Internals: Docking, Tab Bar: Add DockNodeBeginAmendTabBar() and work toward making hybrid dock node with windows tab bars somehow work (not done).

imgui.cpp

@@ -12510,6 +12510,8 @@ bool ImGui::DockContextCalcDropPosForDocking(ImGuiWindow* target, ImGuiDockNode*
 // - DockNodeStartMouseMovingWindow()
 // - DockNodeUpdate()
 // - DockNodeUpdateWindowMenu()
+// - DockNodeBeginAmendTabBar()
+// - DockNodeEndAmendTabBar()
 // - DockNodeUpdateTabBar()
 // - DockNodeAddTabBar()
 // - DockNodeRemoveTabBar()
@@ -13231,7 +13233,8 @@ static ImGuiID ImGui::DockNodeUpdateWindowMenu(ImGuiDockNode* node, ImGuiTabBar*
             for (int tab_n = 0; tab_n < tab_bar->Tabs.Size; tab_n++)
             {
                 ImGuiTabItem* tab = &tab_bar->Tabs[tab_n];
-                IM_ASSERT(tab->Window != NULL);
+                if (tab->Window == NULL)
+                    continue;
                 if (Selectable(tab->Window->Name, tab->ID == tab_bar->SelectedTabId))
                     ret_tab_id = tab->ID;
                 SameLine();
@@ -13243,6 +13246,26 @@ static ImGuiID ImGui::DockNodeUpdateWindowMenu(ImGuiDockNode* node, ImGuiTabBar*
     return ret_tab_id;
 }
 
+// User helper to append/amend into a dock node tab bar. Most commonly used to add e.g. a "+" button.
+bool ImGui::DockNodeBeginAmendTabBar(ImGuiDockNode* node)
+{
+    if (node->TabBar == NULL || node->HostWindow == NULL)
+        return false;
+    Begin(node->HostWindow->Name);
+    PushOverrideID(node->ID);
+    bool ret = BeginTabBarEx(node->TabBar, node->TabBar->BarRect, node->TabBar->Flags, node);
+    IM_ASSERT(ret);
+    return true;
+}
+
+void ImGui::DockNodeEndAmendTabBar()
+{
+    EndTabBar();
+    PopID();
+    End();
+}
+
+// Submit the tab bar corresponding to a dock node and various housekeeping details.
 static void ImGui::DockNodeUpdateTabBar(ImGuiDockNode* node, ImGuiWindow* host_window)
 {
     ImGuiContext& g = *GImGui;
@@ -13446,7 +13469,14 @@ static void ImGui::DockNodeUpdateTabBar(ImGuiDockNode* node, ImGuiWindow* host_w
     if (g.HoveredId == 0 || g.HoveredId == title_bar_id || g.ActiveId == title_bar_id)
     {
         bool held;
-        ButtonBehavior(title_bar_rect, title_bar_id, NULL, &held);
+        ButtonBehavior(title_bar_rect, title_bar_id, NULL, &held, ImGuiButtonFlags_AllowItemOverlap);
+        if (g.HoveredId == title_bar_id)
+        {
+            // ImGuiButtonFlags_AllowItemOverlap + SetItemAllowOverlap() required for appending into dock node tab bar,
+            // otherwise dragging window will steal HoveredId and amended tabs cannot get them.
+            host_window->DC.LastItemId = title_bar_id;
+            SetItemAllowOverlap();
+        }
         if (held)
         {
             if (IsMouseClicked(0))
@@ -15847,13 +15877,13 @@ void ImGui::ShowMetricsWindow(bool* p_open)
             const char* buf_end = buf + IM_ARRAYSIZE(buf);
             const bool is_active = (tab_bar->PrevFrameVisible >= ImGui::GetFrameCount() - 2);
             p += ImFormatString(p, buf_end - p, "Tab Bar 0x%08X (%d tabs)%s", tab_bar->ID, tab_bar->Tabs.Size, is_active ? "" : " *Inactive*");
-            if (tab_bar->Flags & ImGuiTabBarFlags_DockNode)
+            p += ImFormatString(p, buf_end - p, "  { ");
+            for (int tab_n = 0; tab_n < ImMin(tab_bar->Tabs.Size, 3); tab_n++)
             {
-                p += ImFormatString(p, buf_end - p, "  { ");
-                for (int tab_n = 0; tab_n < ImMin(tab_bar->Tabs.Size, 3); tab_n++)
-                    p += ImFormatString(p, buf_end - p, "%s'%s'", tab_n > 0 ? ", " : "", tab_bar->Tabs[tab_n].Window->Name);
-                p += ImFormatString(p, buf_end - p, (tab_bar->Tabs.Size > 3) ? " ... }" : " } ");
+                ImGuiTabItem* tab = &tab_bar->Tabs[tab_n];
+                p += ImFormatString(p, buf_end - p, "%s'%s'", tab_n > 0 ? ", " : "", (tab->Window || tab->NameOffset != -1) ? tab_bar->GetTabName(tab) : "???");
             }
+            p += ImFormatString(p, buf_end - p, (tab_bar->Tabs.Size > 3) ? " ... }" : " } ");
             if (!is_active) { PushStyleColor(ImGuiCol_Text, GetStyleColorVec4(ImGuiCol_TextDisabled)); }
             bool open = ImGui::TreeNode(tab_bar, "%s", buf);
             if (!is_active) { PopStyleColor(); }
@@ -15872,7 +15902,7 @@ void ImGui::ShowMetricsWindow(bool* p_open)
                     ImGui::PushID(tab);
                     if (ImGui::SmallButton("<")) { TabBarQueueReorder(tab_bar, tab, -1); } ImGui::SameLine(0, 2);
                     if (ImGui::SmallButton(">")) { TabBarQueueReorder(tab_bar, tab, +1); } ImGui::SameLine();
-                    ImGui::Text("%02d%c Tab 0x%08X '%s' Offset: %.1f, Width: %.1f/%.1f", tab_n, (tab->ID == tab_bar->SelectedTabId) ? '*' : ' ', tab->ID, (tab->Window || tab->NameOffset != -1) ? tab_bar->GetTabName(tab) : "", tab->Offset, tab->Width, tab->ContentWidth);
+                    ImGui::Text("%02d%c Tab 0x%08X '%s' Offset: %.1f, Width: %.1f/%.1f", tab_n, (tab->ID == tab_bar->SelectedTabId) ? '*' : ' ', tab->ID, (tab->Window || tab->NameOffset != -1) ? tab_bar->GetTabName(tab) : "???", tab->Offset, tab->Width, tab->ContentWidth);
                     ImGui::PopID();
                 }
                 ImGui::TreePop();

