Add QgsFontUtils class to handle system font queries and style changes

src/core/CMakeLists.txt

@@ -71,6 +71,7 @@ SET(QGIS_CORE_SRCS
   qgsfeaturerequest.cpp
   qgsfeaturestore.cpp
   qgsfield.cpp
+  qgsfontutils.cpp
   qgsgeometry.cpp
   qgsgeometrycache.cpp
   qgsgeometryvalidator.cpp
@@ -395,6 +396,7 @@ SET(QGIS_CORE_HDRS
   qgsfeaturerequest.h
   qgsfeaturestore.h
   qgsfield.h
+  qgsfontutils.h
   qgsgeometry.h
   qgsgml.h
   qgsgmlschema.h

src/core/qgsfontutils.cpp

@@ -0,0 +1,192 @@
+/***************************************************************************
+    qgsfontutils.h
+    ---------------------
+    begin                : June 5, 2013
+    copyright            : (C) 2013 by Larry Shaffer
+    email                : larrys at dakotacarto dot com
+ ***************************************************************************
+ *                                                                         *
+ *   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.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#include "qgsfontutils.h"
+
+#include <QApplication>
+#include <QFont>
+#include <QFontDatabase>
+#include <QFontInfo>
+#include <QStringList>
+
+
+bool QgsFontUtils::fontMatchOnSystem( const QFont& f )
+{
+  QFontInfo fi = QFontInfo( f );
+  return fi.exactMatch();
+}
+
+bool QgsFontUtils::fontFamilyOnSystem( const QString& family )
+{
+  QFont tmpFont = QFont( family );
+  // compare just beginning of family string in case 'family [foundry]' differs
+  return family.startsWith( tmpFont.family(), Qt::CaseInsensitive );
+}
+
+bool QgsFontUtils::fontFamilyMatchOnSystem( const QString& family, QString* chosen, bool* match )
+{
+  QFontDatabase fontDB;
+  QStringList fontFamilies = fontDB.families();
+  bool found = false;
+
+  QList<QString>::const_iterator it = fontFamilies.constBegin();
+  for ( ; it != fontFamilies.constEnd(); ++it )
+  {
+    // first compare just beginning of 'family [foundry]' string
+    if ( it->startsWith( family, Qt::CaseInsensitive ) )
+    {
+      found = true;
+      // keep looking if match info is requested
+      if ( match )
+      {
+        // full 'family [foundry]' strings have to match
+        *match = ( *it == family );
+        if ( match ) { break; }
+      }
+      else
+      {
+        break;
+      }
+    }
+  }
+
+  if ( found )
+  {
+    if ( chosen )
+    {
+      // retrieve the family actually assigned by matching algorithm
+      QFont f = QFont( family );
+      *chosen = f.family();
+    }
+  }
+  else
+  {
+    if ( chosen )
+    {
+      *chosen = QString();
+    }
+
+    if ( match )
+    {
+      *match = false;
+    }
+  }
+
+  return found;
+}
+
+bool QgsFontUtils::updateFontViaStyle( QFont& f, const QString& fontstyle, bool fallback )
+{
+  if ( fontstyle.isEmpty() )
+  {
+    return false;
+  }
+
+  QFontDatabase fontDB;
+
+  if ( !fallback )
+  {
+    // does the font even have the requested style?
+    bool hasstyle = false;
+    foreach ( const QString &style, fontDB.styles( f.family() ) )
+    {
+      if ( style == fontstyle )
+      {
+        hasstyle = true;
+        break;
+      }
+    }
+
+    if ( !hasstyle )
+    {
+      return false;
+    }
+  }
+
+  // is the font's style already the same as requested?
+  if ( fontstyle == fontDB.styleString( f ) )
+  {
+    return true;
+  }
+
+  int defaultSize = QApplication::font().pointSize(); // QFontDatabase::font() needs an integer for size
+
+  QFont styledfont;
+  bool foundmatch = false;
+
+  styledfont = fontDB.font( f.family(), fontstyle, defaultSize );
+  if ( QApplication::font() != styledfont )
+  {
+    foundmatch = true;
+  }
+
+  // default to first found style if requested style is unavailable
+  // this helps in the situations where the passed-in font has to have a named style applied
+  if ( fallback && !foundmatch )
+  {
+    QFont testFont = QFont( f );
+    testFont.setPointSize( defaultSize );
+
+    // prefer a style that mostly matches the passed-in font
+    foreach ( const QString &style, fontDB.styles( f.family() ) )
+    {
+      styledfont = fontDB.font( f.family(), style, defaultSize );
+      styledfont = styledfont.resolve( f );
+      if ( testFont.toString() == styledfont.toString() )
+      {
+        foundmatch = true;
+        break;
+      }
+    }
+
+    // fallback to first style found that works
+    if ( !foundmatch )
+    {
+      foreach ( const QString &style, fontDB.styles( f.family() ) )
+      {
+        styledfont = fontDB.font( f.family(), style, defaultSize );
+        if ( QApplication::font() != styledfont )
+        {
+          foundmatch = true;
+          break;
+        }
+      }
+    }
+  }
+
+  // similar to QFont::resolve, but font may already have pixel size set
+  // and we want to make sure that's preserved
+  if ( foundmatch )
+  {
+    if ( f.pointSizeF() != -1 )
+    {
+      styledfont.setPointSizeF( f.pointSizeF() );
+    }
+    else if ( f.pixelSize() != -1 )
+    {
+      styledfont.setPixelSize( f.pixelSize() );
+    }
+    styledfont.setCapitalization( f.capitalization() );
+    styledfont.setUnderline( f.underline() );
+    styledfont.setStrikeOut( f.strikeOut() );
+    styledfont.setWordSpacing( f.wordSpacing() );
+    styledfont.setLetterSpacing( QFont::AbsoluteSpacing, f.letterSpacing() );
+    f = styledfont;
+
+    return true;
+  }
+
+  return false;
+}

