Viewer::keyPressEvent()'s custom matching of these shortcuts is the same
as MainWindowViewer::keyPressEvent()'s before the recent commit
"Reader: make 3 keyboard shortcuts work with non-Latin layouts". That
commit's message details the issues with the custom code.
render->hasLoadedComic() condition in Viewer::keyPressEvent() becomes
true when Comic::_loaded is set to true. This always happens right after
Comic emits its numPages() signal. That is why the 12 fixed actions are
now enabled when Viewer emits its comicLoaded() signal, which is
connected to Render::numPages, which in turn is connected to
Comic::numPages signal.
The 12 fixed actions are now disabled when most other actions are
disabled: before a comic is opened and on comic opening error.
const QPixmap should perform as fast as a pointer
there is a replacement version for Qt5 but it requires Qt5.15, so we are using indirection witch is unsafer but it should be ok as all the action is happen in the main thread
When an issues is open from YACReaderLibrary we can check if it is a manga an update the UI to enable manga reading.
This also fixes going previous/next from the ui/shortcuts
closeEvent is accepted by default, so this commit does not change the
application behavior. But Qt documentation recommends not relying on the
default value as subclasses may choose to clear it in their constructor.
