Error Handling: enabled experimental recovery systems. (#1651, #5654)

Setup a couple of features to configure them, including ways to display error tooltips instead of assserting.

docs/CHANGELOG.txt

@@ -43,8 +43,22 @@ Breaking changes:
 
 Other changes:
 
-- Error Handling: rewired asserts in PopID(), PopFont(), PopItemFlag(), EndDisabled(),
-  PopTextWrapPos(), PopFocusScope(), PopItemWidth() to use IM_ASSERT_USER_ERROR(). (#1651)
+- Error Handling: Enabled/improved error recovery systems. (#1651, #5654)
+  - Error recovery is not perfect nor guaranteed! It is a feature to ease development.
+  - Functions that support error recovery are using IM_ASSERT_USER_ERROR() instead of IM_ASSERT().
+  - You not are not supposed to rely on it in the course of a normal application run.
+  - Possible usage: facilitate recovery from errors triggered from a scripting language or
+    after specific exceptions handlers. Surface errors to programmers in less agressive ways.
+  - Always ensure that on programmers seats you have at minimum Asserts or Tooltips enabled
+    when making direct imgui API calls! Otherwise it would severely hinder your ability to
+    catch and correct mistakes!
+  - Added io.ConfigErrorRecovery to enable error recovery support.
+  - Added io.ConfigErrorRecoveryEnableAssert to assert on recoverable errors.
+  - Added io.ConfigErrorRecoveryEnableDebugLog to output to debug log on recoverable errors.
+  - Added io.ConfigErrorRecoveryEnableTooltip to enable displaying an error tooltip on recoverable errors.
+    The tooltip include a way to enable asserts if they were disabled.
+  - All options are enabled by default.
+  - Read https://github.com/ocornut/imgui/wiki/Error-Handling for a bit more details.
 - Windows: BeginChild(): made it possible to call SetNextWindowSize() on a child window
   using ImGuiChildFlags_ResizeX,ImGuiChildFlags_ResizeY in order to override its current
   size. (#1710, #8020)

imgui.cpp

@@ -1401,6 +1401,11 @@ ImGuiIO::ImGuiIO()
     ConfigDebugBeginReturnValueOnce = false;
     ConfigDebugBeginReturnValueLoop = false;
 
+    ConfigErrorRecovery = true;
+    ConfigErrorRecoveryEnableAssert = true;
+    ConfigErrorRecoveryEnableDebugLog = true;
+    ConfigErrorRecoveryEnableTooltip = true;
+
     // Inputs Behaviors
     MouseDoubleClickTime = 0.30f;
     MouseDoubleClickMaxDist = 6.0f;
@@ -3978,6 +3983,12 @@ ImGuiContext::ImGuiContext(ImFontAtlas* shared_font_atlas)
     LogDepthRef = 0;
     LogDepthToExpand = LogDepthToExpandDefault = 2;
 
+    ErrorCallback = NULL;
+    ErrorCallbackUserData = NULL;
+    ErrorFirst = true;
+    ErrorCountCurrentFrame = 0;
+    StackSizesInBeginForCurrentWindow = NULL;
+
     DebugDrawIdConflictsCount = 0;
     DebugLogFlags = ImGuiDebugLogFlags_EventError | ImGuiDebugLogFlags_OutputToTTY;
     DebugLocateId = 0;
@@ -4211,6 +4222,7 @@ static void SetCurrentWindow(ImGuiWindow* window)
 {
     ImGuiContext& g = *GImGui;
     g.CurrentWindow = window;
+    g.StackSizesInBeginForCurrentWindow = g.CurrentWindow ? &g.CurrentWindowStack.back().StackSizesInBegin : NULL;
     g.CurrentTable = window && window->DC.CurrentTableIdx != -1 ? g.Tables.GetByIndex(window->DC.CurrentTableIdx) : NULL;
     g.CurrentDpiScale = 1.0f; // FIXME-DPI: WIP this is modified in docking
     if (window)
@@ -5249,6 +5261,10 @@ void ImGui::NewFrame()
     Begin("Debug##Default");
     IM_ASSERT(g.CurrentWindow->IsFallbackWindow == true);
 
+    // Store stack sizes
+    g.ErrorCountCurrentFrame = 0;
+    ErrorRecoveryStoreState(&g.StackSizesInNewFrame);
+
     // [DEBUG] When io.ConfigDebugBeginReturnValue is set, we make Begin()/BeginChild() return false at different level of the window-stack,
     // allowing to validate correct Begin/End behavior in user code.
 #ifndef IMGUI_DISABLE_DEBUG_TOOLS
@@ -5467,6 +5483,9 @@ void ImGui::EndFrame()
 