src/core/qgsfontutils.h

@@ -0,0 +1,56 @@
+/***************************************************************************
+    qgsfontutils.h
+    ---------------------
+    begin                : June 5, 2013
+    copyright            : (C) 2013 by Larry Shaffer
+    email                : larrys at dakotacarto dot com
+ ***************************************************************************
+ *                                                                         *
+ *   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.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#ifndef QGSFONTUTILS_H
+#define QGSFONTUTILS_H
+
+#include <QFont>
+#include <QString>
+
+class CORE_EXPORT QgsFontUtils
+{
+  public:
+    /** Check whether exact font is on system
+     * @param font The font to test for match
+     */
+    static bool fontMatchOnSystem( const QFont& f );
+
+    /** Check whether font family is on system in a quick manner, which does not compare [foundry]
+     * @param family The family to test
+     * @returns Whether family was found on system
+     * @note This is good for use in loops of large lists, e.g. registering many features for labeling
+     */
+    static bool fontFamilyOnSystem( const QString& family );
+
+    /** Check whether font family is on system
+     * @param family The family to test
+     * @param chosen The actual family (possibly from different foundry) returned by system
+     * @param match Whether the family [foundry] returned by system is a match
+     * @returns Whether family was found on system
+     */
+    static bool fontFamilyMatchOnSystem( const QString& family, QString* chosen = 0, bool* match = 0 );
+
+    /** Updates font with named style and retain all font properties
+     * @param font The font to update
+     * @param fontstyle The style to try and switch the font to
+     * @param fallback If no matching fontstyle found for font, assign most similar or first style found to font
+     * @returns Whether the font was updated (also returns true if the requested style matches font's current style)
+     * @note This is a more featured replacement for a Qt 4.8+ function: void QFont::setStyleName ( const QString & styleName )
+     */
+    static bool updateFontViaStyle( QFont& f, const QString& fontstyle, bool fallback = false );
+
+};
+
+#endif // QGSFONTUTILS_H