Make values in attribute form better readable

Currently in readonly modus of a form, the line-edits get
a 'disabled'-palette. But because text is then so light readability
is bad.
Removing the palette make the lineedits look like they are writable
input fields. So to distinguish them from input field, the frame
is removed and the background (of the lineEdit) is set to almost
transparent.

Author: rduivenvoorde

src/gui/editorwidgets/qgstexteditwrapper.cpp

@@ -137,7 +137,6 @@ void QgsTextEditWrapper::initWidget( QWidget *editor )
 
     mWritablePalette = mLineEdit->palette();
     mReadOnlyPalette = mLineEdit->palette();
-    mReadOnlyPalette.setColor( QPalette::Text, mWritablePalette.color( QPalette::Disabled, QPalette::Text ) );
   }
 }
 
@@ -195,7 +194,13 @@ void QgsTextEditWrapper::setEnabled( bool enabled )
     if ( enabled )
       mLineEdit->setPalette( mWritablePalette );
     else
+    {
       mLineEdit->setPalette( mReadOnlyPalette );
+      // removing frame + setting transparent background to distinguish the readonly lineEdit from a normal one
+      // did not get this working via the Palette:
+      mLineEdit->setStyleSheet( QStringLiteral( "background-color: rgba(255, 255, 255, 75%);" ) );
+    }
+    mLineEdit->setFrame( enabled );
   }
 }