Tables: amend f799a29 with a better solution + fix potential overflow (#6140)

imgui.cpp

@@ -7514,6 +7514,15 @@ ImGuiID ImGui::GetIDWithSeed(const char* str, const char* str_end, ImGuiID seed)
     return id;
 }
 
+ImGuiID ImGui::GetIDWithSeed(int n, ImGuiID seed)
+{
+    ImGuiID id = ImHashData(&n, sizeof(n), seed);
+    ImGuiContext& g = *GImGui;
+    if (g.DebugHookIdInfo == id)
+        DebugHookIdInfo(id, ImGuiDataType_S32, (void*)(intptr_t)n, NULL);
+    return id;
+}
+
 void ImGui::PopID()
 {
     ImGuiWindow* window = GImGui->CurrentWindow;

imgui_internal.h

@@ -2802,6 +2802,7 @@ namespace ImGui
     IMGUI_API void          MarkItemEdited(ImGuiID id);     // Mark data associated to given item as "edited", used by IsItemDeactivatedAfterEdit() function.
     IMGUI_API void          PushOverrideID(ImGuiID id);     // Push given value as-is at the top of the ID stack (whereas PushID combines old and new hashes)
     IMGUI_API ImGuiID       GetIDWithSeed(const char* str_id_begin, const char* str_id_end, ImGuiID seed);
+    IMGUI_API ImGuiID       GetIDWithSeed(int n, ImGuiID seed);
 
     // Basic Helpers for widget code
     IMGUI_API void          ItemSize(const ImVec2& size, float text_baseline_y = -1.0f);

imgui_tables.cpp

@@ -366,9 +366,7 @@ bool    ImGui::BeginTableEx(const char* name, ImGuiID id, int columns_count, ImG
         IM_ASSERT(table->ColumnsCount == columns_count && "BeginTable(): Cannot change columns count mid-frame while preserving same ID");
         if (table->InstanceDataExtra.Size < instance_no)
             table->InstanceDataExtra.push_back(ImGuiTableInstanceData());
-        char instance_desc[12];
-        int instance_desc_len = ImFormatString(instance_desc, IM_ARRAYSIZE(instance_desc), "##Instance%d", instance_no);
-        instance_id = GetIDWithSeed(instance_desc, instance_desc + instance_desc_len, id);
+        instance_id = GetIDWithSeed(instance_no, GetIDWithSeed("##Instances", NULL, id)); // Push "##Instance" followed by (int)instance_no in ID stack.
     }
     else
     {