Nav, TreeNode: Pressing Left with ImGuiTreeNodeFlags_NavLeftJumpsBackHere now goes through proper navigation logic: honor scrolling and selection. (ocornut#1079, ocornut#1131)

Added a stack for this purpose which other features might build on (e.g. ocornut#2920). However this is currently gated by many tests and not a performance concern, but making stack happen all the time may be undesirable.

Author: ocornut

docs/CHANGELOG.txt

@@ -44,6 +44,8 @@ Breaking changes:
 
 Other changes:
 
+- Nav, TreeNode: Pressing Left with ImGuiTreeNodeFlags_NavLeftJumpsBackHere now goes
+  through proper navigation logic: honor scrolling and selection. (#1079, #1131)
 - Sliders: Fixed an integer overflow and div-by-zero in SliderInt() when
   v_max=INT_MAX (#6675, #6679) [@jbarthelmes]
 - ImDrawList: Fixed OOB access in _CalcCircleAutoSegmentCount when passing excessively

imgui.cpp

@@ -3653,6 +3653,7 @@ void ImGui::Shutdown()
     g.FontStack.clear();
     g.OpenPopupStack.clear();
     g.BeginPopupStack.clear();
+    g.NavTreeNodeStack.clear();
 
     g.Viewports.clear_delete();
 
@@ -11191,6 +11192,19 @@ void ImGui::NavMoveRequestResolveWithLastItem(ImGuiNavItemData* result)
     NavUpdateAnyRequestFlag();
 }
 
+// Called by TreePop() to implement ImGuiTreeNodeFlags_NavLeftJumpsBackHere
+void ImGui::NavMoveRequestResolveWithPastTreeNode(ImGuiNavItemData* result, ImGuiNavTreeNodeData* tree_node_data)
+{
+    ImGuiContext& g = *GImGui;
+    g.NavMoveScoringItems = false;
+    g.LastItemData.ID = tree_node_data->ID;
+    g.LastItemData.InFlags = tree_node_data->InFlags;
+    g.LastItemData.NavRect = tree_node_data->NavRect;
+    NavApplyItemToResult(result); // Result this instead of implementing a NavApplyPastTreeNodeToResult()
+    NavClearPreferredPosForAxis(ImGuiAxis_Y);
+    NavUpdateAnyRequestFlag();
+}
+
 void ImGui::NavMoveRequestCancel()
 {
     ImGuiContext& g = *GImGui;

imgui.h

@@ -26,7 +26,7 @@
 // Library Version
 // (Integer encoded as XYYZZ for use in #if preprocessor conditionals, e.g. '#if IMGUI_VERSION_NUM >= 12345')
 #define IMGUI_VERSION       "1.89.9 WIP"
-#define IMGUI_VERSION_NUM   18981
+#define IMGUI_VERSION_NUM   18982
 #define IMGUI_HAS_TABLE
 
 /*

imgui_internal.h

@@ -135,6 +135,7 @@ struct ImGuiLastItemData;           // Status storage for last submitted items
 struct ImGuiLocEntry;               // A localization entry.
 struct ImGuiMenuColumns;            // Simple column measurement, currently used for MenuItem() only
 struct ImGuiNavItemData;            // Result of a gamepad/keyboard directional navigation move query result
+struct ImGuiNavTreeNodeData;        // Temporary storage for last TreeNode() being a Left arrow landing candidate.
 struct ImGuiMetricsConfig;          // Storage for ShowMetricsWindow() and DebugNodeXXX() functions
 struct ImGuiNextWindowData;         // Storage for SetNextWindow** functions
 struct ImGuiNextItemData;           // Storage for SetNextItem** functions
@@ -1201,6 +1202,16 @@ struct ImGuiLastItemData
     ImGuiLastItemData()     { memset(this, 0, sizeof(*this)); }
 };
 
+// Store data emitted by TreeNode() for usage by TreePop() to implement ImGuiTreeNodeFlags_NavLeftJumpsBackHere.
+// This is the minimum amount of data that we need to perform the equivalent of NavApplyItemToResult() and which we can't infer in TreePop()
+// Only stored when the node is a potential candidate for landing on a Left arrow jump.
+struct ImGuiNavTreeNodeData
+{
+    ImGuiID                 ID;
+    ImGuiItemFlags          InFlags;
+    ImRect                  NavRect;
+};
+
 struct IMGUI_API ImGuiStackSizes
 {
     short   SizeOfIDStack;
@@ -1865,6 +1876,8 @@ struct ImGuiContext
     ImVector<ImGuiGroupData>GroupStack;                         // Stack for BeginGroup()/EndGroup() - not inherited by Begin()
     ImVector<ImGuiPopupData>OpenPopupStack;                     // Which popups are open (persistent)
     ImVector<ImGuiPopupData>BeginPopupStack;                    // Which level of BeginPopup() we are in (reset every frame)
+    ImVector<ImGuiNavTreeNodeData> NavTreeNodeStack;            // Stack for TreeNode() when a NavLeft requested is emitted.
+
     int                     BeginMenuCount;
 
