TreeNode: added ImGuiTreeNodeFlags_DrawTreeXXX flags. (#2920)

# Conflicts:
#	docs/CHANGELOG.txt

docs/CHANGELOG.txt

@@ -55,6 +55,18 @@ Other changes:
 - Windows: loosened code to allow hovering of resize grips, borders, and table
   borders while hovering a sibling child window, so that the code in master matches
   one in docking (they accidentally diverged). (#8554)
+- TreeNode: added flags to draw tree hierarchy outlines linking parent
+  and tree nodes: (#2920)
+  - ImGuiTreeNodeFlags_DrawLinesNone: No lines drawn.
+  - ImGuiTreeNodeFlags_DrawLinesFull: Horizontal lines to child nodes. Vertical line drawn down to TreePop() position: cover full contents.
+  - ImGuiTreeNodeFlags_DrawLinesToNodes: Horizontal lines to child nodes. Vertical line drawn down to bottom-most child node.
+  - Added style.TreeLinesFlags which stores the default setting, 
+    which may be overriden in individual TreeNode() calls.
+  - Added style.TreeLinesSize (default to 1.0f).
+  - Added ImGuiCol_TreeLines (in default style this is the same as ImGuiCol_Border).
+    The color for a given hierarchy level is latched in TreeNode(),
+    allowing advanced tree drawing code to potentially alter it. 
+  - The feature adds a little cost as extra data needs to be stored.
 - Nav: fixed assertion when holding gamepad FaceLeft/West button to open
   CTRL+Tab windowing + pressing a keyboard key. (#8525)
 - Error Handling: added better error report and recovery for extraneous

imgui.cpp

@@ -1360,6 +1360,8 @@ ImGuiStyle::ImGuiStyle()
     TabBarOverlineSize          = 1.0f;             // Thickness of tab-bar overline, which highlights the selected tab-bar.
     TableAngledHeadersAngle     = 35.0f * (IM_PI / 180.0f); // Angle of angled headers (supported values range from -50 degrees to +50 degrees).
     TableAngledHeadersTextAlign = ImVec2(0.5f,0.0f);// Alignment of angled headers within the cell
+    TreeLinesFlags              = ImGuiTreeNodeFlags_DrawLinesNone;
+    TreeLinesSize               = 1.0f;             // Thickness of outlines when using ImGuiTreeNodeFlags_DrawLines.
     ColorButtonPosition         = ImGuiDir_Right;   // Side of the color button in the ColorEdit4 widget (left/right). Defaults to ImGuiDir_Right.
     ButtonTextAlign             = ImVec2(0.5f,0.5f);// Alignment of button text when button is larger than text.
     SelectableTextAlign         = ImVec2(0.0f,0.0f);// Alignment of selectable text. Defaults to (0.0f, 0.0f) (top-left aligned). It's generally important to keep this left-aligned if you want to lay multiple items on a same line.
@@ -3415,6 +3417,7 @@ static const ImGuiStyleVarInfo GStyleVarsInfo[] =
     { 1, ImGuiDataType_Float, (ImU32)offsetof(ImGuiStyle, TabBarOverlineSize) },        // ImGuiStyleVar_TabBarOverlineSize
     { 1, ImGuiDataType_Float, (ImU32)offsetof(ImGuiStyle, TableAngledHeadersAngle)},    // ImGuiStyleVar_TableAngledHeadersAngle
     { 2, ImGuiDataType_Float, (ImU32)offsetof(ImGuiStyle, TableAngledHeadersTextAlign)},// ImGuiStyleVar_TableAngledHeadersTextAlign
+    { 1, ImGuiDataType_Float, (ImU32)offsetof(ImGuiStyle, TreeLinesSize)},              // ImGuiStyleVar_TreeLinesSize
     { 2, ImGuiDataType_Float, (ImU32)offsetof(ImGuiStyle, ButtonTextAlign) },           // ImGuiStyleVar_ButtonTextAlign
     { 2, ImGuiDataType_Float, (ImU32)offsetof(ImGuiStyle, SelectableTextAlign) },       // ImGuiStyleVar_SelectableTextAlign
     { 1, ImGuiDataType_Float, (ImU32)offsetof(ImGuiStyle, SeparatorTextBorderSize)},    // ImGuiStyleVar_SeparatorTextBorderSize
@@ -3563,6 +3566,7 @@ const char* ImGui::GetStyleColorName(ImGuiCol idx)
     case ImGuiCol_TableRowBgAlt: return "TableRowBgAlt";
     case ImGuiCol_TextLink: return "TextLink";
     case ImGuiCol_TextSelectedBg: return "TextSelectedBg";
+    case ImGuiCol_TreeLines: return "TreeLines";
     case ImGuiCol_DragDropTarget: return "DragDropTarget";
     case ImGuiCol_NavCursor: return "NavCursor";
     case ImGuiCol_NavWindowingHighlight: return "NavWindowingHighlight";
@@ -10243,6 +10247,7 @@ static void ImGui::ErrorCheckNewFrameSanityChecks()
     IM_ASSERT(g.Style.WindowBorderHoverPadding > 0.0f                   && "Invalid style setting!"); // Required otherwise cannot resize from borders.
     IM_ASSERT(g.Style.WindowMenuButtonPosition == ImGuiDir_None || g.Style.WindowMenuButtonPosition == ImGuiDir_Left || g.Style.WindowMenuButtonPosition == ImGuiDir_Right);
     IM_ASSERT(g.Style.ColorButtonPosition == ImGuiDir_Left || g.Style.ColorButtonPosition == ImGuiDir_Right);
+    IM_ASSERT(g.Style.TreeLinesFlags == ImGuiTreeNodeFlags_DrawLinesNone || g.Style.TreeLinesFlags == ImGuiTreeNodeFlags_DrawLinesFull || g.Style.TreeLinesFlags == ImGuiTreeNodeFlags_DrawLinesToNodes);
 
