* Old code keep destory the scanpopup, then recreate it whenever the dict list or group list changed.
* New code keep a single instance of scanpopup, and only update necessary info.
* There is no difference between those two on Windows and MacOS which only support clipboard (Ctrl+C) scanning
* Q_WS_X11 was defined on Qt4, and it causes the super weird trackClipboardChanges to occur on Windows
Silently ignore empty or whitespace-only translation requests. It should
be clear to most users why GoldenDict ignores them.
The translated word ends up as the "word" URL query item value, which is
trimmed in ArticleNetworkAccessManager::getResource(). So the added
trimming in MainWindow::translateInputFinished() should be fine.
When a trimmed translated word was empty, InputPhrase::isValid()
returned false, ArticleNetworkAccessManager::getResource() returned a
null pointer and ArticleNetworkAccessManager::createRequest() fell back
to QNetworkAccessManager::createRequest(), which:
* failed silently in the Qt 4 version;
* displayed the
Protocol "gdlookup" is unknown
Failed to load URL gdlookup://localhost?word= &group=4.
QtNetwork Error 301
error page in the Qt 5 version.
Fixes #1179.
When not-escaped wildcard symbols are placed in the translate box/line,
word completion can occupy the CPU for seconds. So it is safer to err on
the side of escaping than the other way around.
The missed unescaping in ScanPopup::translateInputFinished() was
inconsistent with the main window. It made escaping in the scan popup's
translate box unusable by attempting to translate e.g. "\*" verbatim.
Each of the 3 removed history addition requests follows a call to
ArticleView::showDefinition() with the same phrase/word as an argument.
Each showDefinition() overload adds its phrase/word argument to history.
These duplicate history additions weren't noticeable because
History::addItem() searches for and removes its argument from items to
avoid duplicate history entries. But the extra function calls, signal
emissions, linear searches and QList manipulation wasted processor time.
