Internals: Extracted StartMouseMovingWindow so we can add code to turn an arbitrary widget into a window mover (will be useful to make the Collapse button a window mover past a mouse drag threshold) + added a couple of _None flags.

imgui.cpp

@@ -3590,7 +3590,21 @@ static void ImGui::NavUpdate()
 #endif
 }
 
-void ImGui::UpdateMovingWindow()
+void ImGui::StartMouseMovingWindow(ImGuiWindow* window)
+{
+    // Set ActiveId even if the _NoMove flag is set. Without it, dragging away from a window with _NoMove would activate hover on other windows.
+    ImGuiContext& g = *GImGui;
+    FocusWindow(window);
+    SetActiveID(window->MoveId, window);
+    g.NavDisableHighlight = true;
+    g.ActiveIdClickOffset = g.IO.MousePos - window->RootWindow->Pos;
+    if (!(window->Flags & ImGuiWindowFlags_NoMove) && !(window->RootWindow->Flags & ImGuiWindowFlags_NoMove))
+        g.MovingWindow = window;
+}
+
+// Handle mouse moving window
+// Note: moving window with the navigation keys (Square + d-pad / CTRL+TAB + Arrows) are processed in NavUpdateWindowing()
+void ImGui::UpdateMouseMovingWindow()
 {
     ImGuiContext& g = *GImGui;
     if (g.MovingWindow != NULL)
@@ -3858,7 +3872,7 @@ void ImGui::NewFrame()
     g.IO.Framerate = (g.FramerateSecPerFrameAccum > 0.0f) ? (1.0f / (g.FramerateSecPerFrameAccum / (float)IM_ARRAYSIZE(g.FramerateSecPerFrame))) : FLT_MAX;
 
     // Handle user moving window with mouse (at the beginning of the frame to avoid input lag or sheering)
-    UpdateMovingWindow();
+    UpdateMouseMovingWindow();
     UpdateHoveredWindowAndCaptureFlags();
 
     // Background darkening/whitening
@@ -4391,20 +4405,9 @@ void ImGui::EndFrame()
             if (g.IO.MouseClicked[0])
             {
                 if (g.HoveredRootWindow != NULL)
-                {
-                    // Set ActiveId even if the _NoMove flag is set, without it dragging away from a window with _NoMove would activate hover on other windows.
-                    FocusWindow(g.HoveredWindow);
-                    SetActiveID(g.HoveredWindow->MoveId, g.HoveredWindow);
-                    g.NavDisableHighlight = true;
-                    g.ActiveIdClickOffset = g.IO.MousePos - g.HoveredRootWindow->Pos;
-                    if (!(g.HoveredWindow->Flags & ImGuiWindowFlags_NoMove) && !(g.HoveredRootWindow->Flags & ImGuiWindowFlags_NoMove))
-                        g.MovingWindow = g.HoveredWindow;
-                }
+                    StartMouseMovingWindow(g.HoveredWindow);
                 else if (g.NavWindow != NULL && GetFrontMostPopupModal() == NULL)
-                {
-                    // Clicking on void disable focus
-                    FocusWindow(NULL);
-                }
+                    FocusWindow(NULL);  // Clicking on void disable focus
             }
 
             // With right mouse button we close popups without changing focus

imgui_internal.h

@@ -210,6 +210,7 @@ static inline ImVec2 ImMul(const ImVec2& lhs, const ImVec2& rhs)
 
 enum ImGuiButtonFlags_
 {
+    ImGuiButtonFlags_None                   = 0,
     ImGuiButtonFlags_Repeat                 = 1 << 0,   // hold to repeat
     ImGuiButtonFlags_PressedOnClickRelease  = 1 << 1,   // return true on click + release on same item [DEFAULT if no PressedOn* flag is set]
     ImGuiButtonFlags_PressedOnClick         = 1 << 2,   // return true on click (default requires click+release)
@@ -228,12 +229,14 @@ enum ImGuiButtonFlags_
 
 enum ImGuiSliderFlags_
 {
+    ImGuiSliderFlags_None                   = 0,
     ImGuiSliderFlags_Vertical               = 1 << 0
 };
 
 enum ImGuiColumnsFlags_
 {
     // Default: 0
+    ImGuiColumnsFlags_None                  = 0,
     ImGuiColumnsFlags_NoBorder              = 1 << 0,   // Disable column dividers
     ImGuiColumnsFlags_NoResize              = 1 << 1,   // Disable resizing columns when clicking on the dividers
     ImGuiColumnsFlags_NoPreserveWidths      = 1 << 2,   // Disable column width preservation when adjusting columns
@@ -253,6 +256,7 @@ enum ImGuiSelectableFlagsPrivate_
 
 enum ImGuiSeparatorFlags_
 {
+    ImGuiSeparatorFlags_None                = 0,
     ImGuiSeparatorFlags_Horizontal          = 1 << 0,   // Axis default to current layout type, so generally Horizontal unless e.g. in a menu bar
     ImGuiSeparatorFlags_Vertical            = 1 << 1
 };
@@ -260,6 +264,7 @@ enum ImGuiSeparatorFlags_
 // Storage for LastItem data
 enum ImGuiItemStatusFlags_
 {
+    ImGuiItemStatusFlags_None               = 0,
     ImGuiItemStatusFlags_HoveredRect        = 1 << 0,
     ImGuiItemStatusFlags_HasDisplayRect     = 1 << 1
 };
@@ -1080,7 +1085,8 @@ namespace ImGui
     IMGUI_API void          Shutdown(ImGuiContext* context);    // Since 1.60 this is a _private_ function. You can call DestroyContext() to destroy the context created by CreateContext().
 
     IMGUI_API void          UpdateHoveredWindowAndCaptureFlags();
-    IMGUI_API void          UpdateMovingWindow();
+    IMGUI_API void          StartMouseMovingWindow(ImGuiWindow* window);
+    IMGUI_API void          UpdateMouseMovingWindow();
 
     IMGUI_API void                  MarkIniSettingsDirty();
     IMGUI_API void                  MarkIniSettingsDirty(ImGuiWindow* window);