     // Error handling: we do not accept 100% silent recovery! Please contact me if you feel this is getting in your way.
     if (g.IO.ConfigErrorRecovery)
@@ -12794,7 +12799,7 @@ void ImGui::NavMoveRequestResolveWithLastItem(ImGuiNavItemData* result)
 }
 
 // Called by TreePop() to implement ImGuiTreeNodeFlags_NavLeftJumpsBackHere
-void ImGui::NavMoveRequestResolveWithPastTreeNode(ImGuiNavItemData* result, ImGuiTreeNodeStackData* tree_node_data)
+void ImGui::NavMoveRequestResolveWithPastTreeNode(ImGuiNavItemData* result, const ImGuiTreeNodeStackData* tree_node_data)
 {
     ImGuiContext& g = *GImGui;
     g.NavMoveScoringItems = false;

imgui.h

@@ -1214,6 +1214,12 @@ enum ImGuiTreeNodeFlags_
     ImGuiTreeNodeFlags_NavLeftJumpsBackHere = 1 << 17,  // (WIP) Nav: left direction may move to this TreeNode() from any of its child (items submitted between TreeNode and TreePop)
     ImGuiTreeNodeFlags_CollapsingHeader     = ImGuiTreeNodeFlags_Framed | ImGuiTreeNodeFlags_NoTreePushOnOpen | ImGuiTreeNodeFlags_NoAutoOpenOnLog,
 
