From 4405c5e015efaa9895c9bbbd9b41cfbb47de22af Mon Sep 17 00:00:00 2001
From: ocornut <omarcornut@gmail.com>
Date: Wed, 3 Jul 2024 19:03:25 +0200
Subject: [PATCH] WIP TreeNode: todying with experimental
 ImGuiTreeNodeFlags_DrawTreeLines() (#2920)

---
 imgui_internal.h  |  6 ++++--
 imgui_widgets.cpp | 28 ++++++++++++++++++++++++++++
 2 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/imgui_internal.h b/imgui_internal.h
index ff1a8d8aca..5ea3883234 100644
--- a/imgui_internal.h
+++ b/imgui_internal.h
@@ -994,6 +994,7 @@ enum ImGuiSelectableFlagsPrivate_
 // Extend ImGuiTreeNodeFlags_
 enum ImGuiTreeNodeFlagsPrivate_
 {
+    ImGuiTreeNodeFlags_DrawTreeLines              = 1 << 27,  // FIXME-EXPERIMENTAL: #2920
     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,
@@ -1290,8 +1291,9 @@ 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
+    float                   DrawTreeLinesY2;
 };
 
 // sizeof() = 20
diff --git a/imgui_widgets.cpp b/imgui_widgets.cpp
index 883a2648d0..2be18a5ac1 100644
--- a/imgui_widgets.cpp
+++ b/imgui_widgets.cpp
@@ -6559,6 +6559,7 @@ static void TreeNodeStoreStackData(ImGuiTreeNodeFlags flags)
     tree_node_data->TreeFlags = flags;
     tree_node_data->ItemFlags = g.LastItemData.ItemFlags;
     tree_node_data->NavRect = g.LastItemData.NavRect;
+    tree_node_data->DrawTreeLinesY2 = g.LastItemData.NavRect.Max.y;
     window->DC.TreeHasStackDataDepthMask |= (1 << window->DC.TreeDepth);
 }
 
@@ -6639,11 +6640,19 @@ bool ImGui::TreeNodeBehavior(ImGuiID id, ImGuiTreeNodeFlags flags, const char* l
         if ((flags & ImGuiTreeNodeFlags_NavLeftJumpsBackHere) && is_open && !g.NavIdIsAlive)
             if (g.NavMoveDir == ImGuiDir_Left && g.NavWindow == window && NavMoveRequestButNoResultYet())
                 store_tree_node_stack_data = true;
+        flags |= ImGuiTreeNodeFlags_DrawTreeLines; // Always on by default
+        if (flags & ImGuiTreeNodeFlags_DrawTreeLines)
+            store_tree_node_stack_data = true;
     }
 
     const bool is_leaf = (flags & ImGuiTreeNodeFlags_Leaf) != 0;
     if (!is_visible)
     {
+        if ((flags & ImGuiTreeNodeFlags_DrawTreeLines) && (window->DC.TreeHasStackDataDepthMask & (1 << (window->DC.TreeDepth - 1))))
+        {
+            ImGuiTreeNodeStackData* parent_data = &g.TreeNodeStack.back();
+            parent_data->DrawTreeLinesY2 = ImMax(parent_data->DrawTreeLinesY2, window->DC.CursorPos.y); // Don't need to aim to mid Y position as we are clipped anyway.
+        }
         if (store_tree_node_stack_data && is_open)
             TreeNodeStoreStackData(flags); // Call before TreePushOverrideID()
         if (is_open && !(flags & ImGuiTreeNodeFlags_NoTreePushOnOpen))
@@ -6805,6 +6814,17 @@ bool ImGui::TreeNodeBehavior(ImGuiID id, ImGuiTreeNodeFlags flags, const char* l
                 LogSetNextTextDecoration(">", NULL);
         }
 
+        if ((flags & ImGuiTreeNodeFlags_DrawTreeLines) && (window->DC.TreeHasStackDataDepthMask & (1 << (window->DC.TreeDepth - 1))))
+        {
+            ImGuiTreeNodeStackData* parent_data = &g.TreeNodeStack.back();
+            float x1 = parent_data->NavRect.Min.x + 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->DrawTreeLinesY2 = ImMax(parent_data->DrawTreeLinesY2, y);
+            if (x1 < x2)
+                window->DrawList->AddLine(ImVec2(x1, y), ImVec2(x2, y), GetColorU32(ImGuiCol_Border), 1.0f);
+        }
+
         if (span_all_columns && !span_all_columns_label)
             TablePopBackgroundChannel();
 
@@ -6871,6 +6891,14 @@ void ImGui::TreePop()
             if (g.NavIdIsAlive && g.NavMoveDir == ImGuiDir_Left && g.NavWindow == window && NavMoveRequestButNoResultYet())
                 NavMoveRequestResolveWithPastTreeNode(&g.NavMoveResultLocal, data);
         }
+        if (data->TreeFlags & ImGuiTreeNodeFlags_DrawTreeLines)
+        {
+            float x = data->NavRect.Min.x + ImTrunc(g.FontSize * 0.5f + g.Style.FramePadding.x); // GetTreeNodeToLabelSpacing() * 0.5f
+            float y1 = ImMax(data->NavRect.Max.y, window->ClipRect.Min.y);
+            float y2 = ImMin(data->DrawTreeLinesY2, window->ClipRect.Max.y);
+            if (y1 < y2)
+                window->DrawList->AddLine(ImVec2(x, y1), ImVec2(x, y2), GetColorU32(ImGuiCol_Border), 1.0f);
+        }
         g.TreeNodeStack.pop_back();
         window->DC.TreeHasStackDataDepthMask &= ~tree_depth_mask;
     }
-- 
2.45.2.windows.1