h2. Summary

The right side of the tooltip is cut off at the Calendar View.

h2. Description

In normal mode, the right side of the issue's tooltip is clipped.
The contents of the tooltip are hidden under the sidebar.

In responsive mode, not only the right side of the issue but also the issues on Friday are the same.

h2. Environment

Environment:
  Redmine version                4.1.1.stable.19819
  Ruby version                   2.5.3-p105 (2018-10-18) [x86_64-darwin18]
  Rails version                  5.2.4.2
  Environment                    development
  Database adapter               SQLite
  Mailer queue                   ActiveJob::QueueAdapters::AsyncAdapter

The trunk is the same situation.

h2. Visual Proof / Screenshot

!sample-capture.png!

h2. Expected Results

The tooltip is displayed without cutting off.

h2. Actual Results

Cut off because of the content's overflow.

h2. Workaround

Modify the application.css and responsive.css

h3. application.css

Index: public/stylesheets/application.css
===================================================================
--- public/stylesheets/application.css  (revision 19834)
+++ public/stylesheets/application.css  (working copy)
@@ -109,6 +109,7 @@
 #content { flex-grow: 1; background-color: #fff; margin: 0px; padding: 6px 10px 10px 10px; overflow-x: auto;}
 html>body #content { min-height: 600px; }
 * html body #content { height: 600px; } /* IE */
+html>body.controller-calendars.action-show #content { overflow-x: visible; }

 #main.nosidebar #sidebar{ display: none; }

I'm not sure if the changing of overflow-x has some unexpected effects, so I specify more specific conditions.
(Calendar view only)

h3. responsive.css

Index: public/stylesheets/responsive.css
===================================================================
--- public/stylesheets/responsive.css   (revision 19834)
+++ public/stylesheets/responsive.css   (working copy)
@@ -847,6 +847,9 @@
     margin-left: 0;
     width: 100%;
   }
+
+  /* calendar tooltip */
+  table.cal td:not(.week-number):nth-child(n+5) span.tip { right: 10px; }
 }

 @media all and (max-width: 599px) {

h3. Result

!after-normal-mode.png!

!after-responsive-mode.png!