+    // [EXPERIMENTAL] Draw lines connecting TreeNode hierarchy. Discuss in GitHub issue #2920.
+    // Default value is pulled from style.TreeLinesFlags. May be overridden in TreeNode calls.
+    ImGuiTreeNodeFlags_DrawLinesNone        = 1 << 18,  // No lines drawn
+    ImGuiTreeNodeFlags_DrawLinesFull        = 1 << 19,  // Horizontal lines to child nodes. Vertical line drawn down to TreePop() position: cover full contents.
+    ImGuiTreeNodeFlags_DrawLinesToNodes     = 1 << 20,  // Horizontal lines to child nodes. Vertical line drawn down to bottom-most child node. A little bit slower.
+
 #ifndef IMGUI_DISABLE_OBSOLETE_FUNCTIONS
     ImGuiTreeNodeFlags_AllowItemOverlap     = ImGuiTreeNodeFlags_AllowOverlap,  // Renamed in 1.89.7
     ImGuiTreeNodeFlags_SpanTextWidth        = ImGuiTreeNodeFlags_SpanLabelWidth,// Renamed in 1.90.7
@@ -1666,7 +1672,8 @@ enum ImGuiCol_
     ImGuiCol_TableRowBg,            // Table row background (even rows)
     ImGuiCol_TableRowBgAlt,         // Table row background (odd rows)
     ImGuiCol_TextLink,              // Hyperlink color
-    ImGuiCol_TextSelectedBg,
+    ImGuiCol_TextSelectedBg,        // Selected text inside an InputText
+    ImGuiCol_TreeLines,             // Tree node hierarchy outlines when using ImGuiTreeNodeFlags_DrawLines
     ImGuiCol_DragDropTarget,        // Rectangle highlighting a drop target
     ImGuiCol_NavCursor,             // Color of keyboard/gamepad navigation cursor/rectangle, when visible
     ImGuiCol_NavWindowingHighlight, // Highlight window when using CTRL+TAB
@@ -1722,6 +1729,7 @@ enum ImGuiStyleVar_
     ImGuiStyleVar_TabBarOverlineSize,       // float     TabBarOverlineSize
     ImGuiStyleVar_TableAngledHeadersAngle,  // float     TableAngledHeadersAngle
     ImGuiStyleVar_TableAngledHeadersTextAlign,// ImVec2  TableAngledHeadersTextAlign
+    ImGuiStyleVar_TreeLinesSize,            // float     TreeLinesSize
     ImGuiStyleVar_ButtonTextAlign,          // ImVec2    ButtonTextAlign
     ImGuiStyleVar_SelectableTextAlign,      // ImVec2    SelectableTextAlign
     ImGuiStyleVar_SeparatorTextBorderSize,  // float     SeparatorTextBorderSize
@@ -2181,6 +2189,8 @@ struct ImGuiStyle
     float       TabBarOverlineSize;         // Thickness of tab-bar overline, which highlights the selected tab-bar.
     float       TableAngledHeadersAngle;    // Angle of angled headers (supported values range from -50.0f degrees to +50.0f degrees).
     ImVec2      TableAngledHeadersTextAlign;// Alignment of angled headers within the cell
+    ImGuiTreeNodeFlags TreeLinesFlags;      // Default way to draw lines connecting TreeNode hierarchy. ImGuiTreeNodeFlags_DrawLinesNone or ImGuiTreeNodeFlags_DrawLinesFull or ImGuiTreeNodeFlags_DrawLinesToNodes.
+    float              TreeLinesSize;       // Thickness of outlines when using ImGuiTreeNodeFlags_DrawLines.
     ImGuiDir    ColorButtonPosition;        // Side of the color button in the ColorEdit4 widget (left/right). Defaults to ImGuiDir_Right.
     ImVec2      ButtonTextAlign;            // Alignment of button text when button is larger than text. Defaults to (0.5f, 0.5f) (centered).
     ImVec2      SelectableTextAlign;        // Alignment of selectable text. Defaults to (0.0f, 0.0f) (top-left aligned). It's generally important to keep this left-aligned if you want to lay multiple items on a same line.

imgui_demo.cpp

@@ -3920,6 +3920,7 @@ static void DemoWindowWidgetsTreeNodes()
     IMGUI_DEMO_MARKER("Widgets/Tree Nodes");
     if (ImGui::TreeNode("Tree Nodes"))
     {
+        // See see "Examples -> Property Editor" (ShowExampleAppPropertyEditor() function) for a fancier, data-driven tree.
         IMGUI_DEMO_MARKER("Widgets/Tree Nodes/Basic trees");
         if (ImGui::TreeNode("Basic trees"))
         {
@@ -3946,6 +3947,35 @@ static void DemoWindowWidgetsTreeNodes()
             ImGui::TreePop();
         }
 
