Popups: Fix popups being closed by newly appearing windows. (#4317)

* Popups/modals now remain open when new windows are created from within popup/modal begin stack.
* Modals are not closed when new window appears behind active modal.
Tested by "window_popup_interruptions"

docs/CHANGELOG.txt

@@ -45,6 +45,10 @@ Other Changes:
   (so IsMouseDoubleClicked(ImGuiMouseButton_Left) is same as GetMouseClickedCount(ImGuiMouseButton_Left) == 2,
   but it allows testing for triple clicks and more).
 - Modals: fixed issue hovering popups inside a child inside a modal. (#4676, #4527)
+- Modals, Popups, Windows: changes how appearing windows are interrupting popups and modals. (#4317) [@rokups]
+  - appearing windows created from within the begin stack of a popup/modal will no longer close it.
+  - appearing windows created not within the begin stack of a modal will no longer close the modal,
+    and automatically appear behind it.
 - Fixed IsWindowFocused()/IsWindowHovered() issues with childs inside popups. (#4676)
 - Nav: Ctrl+tabbing to cycle through windows is now enabled regardless of using the _NavEnableKeyboard
   configuration flag. This is part of an effort to generalize the use of keyboard inputs. (#4023, #787).

imgui.cpp

@@ -948,6 +948,7 @@ static void             RenderWindowDecorations(ImGuiWindow* window, const ImRec
 static void             RenderWindowTitleBarContents(ImGuiWindow* window, const ImRect& title_bar_rect, const char* name, bool* p_open);
 static void             RenderDimmedBackgroundBehindWindow(ImGuiWindow* window, ImU32 col);
 static void             RenderDimmedBackgrounds();
+static ImGuiWindow*     FindBlockingModal(ImGuiWindow* window);
 
 // Viewports
 static void             UpdateViewportsNewFrame();
@@ -3910,7 +3911,7 @@ void ImGui::UpdateHoveredWindowAndCaptureFlags()
 
     // Modal windows prevents mouse from hovering behind them.
     ImGuiWindow* modal_window = GetTopMostPopupModal();
-    if (modal_window && g.HoveredWindow && !IsWindowChildOf(g.HoveredWindow->RootWindow, modal_window, true))
+    if (modal_window && g.HoveredWindow && !IsWindowWithinBeginStackOf(g.HoveredWindow->RootWindow, modal_window))
         clear_hovered_windows = true;
 
     // Disabled mouse?
@@ -4466,6 +4467,23 @@ static void ImGui::RenderDimmedBackgroundBehindWindow(ImGuiWindow* window, ImU32
     }
 }
 
+ImGuiWindow* ImGui::FindBottomMostVisibleWindowWithinBeginStack(ImGuiWindow* parent_window)
+{
+    ImGuiContext& g = *GImGui;
+    ImGuiWindow* bottom_most_visible_window = parent_window;
+    for (int i = FindWindowDisplayIndex(parent_window); i >= 0; i--)
+    {
+        ImGuiWindow* window = g.Windows[i];
+        if (window->Flags & ImGuiWindowFlags_ChildWindow)
+            continue;
+        if (!IsWindowWithinBeginStackOf(window, parent_window))
+            break;
+        if (IsWindowActiveAndVisible(window))
+            bottom_most_visible_window = window;
+    }
+    return bottom_most_visible_window;
+}
+
 static void ImGui::RenderDimmedBackgrounds()
 {
     ImGuiContext& g = *GImGui;
@@ -4477,8 +4495,9 @@ static void ImGui::RenderDimmedBackgrounds()
 
     if (dim_bg_for_modal)
     {
-        // Draw dimming behind modal
-        RenderDimmedBackgroundBehindWindow(modal_window, GetColorU32(ImGuiCol_ModalWindowDimBg, g.DimBgRatio));
+        // Draw dimming behind modal or a begin stack child, whichever comes first in draw order.
+        ImGuiWindow* dim_behind_window = FindBottomMostVisibleWindowWithinBeginStack(modal_window);
+        RenderDimmedBackgroundBehindWindow(dim_behind_window, GetColorU32(ImGuiCol_ModalWindowDimBg, g.DimBgRatio));
     }
     else if (dim_bg_for_window_list)
     {
@@ -5859,6 +5878,36 @@ void ImGui::UpdateWindowParentAndRootLinks(ImGuiWindow* window, ImGuiWindowFlags
     }
 }
 
