ImVector: Made a struct. Using T/T* in the code instead of value_type/iterator. Renamed index_from_pointer() to index_from_ptr() (was not documented, added in 1.63, users not supposed to use ImVector, hopefully not a big deal).

imgui.cpp

@@ -4384,7 +4384,7 @@ static ImGuiWindow* CreateNewWindow(const char* name, ImVec2 size, ImGuiWindowFl
         if (ImGuiWindowSettings* settings = ImGui::FindWindowSettings(window->ID))
         {
             // Retrieve settings from .ini file
-            window->SettingsIdx = g.SettingsWindows.index_from_pointer(settings);
+            window->SettingsIdx = g.SettingsWindows.index_from_ptr(settings);
             SetWindowConditionAllowFlags(window, ImGuiCond_FirstUseEver, false);
             window->Pos = ImFloor(settings->Pos);
             window->Collapsed = settings->Collapsed;
@@ -8940,7 +8940,7 @@ static void SettingsHandlerWindow_WriteAll(ImGuiContext* imgui_ctx, ImGuiSetting
         if (!settings)
         {
             settings = ImGui::CreateNewWindowSettings(window->Name);
-            window->SettingsIdx = g.SettingsWindows.index_from_pointer(settings);
+            window->SettingsIdx = g.SettingsWindows.index_from_ptr(settings);
         }
         IM_ASSERT(settings->ID == window->ID);
         settings->Pos = window->Pos;

imgui.h

@@ -1157,55 +1157,57 @@ enum ImGuiCond_
 // Helper: ImVector<>
 // Lightweight std::vector<>-like class to avoid dragging dependencies (also: some implementations of STL with debug enabled are absurdly slow, we bypass it so our code runs fast in debug).
 // You generally do NOT need to care or use this ever. But we need to make it available in imgui.h because some of our data structures are relying on it.
+// Important: clear() frees memory, resize(0) keep the allocated buffer. We use resize(0) a lot to intentionally recycle allocated buffers across frames and amortize our costs.
 // Important: our implementation does NOT call C++ constructors/destructors, we treat everything as raw data! This is intentional but be extra mindful of that, 
 // do NOT use this class as a std::vector replacement in your own code!
 //-----------------------------------------------------------------------------
 
 template<typename T>
-class ImVector
+struct ImVector
 {
-public:
-    int                         Size;
-    int                         Capacity;
-    T*                          Data;
+    int                 Size;
+    int                 Capacity;
+    T*                  Data;
 
+    // Provide standard typedefs but we don't use them ourselves.
     typedef T                   value_type;
     typedef value_type*         iterator;
     typedef const value_type*   const_iterator;
 