+        IMGUI_DEMO_MARKER("Widgets/Tree Nodes/Hierarchy lines");
+        if (ImGui::TreeNode("Hierarchy lines"))
+        {
+            static ImGuiTreeNodeFlags base_flags = ImGuiTreeNodeFlags_DrawLinesFull | ImGuiTreeNodeFlags_DefaultOpen;
+            HelpMarker("Default option for DrawLinesXXX is stored in style.TreeLinesFlags");
+            ImGui::CheckboxFlags("ImGuiTreeNodeFlags_DrawLinesNone", &base_flags, ImGuiTreeNodeFlags_DrawLinesNone);
+            ImGui::CheckboxFlags("ImGuiTreeNodeFlags_DrawLinesFull", &base_flags, ImGuiTreeNodeFlags_DrawLinesFull);
+            ImGui::CheckboxFlags("ImGuiTreeNodeFlags_DrawLinesToNodes", &base_flags, ImGuiTreeNodeFlags_DrawLinesToNodes);
+
+            if (ImGui::TreeNodeEx("Parent", base_flags))
+            {
+                if (ImGui::TreeNodeEx("Child 1", base_flags))
+                {
+                    ImGui::Button("Button for Child 1");
+                    ImGui::TreePop();
+                }
+                if (ImGui::TreeNodeEx("Child 2", base_flags))
+                {
+                    ImGui::Button("Button for Child 2");
+                    ImGui::TreePop();
+                }
+                ImGui::Text("Remaining contents");
+                ImGui::Text("Remaining contents");
+                ImGui::TreePop();
+            }
+
+            ImGui::TreePop();
+        }
+
         IMGUI_DEMO_MARKER("Widgets/Tree Nodes/Advanced, with Selectable nodes");
         if (ImGui::TreeNode("Advanced, with Selectable nodes"))
         {
@@ -3964,6 +3994,12 @@ static void DemoWindowWidgetsTreeNodes()
             ImGui::CheckboxFlags("ImGuiTreeNodeFlags_AllowOverlap", &base_flags, ImGuiTreeNodeFlags_AllowOverlap);
             ImGui::CheckboxFlags("ImGuiTreeNodeFlags_Framed", &base_flags, ImGuiTreeNodeFlags_Framed); ImGui::SameLine(); HelpMarker("Draw frame with background (e.g. for CollapsingHeader)");
             ImGui::CheckboxFlags("ImGuiTreeNodeFlags_NavLeftJumpsBackHere", &base_flags, ImGuiTreeNodeFlags_NavLeftJumpsBackHere);
+
+            HelpMarker("Default option for DrawLinesXXX is stored in style.TreeLinesFlags");
+            ImGui::CheckboxFlags("ImGuiTreeNodeFlags_DrawLinesNone", &base_flags, ImGuiTreeNodeFlags_DrawLinesNone);
+            ImGui::CheckboxFlags("ImGuiTreeNodeFlags_DrawLinesFull", &base_flags, ImGuiTreeNodeFlags_DrawLinesFull);
+            ImGui::CheckboxFlags("ImGuiTreeNodeFlags_DrawLinesToNodes", &base_flags, ImGuiTreeNodeFlags_DrawLinesToNodes);
+
             ImGui::Checkbox("Align label with current X position", &align_label_with_current_x_position);
             ImGui::Checkbox("Test tree node as drag source", &test_drag_and_drop);
             ImGui::Text("Hello!");
@@ -4607,10 +4643,11 @@ static void DemoWindowLayout()
             ImGui::SmallButton("SmallButton()");
 
             // Tree
+            // (here the node appears after a button and has odd intent, so we use ImGuiTreeNodeFlags_DrawLinesNone to disable hierarchy outline)
             const float spacing = ImGui::GetStyle().ItemInnerSpacing.x;
             ImGui::Button("Button##1");
             ImGui::SameLine(0.0f, spacing);
-            if (ImGui::TreeNode("Node##1"))
+            if (ImGui::TreeNodeEx("Node##1", ImGuiTreeNodeFlags_DrawLinesNone))
             {
                 // Placeholder tree data
                 for (int i = 0; i < 6; i++)
@@ -6592,7 +6629,7 @@ static void DemoWindowTables()
     {
         static ImGuiTableFlags table_flags = ImGuiTableFlags_BordersV | ImGuiTableFlags_BordersOuterH | ImGuiTableFlags_Resizable | ImGuiTableFlags_RowBg | ImGuiTableFlags_NoBordersInBody;
 
-        static ImGuiTreeNodeFlags tree_node_flags_base = ImGuiTreeNodeFlags_SpanAllColumns;
+        static ImGuiTreeNodeFlags tree_node_flags_base = ImGuiTreeNodeFlags_SpanAllColumns | ImGuiTreeNodeFlags_DefaultOpen | ImGuiTreeNodeFlags_DrawLinesFull;
         ImGui::CheckboxFlags("ImGuiTreeNodeFlags_SpanFullWidth",  &tree_node_flags_base, ImGuiTreeNodeFlags_SpanFullWidth);
         ImGui::CheckboxFlags("ImGuiTreeNodeFlags_SpanLabelWidth",  &tree_node_flags_base, ImGuiTreeNodeFlags_SpanLabelWidth);
         ImGui::CheckboxFlags("ImGuiTreeNodeFlags_SpanAllColumns", &tree_node_flags_base, ImGuiTreeNodeFlags_SpanAllColumns);
@@ -8139,6 +8176,14 @@ bool ImGui::ShowStyleSelector(const char* label)
     return false;
 }
 
+static const char* GetTreeLinesFlagsName(ImGuiTreeNodeFlags flags)
+{
+    if (flags == ImGuiTreeNodeFlags_DrawLinesNone) return "DrawLinesNone";
+    if (flags == ImGuiTreeNodeFlags_DrawLinesFull) return "DrawLinesFull";
+    if (flags == ImGuiTreeNodeFlags_DrawLinesToNodes) return "DrawLinesToNodes";
+    return "";
+}
+
 void ImGui::ShowStyleEditor(ImGuiStyle* ref)
 {
     IMGUI_DEMO_MARKER("Tools/Style Editor");
@@ -8233,6 +8278,15 @@ void ImGui::ShowStyleEditor(ImGuiStyle* ref)
                 style.WindowMenuButtonPosition = (ImGuiDir)(window_menu_button_position - 1);
 
