Merge bitcoin-core/gui#390: Add SubFeeFromAmount to options

62b125fd197879f112322a1f67a318d6ab22e67a qt, refactor: Fix indentation (Prateek Sancheti)
ad28b66e98c9bb3bc7af2545654842544a798601 qt: Add SubFeeFromAmount option (Prateek Sancheti)

Pull request description:

  This PR adds **_SubFeeFromAmount_** option which lets the user select their preferred setting of whether fee for a transaction is to be subtracted from the amount or not for future transactions. The setting chosen by the user is remembered even when the GUI mode is turned off.

  **_Functionality and Usage:_**

  - Go to `Settings > Options > Wallet` on _Windows/Linux_ or `bitcoin-qt > Preferences > Wallet` on _macOS_.
  - The checkbox **Subtract Fee From Amount** corresponds to the added option **SubFeeFromAmount**.
  - The preferred setting intended to be the default for all future send transactions should be selected by the user.
  - Click on **OK**.
  - Go to the **Send** tab in the wallet.
  - You shall notice, any new Send transaction created will have the preferred setting as chosen by the user.<br> (Try clicking on Add recipient or even restarting the Node in GUI)

  Attaching ScreenRecordings to explain the added feature.

  > Master.mov: Master Branch

  https://user-images.githubusercontent.com/54016434/127763378-be91837d-d0ab-4ae5-87c0-d303fa70a336.mov

  > PR.mov: PullRequest

  https://user-images.githubusercontent.com/54016434/127763404-05b834c1-4082-4fbd-9b05-1528ac898a21.mov

  Close #386

ACKs for top commit:
  Talkless:
    tACK 62b125fd197879f112322a1f67a318d6ab22e67a, tested on Debian Sid with 5.15.2 and it works as described.
  hebasto:
    re-ACK 62b125fd197879f112322a1f67a318d6ab22e67a, only removed the unused `SubFeeFromAmountChanged` signal since my [previous](https://github.com/bitcoin-core/gui/pull/390#pullrequestreview-726531766) review.
  meshcollider:
    utACK 62b125fd197879f112322a1f67a318d6ab22e67a

Tree-SHA512: 932ca89ae578a1e1c426561400d87cf005c231944feaf0f662ff8d88f32bdd65a927a090ea41510a15f8ec0ebcd5529672e9917720eb5ea85f413f081e45d5bb

5 files changed, 63 insertions, 36 deletions

diff --git a/src/qt/forms/optionsdialog.ui b/src/qt/forms/optionsdialog.ui
index bd72328c02..2ff1445709 100644
--- a/src/qt/forms/optionsdialog.ui
+++ b/src/qt/forms/optionsdialog.ui
@@ -51,20 +51,20 @@
         </spacer>
        </item>
        <item>
-       <layout class="QHBoxLayout" name="horizontalLayout_Main_Prune">
-        <item>
-         <widget class="QCheckBox" name="prune">
-          <property name="toolTip">
-           <string>Enabling pruning significantly reduces the disk space required to store transactions. All blocks are still fully validated. Reverting this setting requires re-downloading the entire blockchain.</string>
-          </property>
-          <property name="text">
-           <string>Prune &amp;block storage to</string>
-          </property>
-         </widget>
-        </item>
-        <item>
-         <widget class="QSpinBox" name="pruneSize"/>
-        </item>
+        <layout class="QHBoxLayout" name="horizontalLayout_Main_Prune">
+         <item>
+          <widget class="QCheckBox" name="prune">
+           <property name="toolTip">
+            <string>Enabling pruning significantly reduces the disk space required to store transactions. All blocks are still fully validated. Reverting this setting requires re-downloading the entire blockchain.</string>
+           </property>
+           <property name="text">
+            <string>Prune &amp;block storage to</string>
+           </property>
+          </widget>
+         </item>
+         <item>
+          <widget class="QSpinBox" name="pruneSize"/>
+         </item>
          <item>
           <widget class="QLabel" name="pruneSizeUnitLabel">
            <property name="text">
@@ -201,6 +201,16 @@
       </attribute>
       <layout class="QVBoxLayout" name="verticalLayout_Wallet">
        <item>
+        <widget class="QCheckBox" name="subFeeFromAmount">
+         <property name="toolTip">
+          <string extracomment="Tooltip text for Options window setting that sets subtracting the fee from a sending amount as default.">Whether to set subtract fee from amount as default or not.</string>
+         </property>
+         <property name="text">
+          <string extracomment="An Options window setting to set subtracting the fee from a sending amount as default.">Subtract &amp;fee from amount by default</string>
+         </property>
+        </widget>
+       </item>
+       <item>
         <widget class="QGroupBox" name="groupBox">
          <property name="title">
           <string>Expert</string>
@@ -235,27 +245,27 @@
           <string>External Signer (e.g. hardware wallet)</string>
          </property>
          <layout class="QVBoxLayout" name="verticalLayoutHww">
-           <item>
-            <layout class="QHBoxLayout" name="horizontalLayoutHww">
-             <item>
-              <widget class="QLabel" name="externalSignerPathLabel">
-               <property name="text">
-                <string>&amp;External signer script path</string>
-               </property>
-               <property name="buddy">
-                <cstring>externalSignerPath</cstring>
-               </property>
-              </widget>
-             </item>
-             <item>
-              <widget class="QLineEdit" name="externalSignerPath">
-                <property name="toolTip">
-                  <string>Full path to a Bitcoin Core compatible script (e.g. C:\Downloads\hwi.exe or /Users/you/Downloads/hwi.py). Beware: malware can steal your coins!</string>
-                </property>
-              </widget>
-             </item>
-            </layout>
-           </item>
+          <item>
+           <layout class="QHBoxLayout" name="horizontalLayoutHww">
+            <item>
+             <widget class="QLabel" name="externalSignerPathLabel">
+              <property name="text">
+               <string>&amp;External signer script path</string>
+              </property>
+              <property name="buddy">
+               <cstring>externalSignerPath</cstring>
+              </property>
+             </widget>
+            </item>
+            <item>
+             <widget class="QLineEdit" name="externalSignerPath">
+              <property name="toolTip">
+               <string>Full path to a Bitcoin Core compatible script (e.g. C:\Downloads\hwi.exe or /Users/you/Downloads/hwi.py). Beware: malware can steal your coins!</string>
+              </property>
+             </widget>
+            </item>
+           </layout>
+          </item>
          </layout>
         </widget>
        </item>
diff --git a/src/qt/optionsdialog.cpp b/src/qt/optionsdialog.cpp
index b12fe96567..5ad4fc9b33 100644
--- a/src/qt/optionsdialog.cpp
+++ b/src/qt/optionsdialog.cpp
@@ -239,6 +239,7 @@ void OptionsDialog::setMapper()
     /* Wallet */
     mapper->addMapping(ui->spendZeroConfChange, OptionsModel::SpendZeroConfChange);
     mapper->addMapping(ui->coinControlFeatures, OptionsModel::CoinControlFeatures);
+    mapper->addMapping(ui->subFeeFromAmount, OptionsModel::SubFeeFromAmount);
     mapper->addMapping(ui->externalSignerPath, OptionsModel::ExternalSignerPath);
 
