LookAndFeel: Make portable typeface metrics the default

BREAKING_CHANGES.md

@@ -2,6 +2,32 @@
 
 # Version 8.0.0
 
+## Change
+
+JUCE widgets now query the LookAndFeel to determine the TypefaceMetricsKind to
+use. By default, the LookAndFeel will specify the "portable" metrics kind,
+which may change the size of text in JUCE widgets, depending on the font and
+platform.
+
+**Possible Issues**
+
+Using "portable" metrics may cause text to render at a different scale when
+compared to the old "legacy" metrics.
+
+**Workaround**
+
+If you want to restore the old metrics, e.g. to maintain the same text scaling
+in an existing app, you can override LookAndFeel::getDefaultMetricsKind() on
+each LookAndFeel in your application, to return the "legacy" metrics kind.
+
+**Rationale**
+
+Using portable font metrics streamlines the development experience when working
+on applications that must run on multiple platforms. Using portable metrics by
+default means that new projects will benefit from this improved cross-platform
+behaviour from the outset.
+
+
 ## Change
 
 Signatures of several Typeface member functions have been updated to accept a

modules/juce_gui_basics/lookandfeel/juce_LookAndFeel.h

@@ -187,12 +187,13 @@ public:
     /** Widgets can call this to find out the kind of metrics they should use when creating their
         own fonts.
 
-        The default implementation returns the legacy metrics kind, but you can override this if
+        The default implementation returns the portable metrics kind, but you can override this if
-        you want to use the portable metrics kind instead. Using portable metrics may cause text
+        you want to use the legacy metrics kind instead, to avoid rendering changes in existing
-        to render at a different size, so you should check that text in your app still renders at an
+        projects. Switching between metrics kinds may cause text to render at a different size, so you
-        appropriate size, and potentially adjust font sizes where necessary after overriding this.
+        should check that text in your app still renders at an appropriate size, and potentially adjust
+        font sizes where necessary after overriding this function.
     */
-    virtual TypefaceMetricsKind getDefaultMetricsKind() const { return TypefaceMetricsKind::legacy; }
+    virtual TypefaceMetricsKind getDefaultMetricsKind() const { return TypefaceMetricsKind::portable; }
 
     /** Returns a copy of the FontOptions with the LookAndFeel's default metrics kind set. */
     FontOptions withDefaultMetrics (FontOptions opt) const { return opt.withMetricsKind (getDefaultMetricsKind()); }