-    inline ImVector()           { Size = Capacity = 0; Data = NULL; }
-    inline ~ImVector()          { if (Data) ImGui::MemFree(Data); }
-    inline ImVector(const ImVector<T>& src)                     { Size = Capacity = 0; Data = NULL; operator=(src); }
-    inline ImVector<T>& operator=(const ImVector<T>& src)       { clear(); resize(src.Size); memcpy(Data, src.Data, (size_t)Size * sizeof(value_type)); return *this; }
-
-    inline bool                 empty() const                   { return Size == 0; }
-    inline int                  size() const                    { return Size; }
-    inline int                  capacity() const                { return Capacity; }
-    inline value_type&          operator[](int i)               { IM_ASSERT(i < Size); return Data[i]; }
-    inline const value_type&    operator[](int i) const         { IM_ASSERT(i < Size); return Data[i]; }
-
-    inline void                 clear()                         { if (Data) { Size = Capacity = 0; ImGui::MemFree(Data); Data = NULL; } }
-    inline iterator             begin()                         { return Data; }
-    inline const_iterator       begin() const                   { return Data; }
-    inline iterator             end()                           { return Data + Size; }
-    inline const_iterator       end() const                     { return Data + Size; }
-    inline value_type&          front()                         { IM_ASSERT(Size > 0); return Data[0]; }
-    inline const value_type&    front() const                   { IM_ASSERT(Size > 0); return Data[0]; }
-    inline value_type&          back()                          { IM_ASSERT(Size > 0); return Data[Size - 1]; }
-    inline const value_type&    back() const                    { IM_ASSERT(Size > 0); return Data[Size - 1]; }
-    inline void                 swap(ImVector<value_type>& rhs) { int rhs_size = rhs.Size; rhs.Size = Size; Size = rhs_size; int rhs_cap = rhs.Capacity; rhs.Capacity = Capacity; Capacity = rhs_cap; value_type* rhs_data = rhs.Data; rhs.Data = Data; Data = rhs_data; }
-
-    inline int          _grow_capacity(int sz) const            { int new_capacity = Capacity ? (Capacity + Capacity/2) : 8; return new_capacity > sz ? new_capacity : sz; }
-    inline void         resize(int new_size)                    { if (new_size > Capacity) reserve(_grow_capacity(new_size)); Size = new_size; }
-    inline void         resize(int new_size,const value_type& v){ if (new_size > Capacity) reserve(_grow_capacity(new_size)); if (new_size > Size) for (int n = Size; n < new_size; n++) memcpy(&Data[n], &v, sizeof(v)); Size = new_size; }
+    // Constructors, destructor
+    inline ImVector()                                       { Size = Capacity = 0; Data = NULL; }
+    inline ImVector(const ImVector<T>& src)                 { Size = Capacity = 0; Data = NULL; operator=(src); }
+    inline ImVector<T>& operator=(const ImVector<T>& src)   { clear(); resize(src.Size); memcpy(Data, src.Data, (size_t)Size * sizeof(T)); return *this; }
+    inline ~ImVector()                                      { if (Data) ImGui::MemFree(Data); }
+
+    inline bool         empty() const                       { return Size == 0; }
+    inline int          size() const                        { return Size; }
+    inline int          capacity() const                    { return Capacity; }
+    inline T&           operator[](int i)                   { IM_ASSERT(i < Size); return Data[i]; }
+    inline const T&     operator[](int i) const             { IM_ASSERT(i < Size); return Data[i]; }
+
+    inline void         clear()                             { if (Data) { Size = Capacity = 0; ImGui::MemFree(Data); Data = NULL; } }
+    inline T*           begin()                             { return Data; }
+    inline const T*     begin() const                       { return Data; }
+    inline T*           end()                               { return Data + Size; }
+    inline const T*     end() const                         { return Data + Size; }
+    inline T&           front()                             { IM_ASSERT(Size > 0); return Data[0]; }
+    inline const T&     front() const                       { IM_ASSERT(Size > 0); return Data[0]; }
+    inline T&           back()                              { IM_ASSERT(Size > 0); return Data[Size - 1]; }
+    inline const T&     back() const                        { IM_ASSERT(Size > 0); return Data[Size - 1]; }
+    inline void         swap(ImVector<T>& rhs)              { int rhs_size = rhs.Size; rhs.Size = Size; Size = rhs_size; int rhs_cap = rhs.Capacity; rhs.Capacity = Capacity; Capacity = rhs_cap; T* rhs_data = rhs.Data; rhs.Data = Data; Data = rhs_data; }
+
+    inline int          _grow_capacity(int sz) const        { int new_capacity = Capacity ? (Capacity + Capacity/2) : 8; return new_capacity > sz ? new_capacity : sz; }
+    inline void         resize(int new_size)                { if (new_size > Capacity) reserve(_grow_capacity(new_size)); Size = new_size; }
+    inline void         resize(int new_size, const T& v)    { if (new_size > Capacity) reserve(_grow_capacity(new_size)); if (new_size > Size) for (int n = Size; n < new_size; n++) memcpy(&Data[n], &v, sizeof(v)); Size = new_size; }
     inline void         reserve(int new_capacity)
     {
         if (new_capacity <= Capacity)
             return;
-        value_type* new_data = (value_type*)ImGui::MemAlloc((size_t)new_capacity * sizeof(value_type));
+        T* new_data = (T*)ImGui::MemAlloc((size_t)new_capacity * sizeof(T));
         if (Data)
         {
-            memcpy(new_data, Data, (size_t)Size * sizeof(value_type));
+            memcpy(new_data, Data, (size_t)Size * sizeof(T));
             ImGui::MemFree(Data);
         }
         Data = new_data;
@@ -1213,15 +1215,15 @@ public:
     }
 