             ImGui::SeparatorText("Widgets");
+            if (ImGui::BeginCombo("TreeLinesFlags", GetTreeLinesFlagsName(style.TreeLinesFlags)))
+            {
+                const ImGuiTreeNodeFlags options[] = { ImGuiTreeNodeFlags_DrawLinesNone, ImGuiTreeNodeFlags_DrawLinesFull, ImGuiTreeNodeFlags_DrawLinesToNodes };
+                for (ImGuiTreeNodeFlags option : options)
+                    if (ImGui::Selectable(GetTreeLinesFlagsName(option), style.TreeLinesFlags == option))
+                        style.TreeLinesFlags = option;
+                ImGui::EndCombo();
+            }
+            ImGui::SliderFloat("TreeLinesSize", &style.TreeLinesSize, 0.0f, 1.0f, "%.0f");
             ImGui::Combo("ColorButtonPosition", (int*)&style.ColorButtonPosition, "Left\0Right\0");
             ImGui::SliderFloat2("ButtonTextAlign", (float*)&style.ButtonTextAlign, 0.0f, 1.0f, "%.2f");
             ImGui::SameLine(); HelpMarker("Alignment applies when a button is larger than its text content.");
@@ -9285,8 +9339,10 @@ struct ExampleAppPropertyEditor
         ImGui::TableNextColumn();
         ImGui::PushID(node->UID);
         ImGuiTreeNodeFlags tree_flags = ImGuiTreeNodeFlags_None;
-        tree_flags |= ImGuiTreeNodeFlags_OpenOnArrow | ImGuiTreeNodeFlags_OpenOnDoubleClick;    // Standard opening mode as we are likely to want to add selection afterwards
-        tree_flags |= ImGuiTreeNodeFlags_NavLeftJumpsBackHere;                                  // Left arrow support
+        tree_flags |= ImGuiTreeNodeFlags_OpenOnArrow | ImGuiTreeNodeFlags_OpenOnDoubleClick;// Standard opening mode as we are likely to want to add selection afterwards
+        tree_flags |= ImGuiTreeNodeFlags_NavLeftJumpsBackHere;  // Left arrow support
+        tree_flags |= ImGuiTreeNodeFlags_SpanFullWidth;         // Span full width for easier mouse reach
+        tree_flags |= ImGuiTreeNodeFlags_DrawLinesToNodes;      // Always draw hierarchy outlines
         if (node == VisibleNode)
             tree_flags |= ImGuiTreeNodeFlags_Selected;
         if (node->Childs.Size == 0)

imgui_draw.cpp

@@ -236,6 +236,7 @@ void ImGui::StyleColorsDark(ImGuiStyle* dst)
     colors[ImGuiCol_TableRowBgAlt]          = ImVec4(1.00f, 1.00f, 1.00f, 0.06f);
     colors[ImGuiCol_TextLink]               = colors[ImGuiCol_HeaderActive];
     colors[ImGuiCol_TextSelectedBg]         = ImVec4(0.26f, 0.59f, 0.98f, 0.35f);
+    colors[ImGuiCol_TreeLines]              = colors[ImGuiCol_Border];
     colors[ImGuiCol_DragDropTarget]         = ImVec4(1.00f, 1.00f, 0.00f, 0.90f);
     colors[ImGuiCol_NavCursor]              = ImVec4(0.26f, 0.59f, 0.98f, 1.00f);
     colors[ImGuiCol_NavWindowingHighlight]  = ImVec4(1.00f, 1.00f, 1.00f, 0.70f);
@@ -300,6 +301,7 @@ void ImGui::StyleColorsClassic(ImGuiStyle* dst)
     colors[ImGuiCol_TableRowBgAlt]          = ImVec4(1.00f, 1.00f, 1.00f, 0.07f);
     colors[ImGuiCol_TextLink]               = colors[ImGuiCol_HeaderActive];
     colors[ImGuiCol_TextSelectedBg]         = ImVec4(0.00f, 0.00f, 1.00f, 0.35f);
+    colors[ImGuiCol_TreeLines]              = colors[ImGuiCol_Border];
     colors[ImGuiCol_DragDropTarget]         = ImVec4(1.00f, 1.00f, 0.00f, 0.90f);
     colors[ImGuiCol_NavCursor]              = colors[ImGuiCol_HeaderHovered];
     colors[ImGuiCol_NavWindowingHighlight]  = ImVec4(1.00f, 1.00f, 1.00f, 0.70f);
@@ -365,6 +367,7 @@ void ImGui::StyleColorsLight(ImGuiStyle* dst)
     colors[ImGuiCol_TableRowBgAlt]          = ImVec4(0.30f, 0.30f, 0.30f, 0.09f);
     colors[ImGuiCol_TextLink]               = colors[ImGuiCol_HeaderActive];
     colors[ImGuiCol_TextSelectedBg]         = ImVec4(0.26f, 0.59f, 0.98f, 0.35f);
+    colors[ImGuiCol_TreeLines]              = colors[ImGuiCol_Border];
     colors[ImGuiCol_DragDropTarget]         = ImVec4(0.26f, 0.59f, 0.98f, 0.95f);
     colors[ImGuiCol_NavCursor]              = colors[ImGuiCol_HeaderHovered];
     colors[ImGuiCol_NavWindowingHighlight]  = ImVec4(0.70f, 0.70f, 0.70f, 0.70f);

