From f2218f14e59984956264b3a4576c078c7ecc5c3e Mon Sep 17 00:00:00 2001 From: reznet Date: Tue, 11 Aug 2015 15:38:09 -0500 Subject: [PATCH] Explain why no TZ conversion is needed for some graph methods The graph cursor and range text strings are computed from the graph's data which do not need to be converted to local time. i.e. 5pm == 5pm. --- sleepyhead/Graphs/gGraphView.cpp | 8 ++++++++ sleepyhead/overview.cpp | 5 ++++- 2 files changed, 12 insertions(+), 1 deletion(-) diff --git a/sleepyhead/Graphs/gGraphView.cpp b/sleepyhead/Graphs/gGraphView.cpp index 8bbf7448..f9ded175 100644 --- a/sleepyhead/Graphs/gGraphView.cpp +++ b/sleepyhead/Graphs/gGraphView.cpp @@ -1385,6 +1385,14 @@ void gGraphView::paintGL() QString gGraphView::getRangeString() { + // a note about time zone usage here + // even though this string will be displayed to the user + // the graph is drawn using UTC times, so no conversion + // is needed to format the date and time for the user + // i.e. if the graph says the cursor is at 5pm, then that + // is what we should display. + // passing in UTC below is necessary to prevent QT + // from automatically converting the time to local time QString fmt; qint64 diff = m_maxx - m_minx; diff --git a/sleepyhead/overview.cpp b/sleepyhead/overview.cpp index 172e4d33..82b80f67 100644 --- a/sleepyhead/overview.cpp +++ b/sleepyhead/overview.cpp @@ -475,7 +475,10 @@ gGraph *Overview::createGraph(QString code, QString name, QString units, YTicker void Overview::on_LineCursorUpdate(double time) { if (time > 1) { - QDateTime dt = QDateTime::fromMSecsSinceEpoch(time,Qt::UTC); + // even though the generated string is displayed to the user + // no time zone conversion is neccessary, so pass UTC + // to prevent QT from automatically converting to local time + QDateTime dt = QDateTime::fromMSecsSinceEpoch(time, Qt::UTC); QString txt = dt.toString("dd MMM yyyy (dddd)"); dateLabel->setText(txt); } else dateLabel->setText(QString(GraphView->emptyText()));