TextEditor: Fix dropping explicitly set codec to System

If we set the default encoding to the System-wide encoding
we failed to distinguish them as separate encodings.
Explicitly handle 'System' encoding to avoid dropping
to the 'System' encoding when setting an encoding that
matches this one exactly.

Fixes: QTCREATORBUG-22843
Change-Id: Ib4fa50268ca6f792cdff001b9b07bb18804c4401
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/texteditor/behaviorsettingspage.cpp

@@ -195,7 +195,7 @@ void BehaviorSettingsPage::apply()
 
     if (s) {
         s->setValue(QLatin1String(Core::Constants::SETTINGS_DEFAULTTEXTENCODING),
-                    d->m_page->behaviorWidget->assignedCodec()->name());
+                    d->m_page->behaviorWidget->assignedCodecName());
     }
 }
 

src/plugins/texteditor/behaviorsettingswidget.cpp

@@ -28,6 +28,9 @@
 
 #include "tabsettingswidget.h"
 
+#include <coreplugin/coreconstants.h>
+#include <coreplugin/icore.h>
+
 #include <texteditor/typingsettings.h>
 #include <texteditor/storagesettings.h>
 #include <texteditor/behaviorsettings.h>
@@ -132,17 +135,30 @@ void BehaviorSettingsWidget::setActive(bool active)
 
 void BehaviorSettingsWidget::setAssignedCodec(QTextCodec *codec)
 {
+    const QString codecName = Core::ICore::settings()->value(
+                Core::Constants::SETTINGS_DEFAULTTEXTENCODING).toString();
+
+    int rememberedSystemPosition = -1;
     for (int i = 0; i < d->m_codecs.size(); ++i) {
         if (codec == d->m_codecs.at(i)) {
+            if (d->m_ui.encodingBox->itemText(i) == codecName) {
                 d->m_ui.encodingBox->setCurrentIndex(i);
-            break;
+                return;
+            } else { // we've got System matching encoding - but have explicitly set the codec
+                rememberedSystemPosition = i;
             }
         }
+    }
+    if (rememberedSystemPosition != -1)
+        d->m_ui.encodingBox->setCurrentIndex(rememberedSystemPosition);
 }
 
-QTextCodec *BehaviorSettingsWidget::assignedCodec() const
+QByteArray BehaviorSettingsWidget::assignedCodecName() const
 {
-    return d->m_codecs.at(d->m_ui.encodingBox->currentIndex());
+    return d->m_ui.encodingBox->currentIndex() == 0
+            ? QByteArray("System")   // we prepend System to the available codecs
+            : d->m_codecs.at(d->m_ui.encodingBox->currentIndex())->name();
+
 }
 
 void BehaviorSettingsWidget::setCodeStyle(ICodeStylePreferences *preferences)

src/plugins/texteditor/behaviorsettingswidget.h

@@ -55,7 +55,7 @@ public:
     void setActive(bool active);
 
     void setAssignedCodec(QTextCodec *codec);
-    QTextCodec *assignedCodec() const;
+    QByteArray assignedCodecName() const;
 
     void setCodeStyle(ICodeStylePreferences *preferences);