Inputs: Internal: added SetItemUsingMouseWheel() and mechanism to request mouse wheel for both HoveredId and ActiveId. (#2891)

Based on @kudaba PR.

imgui.cpp

@@ -3026,6 +3026,7 @@ void ImGui::SetActiveID(ImGuiID id, ImGuiWindow* window)
 
     // Clear declaration of inputs claimed by the widget
     // (Please note that this is WIP and not all keys/inputs are thoroughly declared by all widgets yet)
+    g.ActiveIdUsingMouseWheel = false;
     g.ActiveIdUsingNavDirMask = 0x00;
     g.ActiveIdUsingNavInputMask = 0x00;
     g.ActiveIdUsingKeyInputMask = 0x00;
@@ -3041,6 +3042,7 @@ void ImGui::SetHoveredID(ImGuiID id)
     ImGuiContext& g = *GImGui;
     g.HoveredId = id;
     g.HoveredIdAllowOverlap = false;
+    g.HoveredIdUsingMouseWheel = false;
     if (id != 0 && g.HoveredIdPreviousFrame != id)
         g.HoveredIdTimer = g.HoveredIdNotActiveTimer = 0.0f;
 }
@@ -3606,6 +3608,9 @@ void ImGui::UpdateMouseWheel()
     if (g.IO.MouseWheel == 0.0f && g.IO.MouseWheelH == 0.0f)
         return;
 
+    if ((g.ActiveId != 0 && g.ActiveIdUsingMouseWheel) || (g.HoveredIdPreviousFrame != 0 && g.HoveredIdPreviousFrameUsingMouseWheel))
+        return;
+
     ImGuiWindow* window = g.WheelingWindow ? g.WheelingWindow : g.HoveredWindow;
     if (!window || window->Collapsed)
         return;
@@ -3839,8 +3844,10 @@ void ImGui::NewFrame()
     if (g.HoveredId && g.ActiveId != g.HoveredId)
         g.HoveredIdNotActiveTimer += g.IO.DeltaTime;
     g.HoveredIdPreviousFrame = g.HoveredId;
+    g.HoveredIdPreviousFrameUsingMouseWheel = g.HoveredIdUsingMouseWheel;
     g.HoveredId = 0;
     g.HoveredIdAllowOverlap = false;
+    g.HoveredIdUsingMouseWheel = false;
     g.HoveredIdDisabled = false;
 
     // Update ActiveId data (clear reference to active widget if the widget isn't alive anymore)
@@ -4768,12 +4775,23 @@ bool ImGui::IsItemEdited()
 void ImGui::SetItemAllowOverlap()
 {
     ImGuiContext& g = *GImGui;
-    if (g.HoveredId == g.CurrentWindow->DC.LastItemId)
+    ImGuiID id = g.CurrentWindow->DC.LastItemId;
+    if (g.HoveredId == id)
         g.HoveredIdAllowOverlap = true;
-    if (g.ActiveId == g.CurrentWindow->DC.LastItemId)
+    if (g.ActiveId == id)
         g.ActiveIdAllowOverlap = true;
 }
 
+void ImGui::SetItemUsingMouseWheel()
+{
+    ImGuiContext& g = *GImGui;
+    ImGuiID id = g.CurrentWindow->DC.LastItemId;
+    if (g.HoveredId == id)
+        g.HoveredIdUsingMouseWheel = true;
+    if (g.ActiveId == id)
+        g.ActiveIdUsingMouseWheel = true;
+}
+
 ImVec2 ImGui::GetItemRectMin()
 {
     ImGuiWindow* window = GetCurrentWindowRead();

imgui.h

@@ -59,7 +59,7 @@ Index of this file:
 // Version
 // (Integer encoded as XYYZZ for use in #if preprocessor conditionals. Work in progress versions typically starts at XYY99 then bounce up to XYY00, XYY01 etc. when release tagging happens)
 #define IMGUI_VERSION               "1.80 WIP"
-#define IMGUI_VERSION_NUM           17908
+#define IMGUI_VERSION_NUM           17909
 #define IMGUI_CHECKVERSION()        ImGui::DebugCheckVersionAndDataLayout(IMGUI_VERSION, sizeof(ImGuiIO), sizeof(ImGuiStyle), sizeof(ImVec2), sizeof(ImVec4), sizeof(ImDrawVert), sizeof(ImDrawIdx))
 #define IMGUI_HAS_TABLE
 

imgui_internal.h

@@ -1275,9 +1275,11 @@ struct ImGuiContext
     float                   WheelingWindowTimer;
 