     CallContextHooks(&g, ImGuiContextHookType_EndFramePre);
 
+    // [EXPERIMENTAL] Recover from errors
+    if (g.IO.ConfigErrorRecovery)
+        ErrorRecoveryTryToRecoverState(&g.StackSizesInNewFrame);
     ErrorCheckEndFrameSanityChecks();
     ErrorCheckEndFrameFinalizeErrorTooltip();
 
@@ -6960,12 +6979,13 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
 
     // Add to stack
     g.CurrentWindow = window;
-    ImGuiWindowStackData window_stack_data;
+    g.CurrentWindowStack.resize(g.CurrentWindowStack.Size + 1);
+    ImGuiWindowStackData& window_stack_data = g.CurrentWindowStack.back();
     window_stack_data.Window = window;
     window_stack_data.ParentLastItemDataBackup = g.LastItemData;
-    window_stack_data.StackSizesOnBegin.SetToContextState(&g);
     window_stack_data.DisabledOverrideReenable = (flags & ImGuiWindowFlags_Tooltip) && (g.CurrentItemFlags & ImGuiItemFlags_Disabled);
-    g.CurrentWindowStack.push_back(window_stack_data);
+    ErrorRecoveryStoreState(&window_stack_data.StackSizesInBegin);
+    g.StackSizesInBeginForCurrentWindow = &window_stack_data.StackSizesInBegin;
     if (flags & ImGuiWindowFlags_ChildMenu)
         g.BeginMenuDepth++;
 
@@ -7693,7 +7713,11 @@ void ImGui::End()
         g.BeginMenuDepth--;
     if (window->Flags & ImGuiWindowFlags_Popup)
         g.BeginPopupStack.pop_back();
-    window_stack_data.StackSizesOnBegin.CompareWithContextState(&g);
+
+    // Error handling, state recovery
+    if (g.IO.ConfigErrorRecovery)
+        ErrorRecoveryTryToRecoverWindowState(&window_stack_data.StackSizesInBegin);
+
     g.CurrentWindowStack.pop_back();
     SetCurrentWindow(g.CurrentWindowStack.Size == 0 ? NULL : g.CurrentWindowStack.back().Window);
 }
@@ -8454,7 +8478,7 @@ void ImGui::PushFocusScope(ImGuiID id)
 void ImGui::PopFocusScope()
 {
     ImGuiContext& g = *GImGui;
-    if (g.FocusScopeStack.Size <= 0)
+    if (g.FocusScopeStack.Size <= g.StackSizesInBeginForCurrentWindow->SizeOfFocusScopeStack)
     {
         IM_ASSERT_USER_ERROR(0, "Calling PopFocusScope() too many times!");
         return;
@@ -10303,9 +10327,10 @@ bool ImGui::Shortcut(ImGuiKeyChord key_chord, ImGuiInputFlags flags, ImGuiID own
 // - ErrorCheckUsingSetCursorPosToExtendParentBoundaries()
 // - ErrorCheckNewFrameSanityChecks()
 // - ErrorCheckEndFrameSanityChecks()
-// - ErrorCheckEndFrameRecover()
-// - ErrorCheckEndWindowRecover()
-// - ImGuiStackSizes
+// - ErrorRecoveryStoreState()
+// - ErrorRecoveryTryToRecoverState()
+// - ErrorRecoveryTryToRecoverWindowState()
+// - ErrorLog()
 //-----------------------------------------------------------------------------
 
 // Verify ABI compatibility between caller code and compiled version of Dear ImGui. This helps detects some build issues.
@@ -10404,6 +10429,10 @@ static void ImGui::ErrorCheckNewFrameSanityChecks()
         IM_ASSERT(g.IO.KeyMap[ImGuiKey_Space] != -1 && "ImGuiKey_Space is not mapped, required for keyboard navigation.");
 #endif
 