imgui_internal.h

@@ -998,6 +998,7 @@ enum ImGuiTreeNodeFlagsPrivate_
     ImGuiTreeNodeFlags_ClipLabelForTrailingButton = 1 << 28,// FIXME-WIP: Hard-coded for CollapsingHeader()
     ImGuiTreeNodeFlags_UpsideDownArrow            = 1 << 29,// FIXME-WIP: Turn Down arrow into an Up arrow, for reversed trees (#6517)
     ImGuiTreeNodeFlags_OpenOnMask_                = ImGuiTreeNodeFlags_OpenOnDoubleClick | ImGuiTreeNodeFlags_OpenOnArrow,
+    ImGuiTreeNodeFlags_DrawLinesMask_             = ImGuiTreeNodeFlags_DrawLinesNone | ImGuiTreeNodeFlags_DrawLinesFull | ImGuiTreeNodeFlags_DrawLinesToNodes,
 };
 
 enum ImGuiSeparatorFlags_
@@ -1291,8 +1292,11 @@ struct ImGuiTreeNodeStackData
 {
     ImGuiID                 ID;
     ImGuiTreeNodeFlags      TreeFlags;
-    ImGuiItemFlags          ItemFlags;  // Used for nav landing
-    ImRect                  NavRect;    // Used for nav landing
+    ImGuiItemFlags          ItemFlags;      // Used for nav landing
+    ImRect                  NavRect;        // Used for nav landing
+    ImU32                   DrawLinesCol;
+    float                   DrawLinesX1;
+    float                   DrawLinesY2;
 };
 
 // sizeof() = 20
@@ -3178,7 +3182,7 @@ namespace ImGui
     IMGUI_API void          NavMoveRequestSubmit(ImGuiDir move_dir, ImGuiDir clip_dir, ImGuiNavMoveFlags move_flags, ImGuiScrollFlags scroll_flags);
     IMGUI_API void          NavMoveRequestForward(ImGuiDir move_dir, ImGuiDir clip_dir, ImGuiNavMoveFlags move_flags, ImGuiScrollFlags scroll_flags);
     IMGUI_API void          NavMoveRequestResolveWithLastItem(ImGuiNavItemData* result);
-    IMGUI_API void          NavMoveRequestResolveWithPastTreeNode(ImGuiNavItemData* result, ImGuiTreeNodeStackData* tree_node_data);
+    IMGUI_API void          NavMoveRequestResolveWithPastTreeNode(ImGuiNavItemData* result, const ImGuiTreeNodeStackData* tree_node_data);
     IMGUI_API void          NavMoveRequestCancel();
     IMGUI_API void          NavMoveRequestApplyResult();
     IMGUI_API void          NavMoveRequestTryWrapping(ImGuiWindow* window, ImGuiNavMoveFlags move_flags);

imgui_tables.cpp

@@ -451,6 +451,7 @@ bool    ImGui::BeginTableEx(const char* name, ImGuiID id, int columns_count, ImG
         // But at this point we do NOT have a correct value for .Max.y (unless a height has been explicitly passed in). It will only be updated in EndTable().
         table->WorkRect = table->OuterRect = table->InnerRect = outer_rect;
         table->HasScrollbarYPrev = table->HasScrollbarYCurr = false;
+        table->InnerWindow->DC.TreeDepth++; // This is designed to always linking ImGuiTreeNodeFlags_DrawLines linking accross a table
     }
 
