diff widgets/WidgetScale.h @ 1324:13d9b422f7fe zoom

Merge from default branch

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/widgets/WidgetScale.h	Mon Sep 17 13:51:31 2018 +0100
@@ -0,0 +1,64 @@
+/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */
+
+/*
+    Sonic Visualiser
+    An audio file viewer and annotation editor.
+    Centre for Digital Music, Queen Mary, University of London.
+    
+    This program is free software; you can redistribute it and/or
+    modify it under the terms of the GNU General Public License as
+    published by the Free Software Foundation; either version 2 of the
+    License, or (at your option) any later version.  See the file
+    COPYING included with this distribution for more information.
+*/
+
+#ifndef SV_WIDGET_SCALE_H
+#define SV_WIDGET_SCALE_H
+
+#include <QFont>
+#include <QFontMetrics>
+
+#include "base/Debug.h"
+
+class WidgetScale
+{
+public:   
+    /**
+     * Take a "design pixel" size and scale it for the actual
+     * display. This is relevant to hi-dpi systems that do not do
+     * pixel doubling (i.e. Windows and Linux rather than OS/X).
+     */
+    static int scalePixelSize(int pixels) {
+
+        static double ratio = 0.0;
+        if (ratio == 0.0) {
+            double baseEm;
+#ifdef Q_OS_MAC
+            baseEm = 17.0;
+#else
+            baseEm = 15.0;
+#endif
+            double em = QFontMetrics(QFont()).height();
+            ratio = em / baseEm;
+            SVDEBUG << "WidgetScale::scalePixelSize: baseEm = " << baseEm
+                    << ", platform default font height = " << em
+                    << ", resulting scale factor = " << ratio << endl;
+            if (ratio < 1.0) {
+                SVDEBUG << "WidgetScale::scalePixelSize: rounding up to 1.0"
+                        << endl;
+                ratio = 1.0;
+            }
+        }
+
+        int scaled = int(pixels * ratio + 0.5);
+        if (pixels != 0 && scaled == 0) scaled = 1;
+        return scaled;
+    }
+
+    static QSize scaleQSize(QSize size) {
+        return QSize(scalePixelSize(size.width()),
+                     scalePixelSize(size.height()));
+    }
+};
+
+#endif