+    // Error handling: we do not accept 100% silent recovery! Please contact me if you feel this is getting in your way.
+    if (g.IO.ConfigErrorRecovery)
+        IM_ASSERT(g.IO.ConfigErrorRecoveryEnableAssert || g.IO.ConfigErrorRecoveryEnableDebugLog || g.IO.ConfigErrorRecoveryEnableTooltip || g.ErrorCallback != NULL);
+
     // Remap legacy clipboard handlers (OBSOLETED in 1.91.1, August 2024)
 #ifndef IMGUI_DISABLE_OBSOLETE_FUNCTIONS
     if (g.IO.GetClipboardTextFn != NULL && (g.PlatformIO.Platform_GetClipboardTextFn == NULL || g.PlatformIO.Platform_GetClipboardTextFn == Platform_GetClipboardTextFn_DefaultImpl))
@@ -10426,43 +10455,35 @@ static void ImGui::ErrorCheckEndFrameSanityChecks()
     IM_ASSERT((key_mods == 0 || g.IO.KeyMods == key_mods) && "Mismatching io.KeyCtrl/io.KeyShift/io.KeyAlt/io.KeySuper vs io.KeyMods");
     IM_UNUSED(key_mods);
 
-    // [EXPERIMENTAL] Recover from errors: You may call this yourself before EndFrame().
-    //ErrorCheckEndFrameRecover();
-
-    // Report when there is a mismatch of Begin/BeginChild vs End/EndChild calls. Important: Remember that the Begin/BeginChild API requires you
-    // to always call End/EndChild even if Begin/BeginChild returns false! (this is unfortunately inconsistent with most other Begin* API).
-    if (g.CurrentWindowStack.Size != 1)
-    {
-        if (g.CurrentWindowStack.Size > 1)
-        {
-            ImGuiWindow* window = g.CurrentWindowStack.back().Window; // <-- This window was not Ended!
-            IM_ASSERT_USER_ERROR(g.CurrentWindowStack.Size == 1, "Mismatched Begin/BeginChild vs End/EndChild calls: did you forget to call End/EndChild?");
-            IM_UNUSED(window);
-            while (g.CurrentWindowStack.Size > 1)
-                End();
-        }
-        else
-        {
-            IM_ASSERT_USER_ERROR(g.CurrentWindowStack.Size == 1, "Mismatched Begin/BeginChild vs End/EndChild calls: did you call End/EndChild too much?");
-        }
-    }
-    if (g.CurrentWindowStack.Size >= 1)
-        IM_ASSERT(g.CurrentWindowStack[0].Window->IsFallbackWindow);
+    IM_ASSERT(g.CurrentWindowStack.Size == 1);
+    IM_ASSERT(g.CurrentWindowStack[0].Window->IsFallbackWindow);
+}
 
-    IM_ASSERT_USER_ERROR(g.GroupStack.Size == 0, "Missing EndGroup call!");
+// Save current stack sizes. Called e.g. by NewFrame() and by Begin() but may be called for manual recovery.
+void ImGui::ErrorRecoveryStoreState(ImGuiErrorRecoveryState* state_out)
+{
+    ImGuiContext& g = *GImGui;
+    state_out->SizeOfWindowStack = (short)g.CurrentWindowStack.Size;
+    state_out->SizeOfIDStack = (short)g.CurrentWindow->IDStack.Size;
+    state_out->SizeOfColorStack = (short)g.ColorStack.Size;
+    state_out->SizeOfStyleVarStack = (short)g.StyleVarStack.Size;
+    state_out->SizeOfFontStack = (short)g.FontStack.Size;
+    state_out->SizeOfFocusScopeStack = (short)g.FocusScopeStack.Size;
+    state_out->SizeOfGroupStack = (short)g.GroupStack.Size;
+    state_out->SizeOfItemFlagsStack = (short)g.ItemFlagsStack.Size;
+    state_out->SizeOfBeginPopupStack = (short)g.BeginPopupStack.Size;
+    state_out->SizeOfDisabledStack = (short)g.DisabledStackSize;
 }
 
-// Experimental recovery from incorrect usage of BeginXXX/EndXXX/PushXXX/PopXXX calls.
-// Must be called during or before EndFrame().
-// This is generally flawed as we are not necessarily End/Popping things in the right order.
-// FIXME: Can't recover from inside BeginTabItem/EndTabItem yet.
-void    ImGui::ErrorCheckEndFrameRecover()
+// Chosen name "Try to recover" over e.g. "Restore" to suggest this is not a 100% guaranteed recovery.
+// Called by e.g. EndFrame() but may be called for manual recovery.
+// Attempt to recover full window stack.
+void ImGui::ErrorRecoveryTryToRecoverState(const ImGuiErrorRecoveryState* state_in)
 {
     // PVS-Studio V1044 is "Loop break conditions do not depend on the number of iterations"
     ImGuiContext& g = *GImGui;
-    while (g.CurrentWindowStack.Size > 0) //-V1044
+    while (g.CurrentWindowStack.Size > state_in->SizeOfWindowStack) //-V1044
     {
-        ErrorCheckEndWindowRecover();
         // Recap:
         // - Begin()/BeginChild() return false to indicate the window is collapsed or fully clipped.
         // - Always call a matching End() for each Begin() call, regardless of its return value!
@@ -10480,12 +10501,17 @@ void    ImGui::ErrorCheckEndFrameRecover()
             End();
         }
     }
+    if (g.CurrentWindowStack.Size == state_in->SizeOfWindowStack)
+        ErrorRecoveryTryToRecoverWindowState(state_in);
 }
 
