Debug Tools: added IMGUI_DEBUG_HIGHLIGHT_ALL_ID_CONFLICTS. (#8651, #7961, #7669)

docs/CHANGELOG.txt

@@ -61,6 +61,9 @@ Other changes:
 - Demo: Added "Text -> Font Size" demo section. (#8738) [@Demonese]
 - CI: Fixed dllimport/dllexport tests. (#8757) [@AidanSun05]
 - CI: Updated to use latest Windows image + VS2022.
+- Debug Tools: added IMGUI_DEBUG_HIGHLIGHT_ALL_ID_CONFLICTS to detect
+  id conflicts _before_ hovering. This is very slow and should only be used
+  temporarily. (#8651, #7961, #7669)
 - Examples: GLFW+OpenGL3, GLFW+WGPU: Emscripten Makefiles uses GLFW port 
   'contrib.glfw3' which offers better HiDPI support. (#8742) [@pthom]
 - Backends: GLFW, SDL2 made ImGui_ImplGLFW_GetContentScaleXXX() and 

imconfig.h

@@ -129,6 +129,10 @@
 //#define IM_DEBUG_BREAK  IM_ASSERT(0)
 //#define IM_DEBUG_BREAK  __debugbreak()
 
+//---- Debug Tools: Enable highlight ID conflicts _before_ hovering items. When io.ConfigDebugHighlightIdConflicts is set.
+// (THIS WILL SLOW DOWN DEAR IMGUI. Only use occasionally and disable after use)
+//#define IMGUI_DEBUG_HIGHLIGHT_ALL_ID_CONFLICTS
+
 //---- Debug Tools: Enable slower asserts
 //#define IMGUI_DEBUG_PARANOID
 

imgui.cpp

@@ -4263,6 +4263,12 @@ void ImGui::Initialize()
 #ifdef IMGUI_HAS_DOCK
 #endif
 
+    // Print a debug message when running with debug feature IMGUI_DEBUG_HIGHLIGHT_ALL_ID_CONFLICTS because it is very slow.
+    // DO NOT COMMENT OUT THIS MESSAGE. IT IS DESIGNED TO REMIND YOU THAT IMGUI_DEBUG_HIGHLIGHT_ALL_ID_CONFLICTS SHOULD ONLY BE TEMPORARILY ENABLED.
+#ifdef IMGUI_DEBUG_HIGHLIGHT_ALL_ID_CONFLICTS
+    DebugLog("IMGUI_DEBUG_HIGHLIGHT_ALL_ID_CONFLICTS is enabled.\nMust disable after use! Otherwise Dear ImGui will run slower.\n");
+#endif
+
     // ImDrawList/ImFontAtlas are designed to function without ImGui, and 99% of it works without an ImGui context.
     // But this link allows us to facilitate/handle a few edge cases better.
     ImFontAtlas* atlas = g.IO.Fonts;
@@ -11012,6 +11018,21 @@ bool ImGui::ItemAdd(const ImRect& bb, ImGuiID id, const ImRect* nav_bb_arg, ImGu
         // Empty identifier are valid and useful in a small amount of cases, but 99.9% of the time you want to use "##something".
         // READ THE FAQ: https://dearimgui.com/faq
         IM_ASSERT(id != window->ID && "Cannot have an empty ID at the root of a window. If you need an empty label, use ## and read the FAQ about how the ID Stack works!");
+
+        // [DEBUG] Highlight all conflicts WITHOUT needing to hover. THIS WILL SLOW DOWN DEAR IMGUI. DON'T KEEP ACTIVATED.
+        // This will only work for items submitted with ItemAdd(). Some very rare/odd/unrecommended code patterns are calling ButtonBehavior() without ItemAdd().
+#ifdef IMGUI_DEBUG_HIGHLIGHT_ALL_ID_CONFLICTS
+        if ((g.LastItemData.ItemFlags & ImGuiItemFlags_AllowDuplicateId) == 0)
+        {
+            int* p_alive = g.DebugDrawIdConflictsAliveCount.GetIntRef(id, -1); // Could halve lookups if we knew ImGuiStorage can store 64-bit, or by storing FrameCount as 30-bits + highlight as 2-bits. But the point is that we should not pretend that this is fast.
+            int* p_highlight = g.DebugDrawIdConflictsHighlightSet.GetIntRef(id, -1);
+            if (*p_alive == g.FrameCount)
+                *p_highlight = g.FrameCount;
+            *p_alive = g.FrameCount;
+            if (*p_highlight >= g.FrameCount - 1)
+                window->DrawList->AddRect(bb.Min - ImVec2(1, 1), bb.Max + ImVec2(1, 1), IM_COL32(255, 0, 0, 255), 0.0f, ImDrawFlags_None, 2.0f);
+        }
+#endif
     }
     //if (g.IO.KeyAlt) window->DrawList->AddRect(bb.Min, bb.Max, IM_COL32(255,255,0,120)); // [DEBUG]
     //if ((g.LastItemData.ItemFlags & ImGuiItemFlags_NoNav) == 0)
@@ -16126,6 +16147,10 @@ void ImGui::ShowMetricsWindow(bool* p_open)
         }
     };
 
+#ifdef IMGUI_DEBUG_HIGHLIGHT_ALL_ID_CONFLICTS
+    TextColored(ImVec4(1.0f, 0.0f, 0.0f, 1.0f), "IMGUI_DEBUG_HIGHLIGHT_ALL_ID_CONFLICTS is enabled.\nMust disable after use! Otherwise Dear ImGui will run slower.\n");
+#endif
+
     // Tools
     if (TreeNode("Tools"))
     {

imgui_internal.h

@@ -2495,6 +2495,10 @@ struct ImGuiContext
     ImGuiMetricsConfig      DebugMetricsConfig;
     ImGuiIDStackTool        DebugIDStackTool;
     ImGuiDebugAllocInfo     DebugAllocInfo;
+#if defined(IMGUI_DEBUG_HIGHLIGHT_ALL_ID_CONFLICTS) && !defined(IMGUI_DISABLE_DEBUG_TOOLS)
+    ImGuiStorage            DebugDrawIdConflictsAliveCount;
+    ImGuiStorage            DebugDrawIdConflictsHighlightSet;
+#endif
 
     // Misc
     float                   FramerateSecPerFrame[60];           // Calculate estimate of framerate for user over the last 60 frames..