379" MODIFIED="1557498707229" TEXT="Frage: wo ansiedeln?">
 <icon BUILTIN="button_ok"/>
 <node CREATED="1544849875744" ID="ID_27673928" MODIFIED="1557498707229" TEXT="im TrackPresenter">
@@ -21725,6 +21756,24 @@
 </node>
 </node>
 </node>
+<node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1566406728259" ID="ID_763463375" MODIFIED="1566406748449" TEXT="konkrete Ausgestaltung">
+<icon BUILTIN="flag-yellow"/>
+<node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1563143002107" ID="ID_1177786099" MODIFIED="1566406652163" TEXT="verschiedene Ruler-Arten">
+<linktarget COLOR="#c178a8" DESTINATION="ID_1177786099" ENDARROW="Default" ENDINCLINATION="-1830;0;" ID="Arrow_ID_829837415" SOURCE="ID_104997878" STARTARROW="None" STARTINCLINATION="576;-53;"/>
+<linktarget COLOR="#622e7d" DESTINATION="ID_1177786099" ENDARROW="Default" ENDINCLINATION="556;0;" ID="Arrow_ID_1339566753" SOURCE="ID_1063302647" STARTARROW="Default" STARTINCLINATION="556;0;"/>
+<icon BUILTIN="hourglass"/>
+</node>
+<node CREATED="1566406750272" ID="ID_1606625965" MODIFIED="1566406839560" TEXT="Steuerung der konkreten H&#xf6;he (gem&#xe4;&#xdf; Inhalt)">
+<icon BUILTIN="hourglass"/>
+<node BACKGROUND_COLOR="#fdfdcf" COLOR="#ff0000" CREATED="1566406763774" ID="ID_764785834" MODIFIED="1566406772229" TEXT="verwende bisher Platzhalter-Konstanten">
+<icon BUILTIN="flag-pink"/>
+</node>
+<node CREATED="1566406773325" ID="ID_1516897126" MODIFIED="1566406830389" TEXT="soll einmal aus dem systematischen UI-Modell bzw Session-Modell kommen">
+<arrowlink COLOR="#5287c5" DESTINATION="ID_43593052" ENDARROW="Default" ENDINCLINATION="-197;439;" ID="Arrow_ID_350259030" STARTARROW="None" STARTINCLINATION="-244;0;"/>
+<icon BUILTIN="bell"/>
+</node>
+</node>
+</node>
 </node>
 </node>
 <node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1541814972977" HGAP="8" ID="ID_1482433902" MODIFIED="1557498707230" TEXT="offen..." VSHIFT="5">
@@ -22616,7 +22665,8 @@
 </node>
 </node>
 </node>
-<node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1563143002107" ID="ID_1177786099" MODIFIED="1563143014910" TEXT="verschiedene Ruler-Arten">
+<node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1563143002107" ID="ID_1063302647" MODIFIED="1566406652162" TEXT="verschiedene Ruler-Arten">
+<arrowlink COLOR="#622e7d" DESTINATION="ID_1177786099" ENDARROW="Default" ENDINCLINATION="556;0;" ID="Arrow_ID_1339566753" STARTARROW="Default" STARTINCLINATION="556;0;"/>
 <icon BUILTIN="hourglass"/>
 </node>
 </node>
@@ -22694,8 +22744,8 @@
 <node CREATED="1566401468573" ID="ID_636590903" MODIFIED="1566401510213" TEXT="Beschlu&#xdf;: direkt nach dem Display-Evaluation-Pass">
 <icon BUILTIN="yes"/>
 <node CREATED="1566401506391" ID="ID_116486175" MODIFIED="1566401506391" TEXT="BodyCanvasWidget::maybeRebuildLayout()"/>
-<node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1566401515511" ID="ID_1551253495" MODIFIED="1566401521816" TEXT="neue Funktion hierf&#xfc;r">
-<icon BUILTIN="flag-yellow"/>
+<node COLOR="#338800" CREATED="1566401515511" ID="ID_1551253495" MODIFIED="1566406332332" TEXT="neue Funktion hierf&#xfc;r">
+<icon BUILTIN="button_ok"/>
 </node>
 </node>
 </node>