imgui_internal.h

@@ -2170,6 +2170,8 @@ namespace ImGui
     IMGUI_API void          DockContextQueueUndockWindow(ImGuiContext* ctx, ImGuiWindow* window);
     IMGUI_API void          DockContextQueueUndockNode(ImGuiContext* ctx, ImGuiDockNode* node);
     IMGUI_API bool          DockContextCalcDropPosForDocking(ImGuiWindow* target, ImGuiDockNode* target_node, ImGuiWindow* payload, ImGuiDir split_dir, bool split_outer, ImVec2* out_pos);
+    IMGUI_API bool          DockNodeBeginAmendTabBar(ImGuiDockNode* node);
+    IMGUI_API void          DockNodeEndAmendTabBar();
     inline ImGuiDockNode*   DockNodeGetRootNode(ImGuiDockNode* node)    { while (node->ParentNode) node = node->ParentNode; return node; }
     inline int              DockNodeGetDepth(const ImGuiDockNode* node) { int depth = 0; while (node->ParentNode) { node = node->ParentNode; depth++; } return depth; }
     inline ImGuiDockNode*   GetWindowDockNode()                         { ImGuiContext& g = *GImGui; return g.CurrentWindow->DockNode; }

imgui_widgets.cpp

@@ -6824,7 +6824,7 @@ struct ImGuiTabBarSection
 namespace ImGui
 {
     static void             TabBarLayout(ImGuiTabBar* tab_bar);
-    static ImU32            TabBarCalcTabID(ImGuiTabBar* tab_bar, const char* label);
+    static ImU32            TabBarCalcTabID(ImGuiTabBar* tab_bar, const char* label, ImGuiWindow* docked_window);
     static float            TabBarCalcMaxTabWidth();
     static float            TabBarScrollClamp(ImGuiTabBar* tab_bar, float scrolling);
     static void             TabBarScrollToTab(ImGuiTabBar* tab_bar, ImGuiTabItem* tab, ImGuiTabBarSection* sections);
@@ -6918,7 +6918,7 @@ bool    ImGui::BeginTabBarEx(ImGuiTabBar* tab_bar, const ImRect& tab_bar_bb, ImG
 
     // Ensure correct ordering when toggling ImGuiTabBarFlags_Reorderable flag, or when a new tab was added while being not reorderable
     if ((flags & ImGuiTabBarFlags_Reorderable) != (tab_bar->Flags & ImGuiTabBarFlags_Reorderable) || (tab_bar->TabsAddedNew && !(flags & ImGuiTabBarFlags_Reorderable)))
-        if (tab_bar->Tabs.Size > 1 && (flags & ImGuiTabBarFlags_DockNode) == 0)
+        if (tab_bar->Tabs.Size > 1 && (flags & ImGuiTabBarFlags_DockNode) == 0) // FIXME: TabBar with DockNode can now be hybrid
             ImQsort(tab_bar->Tabs.Data, tab_bar->Tabs.Size, sizeof(ImGuiTabItem), TabItemComparerByBeginOrder);
     tab_bar->TabsAddedNew = false;
 