     // NB: It is illegal to call push_back/push_front/insert with a reference pointing inside the ImVector data itself! e.g. v.push_back(v[10]) is forbidden.
-    inline void         push_back(const value_type& v)                  { if (Size == Capacity) reserve(_grow_capacity(Size + 1)); memcpy(&Data[Size], &v, sizeof(v)); Size++; }
-    inline void         pop_back()                                      { IM_ASSERT(Size > 0); Size--; }
-    inline void         push_front(const value_type& v)                 { if (Size == 0) push_back(v); else insert(Data, v); }
-    inline iterator     erase(const_iterator it)                        { IM_ASSERT(it >= Data && it < Data+Size); const ptrdiff_t off = it - Data; memmove(Data + off, Data + off + 1, ((size_t)Size - (size_t)off - 1) * sizeof(value_type)); Size--; return Data + off; }
-    inline iterator     erase(const_iterator it, const_iterator it_last){ IM_ASSERT(it >= Data && it < Data+Size && it_last > it && it_last <= Data+Size); const ptrdiff_t count = it_last - it; const ptrdiff_t off = it - Data; memmove(Data + off, Data + off + count, ((size_t)Size - (size_t)off - count) * sizeof(value_type)); Size -= (int)count; return Data + off; }
-    inline iterator     erase_unsorted(const_iterator it)               { IM_ASSERT(it >= Data && it < Data+Size);  const ptrdiff_t off = it - Data; if (it < Data+Size-1) memcpy(Data + off, Data + Size - 1, sizeof(value_type)); Size--; return Data + off; }
-    inline iterator     insert(const_iterator it, const value_type& v)  { IM_ASSERT(it >= Data && it <= Data+Size); const ptrdiff_t off = it - Data; if (Size == Capacity) reserve(_grow_capacity(Size + 1)); if (off < (int)Size) memmove(Data + off + 1, Data + off, ((size_t)Size - (size_t)off) * sizeof(value_type)); memcpy(&Data[off], &v, sizeof(v)); Size++; return Data + off; }
-    inline bool         contains(const value_type& v) const             { const T* data = Data;  const T* data_end = Data + Size; while (data < data_end) if (*data++ == v) return true; return false; }
-    inline int          index_from_pointer(const_iterator it) const     { IM_ASSERT(it >= Data && it <= Data+Size); const ptrdiff_t off = it - Data; return (int)off; }
+    inline void         push_back(const T& v)               { if (Size == Capacity) reserve(_grow_capacity(Size + 1)); memcpy(&Data[Size], &v, sizeof(v)); Size++; }
+    inline void         pop_back()                          { IM_ASSERT(Size > 0); Size--; }
+    inline void         push_front(const T& v)              { if (Size == 0) push_back(v); else insert(Data, v); }
+    inline T*           erase(const T* it)                  { IM_ASSERT(it >= Data && it < Data+Size); const ptrdiff_t off = it - Data; memmove(Data + off, Data + off + 1, ((size_t)Size - (size_t)off - 1) * sizeof(T)); Size--; return Data + off; }
+    inline T*           erase(const T* it, const T* it_last){ IM_ASSERT(it >= Data && it < Data+Size && it_last > it && it_last <= Data+Size); const ptrdiff_t count = it_last - it; const ptrdiff_t off = it - Data; memmove(Data + off, Data + off + count, ((size_t)Size - (size_t)off - count) * sizeof(T)); Size -= (int)count; return Data + off; }
+    inline T*           erase_unsorted(const T* it)         { IM_ASSERT(it >= Data && it < Data+Size);  const ptrdiff_t off = it - Data; if (it < Data+Size-1) memcpy(Data + off, Data + Size - 1, sizeof(T)); Size--; return Data + off; }
+    inline T*           insert(const T* it, const T& v)     { IM_ASSERT(it >= Data && it <= Data+Size); const ptrdiff_t off = it - Data; if (Size == Capacity) reserve(_grow_capacity(Size + 1)); if (off < (int)Size) memmove(Data + off + 1, Data + off, ((size_t)Size - (size_t)off) * sizeof(T)); memcpy(&Data[off], &v, sizeof(v)); Size++; return Data + off; }
+    inline bool         contains(const T& v) const          { const T* data = Data;  const T* data_end = Data + Size; while (data < data_end) if (*data++ == v) return true; return false; }
+    inline int          index_from_ptr(const T* it) const   { IM_ASSERT(it >= Data && it <= Data+Size); const ptrdiff_t off = it - Data; return (int)off; }
 };
 
 //-----------------------------------------------------------------------------

imgui_internal.h

@@ -1240,7 +1240,7 @@ struct ImGuiTabBar
     short               LastTabItemIdx;         // For BeginTabItem()/EndTabItem()
 
     ImGuiTabBar();
-    int                 GetTabOrder(const ImGuiTabItem* tab) const { return Tabs.index_from_pointer(tab); }
+    int                 GetTabOrder(const ImGuiTabItem* tab) const { return Tabs.index_from_ptr(tab); }
 };
 
 //-----------------------------------------------------------------------------

imgui_widgets.cpp

@@ -6286,7 +6286,7 @@ bool    ImGui::TabItemEx(ImGuiTabBar* tab_bar, const char* label, bool* p_open,
         tab->Width = size.x;
         tab_is_new = true;
     }
-    tab_bar->LastTabItemIdx = (short)tab_bar->Tabs.index_from_pointer(tab);
+    tab_bar->LastTabItemIdx = (short)tab_bar->Tabs.index_from_ptr(tab);
     tab->WidthContents = size.x;
 
     const bool tab_bar_appearing = (tab_bar->PrevFrameVisible + 1 < g.FrameCount);