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

Amend 7b3d379, 615e9ae3

# Conflicts:
#	imgui.cpp
#	imgui_widgets.cpp

imgui.cpp

@@ -2927,6 +2927,7 @@ void ImGui::SetActiveID(ImGuiID id, ImGuiWindow* window)
     }
     g.ActiveId = id;
     g.ActiveIdAllowOverlap = false;
+    g.ActiveIdNoClearOnFocusLoss = false;
     g.ActiveIdWindow = window;
     g.ActiveIdHasBeenEditedThisFrame = false;
     if (id)
@@ -2944,7 +2945,7 @@ void ImGui::SetActiveID(ImGuiID id, ImGuiWindow* window)
 
 void ImGui::ClearActiveID()
 {
-    SetActiveID(0, NULL);
+    SetActiveID(0, NULL); // g.ActiveId = 0;
 }
 
 void ImGui::SetHoveredID(ImGuiID id)
@@ -3301,6 +3302,7 @@ 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;
@@ -6147,8 +6149,11 @@ void ImGui::FocusWindow(ImGuiWindow* window)
     ImGuiWindow* focus_front_window = window ? window->RootWindow : NULL; // NB: In docking branch this is window->RootWindowDockStop
     ImGuiWindow* display_front_window = window ? window->RootWindow : NULL;
 
-    // Steal focus on active widgets
+    // Steal active widgets. Some of the cases it triggers includes:
+    // - 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)
     if (g.ActiveId != 0 && g.ActiveIdWindow && g.ActiveIdWindow->RootWindow != focus_front_window)
+        if (!g.ActiveIdNoClearOnFocusLoss)
             ClearActiveID();
 
     // Passing NULL allow to disable keyboard focus

imgui_internal.h

@@ -1147,6 +1147,7 @@ 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;