     // Viewports
@@ -2930,6 +2943,7 @@ 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, ImGuiNavTreeNodeData* tree_node_data);
     IMGUI_API void          NavMoveRequestCancel();
     IMGUI_API void          NavMoveRequestApplyResult();
     IMGUI_API void          NavMoveRequestTryWrapping(ImGuiWindow* window, ImGuiNavMoveFlags move_flags);

imgui_widgets.cpp

@@ -6155,18 +6155,29 @@ bool ImGui::TreeNodeBehavior(ImGuiID id, ImGuiTreeNodeFlags flags, const char* l
     if (!display_frame && (flags & (ImGuiTreeNodeFlags_SpanAvailWidth | ImGuiTreeNodeFlags_SpanFullWidth)) == 0)
         interact_bb.Max.x = frame_bb.Min.x + text_width + style.ItemSpacing.x * 2.0f;
 
-    // Store a flag for the current depth to tell if we will allow closing this node when navigating one of its child.
-    // For this purpose we essentially compare if g.NavIdIsAlive went from 0 to 1 between TreeNode() and TreePop().
-    // This is currently only support 32 level deep and we are fine with (1 << Depth) overflowing into a zero.
-    const bool is_leaf = (flags & ImGuiTreeNodeFlags_Leaf) != 0;
+    // Compute open and multi-select states before ItemAdd() as it clear NextItem data.
     bool is_open = TreeNodeUpdateNextOpen(id, flags);
-    if (is_open && !g.NavIdIsAlive && (flags & ImGuiTreeNodeFlags_NavLeftJumpsBackHere) && !(flags & ImGuiTreeNodeFlags_NoTreePushOnOpen))
-        window->DC.TreeJumpToParentOnPopMask |= (1 << window->DC.TreeDepth);
-
     bool item_add = ItemAdd(interact_bb, id);
     g.LastItemData.StatusFlags |= ImGuiItemStatusFlags_HasDisplayRect;
     g.LastItemData.DisplayRect = frame_bb;
 
+    // If a NavLeft request is happening and ImGuiTreeNodeFlags_NavLeftJumpsBackHere enabled:
+    // Store data for the current depth to allow returning to this node from any child item.
+    // 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.
+    // Currently only supports 32 level deep and we are fine with (1 << Depth) overflowing into a zero, easy to increase.
+    if (is_open && !g.NavIdIsAlive && (flags & ImGuiTreeNodeFlags_NavLeftJumpsBackHere) && !(flags & ImGuiTreeNodeFlags_NoTreePushOnOpen))
+        if (g.NavMoveDir == ImGuiDir_Left && g.NavWindow == window && NavMoveRequestButNoResultYet())
+        {
+            g.NavTreeNodeStack.resize(g.NavTreeNodeStack.Size + 1);
+            ImGuiNavTreeNodeData* nav_tree_node_data = &g.NavTreeNodeStack.back();
+            nav_tree_node_data->ID = id;
+            nav_tree_node_data->InFlags = g.LastItemData.InFlags;
+            nav_tree_node_data->NavRect = g.LastItemData.NavRect;
+            window->DC.TreeJumpToParentOnPopMask |= (1 << window->DC.TreeDepth);
+        }
+
+    const bool is_leaf = (flags & ImGuiTreeNodeFlags_Leaf) != 0;
     if (!item_add)
     {
         if (is_open && !(flags & ImGuiTreeNodeFlags_NoTreePushOnOpen))
@@ -6336,12 +6347,14 @@ void ImGui::TreePop()
     ImU32 tree_depth_mask = (1 << window->DC.TreeDepth);
 
     // Handle Left arrow to move to parent tree node (when ImGuiTreeNodeFlags_NavLeftJumpsBackHere is enabled)
-    if (g.NavMoveDir == ImGuiDir_Left && g.NavWindow == window && NavMoveRequestButNoResultYet())
-        if (g.NavIdIsAlive && (window->DC.TreeJumpToParentOnPopMask & tree_depth_mask))
-        {
-            SetNavID(window->IDStack.back(), g.NavLayer, 0, ImRect());
-            NavMoveRequestCancel();
-        }
+    if (window->DC.TreeJumpToParentOnPopMask & tree_depth_mask) // Only set during request
+    {
+        ImGuiNavTreeNodeData* nav_tree_node_data = &g.NavTreeNodeStack.back();
+        IM_ASSERT(nav_tree_node_data->ID == window->IDStack.back());
+        if (g.NavIdIsAlive && g.NavMoveDir == ImGuiDir_Left && g.NavWindow == window && NavMoveRequestButNoResultYet())
+            NavMoveRequestResolveWithPastTreeNode(&g.NavMoveResultLocal, nav_tree_node_data);
+        g.NavTreeNodeStack.pop_back();
+    }
     window->DC.TreeJumpToParentOnPopMask &= tree_depth_mask - 1;
 
     IM_ASSERT(window->IDStack.Size > 1); // There should always be 1 element in the IDStack (pushed during window creation). If this triggers you called TreePop/PopID too much.