Fix application switching (window stack)

This fixes use cases like this:
- launch i18n demo
- back
- launch radio
- click on the app switcher on the top right
- click on the i18n demo thumbnail

expected outcome:
you get i18n demo on foreground

buggy outcome (ie, without this fix):
you get radio again

Change-Id: I9610da4649b7e0ee61791f69f8d92353b2162c07
Reviewed-by: Nedim Hadzic <nedim.hadzic@pelagicore.com>
Reviewed-by: Bramastyo Harimukti Santoso <bramastyo.harimukti.santoso@pelagicore.com>

2 files changed, 25 insertions, 8 deletions

diff --git a/sysui/display/Display.qml b/sysui/display/Display.qml
index 2448760..861bc7c 100644
--- a/sysui/display/Display.qml
+++ b/sysui/display/Display.qml
@@ -73,7 +73,7 @@ Item {
         onLoaded: {
             homePage.anchors.topMargin = 0
             menuScreenLoader.item.homePage = homePage
-            launcherControllerLoader.item.stackView.push(menuScreenLoader.item)
+            launcherControllerLoader.item.homePage = menuScreenLoader.item
             StagedStartupModel.enterFinalState()
         }
     }
diff --git a/sysui/display/LaunchController.qml b/sysui/display/LaunchController.qml
index 9f048cc..10a9424 100644
--- a/sysui/display/LaunchController.qml
+++ b/sysui/display/LaunchController.qml
@@ -38,12 +38,20 @@ import utils 1.0
 import models.application 1.0
 import models.system 1.0
 
+/*
+   A window stack with the home page at the bottom and at most an application window on top of it
+*/
 Item {
     id: root
     width: Style.screenWidth
     height: Style.vspan(20)
 
-    property alias stackView: stackView
+    property Item homePage
+    onHomePageChanged: {
+        if (homePage) {
+            stackView.push(homePage);
+        }
+    }
 
     StackView {
         id: stackView
@@ -113,6 +121,9 @@ Item {
             }
         }
 
+        replaceEnter: popEnter
+        replaceExit: popExit
+
         Item {
             id: dummyitem
             anchors.fill: parent
@@ -129,21 +140,27 @@ Item {
             target: ApplicationManagerModel
 
             onApplicationSurfaceReady: {
-                //Make sure to push the items only once
-                for (var i = 1; i < stackView.depth; ++i) {
-                    if (stackView.get(i) === item)
-                        return
+                if (stackView.currentItem === item) {
+                    // NOOP
+                    return;
                 }
 
                 if (isMinimized) {
                     item.parent = dummyitem
                 } else {
-                    stackView.push(item, {"width": Style.hspan(24), "height": Style.vspan(24)})
+                    var parameters = {"width": Style.hspan(24), "height": Style.vspan(24)};
+                    if (stackView.depth === 1) {
+                        stackView.push(item, parameters)
+                    } else if (stackView.depth > 1) {
+                        stackView.replace(item, parameters)
+                    }
                 }
             }
 
             onReleaseApplicationSurface: {
-                stackView.pop()
+                if (stackView.currentItem === item) {
+                    stackView.pop()
+                }
             }
 
             onUnhandledSurfaceReceived: {