From b50dce54ea0afb7ccc3be479abaeb96976bcdc69 Mon Sep 17 00:00:00 2001
From: omar <omarcornut@gmail.com>
Date: Tue, 6 Feb 2018 13:46:14 +0100
Subject: [PATCH] Drag and Drop: TreeNode as drop target displays rectangle
 over full frame. Added optional internal storage for item display rect. Will
 expose later. (#1597, #143)

---
 imgui.cpp        | 17 +++++++++++------
 imgui_internal.h | 13 ++++++++-----
 2 files changed, 19 insertions(+), 11 deletions(-)

diff --git a/imgui.cpp b/imgui.cpp
index a2db61cc..4312ed18 100644
--- a/imgui.cpp
+++ b/imgui.cpp
@@ -6757,7 +6757,11 @@ bool ImGui::TreeNodeBehavior(ImGuiID id, ImGuiTreeNodeFlags flags, const char* l
     // (Ideally we'd want to add a flag for the user to specify if we want the hit test to be done up to the right side of the content or not)
     const ImRect interact_bb = display_frame ? frame_bb : ImRect(frame_bb.Min.x, frame_bb.Min.y, frame_bb.Min.x + text_width + style.ItemSpacing.x*2, frame_bb.Max.y);
     bool is_open = TreeNodeBehaviorIsOpen(id, flags);
-    if (!ItemAdd(interact_bb, id))
+    bool item_add = ItemAdd(interact_bb, id);
+    window->DC.LastItemStatusFlags |= ImGuiItemStatusFlags_HasDisplayRect;
+    window->DC.LastItemDisplayRect = frame_bb;
+
+    if (!item_add)
     {
         if (is_open && !(flags & ImGuiTreeNodeFlags_NoTreePushOnOpen))
             TreePushRawID(id);
@@ -9537,7 +9541,7 @@ bool ImGui::ListBoxHeader(const char* label, const ImVec2& size_arg)
     ImVec2 frame_size = ImVec2(size.x, ImMax(size.y, label_size.y));
     ImRect frame_bb(window->DC.CursorPos, window->DC.CursorPos + frame_size);
     ImRect bb(frame_bb.Min, frame_bb.Max + ImVec2(label_size.x > 0.0f ? style.ItemInnerSpacing.x + label_size.x : 0.0f, 0.0f));
-    window->DC.LastItemRect = bb;
+    window->DC.LastItemRect = bb; // Forward storage for ListBoxFooter.. dodgy.
 
     BeginGroup();
     if (label_size.x > 0)
@@ -10703,9 +10707,9 @@ bool ImGui::SplitterBehavior(ImGuiID id, const ImRect& bb, ImGuiAxis axis, float
 #ifdef IMGUI_HAS_NAV
     window->DC.ItemFlags |= ImGuiItemFlags_NoNav | ImGuiItemFlags_NoNavDefaultFocus;
 #endif
-    bool add = ItemAdd(bb, id);
+    bool item_add = ItemAdd(bb, id);
     window->DC.ItemFlags = item_flags_backup;
-    if (!add)
+    if (!item_add)
         return false;
 
     bool hovered, held;
@@ -11491,13 +11495,14 @@ bool ImGui::BeginDragDropTarget()
     if (g.HoveredWindow == NULL || window->RootWindow != g.HoveredWindow->RootWindow)
         return false;
 
+    const ImRect& display_rect = (window->DC.LastItemStatusFlags & ImGuiItemStatusFlags_HasDisplayRect) ? window->DC.LastItemDisplayRect : window->DC.LastItemRect;
     ImGuiID id = window->DC.LastItemId;
     if (id == 0)
-        id = window->GetIDFromRectangle(window->DC.LastItemRect);
+        id = window->GetIDFromRectangle(display_rect);
     if (g.DragDropPayload.SourceId == id)
         return false;
 
-    g.DragDropTargetRect = window->DC.LastItemRect;
+    g.DragDropTargetRect = display_rect;
     g.DragDropTargetId = id;
     return true;
 }
diff --git a/imgui_internal.h b/imgui_internal.h
index e80c5297..50046772 100644
--- a/imgui_internal.h
+++ b/imgui_internal.h
@@ -220,7 +220,8 @@ enum ImGuiSeparatorFlags_
 // Storage for LastItem data
 enum ImGuiItemStatusFlags_
 {
-    ImGuiItemStatusFlags_HoveredRect        = 1 << 0
+    ImGuiItemStatusFlags_HoveredRect        = 1 << 0,
+    ImGuiItemStatusFlags_HasDisplayRect     = 1 << 1
 };
 
 // FIXME: this is in development, not exposed/functional as a generic feature yet.
@@ -709,6 +710,7 @@ struct IMGUI_API ImGuiDrawContext
     ImGuiID                 LastItemId;
     ImGuiItemStatusFlags    LastItemStatusFlags;
     ImRect                  LastItemRect;           // Interaction rect
+    ImRect                  LastItemDisplayRect;    // End-user display rect (only valid if LastItemStatusFlags & ImGuiItemStatusFlags_HasDisplayRect)
     bool                    MenuBarAppending;
     float                   MenuBarOffsetX;
     ImVector<ImGuiWindow*>  ChildWindows;
@@ -739,7 +741,7 @@ struct IMGUI_API ImGuiDrawContext
         TreeDepth = 0;
         LastItemId = 0;
         LastItemStatusFlags = 0;
-        LastItemRect = ImRect();
+        LastItemRect = LastItemDisplayRect = ImRect();
         MenuBarAppending = false;
         MenuBarOffsetX = 0.0f;
         StateStorage = NULL;
@@ -847,12 +849,13 @@ public:
 struct ImGuiItemHoveredDataBackup
 {
     ImGuiID                 LastItemId;
-    ImGuiItemStatusFlags    LastItemFlags;
+    ImGuiItemStatusFlags    LastItemStatusFlags;
     ImRect                  LastItemRect;
+    ImRect                  LastItemDisplayRect;
 
     ImGuiItemHoveredDataBackup() { Backup(); }
-    void Backup()        { ImGuiWindow* window = GImGui->CurrentWindow; LastItemId = window->DC.LastItemId; LastItemFlags = window->DC.LastItemStatusFlags; LastItemRect = window->DC.LastItemRect; }
-    void Restore() const { ImGuiWindow* window = GImGui->CurrentWindow; window->DC.LastItemId = LastItemId; window->DC.LastItemStatusFlags = LastItemFlags; window->DC.LastItemRect = LastItemRect; }
+    void Backup()        { ImGuiWindow* window = GImGui->CurrentWindow; LastItemId = window->DC.LastItemId; LastItemStatusFlags = window->DC.LastItemStatusFlags; LastItemRect = window->DC.LastItemRect; LastItemDisplayRect = window->DC.LastItemDisplayRect; }
+    void Restore() const { ImGuiWindow* window = GImGui->CurrentWindow; window->DC.LastItemId = LastItemId; window->DC.LastItemStatusFlags = LastItemStatusFlags; window->DC.LastItemRect = LastItemRect; window->DC.LastItemDisplayRect = LastItemDisplayRect; }
 };
 
 //-----------------------------------------------------------------------------