Fix incorrect font sizes (#321)

Recently, when chasing the font size differences between the wayland and xcb Qt backends, I ended up normalizing on the wayland sizing when bypassing the backend's font metrics calculation (#272).  Unfortunately, the wayland backend was not rendering the font sizes correctly, and it was a mistake to duplicate its behavior. 

* Assume a virtual DPI of 72 pixels/in instead of 96 when compulting font size
  - Based on testing, this produces the correct font size
  - Updated reference labels.
* No longer need to scale fonts when importing glabels-3 files.
  - The glabels-3 font sizes were correct afterall!  (#306)
  - No longer need to compensate for scale factor in unit tests when importing glabels-3 files.

model/ModelTextObject.cpp

@@ -42,13 +42,16 @@ namespace
         ///
         /// Calculate pixel size
         ///
-        /// Assume a virtual DPI of 96 pixels/inch for all QPainter contexts.
+        /// Assume a virtual DPI of 72 pixels/inch for all QPainter contexts.
         /// Ideally, we should use pointSizes for device independence, but as
-        /// Qt-6.4 on X11, Wayland, and MacOS this approach has better results.
+        /// of Qt-6.4, the  xcb (X11) and Wayland backends will render the same
+        /// font differently. Currently this function is basically the unity
+        /// function (i.e. 1 pt = 1 pixel) with rounding, but is a placeholder
+        /// that may need to be tweaked for different backends.
         ///
         int pixelSize( double pointSize )
         {
-                const double virtual_dpi = 96;
+                const double virtual_dpi = 72;
                 return qMax( 1, qRound( pointSize * virtual_dpi/72.0 ) );
         }
 }

model/XmlLabelParser_3.cpp

@@ -53,8 +53,6 @@ namespace
         using namespace glabels::model;
 
         const uint32_t GDK_PIXBUF_MAGIC_NUMBER {0x47646b50};
-
-        const double   FONT_SCALE_FACTOR       {0.75};               // In glabels-3, fonts were rendered at 75% of specified fontsize
         const Distance MARGIN_OFFSET           { Distance::pt(3) };  // In glabels-3, margin was not accounted for in text baseline calculations
 
         typedef enum
@@ -557,7 +555,7 @@ namespace glabels::model
 
                                 /* font attrs */
                                 fontFamily        = XmlUtil::getStringAttr( element, "font_family", "Sans" );
-                                fontSize          = XmlUtil::getDoubleAttr( element, "font_size", 10 ) * FONT_SCALE_FACTOR;
+                                fontSize          = XmlUtil::getDoubleAttr( element, "font_size", 10 );
                                 fontWeight        = getWeightAttr( element, "font_weight", QFont::Normal );
                                 fontItalicFlag    = XmlUtil::getBoolAttr( element, "font_italic", false );
 

model/unit_tests/TestXmlLabel.cpp

@@ -60,12 +60,6 @@ using namespace glabels::barcode;
 using namespace glabels::merge;
 
 
-namespace
-{
-        const double FONT_SCALE_FACTOR {0.75};
-}
-
-
 void TestXmlLabel::initTestCase()
 {
         QCoreApplication::setOrganizationName( glabels::model::Version::ORGANIZATION_NAME );
@@ -548,7 +542,7 @@ void TestXmlLabel::parser_3ReadFile()
         QCOMPARE( modelTextObject0->shadow(), false );
         QCOMPARE( modelTextObject0->text(), QString( "Hello, my name is" ) );
         QCOMPARE( modelTextObject0->fontFamily(), QString( "Sans" ) );
-        QCOMPARE( modelTextObject0->fontSize(), 16 * FONT_SCALE_FACTOR );
+        QCOMPARE( modelTextObject0->fontSize(), 16 );
         QCOMPARE( modelTextObject0->fontWeight(), QFont::Bold );
         QCOMPARE( modelTextObject0->fontItalicFlag(), false );
         QCOMPARE( modelTextObject0->textLineSpacing(), 1.0 );
@@ -566,7 +560,7 @@ void TestXmlLabel::parser_3ReadFile()
         QCOMPARE( modelTextObject1->shadow(), false );
         QCOMPARE( modelTextObject1->text(), QString( "${Name}" ) );
         QCOMPARE( modelTextObject1->fontFamily(), QString( "Sans" ) );
-        QCOMPARE( modelTextObject1->fontSize(), 20 * FONT_SCALE_FACTOR );
+        QCOMPARE( modelTextObject1->fontSize(), 20 );
         QCOMPARE( modelTextObject1->fontWeight(), QFont::Normal );
         QCOMPARE( modelTextObject1->fontItalicFlag(), false );
         QCOMPARE( modelTextObject1->textLineSpacing(), 1.0 );
@@ -584,7 +578,7 @@ void TestXmlLabel::parser_3ReadFile()
         QCOMPARE( modelTextObject2->shadow(), false );
         QCOMPARE( modelTextObject2->text(), QString( "Department: ${Department}" ) );
         QCOMPARE( modelTextObject2->fontFamily(), QString( "Sans" ) );
-        QCOMPARE( modelTextObject2->fontSize(), 11 * FONT_SCALE_FACTOR );
+        QCOMPARE( modelTextObject2->fontSize(), 11 );
         QCOMPARE( modelTextObject2->fontWeight(), QFont::Normal );
         QCOMPARE( modelTextObject2->fontItalicFlag(), false );
         QCOMPARE( modelTextObject2->textLineSpacing(), 1.0 );