improvements for margins/paddings

--fix also how firstVisibleIndex is tracked for
AppletContainer(s)

containment/package/contents/ui/applet/AppletItem.qml

@@ -88,6 +88,10 @@ Item {
     property bool lastChildOfEndLayout: index === layoutsContainer.endLayout.lastVisibleIndex
 
     readonly property bool atScreenEdge: {
+        if (plasmoid.configuration.maxLength!==100 || plasmoid.configuration.offset!==0) {
+            return false;
+        }
+
         if (root.isHorizontal) {
             if (firstChildOfStartLayout) {
                 return latteView && latteView.x === latteView.screenGeometry.x;
@@ -153,7 +157,7 @@ Item {
           is taking all the space needed in order to fill right. For atScreenEdge appplets that should be: applet size + lengthAppletIntMargin + lengthAppletExtMargin.
           The indicator should follow also the applet alignment in this in order to feel right
           */
-        return atScreenEdge ? lengthAppletIntMargin / 2 /*Fitt's*/ : 2 * lengthAppletIntMargin;
+        return 2 * lengthAppletIntMargin;
     }
 
     property int internalHeightMargins: {
@@ -165,7 +169,7 @@ Item {
           is taking all the space needed in order to fill right. For atScreenEdge appplets that should be: applet size + lengthAppletIntMargin + lengthAppletExtMargin.
           The indicator should follow also the applet alignment in this in order to feel right
           */
-        return atScreenEdge ? lengthAppletIntMargin / 2 /*Fitt's*/ : 2 * lengthAppletIntMargin;
+        return 2 * lengthAppletIntMargin;
     }
 
     //! are set by the indicator

containment/package/contents/ui/applet/HiddenSpacer.qml

@@ -47,7 +47,7 @@ Item{
 
     readonly property bool atEdgeForcingFittsLaw: !isSeparator && !parabolicEffectMarginsEnabled && atScreenEdge
     readonly property int subtrackedMargins: atEdgeForcingFittsLaw && ((firstAppletInContainer && rightSpacer) || (lastAppletInContainer && !rightSpacer )) ?
-                                                 root.lengthExtMargin : 0
+                                                 root.lengthExtMargin + root.lengthIntMargin : 0
 
     property real nScale: 0
 

containment/package/contents/ui/layouts/AppletsContainer.qml

@@ -104,7 +104,7 @@ Grid {
             }
 
             var ind = -1;
-            for (var i=0; i>=children[i].length-1; ++i){
+            for (var i=0; i<=children.length-1; ++i){
                 if (children[i]
                         && (children[i].index<ind || ind === -1)
                         && children[i].applet