Added ImGuiDockNodeFlags_AutoHideTabBar. (#2109)

imgui.cpp

@@ -10743,7 +10743,7 @@ ImGuiDockNode::ImGuiDockNode(ImGuiID id)
     InitFromFirstWindowPosSize = InitFromFirstWindowViewport = false;
     IsVisible = true;
     IsFocused = IsCentralNode = IsHiddenTabBar = HasCloseButton = HasCollapseButton = false;
-    WantCloseAll = WantLockSizeOnce = WantMouseMove = WantHiddenTabBarToggle = false;
+    WantCloseAll = WantLockSizeOnce = WantMouseMove = WantHiddenTabBarUpdate = WantHiddenTabBarToggle = false;
 }
 
 ImGuiDockNode::~ImGuiDockNode()
@@ -10774,6 +10774,7 @@ static void ImGui::DockNodeAddWindow(ImGuiDockNode* node, ImGuiWindow* window, b
     IM_ASSERT(window->DockNode == NULL || window->DockNodeAsHost == NULL);
 
     node->Windows.push_back(window);
+    node->WantHiddenTabBarUpdate = true;
     window->DockNode = node;
     window->DockId = node->ID;
     window->DockIsActive = (node->Windows.Size > 1);
@@ -10841,6 +10842,7 @@ static void ImGui::DockNodeRemoveWindow(ImGuiDockNode* node, ImGuiWindow* window
         node->VisibleWindow = NULL;
 
     // Remove tab and possibly tab bar
+    node->WantHiddenTabBarUpdate = true;
     if (node->TabBar)
     {
         TabBarRemoveTab(node->TabBar, window->ID);
@@ -11033,6 +11035,11 @@ static void ImGui::DockNodeUpdateVisibleFlagAndInactiveChilds(ImGuiDockNode* nod
         window_n--;
     }
 
+    // Auto-hide tab bar option
+    if (node->WantHiddenTabBarUpdate && node->Windows.Size == 1 && (node->Flags & ImGuiDockNodeFlags_AutoHideTabBar) && !node->IsHiddenTabBar)
+        node->WantHiddenTabBarToggle = true;
+    node->WantHiddenTabBarUpdate = false;
+
     // Apply toggles at a single point of the frame (here!)
     if (node->Windows.Size > 1)
         node->IsHiddenTabBar = false;
@@ -12863,7 +12870,7 @@ void ImGui::BeginAsDockableDragDropTarget(ImGuiWindow* window)
         else
             allow_null_target_node = true; // Dock into a regular window
 
-        const ImRect explicit_target_rect = (target_node && target_node->TabBar) ? target_node->TabBar->BarRect : ImRect(window->Pos, window->Pos + ImVec2(window->Size.x, GetFrameHeight()));
+        const ImRect explicit_target_rect = (target_node && target_node->TabBar && !target_node->IsHiddenTabBar) ? target_node->TabBar->BarRect : ImRect(window->Pos, window->Pos + ImVec2(window->Size.x, GetFrameHeight()));
         const bool is_explicit_target = g.IO.ConfigDockingWithShift || IsMouseHoveringRect(explicit_target_rect.Min, explicit_target_rect.Max);
 
