Popups: Closing a popup restores the focused/nav window in place at the time of the popup opening, instead of restoring the window that was in the window stack at the time of the OpenPopup call. (#2517)

Among other things, this allows opening a popup while no window are focused, and pressing Escape to clear the focus again.

docs/CHANGELOG.txt

@@ -59,6 +59,10 @@ Other Changes:
   highlight from parent menu items earlier than necessary while approaching the child menu.
 - Window: Close button is horizontally aligned with style.FramePadding.x.
 - Window: Fixed contents region being off by WindowBorderSize amount on the right when scrollbar is active.
+- Popups: Closing a popup restores the focused/nav window in place at the time of the popup opening,
+  instead of restoring the window that was in the window stack at the time of the OpenPopup call. (#2517)
+  Among other things, this allows opening a popup while no window are focused, and pressing Escape to
+  clear the focus again.
 - GetMouseDragDelta(): also returns the delta on the mouse button released frame. (#2419)
 - GetMouseDragDelta(): verify that mouse positions are valid otherwise returns zero.
 - Inputs: Also add support for horizontal scroll with Shift+Mouse Wheel. (#2424, #1463) [@LucaRood]

docs/TODO.txt

@@ -291,6 +291,7 @@ It's mostly a bunch of personal notes, probably incomplete. Feel free to query i
  - nav/menus: allow pressing Menu to leave a sub-menu.
  - nav/menus: a way to access the main menu bar with Alt? (currently needs CTRL+TAB)
  - nav/menus: when using the main menu bar, even though we restore focus after, the underlying window loses its title bar highlight during menu manipulation. could we prevent it?
+ - nav/menus: main menu bar currently cannot restore a NULL focus. Could save NavWindow at the time of being focused, similarly to what popup do?
  - nav: simulate right-click or context activation? (SHIFT+F10)
  - nav: tabs should go through most/all widgets (in submission order?).
  - nav: when CTRL-Tab/windowing is active, the HoveredWindow detection doesn't take account of the window display re-ordering.

imgui.cpp

@@ -3603,7 +3603,7 @@ void ImGui::NewFrame()
 
     // Closing the focused window restore focus to the first active root window in descending z-order
     if (g.NavWindow && !g.NavWindow->WasActive)
-        FocusTopMostWindowIgnoringOne(NULL);
+        FocusTopMostWindowUnderOne(NULL, NULL);
 
     // No window should be open at the beginning of the frame.
     // But in order to allow the user to call NewFrame() multiple times without calling Render(), we are doing an explicit clear.
@@ -5726,10 +5726,18 @@ void ImGui::FocusWindow(ImGuiWindow* window)
         BringWindowToDisplayFront(window);
 }
 
-void ImGui::FocusTopMostWindowIgnoringOne(ImGuiWindow* ignore_window)
+void ImGui::FocusTopMostWindowUnderOne(ImGuiWindow* under_this_window, ImGuiWindow* ignore_window)
 {
     ImGuiContext& g = *GImGui;
-    for (int i = g.WindowsFocusOrder.Size - 1; i >= 0; i--)
+
+    int start_idx = g.WindowsFocusOrder.Size - 1;
+    if (under_this_window != NULL)
+    {
+        int under_this_window_idx = FindWindowFocusIndex(under_this_window);
+        if (under_this_window_idx != -1)
+            start_idx = under_this_window_idx - 1;
+    }
+    for (int i = start_idx; i >= 0; i--)
     {
         // We may later decide to test for different NoXXXInputs based on the active navigation input (mouse vs nav) but that may feel more confusing to the user.
         ImGuiWindow* window = g.WindowsFocusOrder[i];
@@ -5741,6 +5749,7 @@ void ImGui::FocusTopMostWindowIgnoringOne(ImGuiWindow* ignore_window)
                 return;
             }
     }
+    FocusWindow(NULL);
 }
 
 void ImGui::SetNextItemWidth(float item_width)
@@ -6949,7 +6958,7 @@ void ImGui::OpenPopupEx(ImGuiID id)
     ImGuiPopupData popup_ref; // Tagged as new ref as Window will be set back to NULL if we write this into OpenPopupStack.
     popup_ref.PopupId = id;
     popup_ref.Window = NULL;
-    popup_ref.ParentWindow = parent_window;
+    popup_ref.SourceWindow = g.NavWindow;
     popup_ref.OpenFrameCount = g.FrameCount;
     popup_ref.OpenParentId = parent_window->IDStack.back();
     popup_ref.OpenPopupPos = NavCalcPreferredRefPos();
@@ -7035,25 +7044,26 @@ void ImGui::ClosePopupsOverWindow(ImGuiWindow* ref_window)
 
 void ImGui::ClosePopupToLevel(int remaining, bool apply_focus_to_window_under)
 {
-    IM_ASSERT(remaining >= 0);
     ImGuiContext& g = *GImGui;
-    ImGuiWindow* focus_window = (remaining > 0) ? g.OpenPopupStack[remaining-1].Window : g.OpenPopupStack[0].ParentWindow;
+    IM_ASSERT(remaining >= 0 && remaining < g.OpenPopupStack.Size);
+    ImGuiWindow* focus_window = g.OpenPopupStack[remaining].SourceWindow;
+    ImGuiWindow* popup_window = g.OpenPopupStack[remaining].Window;
     g.OpenPopupStack.resize(remaining);
 
