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.
MainWindowViewer::keyPressEvent()'s custom matching of these shortcuts
does not leverage all the features of standard Qt shortcut matching. As
a result, the corresponding actions cannot be triggered when their
assigned shortcuts consist of a single Latin letter without modifiers
and e.g. Ukrainian keyboard layout is active.
Furthermore, some key presses (e.g. Scroll Lock in my customized
keyboard layout) set QKeyEvent::key() to 0, which the custom matching
considers equal to an unassigned shortcut. So an action without shortcut
is triggered by such a key press.
Adding these 3 actions to MainWindowViewer and connecting the
corresponding slots to their triggered() signals allows to remove the
custom matching code and thus eliminates both of its issues.
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
