Docking: Fix IsWindowAppearing() and ImGuiCond_Appearing on docked windows. (#4177, #3982, #1497, #1061)

docs/CHANGELOG.txt

@@ -108,7 +108,10 @@ Other Changes:
   Normally the right way to disable compiling the demo is to set IMGUI_DISABLE_DEMO_WINDOWS, but we want to avoid
   implying that the file is required.
 - Backends: OpenGL3: Handle GL_CLIP_ORIGIN on <4.5 contexts if "GL_ARB_clip_control" extension is detected. (#4170, #3998)
->>>>>>> master
+
+Docking+Viewports Branch:
+
+- Docking: Fix IsWindowAppearing() and ImGuiCond_Appearing on docked windows. (#4177, #3982, #1497, #1061)
 
 
 -----------------------------------------------------------------------

imgui.cpp

@@ -6100,8 +6100,8 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
     const bool first_begin_of_the_frame = (window->LastFrameActive != current_frame);
     window->IsFallbackWindow = (g.CurrentWindowStack.Size == 0 && g.WithinFrameScopeWithImplicitWindow);
 
-    // Update the Appearing flag
-    bool window_just_activated_by_user = (window->LastFrameActive < current_frame - 1);   // Not using !WasActive because the implicit "Debug" window would always toggle off->on
+    // Update the Appearing flag (note: the BeginDocked() path may also set this to true later)
+    bool window_just_activated_by_user = (window->LastFrameActive < current_frame - 1); // Not using !WasActive because the implicit "Debug" window would always toggle off->on
     if (flags & ImGuiWindowFlags_Popup)
     {
         ImGuiPopupData& popup_ref = g.OpenPopupStack[g.BeginPopupStack.Size];
@@ -6136,6 +6136,8 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
     {
         bool has_dock_node = (window->DockId != 0 || window->DockNode != NULL);
         bool new_auto_dock_node = !has_dock_node && GetWindowAlwaysWantOwnTabBar(window);
+        bool dock_node_was_visible = window->DockNodeIsVisible;
+        bool dock_tab_was_visible = window->DockTabIsVisible;
         if (has_dock_node || new_auto_dock_node)
         {
             BeginDocked(window, p_open);
@@ -6146,6 +6148,13 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
             // Docking currently override constraints
             g.NextWindowData.Flags &= ~ImGuiNextWindowDataFlags_HasSizeConstraint;
         }
+
+        // Update the Appearing flag (again)
+        if (window->DockTabIsVisible && !dock_tab_was_visible && dock_node_was_visible && !window->Appearing)
+        {
+            window->Appearing = true;
+            SetWindowConditionAllowFlags(window, ImGuiCond_Appearing, true);
+        }
     }
 
     // Parent window is latched only on the first call to Begin() of the frame, so further append-calls can be done from a different window stack
@@ -12957,7 +12966,7 @@ void ImGui::DockContextProcessUndockWindow(ImGuiContext* ctx, ImGuiWindow* windo
         window->DockId = 0;
     window->Collapsed = false;
     window->DockIsActive = false;
-    window->DockTabIsVisible = false;
+    window->DockNodeIsVisible = window->DockTabIsVisible = false;
     window->Size = window->SizeFull = FixLargeWindowsWhenUndocking(window->SizeFull, window->Viewport);
 
     MarkIniSettingsDirty();
@@ -15503,7 +15512,7 @@ void ImGui::BeginDocked(ImGuiWindow* window, bool* p_open)
         else
         {
             window->DockIsActive = true;
-            window->DockTabIsVisible = false;
+            window->DockNodeIsVisible = window->DockTabIsVisible = false;
         }
         return;
     }
@@ -15518,7 +15527,7 @@ void ImGui::BeginDocked(ImGuiWindow* window, bool* p_open)
     if (node->HostWindow == NULL)
     {
         window->DockIsActive = (node->State == ImGuiDockNodeState_HostWindowHiddenBecauseWindowsAreResizing);
-        window->DockTabIsVisible = false;
+        window->DockNodeIsVisible = window->DockTabIsVisible = false;
         if (node->Windows.Size > 1)
             DockNodeHideWindowDuringHostWindowCreation(window);
         return;
@@ -15542,6 +15551,7 @@ void ImGui::BeginDocked(ImGuiWindow* window, bool* p_open)
     SetNextWindowSize(node->Size);
     g.NextWindowData.PosUndock = false; // Cancel implicit undocking of SetNextWindowPos()
     window->DockIsActive = true;
+    window->DockNodeIsVisible = true;
     window->DockTabIsVisible = false;
     if (node->SharedFlags & ImGuiDockNodeFlags_KeepAliveOnly)
         return;

imgui_internal.h

@@ -2101,6 +2101,7 @@ struct IMGUI_API ImGuiWindow
 
     // Docking
     bool                    DockIsActive        :1;             // When docking artifacts are actually visible. When this is set, DockNode is guaranteed to be != NULL. ~~ (DockNode != NULL) && (DockNode->Windows.Size > 1).
+    bool                    DockNodeIsVisible   :1;
     bool                    DockTabIsVisible    :1;             // Is our window visible this frame? ~~ is the corresponding tab selected?
     bool                    DockTabWantClose    :1;
     short                   DockOrder;                          // Order of the last time the window was visible within its DockNode. This is used to reorder windows that are reappearing on the same frame. Same value between windows that were active and windows that were none are possible.