Metrics: Added io.MetricsActiveAllocations, moving away from the cross-context global counters than we previously used. (#1565, #1599, #586)

CHANGELOG.txt

@@ -70,6 +70,7 @@ Other Changes:
  - Metrics: Changed io.MetricsActiveWindows to reflect the number of active windows (!= from visible windows), which is useful
    for lazy/idle render mechanisms as new windows are typically not visible for one frame.
  - Metrics: Added io.MetricsRenderWindow to reflect the number of visible windows.
+ - Metrics: Added io.MetricsActiveAllocations, moving away from the cross-context global counters than we previously used. (#1565, #1599, #586)
  - Demo: Added basic Drag and Drop demo. (#143)
  - Demo: Clarified the use of IsItemHovered()/IsItemActive() right after being in the "Active, Focused, Hovered & Focused Tests" section.
  - Examples: Tweaked the main.cpp of each example.

imgui.cpp

@@ -933,7 +933,7 @@ static void             SetClipboardTextFn_DefaultImpl(void* user_data, const ch
 static void             ImeSetInputScreenPosFn_DefaultImpl(int x, int y);
 
 //-----------------------------------------------------------------------------
-// Context
+// Context and Memory Allocators
 //-----------------------------------------------------------------------------
 
 // Current context pointer. Implicitly used by all ImGui functions. Always assumed to be != NULL.
@@ -960,7 +960,6 @@ static void    FreeWrapper(void* ptr, void* user_data)        { (void)user_data;
 static void*  (*GImAllocatorAllocFunc)(size_t size, void* user_data) = MallocWrapper;
 static void   (*GImAllocatorFreeFunc)(void* ptr, void* user_data) = FreeWrapper;
 static void*    GImAllocatorUserData = NULL;
-static size_t   GImAllocatorActiveAllocationsCount = 0;
 
 //-----------------------------------------------------------------------------
 // User facing structures
@@ -2845,13 +2844,16 @@ float ImGui::CalcWrapWidthForPos(const ImVec2& pos, float wrap_pos_x)
 
 void* ImGui::MemAlloc(size_t size)
 {
-    GImAllocatorActiveAllocationsCount++;
+    if (ImGuiContext* ctx = GImGui)
+        ctx->IO.MetricsActiveAllocations++;
     return GImAllocatorAllocFunc(size, GImAllocatorUserData);
 }
 
 void ImGui::MemFree(void* ptr)
 {
-    if (ptr) GImAllocatorActiveAllocationsCount--;
+    if (ptr) 
+        if (ImGuiContext* ctx = GImGui)
+            ctx->IO.MetricsActiveAllocations--;
     return GImAllocatorFreeFunc(ptr, GImAllocatorUserData);
 }
 
@@ -14032,7 +14034,7 @@ void ImGui::ShowMetricsWindow(bool* p_open)
         ImGui::Text("Application average %.3f ms/frame (%.1f FPS)", 1000.0f / io.Framerate, io.Framerate);
         ImGui::Text("%d vertices, %d indices (%d triangles)", io.MetricsRenderVertices, io.MetricsRenderIndices, io.MetricsRenderIndices / 3);
         ImGui::Text("%d active windows (%d visible)", io.MetricsActiveWindows, io.MetricsRenderWindows);
-        ImGui::Text("%d allocations", (int)GImAllocatorActiveAllocationsCount);
+        ImGui::Text("%d allocations", io.MetricsActiveAllocations);
         ImGui::Checkbox("Show clipping rectangles when hovering draw commands", &show_draw_cmd_clip_rects);
         ImGui::Checkbox("Ctrl shows window begin order", &show_window_begin_order);
 

imgui.h

@@ -1161,6 +1161,7 @@ struct ImGuiIO
     int         MetricsRenderIndices;       // Indices output during last call to Render() = number of triangles * 3
     int         MetricsRenderWindows;       // Number of visible windows
     int         MetricsActiveWindows;       // Number of active windows
+    int         MetricsActiveAllocations;   // Number of active allocations, updated by MemAlloc/MemFree based on current context. May be off if you have multiple imgui contexts.
     ImVec2      MouseDelta;                 // Mouse delta. Note that this is zero if either current or previous position are invalid (-FLT_MAX,-FLT_MAX), so a disappearing/reappearing mouse won't have a huge delta.
 
     //------------------------------------------------------------------