Docking: fix undocking from tab-bar by moving mouse horizontally, broken by d705192.

Author: ocornut

imgui_widgets.cpp

@@ -7920,17 +7920,20 @@ bool    ImGui::TabItemEx(ImGuiTabBar* tab_bar, const char* label, bool* p_open,
     else if (held && !tab_appearing && IsMouseDragging(0))
     {
         // Drag and drop: re-order tabs
+        int drag_dir = 0;
         float drag_distance_from_edge_x = 0.0f;
         if (!g.DragDropActive && ((tab_bar->Flags & ImGuiTabBarFlags_Reorderable) || (docked_window != NULL)))
         {
             // While moving a tab it will jump on the other side of the mouse, so we also test for MouseDelta.x
             if (g.IO.MouseDelta.x < 0.0f && g.IO.MousePos.x < bb.Min.x)
             {
+                drag_dir = -1;
                 drag_distance_from_edge_x = bb.Min.x - g.IO.MousePos.x;
                 TabBarQueueReorderFromMousePos(tab_bar, tab, g.IO.MousePos);
             }
             else if (g.IO.MouseDelta.x > 0.0f && g.IO.MousePos.x > bb.Max.x)
             {
+                drag_dir = +1;
                 drag_distance_from_edge_x = g.IO.MousePos.x - bb.Max.x;
                 TabBarQueueReorderFromMousePos(tab_bar, tab, g.IO.MousePos);
             }
@@ -7941,20 +7944,18 @@ bool    ImGui::TabItemEx(ImGuiTabBar* tab_bar, const char* label, bool* p_open,
         {
             // We use a variable threshold to distinguish dragging tabs within a tab bar and extracting them out of the tab bar
             bool undocking_tab = (g.DragDropActive && g.DragDropPayload.SourceId == id);
-
             if (!undocking_tab) //&& (!g.IO.ConfigDockingWithShift || g.IO.KeyShift)
             {
                 float threshold_base = g.FontSize;
-                //float threshold_base = g.IO.ConfigDockingWithShift ? g.FontSize * 0.5f : g.FontSize;
                 float threshold_x = (threshold_base * 2.2f);
                 float threshold_y = (threshold_base * 1.5f) + ImClamp((ImFabs(g.IO.MouseDragMaxDistanceAbs[0].x) - threshold_base * 2.0f) * 0.20f, 0.0f, threshold_base * 4.0f);
                 //GetForegroundDrawList()->AddRect(ImVec2(bb.Min.x - threshold_x, bb.Min.y - threshold_y), ImVec2(bb.Max.x + threshold_x, bb.Max.y + threshold_y), IM_COL32_WHITE); // [DEBUG]
 
                 float distance_from_edge_y = ImMax(bb.Min.y - g.IO.MousePos.y, g.IO.MousePos.y - bb.Max.y);
                 if (distance_from_edge_y >= threshold_y)
                     undocking_tab = true;
-                else if (drag_distance_from_edge_x > threshold_x)
-                    if ((tab_bar->ReorderRequestOffset < 0 && tab_bar->GetTabOrder(tab) == 0) || (tab_bar->ReorderRequestOffset > 0 && tab_bar->GetTabOrder(tab) == tab_bar->Tabs.Size - 1))
+                if (drag_distance_from_edge_x > threshold_x)
+                    if ((drag_dir < 0 && tab_bar->GetTabOrder(tab) == 0) || (drag_dir > 0 && tab_bar->GetTabOrder(tab) == tab_bar->Tabs.Size - 1))
                         undocking_tab = true;
             }