QmlJS: Clean up QML console editor

Align the text between editing and display mode, and remove the dead
code. The prompt sign does not have to be part of the text and the
JS parser does not have to retain the code it parses.

Change-Id: I6e41f4fbc2cc863c84677640826d8663bcc648fb
Task-number: QTCREATORBUG-14931
Reviewed-by: hjk <hjk@theqtcompany.com>

src/plugins/qmljstools/qmlconsoleitemdelegate.cpp

@@ -312,6 +312,18 @@ QWidget *QmlConsoleItemDelegate::createEditor(QWidget *parent,
 
 {
     QmlConsoleEdit *editor = new QmlConsoleEdit(index, parent);
+    // Fiddle the prompt into the margin so that we don't have to put it into the text.
+    // Apparently you can have both background-image and background-color, which conveniently
+    // prevents the painted text from shining through.
+    editor->setStyleSheet(QLatin1String("QTextEdit {"
+                                        "margin-left: 24px;"
+                                        "margin-top: 4px;"
+                                        "background-color: white;"
+                                        "background-image: url(:/qmljstools/images/prompt.png);"
+                                        "background-position: baseline left;"
+                                        "background-origin: margin;"
+                                        "background-repeat: none;"
+                                        "}"));
     connect(editor, &QmlConsoleEdit::editingFinished,
             this, &QmlConsoleItemDelegate::commitAndCloseEditor);
     return editor;