Merged a bit of code from Navigation branch to ease further merging (InnerRect is currently not required in the Master branch)

imgui.cpp

@@ -4613,17 +4613,23 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
         */
     }
 
-    // Inner clipping rectangle
+    // Inner rectangle and inner clipping rectangle
     // We set this up after processing the resize grip so that our clip rectangle doesn't lag by a frame
     // Note that if our window is collapsed we will end up with a null clipping rectangle which is the correct behavior.
     const ImRect title_bar_rect = window->TitleBarRect();
     const float border_size = window->BorderSize;
-	// Force round to ensure that e.g. (int)(max.x-min.x) in user's render code produce correct result.
+    window->InnerRect.Min.x = title_bar_rect.Min.x;
+    window->InnerRect.Min.y = title_bar_rect.Max.y + window->MenuBarHeight();
+    window->InnerRect.Max.x = window->Pos.x + window->Size.x - window->ScrollbarSizes.x;
+    window->InnerRect.Max.y = window->Pos.y + window->Size.y - window->ScrollbarSizes.y;
+    //window->DrawList->AddRect(window->InnerRect.Min, window->InnerRect.Max, IM_COL32_WHITE);
+
+    // Force round operator last to ensure that e.g. (int)(max.x-min.x) in user's render code produce correct result.
     ImRect clip_rect;
-    clip_rect.Min.x = ImFloor(0.5f + title_bar_rect.Min.x + ImMax(border_size, ImFloor(window->WindowPadding.x*0.5f)));
-    clip_rect.Min.y = ImFloor(0.5f + title_bar_rect.Max.y + window->MenuBarHeight() + border_size);
-    clip_rect.Max.x = ImFloor(0.5f + window->Pos.x + window->Size.x - window->ScrollbarSizes.x - ImMax(border_size, ImFloor(window->WindowPadding.x*0.5f)));
-    clip_rect.Max.y = ImFloor(0.5f + window->Pos.y + window->Size.y - window->ScrollbarSizes.y - border_size);
+    clip_rect.Min.x = ImFloor(0.5f + window->InnerRect.Min.x + ImMax(border_size, ImFloor(window->WindowPadding.x*0.5f)));
+    clip_rect.Min.y = ImFloor(0.5f + window->InnerRect.Min.y + border_size);
+    clip_rect.Max.x = ImFloor(0.5f + window->InnerRect.Max.x - ImMax(border_size, ImFloor(window->WindowPadding.x*0.5f)));
+    clip_rect.Max.y = ImFloor(0.5f + window->InnerRect.Max.y - border_size);
     PushClipRect(clip_rect.Min, clip_rect.Max, true);
 
     // Clear 'accessed' flag last thing

imgui_internal.h

@@ -714,6 +714,7 @@ struct IMGUI_API ImGuiWindow
     ImVector<ImGuiID>       IDStack;                            // ID stack. ID are hashes seeded with the value at the top of the stack
     ImRect                  ClipRect;                           // = DrawList->clip_rect_stack.back(). Scissoring / clipping rectangle. x1, y1, x2, y2.
     ImRect                  WindowRectClipped;                  // = WindowRect just after setup in Begin(). == window->Rect() for root window.
+    ImRect                  InnerRect;
     int                     LastFrameActive;
     float                   ItemWidthDefault;
     ImGuiSimpleColumns      MenuColumns;                        // Simplified columns storage for menu items