Inputs: modulate wheel lock timer for small amount of wheeling. Slightly lower timer. (#3795)

docs/CHANGELOG.txt

@@ -119,7 +119,7 @@ Other Changes:
     systems while letting early adopters adopters toy with internals.
     (#456, #2637, #2620, #2891, #3370, #3724, #4828, #5108, #5242, #5641)
 - Scrolling: Tweak mouse-wheel locked window timer so it is shorter but also gets reset
-  whenever scrolling again (#2604).
+  whenever scrolling again. Modulate for small (sub-pixel) amounts. (#2604)
 - Scrolling: Mitigated issue where multi-axis mouse-wheel inputs (usually from touch pad
   events) are incorrectly locking scrolling in a parent window. (#4559, #3795, #2604)
 - Scrolling: Exposed SetNextWindowScroll() in public API. Useful to remove a scrolling

imgui.cpp

@@ -954,7 +954,7 @@ 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    = 0.80f;    // 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    = 0.70f;    // Lock scrolled window (so it doesn't pick child windows that are scrolling through) for a certain time, unless mouse moved.
 
 //-------------------------------------------------------------------------
 // [SECTION] FORWARD DECLARATIONS
@@ -4338,10 +4338,13 @@ static void ImGui::UpdateMouseInputs()
     }
 }
 
-static void LockWheelingWindow(ImGuiWindow* window)
+static void LockWheelingWindow(ImGuiWindow* window, float wheel_amount)
 {
     ImGuiContext& g = *GImGui;
-    g.WheelingWindowReleaseTimer = window ? WINDOWS_MOUSE_WHEEL_SCROLL_LOCK_TIMER : 0.0f;
+    if (window)
+        g.WheelingWindowReleaseTimer = ImMin(g.WheelingWindowReleaseTimer + ImAbs(wheel_amount) * WINDOWS_MOUSE_WHEEL_SCROLL_LOCK_TIMER, WINDOWS_MOUSE_WHEEL_SCROLL_LOCK_TIMER);
+    else
+        g.WheelingWindowReleaseTimer = NULL;
     if (g.WheelingWindow == window)
         return;
     IMGUI_DEBUG_LOG_IO("LockWheelingWindow() \"%s\"\n", window ? window->Name : "NULL");
@@ -4360,7 +4363,7 @@ void ImGui::UpdateMouseWheel()
         if (IsMousePosValid() && ImLengthSqr(g.IO.MousePos - g.WheelingWindowRefMousePos) > g.IO.MouseDragThreshold * g.IO.MouseDragThreshold)
             g.WheelingWindowReleaseTimer = 0.0f;
         if (g.WheelingWindowReleaseTimer <= 0.0f)
-            LockWheelingWindow(NULL);
+            LockWheelingWindow(NULL, 0.0f);
     }
 
     ImVec2 wheel;
@@ -4378,7 +4381,7 @@ 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)
     {
-        LockWheelingWindow(mouse_window);
+        LockWheelingWindow(mouse_window, wheel.y);
         ImGuiWindow* window = mouse_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;
@@ -4417,7 +4420,7 @@ void ImGui::UpdateMouseWheel()
             window = window->ParentWindow;
         if (!(window->Flags & ImGuiWindowFlags_NoScrollWithMouse) && !(window->Flags & ImGuiWindowFlags_NoMouseInputs))
         {
-            LockWheelingWindow(mouse_window);
+            LockWheelingWindow(mouse_window, wheel.y);
             float max_step = window->InnerRect.GetHeight() * 0.67f;
             float scroll_step = ImFloor(ImMin(5 * window->CalcFontSize(), max_step));
             SetScrollY(window, window->Scroll.y - wheel.y * scroll_step);
@@ -4432,7 +4435,7 @@ void ImGui::UpdateMouseWheel()
             window = window->ParentWindow;
         if (!(window->Flags & ImGuiWindowFlags_NoScrollWithMouse) && !(window->Flags & ImGuiWindowFlags_NoMouseInputs))
         {
-            LockWheelingWindow(mouse_window);
+            LockWheelingWindow(mouse_window, wheel.x);
             float max_step = window->InnerRect.GetWidth() * 0.67f;
             float scroll_step = ImFloor(ImMin(2 * window->CalcFontSize(), max_step));
             SetScrollX(window, window->Scroll.x - wheel.x * scroll_step);