For #14974 - Ensure website bottom elements stay at bottom

engineView.setDynamicToolbarMaxHeight(0) vs
engineView.setDynamicToolbarMaxHeight(toolbarHeight)
ensures webpage's bottom elements are aligned to the bottom of the browser.

We also need to make sure that when the toolbar is static it does not cover the
bottom of the page - something desired when the toolbar was dynamic.
For this the engineView will have a toolbarHeight bottom margin.

app/src/main/java/org/mozilla/fenix/browser/BaseBrowserFragment.kt

@@ -770,20 +770,35 @@ abstract class BaseBrowserFragment : Fragment(), UserInteractionHandler, Session
     }
 
     private fun initializeEngineView(toolbarHeight: Int) {
-        engineView.setDynamicToolbarMaxHeight(toolbarHeight)
-
         val context = requireContext()
-        val behavior = when (context.settings().toolbarPosition) {
-            ToolbarPosition.BOTTOM -> EngineViewBottomBehavior(context, null)
-            ToolbarPosition.TOP -> SwipeRefreshScrollingViewBehavior(
-                context,
-                null,
-                engineView,
-                browserToolbarView
-            )
-        }
 
-        (swipeRefresh.layoutParams as CoordinatorLayout.LayoutParams).behavior = behavior
+        if (context.settings().isDynamicToolbarEnabled) {
+            engineView.setDynamicToolbarMaxHeight(toolbarHeight)
+
+            val behavior = when (context.settings().toolbarPosition) {
+                // Set engineView dynamic vertical clipping depending on the toolbar position.
+                ToolbarPosition.BOTTOM -> EngineViewBottomBehavior(context, null)
+                // Set scroll flags depending on if if the browser or the website is doing the scroll.
+                ToolbarPosition.TOP -> SwipeRefreshScrollingViewBehavior(
+                    context,
+                    null,
+                    engineView,
+                    browserToolbarView
+                )
+            }
+
+            (swipeRefresh.layoutParams as CoordinatorLayout.LayoutParams).behavior = behavior
+        } else {
+            // Ensure webpage's bottom elements are aligned to the very bottom of the engineView.
+            engineView.setDynamicToolbarMaxHeight(0)
+
+            // Effectively place the engineView on top of the toolbar if that is not dynamic.
+            if (context.settings().shouldUseBottomToolbar) {
+                val browserEngine = swipeRefresh.layoutParams as CoordinatorLayout.LayoutParams
+                browserEngine.bottomMargin =
+                    requireContext().resources.getDimensionPixelSize(R.dimen.browser_toolbar_height)
+            }
+        }
     }
 
     /**
@@ -1097,7 +1112,7 @@ abstract class BaseBrowserFragment : Fragment(), UserInteractionHandler, Session
             if (webAppToolbarShouldBeVisible) {
                 browserToolbarView.view.isVisible = true
                 val toolbarHeight = resources.getDimensionPixelSize(R.dimen.browser_toolbar_height)
-                engineView.setDynamicToolbarMaxHeight(toolbarHeight)
+                initializeEngineView(toolbarHeight)
             }
         }
     }

app/src/main/java/org/mozilla/fenix/components/toolbar/BrowserToolbarController.kt

@@ -22,6 +22,7 @@ import org.mozilla.fenix.components.metrics.MetricController
 import org.mozilla.fenix.ext.components
 import org.mozilla.fenix.ext.nav
 import org.mozilla.fenix.ext.sessionsOfType
+import org.mozilla.fenix.ext.settings
 
 /**
  * An interface that handles the view manipulation of the BrowserToolbar, triggered by the Interactor
@@ -156,7 +157,9 @@ class DefaultBrowserToolbarController(
     }
 
     override fun handleScroll(offset: Int) {
-        engineView.setVerticalClipping(offset)
+        if (activity.settings().isDynamicToolbarEnabled) {
+            engineView.setVerticalClipping(offset)
+        }
     }
 
     companion object {

app/src/test/java/org/mozilla/fenix/components/toolbar/DefaultBrowserToolbarControllerTest.kt

@@ -37,6 +37,7 @@ import org.mozilla.fenix.browser.readermode.ReaderModeController
 import org.mozilla.fenix.components.metrics.Event
 import org.mozilla.fenix.components.metrics.MetricController
 import org.mozilla.fenix.ext.components
+import org.mozilla.fenix.ext.settings
 import org.mozilla.fenix.helpers.FenixRobolectricTestRunner
 
 @RunWith(FenixRobolectricTestRunner::class)
@@ -241,12 +242,23 @@ class DefaultBrowserToolbarControllerTest {
     }
 
     @Test
-    fun handleScroll() {
+    fun `handleScroll for dynamic toolbars`() {
         val controller = createController()
+        every { activity.settings().isDynamicToolbarEnabled } returns true
+
         controller.handleScroll(10)
         verify { engineView.setVerticalClipping(10) }
     }
 
+    @Test
+    fun `handleScroll for static toolbars`() {
+        val controller = createController()
+        every { activity.settings().isDynamicToolbarEnabled } returns false
+
+        controller.handleScroll(10)
+        verify(exactly = 0) { engineView.setVerticalClipping(10) }
+    }
+
     private fun createController(
         activity: HomeActivity = this.activity,
         customTabSession: Session? = null,