Docking: Can undock from the small triangle button. (#2109,. #2645)

imgui.cpp

@@ -5511,18 +5511,22 @@ void ImGui::RenderWindowDecorations(ImGuiWindow* window, const ImRect& title_bar
                 window->DrawList->AddLine(menu_bar_rect.GetBL(), menu_bar_rect.GetBR(), GetColorU32(ImGuiCol_Border), style.FrameBorderSize);
         }
 
-        // Docking: Unhide tab bar (small triangle in the corner)
-        if (window->DockNode && window->DockNode->IsHiddenTabBar() && !window->DockNode->IsNoTabBar())
+        // Docking: Unhide tab bar (small triangle in the corner), drag from small triangle to quickly undock
+        ImGuiDockNode* node = window->DockNode;
+        if (node && window->DockIsActive && node->IsHiddenTabBar() && !node->IsNoTabBar())
         {
             float unhide_sz_draw = ImFloor(g.FontSize * 0.70f);
             float unhide_sz_hit = ImFloor(g.FontSize * 0.55f);
-            ImVec2 p = window->DockNode->Pos;
+            ImVec2 p = node->Pos;
             ImRect r(p, p + ImVec2(unhide_sz_hit, unhide_sz_hit));
             bool hovered, held;
             if (ButtonBehavior(r, window->GetID("#UNHIDE"), &hovered, &held, ImGuiButtonFlags_FlattenChildren))
-                window->DockNode->WantHiddenTabBarToggle = true;
+                node->WantHiddenTabBarToggle = true;
+            else if (held && IsMouseDragging(0))
+                StartMouseDragFromTitleBar(window, node, true);
+
             // FIXME-DOCK: Ideally we'd use ImGuiCol_TitleBgActive/ImGuiCol_TitleBg here, but neither is guaranteed to be visible enough at this sort of size..
-            ImU32 col = GetColorU32(((held && hovered) || (window->DockNode->IsFocused && !hovered)) ? ImGuiCol_ButtonActive : hovered ? ImGuiCol_ButtonHovered : ImGuiCol_Button);
+            ImU32 col = GetColorU32(((held && hovered) || (node->IsFocused && !hovered)) ? ImGuiCol_ButtonActive : hovered ? ImGuiCol_ButtonHovered : ImGuiCol_Button);
             window->DrawList->AddTriangleFilled(p, p + ImVec2(unhide_sz_draw, 0.0f), p + ImVec2(0.0f, unhide_sz_draw), col);
         }
 

imgui.h

@@ -1610,11 +1610,11 @@ struct ImGuiSizeCallbackData
 // Provide hints to the platform back-end via altered viewport flags (enable/disable OS decoration, OS task bar icons, etc.) and OS level parent/child relationships.
 struct ImGuiWindowClass
 {
-    ImGuiID             ClassId;                    // User data. 0 = Default class (unclassed)
+    ImGuiID             ClassId;                    // User data. 0 = Default class (unclassed). Windows of different classes cannot be docked with each others.
     ImGuiID             ParentViewportId;           // Hint for the platform back-end. If non-zero, the platform back-end can create a parent<>child relationship between the platform windows. Not conforming back-ends 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.
-    bool                DockingAlwaysTabBar;        // Set to true to enforce single floating windows of this class always having their own tab bar (equivalent of setting the global io.ConfigDockingAlwaysTabBar)
+    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.
 
     ImGuiWindowClass() { ClassId = 0; ParentViewportId = 0; ViewportFlagsOverrideSet = ViewportFlagsOverrideClear = 0x00; DockingAlwaysTabBar = false; DockingAllowUnclassed = true; }