     // Push a standardized ID for both child-using and not-child-using tables
@@ -1510,6 +1511,7 @@ void    ImGui::EndTable()
     }
     else
     {
+        table->InnerWindow->DC.TreeDepth--;
         ItemSize(table->OuterRect.GetSize());
         ItemAdd(table->OuterRect, 0);
     }

imgui_widgets.cpp

@@ -6390,6 +6390,7 @@ void ImGui::ColorPickerOptionsPopup(const float* ref_col, ImGuiColorEditFlags fl
 // - TreeNodeV()
 // - TreeNodeEx()
 // - TreeNodeExV()
+// - TreeNodeStoreStackData() [Internal]
 // - TreeNodeBehavior() [Internal]
 // - TreePush()
 // - TreePop()
@@ -6548,17 +6549,27 @@ bool ImGui::TreeNodeUpdateNextOpen(ImGuiID storage_id, ImGuiTreeNodeFlags flags)
 
 // Store ImGuiTreeNodeStackData for just submitted node.
 // Currently only supports 32 level deep and we are fine with (1 << Depth) overflowing into a zero, easy to increase.
-static void TreeNodeStoreStackData(ImGuiTreeNodeFlags flags)
+static void TreeNodeStoreStackData(ImGuiTreeNodeFlags flags, float x1)
 {
     ImGuiContext& g = *GImGui;
     ImGuiWindow* window = g.CurrentWindow;
 
     g.TreeNodeStack.resize(g.TreeNodeStack.Size + 1);
-    ImGuiTreeNodeStackData* tree_node_data = &g.TreeNodeStack.back();
+    ImGuiTreeNodeStackData* tree_node_data = &g.TreeNodeStack.Data[g.TreeNodeStack.Size - 1];
     tree_node_data->ID = g.LastItemData.ID;
     tree_node_data->TreeFlags = flags;
     tree_node_data->ItemFlags = g.LastItemData.ItemFlags;
     tree_node_data->NavRect = g.LastItemData.NavRect;
+    if (flags & (ImGuiTreeNodeFlags_DrawLinesFull | ImGuiTreeNodeFlags_DrawLinesToNodes))
+    {
+        tree_node_data->DrawLinesCol = ImGui::GetColorU32(ImGuiCol_TreeLines);
+        tree_node_data->DrawLinesX1 = x1;
+        tree_node_data->DrawLinesY2 = -FLT_MAX;
+    }
+    else
+    {
+        tree_node_data->DrawLinesCol = 0;
+    }    
     window->DC.TreeHasStackDataDepthMask |= (1 << window->DC.TreeDepth);
 }
 
@@ -6634,18 +6645,28 @@ bool ImGui::TreeNodeBehavior(ImGuiID id, ImGuiTreeNodeFlags flags, const char* l
     // For this purpose we essentially compare if g.NavIdIsAlive went from 0 to 1 between TreeNode() and TreePop().
     // It will become tempting to enable ImGuiTreeNodeFlags_NavLeftJumpsBackHere by default or move it to ImGuiStyle.
     bool store_tree_node_stack_data = false;
-    if (!(flags & ImGuiTreeNodeFlags_NoTreePushOnOpen))
+    if ((flags & ImGuiTreeNodeFlags_DrawLinesMask_) == 0)
+        flags |= g.Style.TreeLinesFlags;
+    const bool draw_tree_lines = (flags & (ImGuiTreeNodeFlags_DrawLinesFull | ImGuiTreeNodeFlags_DrawLinesToNodes)) && (frame_bb.Min.y < window->ClipRect.Max.y);// && (g.Style.TreeLinesSize > 0.0f);
+    if (is_open && !(flags & ImGuiTreeNodeFlags_NoTreePushOnOpen))
     {
-        if ((flags & ImGuiTreeNodeFlags_NavLeftJumpsBackHere) && is_open && !g.NavIdIsAlive)
+        if ((flags & ImGuiTreeNodeFlags_NavLeftJumpsBackHere) && !g.NavIdIsAlive)
             if (g.NavMoveDir == ImGuiDir_Left && g.NavWindow == window && NavMoveRequestButNoResultYet())
                 store_tree_node_stack_data = true;
+        if (draw_tree_lines)
+            store_tree_node_stack_data = true;
     }
 
