Internals: Settings: Simple optimization caching index into the settings buffer, to remove an unnecessary O(N*M) search during saving. (with N=active root windows during the session, M=stored settings which grows over time)

imgui.cpp

@@ -2085,6 +2085,7 @@ ImGuiWindow::ImGuiWindow(ImGuiContext* context, const char* name)
     LastFrameActive = -1;
     ItemWidthDefault = 0.0f;
     FontWindowScale = 1.0f;
+    SettingsIdx = -1;
 
     DrawList = &DrawListInst;
     DrawList->_OwnerName = Name;
@@ -3876,9 +3877,14 @@ static void SettingsHandlerWindow_WriteAll(ImGuiContext* imgui_ctx, ImGuiSetting
         ImGuiWindow* window = g.Windows[i];
         if (window->Flags & ImGuiWindowFlags_NoSavedSettings)
             continue;
-        ImGuiWindowSettings* settings = ImGui::FindWindowSettings(window->ID);
+
+        ImGuiWindowSettings* settings = (window->SettingsIdx != -1) ? &g.SettingsWindows[window->SettingsIdx] : ImGui::FindWindowSettings(window->ID);
         if (!settings)
+        {
             settings = AddWindowSettings(window->Name);
+            window->SettingsIdx = g.SettingsWindows.index_from_pointer(settings);
+        }
+        IM_ASSERT(settings->ID == window->ID);
         settings->Pos = window->Pos;
         settings->Size = window->SizeFull;
         settings->Collapsed = window->Collapsed;
@@ -3981,7 +3987,7 @@ ImGuiWindowSettings* ImGui::FindWindowSettings(ImGuiID id)
 {
     ImGuiContext& g = *GImGui;
     for (int i = 0; i != g.SettingsWindows.Size; i++)
-        if (g.SettingsWindows[i].Id == id)
+        if (g.SettingsWindows[i].ID == id)
             return &g.SettingsWindows[i];
     return NULL;
 }
@@ -3992,7 +3998,7 @@ static ImGuiWindowSettings* AddWindowSettings(const char* name)
     g.SettingsWindows.push_back(ImGuiWindowSettings());
     ImGuiWindowSettings* settings = &g.SettingsWindows.back();
     settings->Name = ImStrdup(name);
-    settings->Id = ImHash(name, 0);
+    settings->ID = ImHash(name, 0);
     return settings;
 }
 
@@ -5695,6 +5701,7 @@ static ImGuiWindow* CreateNewWindow(const char* name, ImVec2 size, ImGuiWindowFl
         // Retrieve settings from .ini file
         if (ImGuiWindowSettings* settings = ImGui::FindWindowSettings(window->ID))
         {
+            window->SettingsIdx = g.SettingsWindows.index_from_pointer(settings);
             SetWindowConditionAllowFlags(window, ImGuiCond_FirstUseEver, false);
             window->Pos = ImFloor(settings->Pos);
             window->Collapsed = settings->Collapsed;

imgui_internal.h

@@ -440,12 +440,12 @@ struct IMGUI_API ImGuiTextEditState
 struct ImGuiWindowSettings
 {
     char*       Name;
-    ImGuiID     Id;
+    ImGuiID     ID;
     ImVec2      Pos;
     ImVec2      Size;
     bool        Collapsed;
 
-    ImGuiWindowSettings() { Name = NULL; Id = 0; Pos = Size = ImVec2(0,0); Collapsed = false; }
+    ImGuiWindowSettings() { Name = NULL; ID = 0; Pos = Size = ImVec2(0,0); Collapsed = false; }
 };
 
 struct ImGuiSettingsHandler
@@ -994,6 +994,7 @@ struct IMGUI_API ImGuiWindow
     ImGuiStorage            StateStorage;
     ImVector<ImGuiColumnsSet> ColumnsStorage;
     float                   FontWindowScale;                    // User scale multiplier per-window
+    int                     SettingsIdx;                        // Index into SettingsWindow[] (indices are always valid as we only grow the array from the back)
 
     ImDrawList*             DrawList;                           // == &DrawListInst (for backward compatibility reason with code using imgui_internal.h we keep this a pointer)
     ImDrawList              DrawListInst;