Added GetCursorStartPos() necessary for using scroll target relative to beginning of window content (#150)

imgui.cpp

@@ -4797,6 +4797,12 @@ void ImGui::SetCursorPosY(float y)
     window->DC.CursorMaxPos.y = ImMax(window->DC.CursorMaxPos.y, window->DC.CursorPos.y);
 }
 
+ImVec2 ImGui::GetCursorStartPos()
+{
+    ImGuiWindow* window = GetCurrentWindow();
+    return window->DC.CursorStartPos - window->Pos;
+}
+
 ImVec2 ImGui::GetCursorScreenPos()
 {
     ImGuiWindow* window = GetCurrentWindow();

imgui.h

@@ -201,6 +201,7 @@ namespace ImGui
     IMGUI_API void          SetCursorPos(const ImVec2& pos);                                    // "
     IMGUI_API void          SetCursorPosX(float x);                                             // "
     IMGUI_API void          SetCursorPosY(float y);                                             // "
+    IMGUI_API ImVec2        GetCursorStartPos();                                                // initial cursor position 
     IMGUI_API ImVec2        GetCursorScreenPos();                                               // cursor position in absolute screen coordinates [0..io.DisplaySize]
     IMGUI_API void          SetCursorScreenPos(const ImVec2& pos);                              // cursor position in absolute screen coordinates [0..io.DisplaySize]
     IMGUI_API void          AlignFirstTextHeightToWidgets();                                    // call once if the first item on the line is a Text() item and you want to vertically lower it to match subsequent (bigger) widgets