     const bool is_leaf = (flags & ImGuiTreeNodeFlags_Leaf) != 0;
     if (!is_visible)
     {
-        if (store_tree_node_stack_data && is_open)
-            TreeNodeStoreStackData(flags); // Call before TreePushOverrideID()
+        if (draw_tree_lines && (flags & ImGuiTreeNodeFlags_DrawLinesToNodes) && (window->DC.TreeHasStackDataDepthMask & (1 << window->DC.TreeDepth)))
+        {
+            ImGuiTreeNodeStackData* parent_data = &g.TreeNodeStack.Data[g.TreeNodeStack.Size - 1];
+            parent_data->DrawLinesY2 = ImMax(parent_data->DrawLinesY2, window->DC.CursorPos.y); // Don't need to aim to mid Y position as we are clipped anyway.
+        }
+        if (is_open && store_tree_node_stack_data)
+            TreeNodeStoreStackData(flags, text_pos.x - text_offset_x); // Call before TreePushOverrideID()
         if (is_open && !(flags & ImGuiTreeNodeFlags_NoTreePushOnOpen))
             TreePushOverrideID(id);
         IMGUI_TEST_ENGINE_ITEM_INFO(g.LastItemData.ID, label, g.LastItemData.StatusFlags | (is_leaf ? 0 : ImGuiItemStatusFlags_Openable) | (is_open ? ImGuiItemStatusFlags_Opened : 0));
@@ -6807,6 +6828,18 @@ bool ImGui::TreeNodeBehavior(ImGuiID id, ImGuiTreeNodeFlags flags, const char* l
                 LogSetNextTextDecoration(">", NULL);
         }
 
+        if (draw_tree_lines && (window->DC.TreeHasStackDataDepthMask & (1 << (window->DC.TreeDepth - 1))))
+        {
+            // Draw horizontal line from our parent node
+            ImGuiTreeNodeStackData* parent_data = &g.TreeNodeStack.Data[g.TreeNodeStack.Size - 1];
+            float x1 = parent_data->DrawLinesX1 + ImTrunc(g.FontSize * 0.5f + g.Style.FramePadding.x); // GetTreeNodeToLabelSpacing() * 0.5f
+            float x2 = text_pos.x - text_offset_x;
+            float y = text_pos.y + ImTrunc(g.FontSize * 0.5f);
+            parent_data->DrawLinesY2 = ImMax(parent_data->DrawLinesY2, y);
+            if (x1 < x2)
+                window->DrawList->AddLine(ImVec2(x1, y), ImVec2(x2, y), parent_data->DrawLinesCol, g.Style.TreeLinesSize);
+        }
+
         if (span_all_columns && !span_all_columns_label)
             TablePopBackgroundChannel();
 
@@ -6821,7 +6854,7 @@ bool ImGui::TreeNodeBehavior(ImGuiID id, ImGuiTreeNodeFlags flags, const char* l
     }
 
     if (store_tree_node_stack_data && is_open)
-        TreeNodeStoreStackData(flags); // Call before TreePushOverrideID()
+        TreeNodeStoreStackData(flags, text_pos.x - text_offset_x); // Call before TreePushOverrideID()
     if (is_open && !(flags & ImGuiTreeNodeFlags_NoTreePushOnOpen))
         TreePushOverrideID(id); // Could use TreePush(label) but this avoid computing twice
 
@@ -6865,7 +6898,7 @@ void ImGui::TreePop()
 
     if (window->DC.TreeHasStackDataDepthMask & tree_depth_mask) // Only set during request
     {
-        ImGuiTreeNodeStackData* data = &g.TreeNodeStack.back();
+        const ImGuiTreeNodeStackData* data = &g.TreeNodeStack.Data[g.TreeNodeStack.Size - 1];
         IM_ASSERT(data->ID == window->IDStack.back());
         if (data->TreeFlags & ImGuiTreeNodeFlags_NavLeftJumpsBackHere)
         {
@@ -6873,6 +6906,18 @@ void ImGui::TreePop()
             if (g.NavIdIsAlive && g.NavMoveDir == ImGuiDir_Left && g.NavWindow == window && NavMoveRequestButNoResultYet())
                 NavMoveRequestResolveWithPastTreeNode(&g.NavMoveResultLocal, data);
         }
+        if (data->DrawLinesCol != 0 && window->DC.CursorPos.y >= window->ClipRect.Min.y)
+        {
+            // Draw vertical line of the hierarchy
+            float y1 = ImMax(data->NavRect.Max.y, window->ClipRect.Min.y);
+            float y2 = (data->TreeFlags & ImGuiTreeNodeFlags_DrawLinesToNodes) ? data->DrawLinesY2 : ImTrunc(window->DC.CursorPos.y - g.Style.ItemSpacing.y - g.FontSize * 0.5f);
+            y2 = ImMin(y2, window->ClipRect.Max.y);
+            if (y1 < y2)
+            {
+                float x = data->DrawLinesX1 + ImTrunc(g.FontSize * 0.5f + g.Style.FramePadding.x); // GetTreeNodeToLabelSpacing() * 0.5f
+                window->DrawList->AddLine(ImVec2(x, y1), ImVec2(x, y2), data->DrawLinesCol, g.Style.TreeLinesSize);
+            }
+        }
         g.TreeNodeStack.pop_back();
         window->DC.TreeHasStackDataDepthMask &= ~tree_depth_mask;
     }