         // Preview docking request and find out split direction/ratio

imgui.h

@@ -879,7 +879,8 @@ enum ImGuiDockNodeFlags_
     ImGuiDockNodeFlags_NoDockingInCentralNode       = 1 << 3,   // Disable docking inside the Central Node, which will be always kept empty.
     //ImGuiDockNodeFlags_NoLayoutChanges            = 1 << 4,   // Disable adding/removing nodes interactively. Useful with programatically setup dockspaces.
     ImGuiDockNodeFlags_NoResize                     = 1 << 5,   // Disable resizing child nodes using the splitter/separators. Useful with programatically setup dockspaces. 
-    ImGuiDockNodeFlags_PassthruDockspace            = 1 << 6    // 1) DockSpace() will render a ImGuiCol_WindowBg background covering everything excepted the Central Node when empty. Meaning the host window should probably use SetNextWindowBgAlpha(0.0f) prior to Begin() when using this. 2) When Central Node is empty: let inputs pass-through + won't display a DockingEmptyBg background.
+    ImGuiDockNodeFlags_PassthruDockspace            = 1 << 6,   // Enable passthru dockspace: 1) DockSpace() will render a ImGuiCol_WindowBg background covering everything excepted the Central Node when empty. Meaning the host window should probably use SetNextWindowBgAlpha(0.0f) prior to Begin() when using this. 2) When Central Node is empty: let inputs pass-through + won't display a DockingEmptyBg background.
+    ImGuiDockNodeFlags_AutoHideTabBar               = 1 << 7    // Tab bar will automatically hide when there is a single window in the dock node.
 };
 
 // Flags for ImGui::IsWindowFocused()
@@ -1373,7 +1374,7 @@ struct ImGuiIO
     bool        ConfigDockingNoSplit;           // = false          // Simplified docking mode: disable window splitting, so docking is limited to merging multiple windows together into tab-bars.
     bool        ConfigDockingWithShift;         // = false          // Enable docking with holding Shift key (reduce visual noise, allows dropping in wider space)
     bool        ConfigDockingTabBarOnSingleWindows; // = false      // [BETA] Make every single floating window display within a docking node.
-    bool        ConfigDockingTransparentPayload;// = false          // [BETA] Make window or viewport transparent when docking and only display docking boxes on the target viewport. Useful if rendering of multiple viewport can be synced. Best used with ImGuiConfigFlags_ViewportsNoMerge.
+    bool        ConfigDockingTransparentPayload;// = false          // [BETA] Make window or viewport transparent when docking and only display docking boxes on the target viewport. Useful if rendering of multiple viewport cannot be synced. Best used with ConfigViewportsNoAutoMerge.
     
     // Viewport options (when ImGuiConfigFlags_ViewportsEnable is set)
     bool        ConfigViewportsNoAutoMerge;     // = false;         // Set to make all floating imgui windows always create their own viewport. Otherwise, they are merged into the main host viewports when overlapping it.

imgui_demo.cpp

@@ -4100,6 +4100,7 @@ void ShowExampleAppDockSpace(bool* p_open)
             if (ImGui::MenuItem("Flag: NoDockingInCentralNode", "", (opt_flags & ImGuiDockNodeFlags_NoDockingInCentralNode) != 0))  opt_flags ^= ImGuiDockNodeFlags_NoDockingInCentralNode;
             if (ImGui::MenuItem("Flag: NoResize",               "", (opt_flags & ImGuiDockNodeFlags_NoResize) != 0))                opt_flags ^= ImGuiDockNodeFlags_NoResize;
             if (ImGui::MenuItem("Flag: PassthruDockspace",      "", (opt_flags & ImGuiDockNodeFlags_PassthruDockspace) != 0))       opt_flags ^= ImGuiDockNodeFlags_PassthruDockspace;
+            if (ImGui::MenuItem("Flag: AutoHideTabBar",         "", (opt_flags & ImGuiDockNodeFlags_AutoHideTabBar) != 0))          opt_flags ^= ImGuiDockNodeFlags_AutoHideTabBar;
             ImGui::Separator();
             if (ImGui::MenuItem("Close DockSpace", NULL, false, p_open != NULL))
                 *p_open = false;

imgui_internal.h

@@ -854,6 +854,7 @@ struct ImGuiDockNode
     bool                    WantCloseAll            :1; // Set when closing all tabs at once.
     bool                    WantLockSizeOnce        :1;
     bool                    WantMouseMove           :1; // After a node extraction we need to transition toward moving the newly created host window
+    bool                    WantHiddenTabBarUpdate  :1;
     bool                    WantHiddenTabBarToggle  :1;
 
     ImGuiDockNode(ImGuiID id);