-    // FIXME: This code is faulty and we may want to eventually to replace or remove the 'apply_focus_to_window_under=true' path completely.
-    // Instead of using g.OpenPopupStack[remaining-1].Window etc. we should find the highest root window that is behind the popups we are closing.
-    // The current code will set focus to the parent of the popup window which is incorrect.
-    // It rarely manifested until now because UpdateMouseMovingWindowNewFrame() would call FocusWindow() again on the clicked window,
-    // leading to a chain of focusing A (clicked window) then B (parent window of the popup) then A again.
-    // However if the clicked window has the _NoMove flag set we would be left with B focused.
-    // For now, we have disabled this path when called from ClosePopupsOverWindow() because the users of ClosePopupsOverWindow() don't need to alter focus anyway,
-    // but we should inspect and fix this properly.
     if (apply_focus_to_window_under)
     {
-        if (g.NavLayer == 0)
+        if (focus_window && !focus_window->WasActive && popup_window)
+        {
+            // Fallback
+            FocusTopMostWindowUnderOne(popup_window, NULL);
+        }
+        else
+        {
+            if (g.NavLayer == 0 && focus_window)
                 focus_window = NavRestoreLastChildNavWindow(focus_window);
             FocusWindow(focus_window);
         }
+    }
 }
 
 // Close the popup we have begin-ed into.

imgui_internal.h

@@ -652,13 +652,13 @@ struct ImGuiPopupData
 {
     ImGuiID             PopupId;        // Set on OpenPopup()
     ImGuiWindow*        Window;         // Resolved on BeginPopup() - may stay unresolved if user never calls OpenPopup()
-    ImGuiWindow*        ParentWindow;   // Set on OpenPopup()
+    ImGuiWindow*        SourceWindow;   // Set on OpenPopup() copy of NavWindow at the time of opening the popup
     int                 OpenFrameCount; // Set on OpenPopup()
     ImGuiID             OpenParentId;   // Set on OpenPopup(), we need this to differentiate multiple menu sets from each others (e.g. inside menu bar vs loose menu items)
     ImVec2              OpenPopupPos;   // Set on OpenPopup(), preferred popup position (typically == OpenMousePos when using mouse)
     ImVec2              OpenMousePos;   // Set on OpenPopup(), copy of mouse position at the time of opening popup
 
-    ImGuiPopupData() { PopupId = 0; Window = ParentWindow = NULL; OpenFrameCount = -1; OpenParentId = 0; }
+    ImGuiPopupData() { PopupId = 0; Window = SourceWindow = NULL; OpenFrameCount = -1; OpenParentId = 0; }
 };
 
 struct ImGuiColumnData
@@ -1392,7 +1392,7 @@ namespace ImGui
     IMGUI_API ImGuiWindow*  FindWindowByID(ImGuiID id);
     IMGUI_API ImGuiWindow*  FindWindowByName(const char* name);
     IMGUI_API void          FocusWindow(ImGuiWindow* window);
-    IMGUI_API void          FocusTopMostWindowIgnoringOne(ImGuiWindow* ignore_window);
+    IMGUI_API void          FocusTopMostWindowUnderOne(ImGuiWindow* under_this_window, ImGuiWindow* ignore_window);
     IMGUI_API void          BringWindowToFocusFront(ImGuiWindow* window);
     IMGUI_API void          BringWindowToDisplayFront(ImGuiWindow* window);
     IMGUI_API void          BringWindowToDisplayBack(ImGuiWindow* window);

imgui_widgets.cpp

@@ -5818,9 +5818,10 @@ void ImGui::EndMainMenuBar()
     EndMenuBar();
 
     // When the user has left the menu layer (typically: closed menus through activation of an item), we restore focus to the previous window
+    // FIXME: With this strategy we won't be able to restore a NULL focus.
     ImGuiContext& g = *GImGui;
     if (g.CurrentWindow == g.NavWindow && g.NavLayer == 0)
-        FocusTopMostWindowIgnoringOne(g.NavWindow);
+        FocusTopMostWindowUnderOne(g.NavWindow, NULL);
 
     End();
 }
@@ -5951,7 +5952,7 @@ bool ImGui::BeginMenu(const char* label, bool enabled)
     {
         // Implement http://bjk5.com/post/44698559168/breaking-down-amazons-mega-dropdown to avoid using timers, so menus feels more reactive.
         bool moving_within_opened_triangle = false;
-        if (g.HoveredWindow == window && g.OpenPopupStack.Size > g.BeginPopupStack.Size && g.OpenPopupStack[g.BeginPopupStack.Size].ParentWindow == window && !(window->Flags & ImGuiWindowFlags_MenuBar))
+        if (g.HoveredWindow == window && g.OpenPopupStack.Size > g.BeginPopupStack.Size && g.OpenPopupStack[g.BeginPopupStack.Size].SourceWindow == window && !(window->Flags & ImGuiWindowFlags_MenuBar))
         {
             if (ImGuiWindow* next_window = g.OpenPopupStack[g.BeginPopupStack.Size].Window)
             {