Scrolling: Tweak mouse-wheel locked window timer so it is shorter but also gets reset whenever scrolling again (#2604) + small refactor

Somehow interesting for (#3795, #4559). sorry this will break PR for 3795 but we got the info.

docs/CHANGELOG.txt

@@ -103,6 +103,8 @@ Other Changes:
 - Popups & Modals: fixed nested Begin() being erroneously input-inhibited. While it is
   unusual, you can nest a Begin() inside a popup or modal, it is occasionally useful to
   achieve certains things (e.g. some ways to implement suggestion popup #718, #4461).
+- Scrolling: Tweak mouse-wheel locked window timer so it is shorter but also gets reset
+  whenever scrolling again (#2604).
 - InputText: added experimental io.ConfigInputTextEnterKeepActive feature to make pressing
   Enter keep the input active and select all text.
 - InputText: numerical fields automatically accept full-width characters (U+FF01..U+FF5E)

imgui.cpp

@@ -953,7 +953,7 @@ static const float NAV_WINDOWING_LIST_APPEAR_DELAY          = 0.15f;    // Time
 // Window resizing from edges (when io.ConfigWindowsResizeFromEdges = true and ImGuiBackendFlags_HasMouseCursors is set in io.BackendFlags by backend)
 static const float WINDOWS_HOVER_PADDING                    = 4.0f;     // Extend outside window for hovering/resizing (maxxed with TouchPadding) and inside windows for borders. Affect FindHoveredWindow().
 static const float WINDOWS_RESIZE_FROM_EDGES_FEEDBACK_TIMER = 0.04f;    // Reduce visual noise by only highlighting the border after a certain time.
-static const float WINDOWS_MOUSE_WHEEL_SCROLL_LOCK_TIMER    = 2.00f;    // Lock scrolled window (so it doesn't pick child windows that are scrolling through) for a certain time, unless mouse moved.
+static const float WINDOWS_MOUSE_WHEEL_SCROLL_LOCK_TIMER    = 1.50f;    // Lock scrolled window (so it doesn't pick child windows that are scrolling through) for a certain time, unless mouse moved.
 
 //-------------------------------------------------------------------------
 // [SECTION] FORWARD DECLARATIONS
@@ -4265,15 +4265,15 @@ static void ImGui::UpdateMouseInputs()
     }
 }
 
-static void StartLockWheelingWindow(ImGuiWindow* window)
+static void LockWheelingWindow(ImGuiWindow* window)
 {
     ImGuiContext& g = *GImGui;
+    g.WheelingWindowTimer = window ? WINDOWS_MOUSE_WHEEL_SCROLL_LOCK_TIMER : 0.0f;
     if (g.WheelingWindow == window)
         return;
-    IMGUI_DEBUG_LOG_IO("StartLockWheelingWindow() \"%s\"\n", window ? window->Name : "NULL");
+    IMGUI_DEBUG_LOG_IO("LockWheelingWindow() \"%s\"\n", window ? window->Name : "NULL");
     g.WheelingWindow = window;
     g.WheelingWindowRefMousePos = g.IO.MousePos;
-    g.WheelingWindowTimer = WINDOWS_MOUSE_WHEEL_SCROLL_LOCK_TIMER;
 }
 
 void ImGui::UpdateMouseWheel()
@@ -4287,11 +4287,7 @@ void ImGui::UpdateMouseWheel()
         if (IsMousePosValid() && ImLengthSqr(g.IO.MousePos - g.WheelingWindowRefMousePos) > g.IO.MouseDragThreshold * g.IO.MouseDragThreshold)
             g.WheelingWindowTimer = 0.0f;
         if (g.WheelingWindowTimer <= 0.0f)
-        {
-            IMGUI_DEBUG_LOG_IO("UpdateMouseWheel() release WheelingWindow lock \"%s\"\n", g.WheelingWindow->Name);
-            g.WheelingWindow = NULL;
-            g.WheelingWindowTimer = 0.0f;
-        }
+            LockWheelingWindow(NULL);
     }
 
     const bool hovered_id_using_mouse_wheel = (g.HoveredIdPreviousFrame != 0 && g.HoveredIdPreviousFrameUsingMouseWheel);
@@ -4311,7 +4307,7 @@ void ImGui::UpdateMouseWheel()
     // FIXME-OBSOLETE: This is an old feature, it still works but pretty much nobody is using it and may be best redesigned.
     if (wheel_y != 0.0f && g.IO.KeyCtrl && g.IO.FontAllowUserScaling)
     {
-        StartLockWheelingWindow(window);
+        LockWheelingWindow(window);
         const float new_font_scale = ImClamp(window->FontWindowScale + g.IO.MouseWheel * 0.10f, 0.50f, 2.50f);
         const float scale = new_font_scale / window->FontWindowScale;
         window->FontWindowScale = new_font_scale;
@@ -4342,7 +4338,7 @@ void ImGui::UpdateMouseWheel()
     // Vertical Mouse Wheel scrolling
     if (wheel_y != 0.0f)
     {
-        StartLockWheelingWindow(window);
+        LockWheelingWindow(window);
         while ((window->Flags & ImGuiWindowFlags_ChildWindow) && ((window->ScrollMax.y == 0.0f) || ((window->Flags & ImGuiWindowFlags_NoScrollWithMouse) && !(window->Flags & ImGuiWindowFlags_NoMouseInputs))))
             window = window->ParentWindow;
         if (!(window->Flags & ImGuiWindowFlags_NoScrollWithMouse) && !(window->Flags & ImGuiWindowFlags_NoMouseInputs))
@@ -4356,7 +4352,7 @@ void ImGui::UpdateMouseWheel()
     // Horizontal Mouse Wheel scrolling, or Vertical Mouse Wheel w/ Shift held
     if (wheel_x != 0.0f)
     {
-        StartLockWheelingWindow(window);
+        LockWheelingWindow(window);
         while ((window->Flags & ImGuiWindowFlags_ChildWindow) && ((window->ScrollMax.x == 0.0f) || ((window->Flags & ImGuiWindowFlags_NoScrollWithMouse) && !(window->Flags & ImGuiWindowFlags_NoMouseInputs))))
             window = window->ParentWindow;
         if (!(window->Flags & ImGuiWindowFlags_NoScrollWithMouse) && !(window->Flags & ImGuiWindowFlags_NoMouseInputs))