     /* Network */
diff --git a/src/qt/optionsmodel.cpp b/src/qt/optionsmodel.cpp
index 24a4e9ee96..d87fc1f84a 100644
--- a/src/qt/optionsmodel.cpp
+++ b/src/qt/optionsmodel.cpp
@@ -124,6 +124,11 @@ void OptionsModel::Init(bool resetSettings)
     if (!gArgs.SoftSetArg("-signer", settings.value("external_signer_path").toString().toStdString())) {
         addOverriddenOption("-signer");
     }
+
+    if (!settings.contains("SubFeeFromAmount")) {
+        settings.setValue("SubFeeFromAmount", false);
+    }
+    m_sub_fee_from_amount = settings.value("SubFeeFromAmount", false).toBool();
 #endif
 
     // Network
@@ -335,6 +340,8 @@ QVariant OptionsModel::data(const QModelIndex & index, int role) const
             return settings.value("bSpendZeroConfChange");
         case ExternalSignerPath:
             return settings.value("external_signer_path");
+        case SubFeeFromAmount:
+            return m_sub_fee_from_amount;
 #endif
         case DisplayUnit:
             return nDisplayUnit;
@@ -460,6 +467,10 @@ bool OptionsModel::setData(const QModelIndex & index, const QVariant & value, in
                 setRestartRequired(true);
             }
             break;
+        case SubFeeFromAmount:
+            m_sub_fee_from_amount = value.toBool();
+            settings.setValue("SubFeeFromAmount", m_sub_fee_from_amount);
+            break;
 #endif
         case DisplayUnit:
             setDisplayUnit(value);
diff --git a/src/qt/optionsmodel.h b/src/qt/optionsmodel.h
index 535843e8ba..203ee27ad8 100644
--- a/src/qt/optionsmodel.h
+++ b/src/qt/optionsmodel.h
@@ -61,6 +61,7 @@ public:
         Language,               // QString
         UseEmbeddedMonospacedFont, // bool
         CoinControlFeatures,    // bool
+        SubFeeFromAmount,       // bool
         ThreadsScriptVerif,     // int
         Prune,                  // bool
         PruneSize,              // int
@@ -88,6 +89,7 @@ public:
     QString getThirdPartyTxUrls() const { return strThirdPartyTxUrls; }
     bool getUseEmbeddedMonospacedFont() const { return m_use_embedded_monospaced_font; }
     bool getCoinControlFeatures() const { return fCoinControlFeatures; }
+    bool getSubFeeFromAmount() const { return m_sub_fee_from_amount; }
     const QString& getOverriddenByCommandLine() { return strOverriddenByCommandLine; }
 
     /* Explicit setters */
@@ -112,6 +114,7 @@ private:
     QString strThirdPartyTxUrls;
     bool m_use_embedded_monospaced_font;
     bool fCoinControlFeatures;
+    bool m_sub_fee_from_amount;
     /* settings that were overridden by command-line */
     QString strOverriddenByCommandLine;
 
diff --git a/src/qt/sendcoinsentry.cpp b/src/qt/sendcoinsentry.cpp
index 683c0441fa..5fa5165615 100644
--- a/src/qt/sendcoinsentry.cpp
+++ b/src/qt/sendcoinsentry.cpp
@@ -97,7 +97,9 @@ void SendCoinsEntry::clear()
     ui->payTo->clear();
     ui->addAsLabel->clear();
     ui->payAmount->clear();
-    ui->checkboxSubtractFeeFromAmount->setCheckState(Qt::Unchecked);
+    if (model && model->getOptionsModel()) {
+        ui->checkboxSubtractFeeFromAmount->setChecked(model->getOptionsModel()->getSubFeeFromAmount());
+    }
     ui->messageTextLabel->clear();
     ui->messageTextLabel->hide();
     ui->messageLabel->hide();