-// Must be called before End()/EndChild()
-void    ImGui::ErrorCheckEndWindowRecover()
+// Called by e.g. End() but may be called for manual recovery.
+// Read '// Error Handling [BETA]' block in imgui_internal.h for details.
+// Attempt to recover from incorrect usage of BeginXXX/EndXXX/PushXXX/PopXXX calls.
+void    ImGui::ErrorRecoveryTryToRecoverWindowState(const ImGuiErrorRecoveryState* state_in)
 {
     ImGuiContext& g = *GImGui;
+
     while (g.CurrentTable != NULL && g.CurrentTable->InnerWindow == g.CurrentWindow)
     {
         IM_ASSERT_USER_ERROR(0, "Missing EndTable()");
@@ -10493,8 +10519,6 @@ void    ImGui::ErrorCheckEndWindowRecover()
     }
 
     ImGuiWindow* window = g.CurrentWindow;
-    IM_ASSERT(window != NULL);
-    ImGuiStackSizes* state_in = &g.CurrentWindowStack.back().StackSizesOnBegin;
 
     // FIXME: Can't recover from inside BeginTabItem/EndTabItem yet.
     while (g.CurrentTabBar != NULL && g.CurrentTabBar->Window == window) //-V1044
@@ -10560,45 +10584,52 @@ void    ImGui::ErrorCheckEndWindowRecover()
         IM_ASSERT_USER_ERROR(0, "Missing PopFocusScope()");
         PopFocusScope();
     }
+    //IM_ASSERT(g.FocusScopeStack.Size == state_in->SizeOfFocusScopeStack);
 }
 
-// Save current stack sizes for later compare
-void ImGuiStackSizes::SetToContextState(ImGuiContext* ctx)
+bool    ImGui::ErrorLog(const char* msg)
 {
-    ImGuiContext& g = *ctx;
-    ImGuiWindow* window = g.CurrentWindow;
-    SizeOfIDStack = (short)window->IDStack.Size;
-    SizeOfColorStack = (short)g.ColorStack.Size;
-    SizeOfStyleVarStack = (short)g.StyleVarStack.Size;
-    SizeOfFontStack = (short)g.FontStack.Size;
-    SizeOfFocusScopeStack = (short)g.FocusScopeStack.Size;
-    SizeOfGroupStack = (short)g.GroupStack.Size;
-    SizeOfItemFlagsStack = (short)g.ItemFlagsStack.Size;
-    SizeOfBeginPopupStack = (short)g.BeginPopupStack.Size;
-    SizeOfDisabledStack = (short)g.DisabledStackSize;
-}
+    ImGuiContext& g = *GImGui;
 
-// Compare to detect usage errors
-void ImGuiStackSizes::CompareWithContextState(ImGuiContext* ctx)
-{
-    ImGuiContext& g = *ctx;
+    // Output to debug log
+#ifndef IMGUI_DISABLE_DEBUG_TOOLS
     ImGuiWindow* window = g.CurrentWindow;
-    IM_UNUSED(window);
 
