Merge bitcoin-core/gui#399: Fix "Load PSBT" functionality when no wallet loaded

0237d95323dec7c65b7223c314afdf63aab6b11b qt: Add Load PSBT functionaliy with nowallet (Prateek Sancheti)

Pull request description:

  This PR provides a fix to the issue mentioned in #232.

  Currently, the **_Load PSBT_** functionality works well in case a wallet is loaded but does nothing when a wallet isn't loaded.

  If a function cannot work without a wallet being loaded, it is disabled by default (It is unclickable as shown in the image).

  For e.g. One cannot `Close Wallet` or `Backup Wallet` or `Sign Messages` without a wallet being loaded. And hence they are disabled. But if you notice, `Load PSBT` options are not disabled by default even when a wallet isn't loaded.

  >  ![Screenshot 2021-08-07 at 11 46 30 PM](https://user-images.githubusercontent.com/54016434/128610208-45376026-0e91-4268-abdf-342e3cec5917.png)

  As mentioned by hebasto in the issue description :

  ```
  <hebasto> achow101: does "File" -> "Load PSBT from {file|clipboard}" make any sense when no wallet is loaded?
  <achow101> hebasto: yes, for finalize and sending
  ```

  This means **_Load PSBT_**  should be working just as similar whether wallets are being loaded or not.

  After making the required changes to the code, The **_Load PSBT_** works as expected even with no wallet loaded and the PSBT is finalized.

  | Master | PR |
  |-------------|---------------|
  | ![Hnet com-image (1)](https://user-images.githubusercontent.com/54016434/128611454-4dfc3fd3-ecc0-48f0-8408-60eb98035694.gif) | ![Hnet com-image (2)](https://user-images.githubusercontent.com/54016434/128611461-982468d2-9cd0-4f9b-9392-c25b6c8857e2.gif) |

  Close #232

ACKs for top commit:
  achow101:
    re-ACK 0237d95323dec7c65b7223c314afdf63aab6b11b
  hebasto:
    ACK 0237d95323dec7c65b7223c314afdf63aab6b11b, tested on Linux Mint 20.2 (Qt 5.12.8).

Tree-SHA512: 8d928c5bfd3c2b286ddcacd0b367c872de8bc3d3d9d82280faeadc60d738b86af328c060b5763ade364c9b386b23f95580c2eb1147b16373fbb713170c100350

6 files changed, 65 insertions, 58 deletions

diff --git a/src/qt/bitcoingui.cpp b/src/qt/bitcoingui.cpp
index 863225099a..fe606519af 100644
--- a/src/qt/bitcoingui.cpp
+++ b/src/qt/bitcoingui.cpp
@@ -110,6 +110,9 @@ BitcoinGUI::BitcoinGUI(interfaces::Node& node, const PlatformStyle *_platformSty
             connect(activity, &CreateWalletActivity::finished, activity, &QObject::deleteLater);
             activity->create();
         });
+        connect(walletFrame, &WalletFrame::message, [this](const QString& title, const QString& message, unsigned int style) {
+            this->message(title, message, style);
+        });
         setCentralWidget(walletFrame);
     } else
 #endif // ENABLE_WALLET
diff --git a/src/qt/psbtoperationsdialog.cpp b/src/qt/psbtoperationsdialog.cpp
index 2adfeeaaf0..289fb9f7c8 100644
--- a/src/qt/psbtoperationsdialog.cpp
+++ b/src/qt/psbtoperationsdialog.cpp
@@ -47,18 +47,22 @@ void PSBTOperationsDialog::openWithPSBT(PartiallySignedTransaction psbtx)
 {
     m_transaction_data = psbtx;
 
-    bool complete;
-    size_t n_could_sign;
-    FinalizePSBT(psbtx);  // Make sure all existing signatures are fully combined before checking for completeness.
-    TransactionError err = m_wallet_model->wallet().fillPSBT(SIGHASH_ALL, false /* sign */, true /* bip32derivs */, &n_could_sign, m_transaction_data, complete);
-    if (err != TransactionError::OK) {
-        showStatus(tr("Failed to load transaction: %1")
-            .arg(QString::fromStdString(TransactionErrorString(err).translated)), StatusLevel::ERR);
-        return;
+    bool complete = FinalizePSBT(psbtx); // Make sure all existing signatures are fully combined before checking for completeness.
+    if (m_wallet_model) {
+        size_t n_could_sign;
+        TransactionError err = m_wallet_model->wallet().fillPSBT(SIGHASH_ALL, false /* sign */, true /* bip32derivs */, &n_could_sign, m_transaction_data, complete);
+        if (err != TransactionError::OK) {
+            showStatus(tr("Failed to load transaction: %1")
+                           .arg(QString::fromStdString(TransactionErrorString(err).translated)),
+                       StatusLevel::ERR);
+            return;
+        }
+        m_ui->signTransactionButton->setEnabled(!complete && !m_wallet_model->wallet().privateKeysDisabled() && n_could_sign > 0);
+    } else {
+        m_ui->signTransactionButton->setEnabled(false);
     }
 