@@ -7177,6 +7177,7 @@ static void ImGui::TabBarLayout(ImGuiTabBar* tab_bar)
         {
             ImGuiTabItem* tab = &tab_bar->Tabs[section_tab_index + tab_n];
             tab->Offset = tab_offset;
+            tab->NameOffset = -1;
             tab_offset += tab->Width + (tab_n < section->TabCount - 1 ? g.Style.ItemInnerSpacing.x : 0.0f);
         }
         tab_bar->WidthAllTabs += ImMax(section->Width + section->Spacing, 0.0f);
@@ -7184,6 +7185,9 @@ static void ImGui::TabBarLayout(ImGuiTabBar* tab_bar)
         section_tab_index += section->TabCount;
     }
 
+    // Clear name buffers
+    tab_bar->TabsNames.Buf.resize(0);
+
     // If we have lost the selected tab, select the next most recently active one
     if (found_selected_tab_id == false)
         tab_bar->SelectedTabId = 0;
@@ -7220,21 +7224,18 @@ static void ImGui::TabBarLayout(ImGuiTabBar* tab_bar)
     tab_bar->ScrollingRectMinX = tab_bar->BarRect.Min.x + sections[0].Width + sections[0].Spacing;
     tab_bar->ScrollingRectMaxX = tab_bar->BarRect.Max.x - sections[2].Width - sections[1].Spacing;
 
-    // Clear name buffers
-    if ((tab_bar->Flags & ImGuiTabBarFlags_DockNode) == 0)
-        tab_bar->TabsNames.Buf.resize(0);
-
     // Actual layout in host window (we don't do it in BeginTabBar() so as not to waste an extra frame)
     ImGuiWindow* window = g.CurrentWindow;
     window->DC.CursorPos = tab_bar->BarRect.Min;
     ItemSize(ImVec2(tab_bar->WidthAllTabsIdeal, tab_bar->BarRect.GetHeight()), tab_bar->FramePadding.y);
 }
 
-// Dockables uses Name/ID in the global namespace. Non-dockable items use the ID stack.
-static ImU32   ImGui::TabBarCalcTabID(ImGuiTabBar* tab_bar, const char* label)
+// Dockable uses Name/ID in the global namespace. Non-dockable items use the ID stack.
+static ImU32   ImGui::TabBarCalcTabID(ImGuiTabBar* tab_bar, const char* label, ImGuiWindow* docked_window)
 {
-    if (tab_bar->Flags & ImGuiTabBarFlags_DockNode)
+    if (docked_window != NULL)
     {
+        IM_ASSERT(tab_bar->Flags & ImGuiTabBarFlags_DockNode);
         ImGuiID id = ImHashStr(label);
         KeepAliveID(id);
         return id;
@@ -7581,7 +7582,7 @@ bool    ImGui::TabItemEx(ImGuiTabBar* tab_bar, const char* label, bool* p_open,
         return false;
 
     const ImGuiStyle& style = g.Style;
-    const ImGuiID id = TabBarCalcTabID(tab_bar, label);
+    const ImGuiID id = TabBarCalcTabID(tab_bar, label, docked_window);
 
     // If the user called us with *p_open == false, we early out and don't render.
     // We make a call to ItemAdd() so that attempts to use a contextual popup menu with an implicit ID won't use an older ID.
@@ -7631,9 +7632,10 @@ bool    ImGui::TabItemEx(ImGuiTabBar* tab_bar, const char* label, bool* p_open,
     tab->Window = docked_window;
 
     // Append name with zero-terminator
-    if (tab_bar->Flags & ImGuiTabBarFlags_DockNode)
+    // (regular tabs are permitted in a DockNode tab bar, but window tabs not permitted in a non-DockNode tab bar)
+    if (tab->Window != NULL)
     {
-        IM_ASSERT(tab->Window != NULL);
+        IM_ASSERT(tab_bar->Flags & ImGuiTabBarFlags_DockNode);
         tab->NameOffset = -1;
     }
     else
@@ -7851,7 +7853,7 @@ void    ImGui::SetTabItemClosed(const char* label)
     if (is_within_manual_tab_bar)
     {
         ImGuiTabBar* tab_bar = g.CurrentTabBar;
-        ImGuiID tab_id = TabBarCalcTabID(tab_bar, label);
+        ImGuiID tab_id = TabBarCalcTabID(tab_bar, label, NULL);
         if (ImGuiTabItem* tab = TabBarFindTabByID(tab_bar, tab_id))
             tab->WantClose = true; // Will be processed by next call to TabBarLayout()
     }
@@ -7860,7 +7862,7 @@ void    ImGui::SetTabItemClosed(const char* label)
         if (window->DockIsActive)
             if (ImGuiDockNode* node = window->DockNode)
             {
-                ImGuiID tab_id = TabBarCalcTabID(node->TabBar, label);
+                ImGuiID tab_id = TabBarCalcTabID(node->TabBar, label, window);
                 TabBarRemoveTab(node->TabBar, tab_id);
                 window->DockTabWantClose = true;
             }