-    // Window stacks
-    // NOT checking: DC.ItemWidth, DC.TextWrapPos (per window) to allow user to conveniently push once and not pop (they are cleared on Begin)
-    IM_ASSERT(SizeOfIDStack         == window->IDStack.Size     && "PushID/PopID or TreeNode/TreePop Mismatch!");
+    if (g.IO.ConfigErrorRecoveryEnableDebugLog)
+    {
+        if (g.ErrorFirst)
+            IMGUI_DEBUG_LOG_ERROR("[imgui-error] (current settings: Assert=%d, Log=%d, Tooltip=%d)\n",
+                g.IO.ConfigErrorRecoveryEnableAssert, g.IO.ConfigErrorRecoveryEnableDebugLog, g.IO.ConfigErrorRecoveryEnableTooltip);
+        IMGUI_DEBUG_LOG_ERROR("[imgui-error] In window '%s': %s\n", window ? window->Name : "NULL", msg);
+    }
+    g.ErrorFirst = false;
+
+    // Output to tooltip
+    if (g.IO.ConfigErrorRecoveryEnableTooltip)
+    {
+        if (BeginErrorTooltip())
+        {
+            if (g.ErrorCountCurrentFrame < 20)
+            {
+                Text("In window '%s': %s", window ? window->Name : "NULL", msg);
+                if (window && (!window->IsFallbackWindow || window->WasActive))
+                    GetForegroundDrawList(window)->AddRect(window->Pos, window->Pos + window->Size, IM_COL32(255, 0, 0, 255));
+            }
+            if (g.ErrorCountCurrentFrame == 20)
+                Text("(and more errors)");
+            // EndFrame() will amend debug buttons to this window, after all errors have been submitted.
+            EndErrorTooltip();
+        }
+        g.ErrorCountCurrentFrame++;
+    }
+#endif
+
+    // Output to callback
+    if (g.ErrorCallback != NULL)
+        g.ErrorCallback(&g, g.ErrorCallbackUserData, msg);
 
-    // Global stacks
-    // For color, style and font stacks there is an incentive to use Push/Begin/Pop/.../End patterns, so we relax our checks a little to allow them.
-    IM_ASSERT(SizeOfGroupStack      == g.GroupStack.Size        && "BeginGroup/EndGroup Mismatch!");
-    IM_ASSERT(SizeOfBeginPopupStack == g.BeginPopupStack.Size   && "BeginPopup/EndPopup or BeginMenu/EndMenu Mismatch!");
-    IM_ASSERT(SizeOfDisabledStack   == g.DisabledStackSize      && "BeginDisabled/EndDisabled Mismatch!");
-    IM_ASSERT(SizeOfItemFlagsStack  >= g.ItemFlagsStack.Size    && "PushItemFlag/PopItemFlag Mismatch!");
-    IM_ASSERT(SizeOfColorStack      >= g.ColorStack.Size        && "PushStyleColor/PopStyleColor Mismatch!");
-    IM_ASSERT(SizeOfStyleVarStack   >= g.StyleVarStack.Size     && "PushStyleVar/PopStyleVar Mismatch!");
-    IM_ASSERT(SizeOfFontStack       >= g.FontStack.Size         && "PushFont/PopFont Mismatch!");
-    IM_ASSERT(SizeOfFocusScopeStack == g.FocusScopeStack.Size   && "PushFocusScope/PopFocusScope Mismatch!");
+    // Return whether we should assert
+    return g.IO.ConfigErrorRecoveryEnableAssert;
 }
 
 void ImGui::ErrorCheckEndFrameFinalizeErrorTooltip()
@@ -10625,6 +10656,21 @@ void ImGui::ErrorCheckEndFrameFinalizeErrorTooltip()
             g.PlatformIO.Platform_OpenInShellFn(&g, "https://github.com/ocornut/imgui/blob/master/docs/FAQ.md#qa-usage");
         EndErrorTooltip();
     }
+
+    if (g.ErrorCountCurrentFrame > 0 && BeginErrorTooltip()) // Amend at end of frame
+    {
+        Separator();
+        Text("(Hold CTRL and:");
+        SameLine();
+        if (SmallButton("Enable Asserts"))
+            g.IO.ConfigErrorRecoveryEnableAssert = true;
+        //SameLine();
+        //if (SmallButton("Hide Error Tooltips"))
+        //    g.IO.ConfigErrorRecoveryEnableTooltip = false; // Too dangerous
+        SameLine(0, 0);
+        Text(")");
+        EndErrorTooltip();
+    }
 #endif
 }
 

imgui.h

@@ -29,7 +29,7 @@
 // Library Version
 // (Integer encoded as XYYZZ for use in #if preprocessor conditionals, e.g. '#if IMGUI_VERSION_NUM >= 12345')
 #define IMGUI_VERSION       "1.91.3 WIP"
-#define IMGUI_VERSION_NUM   19122
+#define IMGUI_VERSION_NUM   19123
 #define IMGUI_HAS_TABLE
 
 /*
@@ -2265,6 +2265,23 @@ struct ImGuiIO
     // Debug options
     //------------------------------------------------------------------
 
