Scrolling: Further reduce unrelease mouse-wheel locked window timer + misc refactor (#2604, #3795, #4559)

The refactor are designed to minimize the diff for changes needed for #3795

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    = 1.50f;    // 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    = 0.80f;    // Lock scrolled window (so it doesn't pick child windows that are scrolling through) for a certain time, unless mouse moved.
 
 //-------------------------------------------------------------------------
 // [SECTION] FORWARD DECLARATIONS
@@ -4268,7 +4268,7 @@ static void ImGui::UpdateMouseInputs()
 static void LockWheelingWindow(ImGuiWindow* window)
 {
     ImGuiContext& g = *GImGui;
-    g.WheelingWindowTimer = window ? WINDOWS_MOUSE_WHEEL_SCROLL_LOCK_TIMER : 0.0f;
+    g.WheelingWindowReleaseTimer = window ? WINDOWS_MOUSE_WHEEL_SCROLL_LOCK_TIMER : 0.0f;
     if (g.WheelingWindow == window)
         return;
     IMGUI_DEBUG_LOG_IO("LockWheelingWindow() \"%s\"\n", window ? window->Name : "NULL");
@@ -4283,10 +4283,10 @@ void ImGui::UpdateMouseWheel()
     // Reset the locked window if we move the mouse or after the timer elapses
     if (g.WheelingWindow != NULL)
     {
-        g.WheelingWindowTimer -= g.IO.DeltaTime;
+        g.WheelingWindowReleaseTimer -= g.IO.DeltaTime;
         if (IsMousePosValid() && ImLengthSqr(g.IO.MousePos - g.WheelingWindowRefMousePos) > g.IO.MouseDragThreshold * g.IO.MouseDragThreshold)
-            g.WheelingWindowTimer = 0.0f;
-        if (g.WheelingWindowTimer <= 0.0f)
+            g.WheelingWindowReleaseTimer = 0.0f;
+        if (g.WheelingWindowReleaseTimer <= 0.0f)
             LockWheelingWindow(NULL);
     }
 
@@ -4294,9 +4294,10 @@ void ImGui::UpdateMouseWheel()
     const bool active_id_using_mouse_wheel_x = g.ActiveIdUsingKeyInputMask.TestBit(ImGuiKey_MouseWheelX);
     const bool active_id_using_mouse_wheel_y = g.ActiveIdUsingKeyInputMask.TestBit(ImGuiKey_MouseWheelY);
 
-    float wheel_x = (!hovered_id_using_mouse_wheel && !active_id_using_mouse_wheel_x) ? g.IO.MouseWheelH : 0.0f;
-    float wheel_y = (!hovered_id_using_mouse_wheel && !active_id_using_mouse_wheel_y) ? g.IO.MouseWheel : 0;
-    if (wheel_x == 0.0f && wheel_y == 0.0f)
+    ImVec2 wheel;
+    wheel.x = (!hovered_id_using_mouse_wheel && !active_id_using_mouse_wheel_x) ? g.IO.MouseWheelH : 0.0f;
+    wheel.y = (!hovered_id_using_mouse_wheel && !active_id_using_mouse_wheel_y) ? g.IO.MouseWheel : 0;
+    if (wheel.x == 0.0f && wheel.y == 0.0f)
         return;
 
     //IMGUI_DEBUG_LOG("MouseWheel X:%.3f Y:%.3f\n", wheel_x, wheel_y);
@@ -4306,7 +4307,7 @@ void ImGui::UpdateMouseWheel()
 
     // Zoom / Scale window
     // 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)
+    if (wheel.y != 0.0f && g.IO.KeyCtrl && g.IO.FontAllowUserScaling)
     {
         LockWheelingWindow(mouse_window);
         ImGuiWindow* window = mouse_window;
@@ -4322,23 +4323,25 @@ void ImGui::UpdateMouseWheel()
         }
         return;
     }
-
-    // Mouse wheel scrolling
-    // If a child window has the ImGuiWindowFlags_NoScrollWithMouse flag, we give a chance to scroll its parent
     if (g.IO.KeyCtrl)
         return;
 
+    // Mouse wheel scrolling
     // As a standard behavior holding SHIFT while using Vertical Mouse Wheel triggers Horizontal scroll instead
     // (we avoid doing it on OSX as it the OS input layer handles this already)
     const bool swap_axis = g.IO.KeyShift && !g.IO.ConfigMacOSXBehaviors;
     if (swap_axis)
     {
-        wheel_x = wheel_y;
-        wheel_y = 0.0f;
+        wheel.x = wheel.y;
+        wheel.y = 0.0f;
     }
 
     // Vertical Mouse Wheel scrolling
-    if (wheel_y != 0.0f)
+    // Bubble up into parent window if:
+    // - a child window doesn't allow any scrolling.
+    // - a child window doesn't need scrolling because it is already at the edge for the direction we are going in.
+    // - a child window has the ImGuiWindowFlags_NoScrollWithMouse flag.
+    if (wheel.y != 0.0f)
     {
         ImGuiWindow* window = mouse_window;
         while ((window->Flags & ImGuiWindowFlags_ChildWindow) && ((window->ScrollMax.y == 0.0f) || ((window->Flags & ImGuiWindowFlags_NoScrollWithMouse) && !(window->Flags & ImGuiWindowFlags_NoMouseInputs))))
@@ -4348,12 +4351,12 @@ void ImGui::UpdateMouseWheel()
             LockWheelingWindow(mouse_window);
             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);
+            SetScrollY(window, window->Scroll.y - wheel.y * scroll_step);
         }
     }
 
     // Horizontal Mouse Wheel scrolling, or Vertical Mouse Wheel w/ Shift held
-    if (wheel_x != 0.0f)
+    if (wheel.x != 0.0f)
     {
         ImGuiWindow* window = mouse_window;
         while ((window->Flags & ImGuiWindowFlags_ChildWindow) && ((window->ScrollMax.x == 0.0f) || ((window->Flags & ImGuiWindowFlags_NoScrollWithMouse) && !(window->Flags & ImGuiWindowFlags_NoMouseInputs))))
@@ -4363,7 +4366,7 @@ void ImGui::UpdateMouseWheel()
             LockWheelingWindow(mouse_window);
             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);
+            SetScrollX(window, window->Scroll.x - wheel.x * scroll_step);
         }
     }
 }

imgui_internal.h

@@ -1631,7 +1631,7 @@ struct ImGuiContext
     ImGuiWindow*            MovingWindow;                       // Track the window we clicked on (in order to preserve focus). The actual window that is moved is generally MovingWindow->RootWindow.
     ImGuiWindow*            WheelingWindow;                     // Track the window we started mouse-wheeling on. Until a timer elapse or mouse has moved, generally keep scrolling the same window even if during the course of scrolling the mouse ends up hovering a child window.
     ImVec2                  WheelingWindowRefMousePos;
-    float                   WheelingWindowTimer;
+    float                   WheelingWindowReleaseTimer;
 
     // Item/widgets state and tracking information
     ImGuiID                 DebugHookIdInfo;                    // Will call core hooks: DebugHookIdInfo() from GetID functions, used by Stack Tool [next HoveredId/ActiveId to not pull in an extra cache-line]
@@ -1885,7 +1885,7 @@ struct ImGuiContext
         HoveredWindowUnderMovingWindow = NULL;
         MovingWindow = NULL;
         WheelingWindow = NULL;
-        WheelingWindowTimer = 0.0f;
+        WheelingWindowReleaseTimer = 0.0f;
 
         DebugHookIdInfo = 0;
         HoveredId = HoveredIdPreviousFrame = 0;