Docking: added comments. added experimental TabItemFlagsOverrideSet to ImGuiWindowClass.

(Could probably do something similar with TabBarFlagsOverrideSet+Clear for #2700 later.)

imgui.cpp

@@ -11930,6 +11930,50 @@ void ImGui::DestroyPlatformWindows()
 // Docking: Settings
 //-----------------------------------------------------------------------------
 
+//-----------------------------------------------------------------------------
+// Typical Docking call flow: (root level is generally public API):
+//-----------------------------------------------------------------------------
+// - NewFrame()                               new dear imgui frame
+//    | DockContextUpdateUndocking()          - process queued undocking requests
+//    | - DockContextProcessUndockWindow()    - process one window undocking request
+//    | - DockContextProcessUndockNode()      - process one whole node undocking request
+//    | DockContextUpdateDocking()            - process queue docking requests, create floating dock nodes
+//    | - update g.HoveredDockNode            - [debug] update node hovered by mouse
+//    | - DockContextProcessDock()            - process one docking request
+//    | - DockNodeUpdate()
+//    |   - DockNodeUpdateForRootNode()
+//    |     - DockNodeUpdateVisibleFlagAndInactiveChilds()
+//    |     - DockNodeFindInfo()
+//    |   - destroy unused node or tab bar
+//    |   - create dock node host window
+//    |      - Begin() etc.
+//    |   - DockNodeStartMouseMovingWindow()
+//    |   - DockNodeTreeUpdatePosSize()
+//    |   - DockNodeTreeUpdateSplitter()
+//    |   - draw node background
+//    |   - DockNodeUpdateTabBar()            - create/update tab bar for a docking node
+//    |     - DockNodeAddTabBar()
+//    |     - DockNodeUpdateWindowMenu()
+//    |     - DockNodeCalcTabBarLayout()
+//    |     - BeginTabBarEx()
+//    |     - TabItemEx() calls
+//    |     - EndTabBar()
+//    |   - BeginDockableDragDropTarget()
+//    |      - DockNodeUpdate()               - recurse into child nodes...
+//-----------------------------------------------------------------------------
+// - DockSpace()                              user submit a dockspace into a window
+//    | Begin(Child)                          - create a child window
+//    | DockNodeUpdate()                      - call main dock node update function
+//    | End(Child)
+//    | ItemSize()
+//-----------------------------------------------------------------------------
+// - Begin()
+//    | BeginDocked()
+//    | BeginDockableDragDropSource()
+//    | BeginDockableDragDropTarget()
+//    | - DockNodePreviewDockRender()
+//-----------------------------------------------------------------------------
+
 //-----------------------------------------------------------------------------
 // Docking: Internal Types
 //-----------------------------------------------------------------------------
@@ -12191,7 +12235,9 @@ void ImGui::DockContextUpdateDocking(ImGuiContext* ctx)
     if (!(g.IO.ConfigFlags & ImGuiConfigFlags_DockingEnable))
         return;
 
-    // Store hovered dock node. We could in theory use DockNodeTreeFindVisibleNodeByPos() on the root host dock node, but using ->DockNode is a good shortcut.
+    // [DEBUG] Store hovered dock node.
+    // We could in theory use DockNodeTreeFindVisibleNodeByPos() on the root host dock node, but using ->DockNode is a good shortcut.
+    // Note this is mostly a debug thing and isn't actually used for docking target, because docking involve more detailed filtering.
     g.HoveredDockNode = NULL;
     if (ImGuiWindow* hovered_window = g.HoveredWindowUnderMovingWindow)
     {
@@ -13582,6 +13628,7 @@ static void ImGui::DockNodeUpdateTabBar(ImGuiDockNode* node, ImGuiWindow* host_w
         if (window->LastFrameActive + 1 >= g.FrameCount || !node_was_active)
         {
             ImGuiTabItemFlags tab_item_flags = 0;
+            tab_item_flags |= window->WindowClass.TabItemFlagsOverrideSet;
             if (window->Flags & ImGuiWindowFlags_UnsavedDocument)
                 tab_item_flags |= ImGuiTabItemFlags_UnsavedDocument;
             if (tab_bar->Flags & ImGuiTabBarFlags_NoCloseWithMiddleMouseButton)

imgui.h

@@ -1995,12 +1995,13 @@ struct ImGuiWindowClass
     ImGuiID             ParentViewportId;           // Hint for the platform backend. If non-zero, the platform backend can create a parent<>child relationship between the platform windows. Not conforming backends are free to e.g. parent every viewport to the main viewport or not.
     ImGuiViewportFlags  ViewportFlagsOverrideSet;   // Viewport flags to set when a window of this class owns a viewport. This allows you to enforce OS decoration or task bar icon, override the defaults on a per-window basis.
     ImGuiViewportFlags  ViewportFlagsOverrideClear; // Viewport flags to clear when a window of this class owns a viewport. This allows you to enforce OS decoration or task bar icon, override the defaults on a per-window basis.
+    ImGuiTabItemFlags   TabItemFlagsOverrideSet;    // [EXPERIMENTAL] TabItem flags to set when a window of this class gets submitted into a dock node tab bar. May use with ImGuiTabItemFlags_Leading or ImGuiTabItemFlags_Trailing.
     ImGuiDockNodeFlags  DockNodeFlagsOverrideSet;   // [EXPERIMENTAL] Dock node flags to set when a window of this class is hosted by a dock node (it doesn't have to be selected!)
     ImGuiDockNodeFlags  DockNodeFlagsOverrideClear; // [EXPERIMENTAL]
     bool                DockingAlwaysTabBar;        // Set to true to enforce single floating windows of this class always having their own docking node (equivalent of setting the global io.ConfigDockingAlwaysTabBar)
     bool                DockingAllowUnclassed;      // Set to true to allow windows of this class to be docked/merged with an unclassed window. // FIXME-DOCK: Move to DockNodeFlags override?
 
-    ImGuiWindowClass() { ClassId = 0; ParentViewportId = 0; ViewportFlagsOverrideSet = ViewportFlagsOverrideClear = 0x00; DockNodeFlagsOverrideSet = DockNodeFlagsOverrideClear = 0x00; DockingAlwaysTabBar = false; DockingAllowUnclassed = true; }
+    ImGuiWindowClass() { memset(this, 0, sizeof(*this)); DockingAllowUnclassed = true; }
 };
 
 // Data payload for Drag and Drop operations: AcceptDragDropPayload(), GetDragDropPayload()

imgui_internal.h

@@ -1253,7 +1253,7 @@ struct ImGuiDockContext
     ImVector<ImGuiDockRequest>      Requests;
     ImVector<ImGuiDockNodeSettings> NodesSettings;
     bool                            WantFullRebuild;
-    ImGuiDockContext()              { WantFullRebuild = false; }
+    ImGuiDockContext()              { memset(this, 0, sizeof(*this)); }
 };
 
 #endif // #ifdef IMGUI_HAS_DOCK