+// When a modal popup is open, newly created windows that want focus (i.e. are not popups and do not specify ImGuiWindowFlags_NoFocusOnAppearing)
+// should be positioned behind that modal window, unless the window was created inside the modal begin-stack.
+// In case of multiple stacked modals newly created window honors begin stack order and does not go below its own modal parent.
+// - Window             // FindBlockingModal() returns Modal1
+//   - Window           //                  .. returns Modal1
+//   - Modal1           //                  .. returns Modal2
+//      - Window        //                  .. returns Modal2
+//          - Window    //                  .. returns Modal2
+//          - Modal2    //                  .. returns Modal2
+static ImGuiWindow* ImGui::FindBlockingModal(ImGuiWindow* window)
+{
+    ImGuiContext& g = *GImGui;
+    if (g.OpenPopupStack.Size <= 0)
+        return NULL;
+
+    // Find a modal that has common parent with specified window. Specified window should be positioned behind that modal.
+    for (int i = g.OpenPopupStack.Size - 1; i >= 0; i--)
+    {
+        ImGuiWindow* popup_window = g.OpenPopupStack.Data[i].Window;
+        if (popup_window == NULL || !popup_window->WasActive || !(popup_window->Flags & ImGuiWindowFlags_Modal)) // Check WasActive, because this code may run before popup renders on current frame.
+            continue;
+        if (IsWindowWithinBeginStackOf(window, popup_window))       // Window is rendered over last modal, no render order change needed.
+            break;
+        for (ImGuiWindow* parent = popup_window->ParentWindowInBeginStack->RootWindow; parent != NULL; parent = parent->ParentWindowInBeginStack->RootWindow)
+            if (IsWindowWithinBeginStackOf(window, parent))
+                return popup_window;                                // Place window above its begin stack parent.
+    }
+    return NULL;
+}
+
 // Push a new Dear ImGui window to add widgets to.
 // - A default window called "Debug" is automatically stacked at the beginning of every frame so you can use widgets without explicitly calling a Begin/End pair.
 // - Begin/End can be called multiple times during the frame with the same window name to append content.
@@ -6204,6 +6253,22 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
                 want_focus = true;
             else if ((flags & (ImGuiWindowFlags_ChildWindow | ImGuiWindowFlags_Tooltip)) == 0)
                 want_focus = true;
+
+            ImGuiWindow* modal = GetTopMostPopupModal();
+            if (modal != NULL && !IsWindowWithinBeginStackOf(window, modal))
+            {
+                // Avoid focusing a window that is created outside of active modal. This will prevent active modal from being closed.
+                // Since window is not focused it would reappear at the same display position like the last time it was visible.
+                // In case of completely new windows it would go to the top (over current modal), but input to such window would still be blocked by modal.
+                // Position window behind a modal that is not a begin-parent of this window.
+                want_focus = false;
+                if (window == window->RootWindow)
+                {
+                    ImGuiWindow* blocking_modal = FindBlockingModal(window);
+                    IM_ASSERT(blocking_modal != NULL);
+                    BringWindowToDisplayBehind(window, blocking_modal);
+                }
+            }
         }
 
         // Handle manual resize: Resize Grips, Borders, Gamepad
@@ -6581,6 +6646,34 @@ void ImGui::BringWindowToDisplayBack(ImGuiWindow* window)
         }
 }
 
+void ImGui::BringWindowToDisplayBehind(ImGuiWindow* window, ImGuiWindow* behind_window)
+{
+    IM_ASSERT(window != NULL && behind_window != NULL);
+    ImGuiContext& g = *GImGui;
+    window = window->RootWindow;
+    behind_window = behind_window->RootWindow;
+    int pos_wnd = FindWindowDisplayIndex(window);
+    int pos_beh = FindWindowDisplayIndex(behind_window);
+    if (pos_wnd < pos_beh)
+    {
+        size_t copy_bytes = (pos_beh - pos_wnd - 1) * sizeof(ImGuiWindow*);
+        memmove(&g.Windows.Data[pos_wnd], &g.Windows.Data[pos_wnd + 1], copy_bytes);
+        g.Windows[pos_beh - 1] = window;
+    }
+    else
+    {
+        size_t copy_bytes = (pos_wnd - pos_beh) * sizeof(ImGuiWindow*);
+        memmove(&g.Windows.Data[pos_beh + 1], &g.Windows.Data[pos_beh], copy_bytes);
+        g.Windows[pos_beh] = window;
+    }
+}
+
+int ImGui::FindWindowDisplayIndex(ImGuiWindow* window)
+{
+    ImGuiContext& g = *GImGui;
+    return g.Windows.index_from_ptr(g.Windows.find(window));
+}
+
 // Moving window to front of display and set focus (which happens to be back of our sorted list)
 void ImGui::FocusWindow(ImGuiWindow* window)
 {
@@ -6810,6 +6903,19 @@ bool ImGui::IsWindowChildOf(ImGuiWindow* window, ImGuiWindow* potential_parent,
     return false;
 }
 
