Add a way to set default font rendering at build time.

QML text rendering elements have a renderType property controlling
whether to use 'Qt' rendering or 'Native' rendering.  There is no reason
to mix different types of rendering in one static ui.  The element-local
properties may be used to change the rendering type during animation
for example, but otherwise there should be an application-wide rendering
mode for text.

That means that all Text-based elements in QML should default to the
same rendering mode.  Additionally, applications wishing to use
NativeRendering, wish to use it for all text-based elements, so they
require changing the defaults of the elements themselves, still allowing
the possibility of changing the rendering mode during animation.

Creating third party wrappers for each of the QML text rendering types
is not a solution because an application requires the same font
rendering for all text.

That is, whether written directly with QML Text* elements, or using
QtQuick controls, or another 3rd party component set, it is necessary to
set the same font rendering mode for all text, except in temporary
execptional cases.

The known options to achieve this are

 1) Create an environment variable to set the default rendering.
 2) Add C++ API to set the default
 3) Add a build-time option to set the default.

The first option is unsatisfying because it is fragile and is easy to
get wrong.

The second option is incomplete because it does not affect qmlscene etc,
so it would require adding a command line argument to qmlscene to change
the default.  That is unsatisfying because it is also fragile.  It is
necessary for the sanity of developers and designers (and also end
users) that qmlscene use the correct default by default.  It must be
easy to create qml files for designers to run with qmlscene and which
look correct.

The third option is the one chosen for this patch.  It is most suitable
for environments where the Qt build and settings are contained because a
particular Qt build is shipped with the application using it (This is
the most common way Qt is used).  It affects all uses of the text
rendering elements, whether used through qmlscene or through another
entry point, and it allows changing the property in QML code away from
the build-time-determined default.

When building Qt, -DQT_QUICK_DEFAULT_TEXT_RENDER_TYPE=NativeRendering
may be passed to configure to affect the default rendering for the Qt
build.

It also leaves the question why the default text rendering is 'Qt'
instead of being 'Native', given that many of the Qt controls need to
switch to Native anyway (though this depends on the platform and the
style).

Change-Id: Ib0eed61caf4895b29e5c05e0418fad9962779f85
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@theqtcompany.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/src/quick/items/qquicktextinput_p_p.h b/src/quick/items/qquicktextinput_p_p.h
index 4946adc7e7..fa7462c0c5 100644
--- a/src/quick/items/qquicktextinput_p_p.h
+++ b/src/quick/items/qquicktextinput_p_p.h
@@ -115,7 +115,11 @@ public:
         , vAlign(QQuickTextInput::AlignTop)
         , wrapMode(QQuickTextInput::NoWrap)
         , m_echoMode(QQuickTextInput::Normal)
+#if defined(QT_QUICK_DEFAULT_TEXT_RENDER_TYPE)
+        , renderType(QQuickTextInput::QT_QUICK_DEFAULT_TEXT_RENDER_TYPE)
+#else
         , renderType(QQuickTextInput::QtRendering)
+#endif
         , updateType(UpdatePaintNode)
         , mouseSelectionMode(QQuickTextInput::SelectCharacters)
         , m_layoutDirection(Qt::LayoutDirectionAuto)