Inputs: SetItemKeyOwner(): does not set ownership is key is already taken.

(#456, #2637, #2620, #2891, #3370, #3724, #4828, #5108, #5242, #5641)

docs/CHANGELOG.txt

@@ -156,6 +156,10 @@ Other Changes:
   - SetItemKeyOwner(): return true if ownership has been requested, which typically
     needs to to checked for gating further tests. This is important as the function
     may fail. (#456, #2637, #2620, #2891, #3370, #3724, #4828, #5108, #5242, #5641)
+  - SetItemKeyOwner(): does not set ownership is key is already taken. Effectively
+    this makes using `SetItemKeyOwner(ImGuiKey_MouseWheelY)` over an item work as
+    expected while not having item react if a scroll wheel is actively in progress.
+    May be subject to further redesign, e.g. conditional flags. Feedback welcome!
 - Style:
   - Fixed vertical scrollbar top coordinates when using thick borders on windows
     with no title bar and no menu bar. (#9366)

imgui.cpp

@@ -10726,6 +10726,8 @@ bool ImGui::SetItemKeyOwner(ImGuiKey key, ImGuiInputFlags flags)
     if ((g.HoveredId == id && (flags & ImGuiInputFlags_CondHovered)) || (g.ActiveId == id && (flags & ImGuiInputFlags_CondActive)))
     {
         IM_ASSERT((flags & ~ImGuiInputFlags_SupportedBySetItemKeyOwner) == 0); // Passing flags not supported by this function!
+        if (!TestKeyOwner(key, id))
+            return false;
         SetKeyOwner(key, id, flags & ~ImGuiInputFlags_CondMask_);
         return true;
     }

imgui_demo.cpp

@@ -875,7 +875,7 @@ static void ExampleImageViewer_DrawCanvas(ExampleImageViewerData* data, ImVec2 c
     data->ViewReset = false;
 
     // Handle inputs
-    if (ImGui::SetItemKeyOwner(ImGuiKey_MouseWheelY)) // FIXME: Not while scrolling?
+    if (ImGui::SetItemKeyOwner(ImGuiKey_MouseWheelY))
         if (io.MouseWheel != 0.0f)
             data->Zoom = IM_CLAMP(data->Zoom * (1.0f + io.MouseWheel * 0.10f), data->ZoomMin, data->ZoomMax);
     float zoom = data->Zoom; // (float)(int)ViewZoom;