Make moving window prevent its active id from being stolen (#3392, #3243, #1738)

Amend 7b3d379, 615e9ae3

imgui.cpp

@@ -2979,6 +2979,7 @@ void ImGui::SetActiveID(ImGuiID id, ImGuiWindow* window)
     }
     g.ActiveId = id;
     g.ActiveIdAllowOverlap = false;
+    g.ActiveIdNoClearOnFocusLoss = false;
     g.ActiveIdWindow = window;
     g.ActiveIdHasBeenEditedThisFrame = false;
     if (id)
@@ -2996,7 +2997,7 @@ void ImGui::SetActiveID(ImGuiID id, ImGuiWindow* window)
 
 void ImGui::ClearActiveID()
 {
-    SetActiveID(0, NULL);
+    SetActiveID(0, NULL); // g.ActiveId = 0;
 }
 
 void ImGui::SetHoveredID(ImGuiID id)
@@ -3401,6 +3402,7 @@ void ImGui::StartMouseMovingWindow(ImGuiWindow* window)
     FocusWindow(window);
     SetActiveID(window->MoveId, window);
     g.NavDisableHighlight = true;
+    g.ActiveIdNoClearOnFocusLoss = true;
     g.ActiveIdClickOffset = g.IO.MousePos - window->RootWindow->Pos;
 
     bool can_move_window = true;
@@ -6775,8 +6777,9 @@ void ImGui::FocusWindow(ImGuiWindow* window)
     // - Focus a window while an InputText in another window is active, if focus happens before the old InputText can run.
     // - When using Nav to activate menu items (due to timing of activating on press->new window appears->losing ActiveId)
     // - Using dock host items (tab, collapse button) can trigger this before we redirect the ActiveIdWindow toward the child window.
-    if (g.ActiveId != 0 && g.ActiveIdWindow && g.ActiveIdWindow->RootWindowDockStop != focus_front_window && !active_id_window_is_dock_node_host)
-        ClearActiveID();
+    if (g.ActiveId != 0 && g.ActiveIdWindow && g.ActiveIdWindow->RootWindowDockStop != focus_front_window)
+        if (!g.ActiveIdNoClearOnFocusLoss && !active_id_window_is_dock_node_host)
+            ClearActiveID();
 
     // Passing NULL allow to disable keyboard focus
     if (!window)

imgui_internal.h

@@ -1314,6 +1314,7 @@ struct ImGuiContext
     float                   ActiveIdTimer;
     bool                    ActiveIdIsJustActivated;            // Set at the time of activation for one frame
     bool                    ActiveIdAllowOverlap;               // Active widget allows another widget to steal active id (generally for overlapping widgets, but not always)
+    bool                    ActiveIdNoClearOnFocusLoss;         // Disable losing active id if the active id window gets unfocused.
     bool                    ActiveIdHasBeenPressedBefore;       // Track whether the active id led to a press (this is to allow changing between PressOnClick and PressOnRelease without pressing twice). Used by range_select branch.
     bool                    ActiveIdHasBeenEditedBefore;        // Was the value associated to the widget Edited over the course of the Active state.
     bool                    ActiveIdHasBeenEditedThisFrame;

imgui_widgets.cpp

@@ -7395,8 +7395,9 @@ bool    ImGui::TabItemEx(ImGuiTabBar* tab_bar, const char* label, bool* p_open,
                 // Undock
                 DockContextQueueUndockWindow(&g, docked_window);
                 g.MovingWindow = docked_window;
-                g.ActiveId = g.MovingWindow->MoveId;
+                SetActiveID(g.MovingWindow->MoveId, g.MovingWindow);
                 g.ActiveIdClickOffset -= g.MovingWindow->Pos - bb.Min;
+                g.ActiveIdNoClearOnFocusLoss = true;
             }
         }
     }