Hotfix for PushFocusScope() being utterly wrong (until we split the stacks), Added asserts on PopID to help catch bugs, Added GC trigger.

imgui.cpp

@@ -3845,7 +3845,7 @@ void ImGui::NewFrame()
 
     // Mark all windows as not visible and compact unused memory.
     IM_ASSERT(g.WindowsFocusOrder.Size == g.Windows.Size);
-    const float memory_compact_start_time = (g.IO.ConfigMemoryCompactTimer >= 0.0f) ? (float)g.Time - g.IO.ConfigMemoryCompactTimer : FLT_MAX;
+    const float memory_compact_start_time = (g.GcCompactAll || g.IO.ConfigMemoryCompactTimer < 0.0f) ? FLT_MAX : (float)g.Time - g.IO.ConfigMemoryCompactTimer;
     for (int i = 0; i != g.Windows.Size; i++)
     {
         ImGuiWindow* window = g.Windows[i];
@@ -3858,6 +3858,7 @@ void ImGui::NewFrame()
         if (!window->WasActive && !window->MemoryCompacted && window->LastTimeActive < memory_compact_start_time)
             GcCompactTransientWindowBuffers(window);
     }
+    g.GcCompactAll = false;
 
     // Closing the focused window restore focus to the first active root window in descending z-order
     if (g.NavWindow && !g.NavWindow->WasActive)
@@ -6650,12 +6651,14 @@ void ImGui::ActivateItem(ImGuiID id)
     g.NavNextActivateId = id;
 }
 
-// Note: this is storing in same stack as IDStack, so Push/Pop mismatch will be reported there.
+// FIXME: this is storing in same stack as IDStack, so Push/Pop mismatch will be reported there. Maybe play nice and a separate in-context stack.
 void ImGui::PushFocusScope(ImGuiID id)
 {
     ImGuiContext& g = *GImGui;
     ImGuiWindow* window = g.CurrentWindow;
+    ImGuiID top_most_id = window->IDStack.back();
     window->IDStack.push_back(window->DC.NavFocusScopeIdCurrent);
+    window->IDStack.push_back(top_most_id);
     window->DC.NavFocusScopeIdCurrent = id;
 }
 
@@ -6665,6 +6668,8 @@ void ImGui::PopFocusScope()
     ImGuiWindow* window = g.CurrentWindow;
     window->DC.NavFocusScopeIdCurrent = window->IDStack.back();
     window->IDStack.pop_back();
+    IM_ASSERT(window->IDStack.Size > 1); // Too many PopID or PopFocusScope (or could be popping in a wrong/different window?)
+    window->IDStack.pop_back();
 }
 
 void ImGui::SetKeyboardFocusHere(int offset)
@@ -6763,6 +6768,7 @@ ImGuiID ImGui::GetIDWithSeed(const char* str, const char* str_end, ImGuiID seed)
 void ImGui::PopID()
 {
     ImGuiWindow* window = GImGui->CurrentWindow;
+    IM_ASSERT(window->IDStack.Size > 1); // Too many PopID or PopFocusScope (or could be popping in a wrong/different window?)
     window->IDStack.pop_back();
 }
 
@@ -10323,12 +10329,14 @@ void ImGui::ShowMetricsWindow(bool* p_open)
     ImGuiMetricsConfig* cfg = &g.DebugMetricsConfig;
 
     // Basic info
-    ImGui::Text("Dear ImGui %s", ImGui::GetVersion());
-    ImGui::Text("Application average %.3f ms/frame (%.1f FPS)", 1000.0f / io.Framerate, io.Framerate);
-    ImGui::Text("%d vertices, %d indices (%d triangles)", io.MetricsRenderVertices, io.MetricsRenderIndices, io.MetricsRenderIndices / 3);
-    ImGui::Text("%d active windows (%d visible)", io.MetricsActiveWindows, io.MetricsRenderWindows);
-    ImGui::Text("%d active allocations", io.MetricsActiveAllocations);
-    ImGui::Separator();
+    Text("Dear ImGui %s", ImGui::GetVersion());
+    Text("Application average %.3f ms/frame (%.1f FPS)", 1000.0f / io.Framerate, io.Framerate);
+    Text("%d vertices, %d indices (%d triangles)", io.MetricsRenderVertices, io.MetricsRenderIndices, io.MetricsRenderIndices / 3);
+    Text("%d active windows (%d visible)", io.MetricsActiveWindows, io.MetricsRenderWindows);
+    Text("%d active allocations", io.MetricsActiveAllocations);
+    //SameLine(); if (SmallButton("GC")) { g.GcCompactAll = true; }
+
+    Separator();
 
     // Debugging enums
     enum { WRT_OuterRect, WRT_OuterRectClipped, WRT_InnerRect, WRT_InnerClipRect, WRT_WorkRect, WRT_Content, WRT_ContentRegionRect, WRT_Count }; // Windows Rect Type

imgui_internal.h

@@ -1148,6 +1148,7 @@ struct ImGuiContext
     bool                    WithinFrameScope;                   // Set by NewFrame(), cleared by EndFrame()
     bool                    WithinFrameScopeWithImplicitWindow; // Set by NewFrame(), cleared by EndFrame() when the implicit debug window has been pushed
     bool                    WithinEndChild;                     // Set within EndChild()
+    bool                    GcCompactAll;                       // Request full GC
     bool                    TestEngineHookItems;                // Will call test engine hooks: ImGuiTestEngineHook_ItemAdd(), ImGuiTestEngineHook_ItemInfo(), ImGuiTestEngineHook_Log()
     ImGuiID                 TestEngineHookIdInfo;               // Will call test engine hooks: ImGuiTestEngineHook_IdInfo() from GetID()
     void*                   TestEngine;                         // Test engine user data

imgui_widgets.cpp

@@ -7489,7 +7489,7 @@ void    ImGui::EndTabItem()
     IM_ASSERT(tab_bar->LastTabItemIdx >= 0);
     ImGuiTabItem* tab = &tab_bar->Tabs[tab_bar->LastTabItemIdx];
     if (!(tab->Flags & ImGuiTabItemFlags_NoPushId))
-        window->IDStack.pop_back();
+        PopID();
 }
 
 bool    ImGui::TabItemButton(const char* label, ImGuiTabItemFlags flags)