+    // Options to configure how we handle recoverable errors [EXPERIMENTAL]
+    // - Error recovery is not perfect nor guaranteed! It is a feature to ease development.
+    // - Functions that support error recovery are using IM_ASSERT_USER_ERROR() instead of IM_ASSERT().
+    // - You not are not supposed to rely on it in the course of a normal application run.
+    // - Possible usage: facilitate recovery from errors triggered from a scripting language or after specific exceptions handlers.
+    // - Always ensure that on programmers seat you have at minimum Asserts or Tooltips enabled when making direct imgui API calls!
+    //   Otherwise it would severely hinder your ability to catch and correct mistakes!
+    // Read https://github.com/ocornut/imgui/wiki/Error-Handling for details about typical usage scenarios:
+    // - Programmer seats: keep asserts (default), or disable asserts and keep error tooltips (new and nice!)
+    // - Non-programmer seats: maybe disable asserts, but make sure errors are resurfaced (visible log entries, use callback etc.)
+    // - Recovery after error from scripting language: record stack sizes before running script, disable assert, trigger breakpoint from ErrorCallback, recover with ErrorRecoveryTryToRecoverState(), restore settings.
+    // - Recovery after an exception handler:  record stack sizes before try {} block, disable assert, set log callback, recover with ErrorRecoveryTryToRecoverState(), restore settings.
+    bool        ConfigErrorRecovery;                // = true       // Enable error recovery support. Some errors won't be detected and lead to direct crashes if recovery is disabled.
+    bool        ConfigErrorRecoveryEnableAssert;    // = true       // Enable asserts on recoverable error. By default call IM_ASSERT() when returning from a failing IM_ASSERT_USER_ERROR()
+    bool        ConfigErrorRecoveryEnableDebugLog;  // = true       // Enable debug log output on recoverable errors.
+    bool        ConfigErrorRecoveryEnableTooltip;   // = true       // Enable tooltip on recoverable errors. The tooltip include a way to enable asserts if they were disabled.
+
     // Option to enable various debug tools showing buttons that will call the IM_DEBUG_BREAK() macro.
     // - The Item Picker tool will be available regardless of this being enabled, in order to maximize its discoverability.
     // - Requires a debugger being attached, otherwise IM_DEBUG_BREAK() options will appear to crash your application.
@@ -2293,7 +2310,7 @@ struct ImGuiIO
     bool        ConfigDebugIniSettings;         // = false          // Save .ini data with extra comments (particularly helpful for Docking, but makes saving slower)
 
     //------------------------------------------------------------------
-    // Platform Functions
+    // Platform Identifiers
     // (the imgui_impl_xxxx backend files are setting those up for you)
     //------------------------------------------------------------------
 

imgui_demo.cpp

@@ -545,6 +545,22 @@ void ImGui::ShowDemoWindow(bool* p_open)
             ImGui::SameLine(); HelpMarker("Swap Cmd<>Ctrl keys, enable various MacOS style behaviors.");
             ImGui::Text("Also see Style->Rendering for rendering options.");
 
+            // Read https://github.com/ocornut/imgui/wiki/Error-Handling
+            ImGui::SeparatorText("Error Handling");
+            ImGui::Checkbox("io.ConfigErrorRecovery", &io.ConfigErrorRecovery);
+            ImGui::SameLine(); HelpMarker(
+                "Options to configure how we handle recoverable errors.\n"
+                "- Error recovery is not perfect nor guaranteed! It is a feature to ease development.\n"
+                "- You not are not supposed to rely on it in the course of a normal application run.\n"
+                "- Possible usage: facilitate recovery from errors triggered from a scripting language or after specific exceptions handlers.\n"
+                "- Always ensure that on programmers seat you have at minimum Asserts or Tooltips enabled when making direct imgui API call!"
+                "Otherwise it would severely hinder your ability to catch and correct mistakes!");
+            ImGui::Checkbox("io.ConfigErrorRecoveryEnableAssert", &io.ConfigErrorRecoveryEnableAssert);
+            ImGui::Checkbox("io.ConfigErrorRecoveryEnableDebugLog", &io.ConfigErrorRecoveryEnableDebugLog);
+            ImGui::Checkbox("io.ConfigErrorRecoveryEnableTooltip", &io.ConfigErrorRecoveryEnableTooltip);
+            if (!io.ConfigErrorRecoveryEnableAssert && !io.ConfigErrorRecoveryEnableDebugLog && !io.ConfigErrorRecoveryEnableTooltip)
+                io.ConfigErrorRecoveryEnableAssert = io.ConfigErrorRecoveryEnableDebugLog = io.ConfigErrorRecoveryEnableTooltip = true;
+
             ImGui::SeparatorText("Debug");
             ImGui::Checkbox("io.ConfigDebugIsDebuggerPresent", &io.ConfigDebugIsDebuggerPresent);
             ImGui::SameLine(); HelpMarker("Enable various tools calling IM_DEBUG_BREAK().\n\nRequires a debugger being attached, otherwise IM_DEBUG_BREAK() options will appear to crash your application.");

