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Gui: Fix NPE when reloading a MISSING_PAGE at start-up [#608]

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gnosygnu 2019-11-03 17:45:30 -05:00
parent de1b9a3991
commit af9d6c3a92
1 changed files with 20 additions and 0 deletions
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20
400_xowa/src/gplx/xowa/guis/views/Xog_win_itm.java
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@ -216,6 +216,7 @@ public class Xog_win_itm implements Gfo_invk, Gfo_evt_itm {
}
public void Page__reload() {
Xog_tab_itm tab = tab_mgr.Active_tab();
if (tab.History_mgr().Count() == 0) return; // MISSING_PAGES will generate NPE if (a) is a startup tab and (b) View -> Reload Page is called; FOOTNOTE:MISSING_PAGES_NPE ISSUE#:608; DATE:2019-11-03
Xoae_page page = tab.History_mgr().Cur_page(tab.Wiki()); // NOTE: must set to CurPage() else changes will be lost when going Bwd,Fwd
tab.Page_(page);
page = page.Wikie().Page_mgr().Load_page(page.Url(), page.Ttl(), tab); // NOTE: must reparse page if (a) Edit -> Read; or (b) "Options" save
@ -419,3 +420,22 @@ class Xog_url_box__selection_changed implements Gfo_evt_itm {
return this;
}
}
/*
== MISSING_PAGES_NPE ==
The NPE occurs because a MISSING_PAGE never adds to the history stack
* Exit point is `usr_dlg.Prog_one("", "", "could not find page in wiki: ~{0}", String_.new_u8(url.Raw()));`
* Several lines later, the add occurs: `history_mgr.Add(page);`
This NPE primiarily occurs for a MISSING_PAGE when loaded at start-up
* It doesn't occur in other situations, because a MISSING_PAGE will always be preceded by a "real" page
** Note that a "real" page includes Special:XowaDefaultTab (or Ctrl+T)
* It does occur for start-up b/c there is no "Special:XowaDefaultTab"; just the MISSING_PAGE
This could be fixed properly by...
* Saving and reloading the entire history stack per tab (right now only the last item is saved)
* Refactoring the GUI to avoid the NPE
** This is tricky b/c moving `history_mgr.Add(page)` above the exit point causes other side-effects
*** MISSING_PAGE will be loaded at start-up as an empty page (no ARTICLE_TEXT, but MediaWiki portal / side bar) instead of a blank page
**** This is probably desirable, but will need to change behavior to fail when someone tries to edit a read-only wiki (right now, this is the only guard)
*** Some possibly unknown behavior by registering missing pages into history
*/