Reset tabsheet scroller when unhiding leftmost tab (#14644)

Checking whether invisible tab are present before the scroll index and
if so resetting the scroll index when tab goes back to visible.

Change-Id: I156dbe93963b0d9f46e21a593ffc3c4c77ebd1c6

3 files changed, 96 insertions, 2 deletions

diff --git a/client/src/com/vaadin/client/ui/VTabsheet.java b/client/src/com/vaadin/client/ui/VTabsheet.java
index 745f2bca61..d5cbc5eb14 100644
--- a/client/src/com/vaadin/client/ui/VTabsheet.java
+++ b/client/src/com/vaadin/client/ui/VTabsheet.java
@@ -78,6 +78,8 @@ import com.vaadin.shared.ui.tabsheet.TabsheetState;
 
 public class VTabsheet extends VTabsheetBase implements Focusable, SubPartAware {
 
+    private static final String PREV_SCROLLER_DISABLED_CLASSNAME = "Prev-disabled";
+
     private static class VCloseEvent {
         private Tab tab;
 
@@ -1016,6 +1018,22 @@ public class VTabsheet extends VTabsheetBase implements Focusable, SubPartAware
         updateOpenTabSize();
     }
 
+    private boolean isAllTabsBeforeIndexInvisible() {
+        boolean invisible = true;
+        for (int i = 0; i < scrollerIndex; i++) {
+            invisible = invisible & !tb.getTab(i).isVisible();
+        }
+        return invisible;
+    }
+
+    private boolean isScrollerPrevDisabled() {
+        return scrollerPrev.getClassName().contains(PREV_SCROLLER_DISABLED_CLASSNAME);
+    }
+
+    private boolean isIndexSkippingHiddenTabs() {
+        return isAllTabsBeforeIndexInvisible() && isScrollerPrevDisabled();
+    }
+
     @Override
     public void renderTab(final TabState tabState, int index) {
         Tab tab = tb.getTab(index);
@@ -1027,10 +1045,15 @@ public class VTabsheet extends VTabsheetBase implements Focusable, SubPartAware
         tab.setEnabledOnServer((!disabledTabKeys.contains(tabKeys.get(index))));
         tab.setHiddenOnServer(!tabState.visible);
 
-        if (scrolledOutOfView(index)) {
+        if (scrolledOutOfView(index) && !isIndexSkippingHiddenTabs()) {
             // Should not set tabs visible if they are scrolled out of view
             tab.setVisible(false);
         } else {
+            //reset the scroller index back to zero if tab is visible
+            //again and tab is in view
+            if(isIndexSkippingHiddenTabs() && tabState.visible) {
+                scrollerIndex = 0;
+            }
             tab.setVisible(tabState.visible);
         }
 
@@ -1170,7 +1193,7 @@ public class VTabsheet extends VTabsheetBase implements Focusable, SubPartAware
         if (tb.getTabCount() > 0 && tb.isVisible() && (scrolled || clipped)) {
             scroller.getStyle().clearDisplay();
             DOM.setElementProperty(scrollerPrev, "className",
-                    SCROLLER_CLASSNAME + (scrolled ? "Prev" : "Prev-disabled"));
+                    SCROLLER_CLASSNAME + (scrolled ? "Prev" : PREV_SCROLLER_DISABLED_CLASSNAME));
             DOM.setElementProperty(scrollerNext, "className",
                     SCROLLER_CLASSNAME + (clipped ? "Next" : "Next-disabled"));
 
diff --git a/uitest/src/com/vaadin/tests/components/tabsheet/FirstTabNotVisibleInTabsheet.java b/uitest/src/com/vaadin/tests/components/tabsheet/FirstTabNotVisibleInTabsheet.java
new file mode 100644
index 0000000000..c21c702bd0
--- /dev/null
+++ b/uitest/src/com/vaadin/tests/components/tabsheet/FirstTabNotVisibleInTabsheet.java
@@ -0,0 +1,44 @@
+package com.vaadin.tests.components.tabsheet;
+
+import com.vaadin.annotations.VaadinServletConfiguration;
+import com.vaadin.server.VaadinRequest;
+import com.vaadin.server.VaadinServlet;
+import com.vaadin.tests.components.AbstractTestUI;
+import com.vaadin.ui.*;
+
+import javax.servlet.annotation.WebServlet;
+
+@SuppressWarnings("serial")
+public class FirstTabNotVisibleInTabsheet extends AbstractTestUI {
+
+    private TabSheet.Tab firstTab;
+
+    @Override
+    protected void setup(VaadinRequest request) {
+        TabSheet tabSheet = new TabSheet();
+        tabSheet.setWidth("600px");
+
+        firstTab = tabSheet.addTab(new Label("first visible tab"), "first visible tab");
+
+        for (int i = 2; i < 10; i++) {
+            tabSheet.addTab(new Label("visible tab " + i), "visible tab " + i);
+        }
+
+        addComponent(new VerticalLayout(tabSheet, new Button("Toggle first tab", new Button.ClickListener() {
+            @Override
+            public void buttonClick(Button.ClickEvent event) {
+                firstTab.setVisible(!firstTab.isVisible());
+            }
+        })));
+    }
+
+    @Override
+    protected Integer getTicketNumber() {
+        return 14644;
+    }
+
+    @Override
+    protected String getTestDescription() {
+        return "First tabsheet tab is not set visible back once it gets invisible";
+    }
+}
\ No newline at end of file
diff --git a/uitest/src/com/vaadin/tests/components/tabsheet/FirstTabNotVisibleInTabsheetTest.java b/uitest/src/com/vaadin/tests/components/tabsheet/FirstTabNotVisibleInTabsheetTest.java
new file mode 100644
index 0000000000..e57651ba03
--- /dev/null
+++ b/uitest/src/com/vaadin/tests/components/tabsheet/FirstTabNotVisibleInTabsheetTest.java
@@ -0,0 +1,27 @@
+package com.vaadin.tests.components.tabsheet;
+
+
+import com.vaadin.testbench.elements.ButtonElement;
+import com.vaadin.testbench.elements.TabSheetElement;
+import com.vaadin.tests.tb3.MultiBrowserTest;
+import junit.framework.Assert;
+import org.junit.Test;
+
+public class FirstTabNotVisibleInTabsheetTest extends MultiBrowserTest {
+    @Test
+    public void testFirstTabIsVisibleAfterBeingInvisible() {
+        openTestURL();
+
+        toggleFirstTabVisibility();
+        toggleFirstTabVisibility();
+
+        TabSheetElement tabSheet = $(TabSheetElement.class).first();
+
+        Assert.assertTrue("TabSheet should have first tab visible",
+                tabSheet.getTabCaptions().contains("first visible tab"));
+    }
+
+    private void toggleFirstTabVisibility() {
+        $(ButtonElement.class).caption("Toggle first tab").first().click();
+    }
+}