Added GetTreeNodeToLabelSpacing() helper - tentative name (#581, #324)

imgui.cpp

@@ -5871,6 +5871,17 @@ bool ImGui::TreeNode(const char* label)
     return TreeNodeBehavior(window->GetID(label), 0, label, NULL);
 }
 
+float ImGui::GetTreeNodeToLabelSpacing(ImGuiTreeNodeFlags flags)
+{
+    ImGuiState& g = *GImGui;
+    float off_from_start;
+    if (flags & ImGuiTreeNodeFlags_Framed)
+        off_from_start = g.FontSize + (g.Style.FramePadding.x * 3.0f) - ((float)(int)(g.CurrentWindow->WindowPadding.x*0.5f) - 1);
+    else
+        off_from_start = g.FontSize + (g.Style.FramePadding.x * 2.0f);
+    return off_from_start;
+}
+
 void ImGui::SetNextTreeNodeOpened(bool opened, ImGuiSetCond cond)
 {
     ImGuiState& g = *GImGui;

imgui.h

@@ -321,6 +321,7 @@ namespace ImGui
     IMGUI_API void          TreePush(const void* ptr_id = NULL);                                    // "
     IMGUI_API void          TreePop();
     IMGUI_API void          SetNextTreeNodeOpened(bool opened, ImGuiSetCond cond = 0);              // set next tree node/collapsing header to be opened.
+    IMGUI_API float         GetTreeNodeToLabelSpacing(ImGuiTreeNodeFlags flags = 0);                // return horizontal distance between cursor and text label due to collapsing node. == (g.FontSize + style.FramePadding.x*2) for a regular unframed TreeNode
     IMGUI_API bool          CollapsingHeader(const char* label, ImGuiTreeNodeFlags flags = 0);      // if returning 'true' the header is open. user doesn't have to call TreePop().
     IMGUI_API bool          CollapsingHeader(const char* label, bool* p_open, ImGuiTreeNodeFlags flags = 0); // when 'p_open' isn't NULL, display an additional small close button on upper right of the header