imgui_internal.h

@@ -132,6 +132,7 @@ struct ImGuiContext;                // Main Dear ImGui context
 struct ImGuiContextHook;            // Hook for extensions like ImGuiTestEngine
 struct ImGuiDataVarInfo;            // Variable information (e.g. to access style variables from an enum)
 struct ImGuiDataTypeInfo;           // Type information associated to a ImGuiDataType enum
+struct ImGuiErrorRecoveryState;     // Storage of stack sizes for error handling and recovery
 struct ImGuiGroupData;              // Stacked storage data for BeginGroup()/EndGroup()
 struct ImGuiInputTextState;         // Internal state of the currently focused/edited text input box
 struct ImGuiInputTextDeactivateData;// Short term storage to backup text of a deactivating InputText() while another is stealing active id
@@ -148,7 +149,6 @@ struct ImGuiOldColumnData;          // Storage data for a single column for lega
 struct ImGuiOldColumns;             // Storage data for a columns set for legacy Columns() api
 struct ImGuiPopupData;              // Storage for current popup stack
 struct ImGuiSettingsHandler;        // Storage for one type registered in the .ini file
-struct ImGuiStackSizes;             // Storage of stack sizes for debugging/asserting
 struct ImGuiStyleMod;               // Stacked style modifier, backup of modified data so we can restore it
 struct ImGuiTabBar;                 // Storage for a tab bar
 struct ImGuiTabItem;                // Storage for a tab item (within a tab bar)
@@ -1253,9 +1253,10 @@ struct ImGuiTreeNodeStackData
     ImRect                  NavRect;    // Used for nav landing
 };
 
-// sizeof() = 18
-struct IMGUI_API ImGuiStackSizes
+// sizeof() = 20
+struct IMGUI_API ImGuiErrorRecoveryState
 {
+    short   SizeOfWindowStack;
     short   SizeOfIDStack;
     short   SizeOfColorStack;
     short   SizeOfStyleVarStack;
@@ -1266,18 +1267,16 @@ struct IMGUI_API ImGuiStackSizes
     short   SizeOfBeginPopupStack;
     short   SizeOfDisabledStack;
 
-    ImGuiStackSizes() { memset(this, 0, sizeof(*this)); }
-    void SetToContextState(ImGuiContext* ctx);
-    void CompareWithContextState(ImGuiContext* ctx);
+    ImGuiErrorRecoveryState() { memset(this, 0, sizeof(*this)); }
 };
 
 // Data saved for each window pushed into the stack
 struct ImGuiWindowStackData
 {
-    ImGuiWindow*        Window;
-    ImGuiLastItemData   ParentLastItemDataBackup;
-    ImGuiStackSizes     StackSizesOnBegin;          // Store size of various stacks for asserting
-    bool                DisabledOverrideReenable;   // Non-child window override disabled flag
+    ImGuiWindow*            Window;
+    ImGuiLastItemData       ParentLastItemDataBackup;
+    ImGuiErrorRecoveryState StackSizesInBegin;          // Store size of various stacks for asserting
+    bool                    DisabledOverrideReenable;   // Non-child window override disabled flag
 };
 
 struct ImGuiShrinkWidthItem
@@ -1885,12 +1884,17 @@ struct ImGuiLocEntry
 //-----------------------------------------------------------------------------
 
 // Macros used by Recoverable Error handling
-// Down the line in some frameworks/languages we would like to have a way to redirect those to the programmer and recover from more faults.
+// - Only dispatch error if _EXPR: evaluate as assert (similar to an assert macro).
+// - The message will always be a string literal, in order to increase likelihood of being display by an assert handler.
+// - The intent is that you may rewire this macro to dispatch dynamically:
+//   - On programmers machines, when debugger is attached, on direct imgui API usage error: always assert!
+//   - On exception recovery and script language recovery: you may decide to error log.
 #ifndef IM_ASSERT_USER_ERROR
-#define IM_ASSERT_USER_ERROR(_EXPR,_MSG)    IM_ASSERT((_EXPR) && _MSG)
+#define IM_ASSERT_USER_ERROR(_EXPR,_MSG)    do { if (!(_EXPR) && ImGui::ErrorLog(_MSG)) { IM_ASSERT((_EXPR) && _MSG); } } while (0)    // Recoverable User Error
 #endif
 