     // Item/widgets state and tracking information
-    ImGuiID                 HoveredId;                          // Hovered widget
+    ImGuiID                 HoveredId;                          // Hovered widget, filled during the frame
     ImGuiID                 HoveredIdPreviousFrame;
     bool                    HoveredIdAllowOverlap;
+    bool                    HoveredIdUsingMouseWheel;           // Hovered widget will use mouse wheel. Blocks scrolling the underlying window.
+    bool                    HoveredIdPreviousFrameUsingMouseWheel;
     bool                    HoveredIdDisabled;                  // At least one widget passed the rect test, but has been discarded by disabled flag or popup inhibit. May be true even if HoveredId == 0.
     float                   HoveredIdTimer;                     // Measure contiguous hovering time
     float                   HoveredIdNotActiveTimer;            // Measure contiguous hovering time where the item has not been active
@@ -1290,6 +1292,7 @@ struct ImGuiContext
     bool                    ActiveIdHasBeenPressedBefore;       // Track whether the active id led to a press (this is to allow changing between PressOnClick and PressOnRelease without pressing twice). Used by range_select branch.
     bool                    ActiveIdHasBeenEditedBefore;        // Was the value associated to the widget Edited over the course of the Active state.
     bool                    ActiveIdHasBeenEditedThisFrame;
+    bool                    ActiveIdUsingMouseWheel;            // Active widget will want to read mouse wheel. Blocks scrolling the underlying window.
     ImU32                   ActiveIdUsingNavDirMask;            // Active widget will want to read those nav move requests (e.g. can activate a button and move away from it)
     ImU32                   ActiveIdUsingNavInputMask;          // Active widget will want to read those nav inputs.
     ImU64                   ActiveIdUsingKeyInputMask;          // Active widget will want to read those key inputs. When we grow the ImGuiKey enum we'll need to either to order the enum to make useful keys come first, either redesign this into e.g. a small array.
@@ -1501,6 +1504,7 @@ struct ImGuiContext
 
         HoveredId = HoveredIdPreviousFrame = 0;
         HoveredIdAllowOverlap = false;
+        HoveredIdUsingMouseWheel = HoveredIdPreviousFrameUsingMouseWheel = false;
         HoveredIdDisabled = false;
         HoveredIdTimer = HoveredIdNotActiveTimer = 0.0f;
         ActiveId = 0;
@@ -1512,6 +1516,7 @@ struct ImGuiContext
         ActiveIdHasBeenPressedBefore = false;
         ActiveIdHasBeenEditedBefore = false;
         ActiveIdHasBeenEditedThisFrame = false;
+        ActiveIdUsingMouseWheel = false;
         ActiveIdUsingNavDirMask = 0x00;
         ActiveIdUsingNavInputMask = 0x00;
         ActiveIdUsingKeyInputMask = 0x00;
@@ -2267,6 +2272,7 @@ namespace ImGui
 
     // Inputs
     // FIXME: Eventually we should aim to move e.g. IsActiveIdUsingKey() into IsKeyXXX functions.
+    IMGUI_API void          SetItemUsingMouseWheel();
     inline bool             IsActiveIdUsingNavDir(ImGuiDir dir)                         { ImGuiContext& g = *GImGui; return (g.ActiveIdUsingNavDirMask & (1 << dir)) != 0; }
     inline bool             IsActiveIdUsingNavInput(ImGuiNavInput input)                { ImGuiContext& g = *GImGui; return (g.ActiveIdUsingNavInputMask & (1 << input)) != 0; }
     inline bool             IsActiveIdUsingKey(ImGuiKey key)                            { ImGuiContext& g = *GImGui; IM_ASSERT(key < 64); return (g.ActiveIdUsingKeyInputMask & ((ImU64)1 << key)) != 0; }