     m_ui->broadcastTransactionButton->setEnabled(complete);
-    m_ui->signTransactionButton->setEnabled(!complete && !m_wallet_model->wallet().privateKeysDisabled() && n_could_sign > 0);
 
     updateTransactionDisplay();
 }
@@ -133,7 +137,7 @@ void PSBTOperationsDialog::saveTransaction() {
         }
         CTxDestination address;
         ExtractDestination(out.scriptPubKey, address);
-        QString amount = BitcoinUnits::format(m_wallet_model->getOptionsModel()->getDisplayUnit(), out.nValue);
+        QString amount = BitcoinUnits::format(m_client_model->getOptionsModel()->getDisplayUnit(), out.nValue);
         QString address_str = QString::fromStdString(EncodeDestination(address));
         filename_suggestion.append(address_str + "-" + amount);
         first = false;
@@ -224,6 +228,10 @@ void PSBTOperationsDialog::showStatus(const QString &msg, StatusLevel level) {
 }
 
 size_t PSBTOperationsDialog::couldSignInputs(const PartiallySignedTransaction &psbtx) {
+    if (!m_wallet_model) {
+        return 0;
+    }
+
     size_t n_signed;
     bool complete;
     TransactionError err = m_wallet_model->wallet().fillPSBT(SIGHASH_ALL, false /* sign */, false /* bip32derivs */, &n_signed, m_transaction_data, complete);
@@ -246,7 +254,10 @@ void PSBTOperationsDialog::showTransactionStatus(const PartiallySignedTransactio
         case PSBTRole::SIGNER: {
             QString need_sig_text = tr("Transaction still needs signature(s).");
             StatusLevel level = StatusLevel::INFO;
-            if (m_wallet_model->wallet().privateKeysDisabled()) {
+            if (!m_wallet_model) {
+                need_sig_text += " " + tr("(But no wallet is loaded.)");
+                level = StatusLevel::WARN;
+            } else if (m_wallet_model->wallet().privateKeysDisabled()) {
                 need_sig_text += " " + tr("(But this wallet cannot sign transactions.)");
                 level = StatusLevel::WARN;
             } else if (n_could_sign < 1) {
diff --git a/src/qt/walletframe.cpp b/src/qt/walletframe.cpp
index a1f357e0db..3d8bc0c7c5 100644
--- a/src/qt/walletframe.cpp
+++ b/src/qt/walletframe.cpp
@@ -4,12 +4,18 @@
 
 #include <qt/walletframe.h>
 
+#include <node/ui_interface.h>
+#include <psbt.h>
+#include <qt/guiutil.h>
 #include <qt/overviewpage.h>
+#include <qt/psbtoperationsdialog.h>
 #include <qt/walletmodel.h>
 #include <qt/walletview.h>
 
 #include <cassert>
 
+#include <QApplication>
+#include <QClipboard>
 #include <QGroupBox>
 #include <QHBoxLayout>
 #include <QLabel>
@@ -184,10 +190,40 @@ void WalletFrame::gotoVerifyMessageTab(QString addr)
 
 void WalletFrame::gotoLoadPSBT(bool from_clipboard)
 {
-    WalletView *walletView = currentWalletView();
-    if (walletView) {
-        walletView->gotoLoadPSBT(from_clipboard);
+    std::string data;
+
+    if (from_clipboard) {
+        std::string raw = QApplication::clipboard()->text().toStdString();
+        bool invalid;
+        data = DecodeBase64(raw, &invalid);
+        if (invalid) {
+            Q_EMIT message(tr("Error"), tr("Unable to decode PSBT from clipboard (invalid base64)"), CClientUIInterface::MSG_ERROR);
+            return;
+        }
+    } else {
+        QString filename = GUIUtil::getOpenFileName(this,
+            tr("Load Transaction Data"), QString(),
+            tr("Partially Signed Transaction (*.psbt)"), nullptr);
+        if (filename.isEmpty()) return;
+        if (GetFileSize(filename.toLocal8Bit().data(), MAX_FILE_SIZE_PSBT) == MAX_FILE_SIZE_PSBT) {
+            Q_EMIT message(tr("Error"), tr("PSBT file must be smaller than 100 MiB"), CClientUIInterface::MSG_ERROR);
+            return;
+        }
+        std::ifstream in(filename.toLocal8Bit().data(), std::ios::binary);
+        data = std::string(std::istreambuf_iterator<char>{in}, {});
     }
+
+    std::string error;
+    PartiallySignedTransaction psbtx;
+    if (!DecodeRawPSBT(psbtx, data, error)) {
+        Q_EMIT message(tr("Error"), tr("Unable to decode PSBT") + "\n" + QString::fromStdString(error), CClientUIInterface::MSG_ERROR);
+        return;
+    }
+
+    PSBTOperationsDialog* dlg = new PSBTOperationsDialog(this, currentWalletModel(), clientModel);
+    dlg->openWithPSBT(psbtx);
+    dlg->setAttribute(Qt::WA_DeleteOnClose);
+    dlg->exec();
 }
 