-typedef void (*ImGuiErrorLogCallback)(void* user_data, const char* fmt, ...);
+
+typedef void    (*ImGuiErrorCallback)(ImGuiContext* ctx, void* user_data, const char* msg); // Function signature for g.ErrorCallback
 
 //-----------------------------------------------------------------------------
 // [SECTION] Metrics, Debug Tools
@@ -2313,8 +2317,14 @@ struct ImGuiContext
     int                     LogDepthToExpand;
     int                     LogDepthToExpandDefault;            // Default/stored value for LogDepthMaxExpand if not specified in the LogXXX function call.
 
-    // Error handling
+    // Error Handling
+    ImGuiErrorCallback      ErrorCallback;                      // = NULL. May be exposed in public API eventually.
+    void*                   ErrorCallbackUserData;              // = NULL
     ImVec2                  ErrorTooltipLockedPos;
+    bool                    ErrorFirst;
+    int                     ErrorCountCurrentFrame;             // [Internal] Number of errors submitted this frame.
+    ImGuiErrorRecoveryState StackSizesInNewFrame;               // [Internal]
+    ImGuiErrorRecoveryState*StackSizesInBeginForCurrentWindow;  // [Internal]
 
     // Debug Tools
     // (some of the highly frequently used data are interleaved in other structures above: DebugBreakXXX fields, DebugHookIdInfo, DebugLocateId etc.)
@@ -3419,9 +3429,11 @@ namespace ImGui
     IMGUI_API void          GcAwakeTransientWindowBuffers(ImGuiWindow* window);
 
     // Error handling, State Recovery
+    IMGUI_API bool          ErrorLog(const char* msg);
+    IMGUI_API void          ErrorRecoveryStoreState(ImGuiErrorRecoveryState* state_out);
+    IMGUI_API void          ErrorRecoveryTryToRecoverState(const ImGuiErrorRecoveryState* state_in);
+    IMGUI_API void          ErrorRecoveryTryToRecoverWindowState(const ImGuiErrorRecoveryState* state_in);
     IMGUI_API void          ErrorCheckUsingSetCursorPosToExtendParentBoundaries();
-    IMGUI_API void          ErrorCheckEndFrameRecover();
-    IMGUI_API void          ErrorCheckEndWindowRecover();
     IMGUI_API void          ErrorCheckEndFrameFinalizeErrorTooltip();
     IMGUI_API bool          BeginErrorTooltip();
     IMGUI_API void          EndErrorTooltip();

imgui_tables.cpp

@@ -1484,7 +1484,9 @@ void    ImGui::EndTable()
     {
         short backup_nav_layers_active_mask = inner_window->DC.NavLayersActiveMask;
         inner_window->DC.NavLayersActiveMask |= 1 << ImGuiNavLayer_Main; // So empty table don't appear to navigate differently.
+        g.CurrentTable = NULL; // To avoid error recovery recursing
         EndChild();
+        g.CurrentTable = table;
         inner_window->DC.NavLayersActiveMask = backup_nav_layers_active_mask;
     }
     else

imgui_widgets.cpp

@@ -7551,7 +7551,7 @@ ImGuiMultiSelectIO* ImGui::EndMultiSelect()
     ImGuiMultiSelectTempData* ms = g.CurrentMultiSelect;
     ImGuiMultiSelectState* storage = ms->Storage;
     ImGuiWindow* window = g.CurrentWindow;
-    IM_ASSERT(ms->FocusScopeId == g.CurrentFocusScopeId);
+    IM_ASSERT_USER_ERROR(ms->FocusScopeId == g.CurrentFocusScopeId, "EndMultiSelect() FocusScope mismatch!");
     IM_ASSERT(g.CurrentMultiSelect != NULL && storage->Window == g.CurrentWindow);
     IM_ASSERT(g.MultiSelectTempDataStacked > 0 && &g.MultiSelectTempData[g.MultiSelectTempDataStacked - 1] == g.CurrentMultiSelect);