From e13e5982ffc61cb83fa90e897dbc9f28ff06c3be Mon Sep 17 00:00:00 2001
From: omar <omarcornut@gmail.com>
Date: Mon, 30 Jul 2018 18:06:41 +0200
Subject: [PATCH] Drag and Drop: Payload stays available and under the mouse if
 the source stops being submitted, however the tooltip is replaced by "..." +
 moved FrameScopeActive = false  at the bottom of EndFrame() for safety.
 (#1725)

---
 CHANGELOG.txt    |  1 +
 imgui.cpp        | 37 ++++++++++++++++++++++++++++---------
 imgui_internal.h |  2 ++
 3 files changed, 31 insertions(+), 9 deletions(-)

diff --git a/CHANGELOG.txt b/CHANGELOG.txt
index 29a736cf5..d9936f343 100644
--- a/CHANGELOG.txt
+++ b/CHANGELOG.txt
@@ -53,6 +53,7 @@ Other Changes:
  - Drag and Drop: Fixed ImGuiDragDropFlags_SourceNoDisableHover to affect hovering state prior to calling IsItemHovered() + fixed description. (#143)
  - Drag and Drop: Calling BeginTooltip() between a BeginDragSource()/EndDragSource() or BeginDropTarget()/EndDropTarget() uses adjusted tooltip
    settings matching the one created when calling BeginDragSource() without the ImGuiDragDropFlags_SourceNoPreviewTooltip flag. (#143)
+ - Drag and Drop: Payload stays available and under the mouse if the source stops being submitted, however the tooltip is replaced by "...". (#1725)
  - IsItemHovered(): Added ImGuiHoveredFlags_AllowWhenDisabled flag to query hovered status on disabled items. (#1940, #211)
  - Misc: Added ImGuiMouseCursor_Hand cursor enum + corresponding software cursor. (#1913, 1914) [@aiekick, @ocornut] 
  - Misc: Tweaked software mouse cursor offset to match the offset of the corresponding Windows 10 cursors.
diff --git a/imgui.cpp b/imgui.cpp
index 594d5fec8..5b99a9889 100644
--- a/imgui.cpp
+++ b/imgui.cpp
@@ -3903,6 +3903,10 @@ void ImGui::NewFrame()
     // Mark rendering data as invalid to prevent user who may have a handle on it to use it
     g.DrawData.Clear();
 
+    // Drag and drop keep the source ID alive so even if the source disappear our state is consistent
+    if (g.DragDropActive && g.DragDropPayload.SourceId == g.ActiveId)
+        KeepAliveID(g.DragDropPayload.SourceId);
+
     // Clear reference to active widget if the widget isn't alive anymore
     if (!g.HoveredIdPreviousFrame)
         g.HoveredIdTimer = 0.0f;
@@ -3924,13 +3928,7 @@ void ImGui::NewFrame()
     if (g.ScalarAsInputTextId && g.ActiveId != g.ScalarAsInputTextId)
         g.ScalarAsInputTextId = 0;
 
-    // Elapse drag & drop payload
-    if (g.DragDropActive && g.DragDropPayload.DataFrameCount + 1 < g.FrameCount)
-    {
-        ClearDragDrop();
-        g.DragDropPayloadBufHeap.clear();
-        memset(&g.DragDropPayloadBufLocal, 0, sizeof(g.DragDropPayloadBufLocal));
-    }
+    // Drag and drop
     g.DragDropAcceptIdPrev = g.DragDropAcceptIdCurr;
     g.DragDropAcceptIdCurr = 0;
     g.DragDropAcceptIdCurrRectSurface = FLT_MAX;
@@ -4426,7 +4424,6 @@ void ImGui::EndFrame()
     if (g.FrameCountEnded == g.FrameCount)          // Don't process EndFrame() multiple times.
         return;
     IM_ASSERT(g.FrameScopeActive && "Forgot to call ImGui::NewFrame()");
-    g.FrameScopeActive = false;
 
     // Notify OS when our Input Method Editor cursor has moved (e.g. CJK inputs using Microsoft IME)
     if (g.IO.ImeSetInputScreenPosFn && ImLengthSqr(g.PlatformImeLastPos - g.PlatformImePos) > 0.0001f)
@@ -4445,6 +4442,22 @@ void ImGui::EndFrame()
     if (g.NavWindowingTarget)
         NavUpdateWindowingList();
 
+    // Drag and Drop: Elapse payload at the end of the frame if mouse has been released
+    if (g.DragDropActive && g.DragDropPayload.DataFrameCount + 1 < g.FrameCount && !IsMouseDown(g.DragDropMouseButton))
+    {
+        ClearDragDrop();
+        g.DragDropPayloadBufHeap.clear();
+        memset(&g.DragDropPayloadBufLocal, 0, sizeof(g.DragDropPayloadBufLocal));
+    }
+
+    // Drag and Drop: Fallback for source tooltip. This is not ideal but better than nothing.
+    if (g.DragDropActive && g.DragDropSourceFrameCount < g.FrameCount)
+    {
+        g.DragDropWithinSourceOrTarget = true;
+        SetTooltip("...");
+        g.DragDropWithinSourceOrTarget = false;
+    }
+
     // Initiate moving window
     if (g.ActiveId == 0 && g.HoveredId == 0)
     {
@@ -4505,6 +4518,7 @@ void ImGui::EndFrame()
     memset(g.IO.InputCharacters, 0, sizeof(g.IO.InputCharacters));
     memset(g.IO.NavInputs, 0, sizeof(g.IO.NavInputs));
 
+    g.FrameScopeActive = false;
     g.FrameCountEnded = g.FrameCount;
 }
 
@@ -5277,7 +5291,11 @@ void ImGui::BeginTooltipEx(ImGuiWindowFlags extra_flags, bool override_previous_
 
 void ImGui::SetTooltipV(const char* fmt, va_list args)
 {
-    BeginTooltipEx(0, true);
+    ImGuiContext& g = *GImGui;
+    if (g.DragDropWithinSourceOrTarget)
+        BeginTooltip();
+    else
+        BeginTooltipEx(0, true);
     TextV(fmt, args);
     EndTooltip();
 }
@@ -13689,6 +13707,7 @@ bool ImGui::BeginDragDropSource(ImGuiDragDropFlags flags)
             g.DragDropSourceFlags = flags;
             g.DragDropMouseButton = mouse_button;
         }
+        g.DragDropSourceFrameCount = g.FrameCount;
         g.DragDropWithinSourceOrTarget = true;
 
         if (!(flags & ImGuiDragDropFlags_SourceNoPreviewTooltip))
diff --git a/imgui_internal.h b/imgui_internal.h
index 1adfde1ca..cdabcd35b 100644
--- a/imgui_internal.h
+++ b/imgui_internal.h
@@ -710,6 +710,7 @@ struct ImGuiContext
     bool                    DragDropActive;
     bool                    DragDropWithinSourceOrTarget;
     ImGuiDragDropFlags      DragDropSourceFlags;
+    int                     DragDropSourceFrameCount;
     int                     DragDropMouseButton;
     ImGuiPayload            DragDropPayload;
     ImRect                  DragDropTargetRect;
@@ -830,6 +831,7 @@ struct ImGuiContext
 
         DragDropActive = DragDropWithinSourceOrTarget = false;
         DragDropSourceFlags = 0;
+        DragDropSourceFrameCount = -1;
         DragDropMouseButton = -1;
         DragDropTargetId = 0;
         DragDropAcceptFlags = 0;