Internals: Cleanup FindBestPopupWindowPos() to be more digestible, since we are bounds to rework the logic there. No functional changes intended. FIXED TYPO.

imgui.cpp

@@ -4037,7 +4037,7 @@ static ImVec2 FindBestPopupWindowPos(const ImVec2& base_pos, const ImVec2& size,
         float avail_w = (dir == ImGuiDir_Left ? r_avoid.Min.x : r_outer.Max.x) - (dir == ImGuiDir_Right ? r_avoid.Max.x : r_outer.Min.x);
         if (avail_w < size.x)
             continue;
-        float avail_h = (dir == ImGuiDir_Down ? r_avoid.Min.y : r_outer.Max.y) - (dir == ImGuiDir_Down ? r_avoid.Max.y : r_outer.Min.y);
+        float avail_h = (dir == ImGuiDir_Up ? r_avoid.Min.y : r_outer.Max.y) - (dir == ImGuiDir_Down ? r_avoid.Max.y : r_outer.Min.y);
         if (avail_h < size.y)
             continue;