Docking: Fixed IsItemHovered() and functions depending on it (e.g. BeginPopupContextItem()) when called after Begin() on a docked window (#3851)

Fix ee643b2a

docs/CHANGELOG.txt

@@ -154,6 +154,8 @@ Docking+Viewports Branch:
   docking hierarchy. Added ImGuiHoveredFlags_DockHierarchy flag to consider docking hierarchy in the test.
 - Nav: Fixed an issue with losing focus on docked windows when pressing Alt while keyboard navigation
   is disabled. (#4547, #4439) [@PathogenDavid]
+- Docking: Fixed IsItemHovered() and functions depending on it (e.g. BeginPopupContextItem()) when
+  called after Begin() on a docked window (broken 2021/03/04). (#3851)
 - Docking: Improved resizing system so that non-central zone are better at keeping their fixed size.
   The algorithm is still not handling the repartition of size idealy for nested sibling, but it got better.
 - Docking: Fixed settings load issue when mouse wheeling. (#4310)

imgui_widgets.cpp

@@ -8158,6 +8158,11 @@ bool    ImGui::TabItemEx(ImGuiTabBar* tab_bar, const char* label, bool* p_open,
         TabBarCloseTab(tab_bar, tab);
     }
 
+    // Forward Hovered state so IsItemHovered() after Begin() can work (even though we are technically hovering our parent)
+    // That state is copied to window->DockTabItemStatusFlags by our caller.
+    if (docked_window && (hovered || g.HoveredId == close_button_id))
+        g.LastItemData.StatusFlags |= ImGuiItemStatusFlags_HoveredWindow;
+
     // Restore main window position so user can draw there
     if (want_clip_rect)
         PopClipRect();