 void WalletFrame::encryptWallet()
diff --git a/src/qt/walletframe.h b/src/qt/walletframe.h
index 4f77bd716f..fe42293abc 100644
--- a/src/qt/walletframe.h
+++ b/src/qt/walletframe.h
@@ -48,6 +48,7 @@ public:
 
 Q_SIGNALS:
     void createWalletButtonClicked();
+    void message(const QString& title, const QString& message, unsigned int style);
 
 private:
     QStackedWidget *walletStack;
diff --git a/src/qt/walletview.cpp b/src/qt/walletview.cpp
index 3b8cf4c7ed..2326af80b6 100644
--- a/src/qt/walletview.cpp
+++ b/src/qt/walletview.cpp
@@ -8,7 +8,6 @@
 #include <qt/askpassphrasedialog.h>
 #include <qt/clientmodel.h>
 #include <qt/guiutil.h>
-#include <qt/psbtoperationsdialog.h>
 #include <qt/optionsmodel.h>
 #include <qt/overviewpage.h>
 #include <qt/platformstyle.h>
@@ -21,13 +20,10 @@
 
 #include <interfaces/node.h>
 #include <node/ui_interface.h>
-#include <psbt.h>
 #include <util/strencodings.h>
 
 #include <QAction>
 #include <QActionGroup>
-#include <QApplication>
-#include <QClipboard>
 #include <QFileDialog>
 #include <QHBoxLayout>
 #include <QProgressDialog>
@@ -205,44 +201,6 @@ void WalletView::gotoVerifyMessageTab(QString addr)
         signVerifyMessageDialog->setAddress_VM(addr);
 }
 
-void WalletView::gotoLoadPSBT(bool from_clipboard)
-{
-    std::string data;
-
-    if (from_clipboard) {
-        std::string raw = QApplication::clipboard()->text().toStdString();
-        bool invalid;
-        data = DecodeBase64(raw, &invalid);
-        if (invalid) {
-            Q_EMIT message(tr("Error"), tr("Unable to decode PSBT from clipboard (invalid base64)"), CClientUIInterface::MSG_ERROR);
-            return;
-        }
-    } else {
-        QString filename = GUIUtil::getOpenFileName(this,
-            tr("Load Transaction Data"), QString(),
-            tr("Partially Signed Transaction (*.psbt)"), nullptr);
-        if (filename.isEmpty()) return;
-        if (GetFileSize(filename.toLocal8Bit().data(), MAX_FILE_SIZE_PSBT) == MAX_FILE_SIZE_PSBT) {
-            Q_EMIT message(tr("Error"), tr("PSBT file must be smaller than 100 MiB"), CClientUIInterface::MSG_ERROR);
-            return;
-        }
-        std::ifstream in(filename.toLocal8Bit().data(), std::ios::binary);
-        data = std::string(std::istreambuf_iterator<char>{in}, {});
-    }
-
-    std::string error;
-    PartiallySignedTransaction psbtx;
-    if (!DecodeRawPSBT(psbtx, data, error)) {
-        Q_EMIT message(tr("Error"), tr("Unable to decode PSBT") + "\n" + QString::fromStdString(error), CClientUIInterface::MSG_ERROR);
-        return;
-    }
-
-    PSBTOperationsDialog* dlg = new PSBTOperationsDialog(this, walletModel, clientModel);
-    dlg->openWithPSBT(psbtx);
-    dlg->setAttribute(Qt::WA_DeleteOnClose);
-    dlg->exec();
-}
-
 bool WalletView::handlePaymentRequest(const SendCoinsRecipient& recipient)
 {
     return sendCoinsPage->handlePaymentRequest(recipient);
diff --git a/src/qt/walletview.h b/src/qt/walletview.h
index fedf06b710..5c42a9ffc0 100644
--- a/src/qt/walletview.h
+++ b/src/qt/walletview.h
@@ -83,8 +83,6 @@ public Q_SLOTS:
     void gotoSignMessageTab(QString addr = "");
     /** Show Sign/Verify Message dialog and switch to verify message tab */
     void gotoVerifyMessageTab(QString addr = "");
-    /** Load Partially Signed Bitcoin Transaction */
-    void gotoLoadPSBT(bool from_clipboard = false);
 
     /** Show incoming transaction notification for new transactions.