+bool ImGui::IsWindowWithinBeginStackOf(ImGuiWindow* window, ImGuiWindow* potential_parent)
+{
+    if (window->RootWindow == potential_parent)
+        return true;
+    while (window != NULL)
+    {
+        if (window == potential_parent)
+            return true;
+        window = window->ParentWindowInBeginStack;
+    }
+    return false;
+}
+
 bool ImGui::IsWindowAbove(ImGuiWindow* potential_above, ImGuiWindow* potential_below)
 {
     ImGuiContext& g = *GImGui;
@@ -8492,7 +8598,7 @@ void ImGui::ClosePopupsOverWindow(ImGuiWindow* ref_window, bool restore_focus_to
             bool ref_window_is_descendent_of_popup = false;
             for (int n = popup_count_to_keep; n < g.OpenPopupStack.Size; n++)
                 if (ImGuiWindow* popup_window = g.OpenPopupStack[n].Window)
-                    if (popup_window->RootWindow == ref_window->RootWindow)
+                    if (IsWindowWithinBeginStackOf(ref_window, popup_window))
                     {
                         ref_window_is_descendent_of_popup = true;
                         break;

imgui.h

@@ -64,7 +64,7 @@ Index of this file:
 // Version
 // (Integer encoded as XYYZZ for use in #if preprocessor conditionals. Work in progress versions typically starts at XYY99 then bounce up to XYY00, XYY01 etc. when release tagging happens)
 #define IMGUI_VERSION               "1.86 WIP"
-#define IMGUI_VERSION_NUM           18516
+#define IMGUI_VERSION_NUM           18517
 #define IMGUI_CHECKVERSION()        ImGui::DebugCheckVersionAndDataLayout(IMGUI_VERSION, sizeof(ImGuiIO), sizeof(ImGuiStyle), sizeof(ImVec2), sizeof(ImVec4), sizeof(ImDrawVert), sizeof(ImDrawIdx))
 #define IMGUI_HAS_TABLE
 

imgui_internal.h

@@ -2418,6 +2418,7 @@ namespace ImGui
     IMGUI_API void          UpdateWindowParentAndRootLinks(ImGuiWindow* window, ImGuiWindowFlags flags, ImGuiWindow* parent_window);
     IMGUI_API ImVec2        CalcWindowNextAutoFitSize(ImGuiWindow* window);
     IMGUI_API bool          IsWindowChildOf(ImGuiWindow* window, ImGuiWindow* potential_parent, bool popup_hierarchy);
+    IMGUI_API bool          IsWindowWithinBeginStackOf(ImGuiWindow* window, ImGuiWindow* potential_parent);
     IMGUI_API bool          IsWindowAbove(ImGuiWindow* potential_above, ImGuiWindow* potential_below);
     IMGUI_API bool          IsWindowNavFocusable(ImGuiWindow* window);
     IMGUI_API void          SetWindowPos(ImGuiWindow* window, const ImVec2& pos, ImGuiCond cond = 0);
@@ -2433,6 +2434,9 @@ namespace ImGui
     IMGUI_API void          BringWindowToFocusFront(ImGuiWindow* window);
     IMGUI_API void          BringWindowToDisplayFront(ImGuiWindow* window);
     IMGUI_API void          BringWindowToDisplayBack(ImGuiWindow* window);
+    IMGUI_API void          BringWindowToDisplayBehind(ImGuiWindow* window, ImGuiWindow* above_window);
+    IMGUI_API int           FindWindowDisplayIndex(ImGuiWindow* window);
+    IMGUI_API ImGuiWindow*  FindBottomMostVisibleWindowWithinBeginStack(ImGuiWindow* window);
 
     // Fonts, drawing
     IMGUI_API void          SetCurrentFont(ImFont* font);