Merge bitcoin-core/gui#336: Do not exit and re-enter main event loop during shutdown

451ca244db8bc71ffc3cc9982d025f144cc8f3bc qt, refactor: Drop intermediate BitcoinApplication::shutdownResult slot (Hennadii Stepanov)
f3a17bbe5f7d23b6ecc20e363920492b50859dad qt: Do not exit and re-enter main event loop during shutdown (Hennadii Stepanov)
b4e0d2c43181ad97c15b252e95181e2c3f6c1d2a qt, refactor: Allocate SendConfirmationDialog instances on heap (Hennadii Stepanov)
332dea2852d9c68f900ed1f0be99b6cea79c7457 qt, refactor: Keep HelpMessageDialog in the main event loop (Hennadii Stepanov)
c8bae37a7a646badf8e79669bf06ac174e13cd6f qt, refactor: Keep PSBTOperationsDialog in the main event loop (Hennadii Stepanov)
7fa91e831227e556bd8a7ae3da64bd59d4f30d5f qt, refactor: Keep AskPassphraseDialog in the main event loop (Hennadii Stepanov)
6f6fde30e7601185a8f6052b3bf1770407fcc14b qt, refactor: Keep EditAddressDialog in the main event loop (Hennadii Stepanov)
59f7ba4fd7a9e4bc73d784ee74d5b777da9cc436 qt, refactor: Keep CoinControlDialog in the main event loop (Hennadii Stepanov)
7830cd0b35f315570d744f4d2719104c08b33ff1 qt, refactor: Keep OptionsDialog in the main event loop (Hennadii Stepanov)
13f618818dc57673ac0287ad8b28ceb450efb374 qt: Add GUIUtil::ShowModalDialogAndDeleteOnClose (Hennadii Stepanov)

Pull request description:

  On master (1ef34ee25ed34b2b092f15bf3dca5c0508092829) during shutdown `QApplication` exits the main event loop, then re-enter again.

  This PR streamlines shutdown process by removing the need to interrupt the main event loop, that is required for #59.

  Also, blocking [`QDialog::exec()`](https://doc.qt.io/qt-5/qdialog.html#exec) calls are replaced with safer [`QDialog::show()`](https://doc.qt.io/qt-5/qwidget.html#show), except for `SendConfirmationDialog` as that change is not trivial (marked as TODO).

  The [`QDialog::open()`](https://doc.qt.io/qt-5/qdialog.html#open) was not used because the actual modality mode (application modal or window modal) of a dialog depends on whether it has a parent.

  This PR does not change behavior, and all touched dialogs are still application modal.
  As a follow up, a design research could suggest to make some dialogs window modal.

  NOTE for reviewers: quitting app while a dialog is open (e.g., via systray icon menu) must work fine.

ACKs for top commit:
  laanwj:
    Code review and lighly tested ACK 451ca244db8bc71ffc3cc9982d025f144cc8f3bc
  promag:
    ACK 451ca244db8bc71ffc3cc9982d025f144cc8f3bc, just changed signal to `quitRequested`.

Tree-SHA512: ef01ab6ed803b202e776019a4e1f592e816f7bc786e00574b25a0bf16be2374ddf9db21f0a26da08700df7ef0ab9e879550df46dcfe3b6d940f5ed02ca5f8447

1 files changed, 2 insertions, 3 deletions

diff --git a/src/qt/walletframe.cpp b/src/qt/walletframe.cpp
index 5eeb2d5308..4ff92bf82c 100644
--- a/src/qt/walletframe.cpp
+++ b/src/qt/walletframe.cpp
@@ -221,10 +221,9 @@ void WalletFrame::gotoLoadPSBT(bool from_clipboard)
         return;
     }
 
-    PSBTOperationsDialog* dlg = new PSBTOperationsDialog(this, currentWalletModel(), clientModel);
+    auto dlg = new PSBTOperationsDialog(this, currentWalletModel(), clientModel);
     dlg->openWithPSBT(psbtx);
-    dlg->setAttribute(Qt::WA_DeleteOnClose);
-    dlg->exec();
+    GUIUtil::ShowModalDialogAndDeleteOnClose(dlg);
 }
 
 void WalletFrame::encryptWallet()