Merge #79: Embed monospaced font

67f26319a0ca7e34e3db17d9330133622a40de09 gui: Add monospaced font settings (Hennadii Stepanov)
22e0114d055b0ac6cdc47af2968b5dc742ba055a qt: Choose monospaced font in C++ code rather in `*.ui` file (Hennadii Stepanov)
623de12d040af89ff7c25de6eb0a19c67179dc5f qt: Make GUIUtil::fixedPitchFont aware of embedded font (Hennadii Stepanov)
89e421918ee8b9c8439317f747e5c37f0733d94b gui: Add Roboto Mono font (Hennadii Stepanov)

Pull request description:

  Qt does not guarantee that the actual applied font matches to the requested one.
  It was noted (https://github.com/bitcoin/bitcoin/pull/16432#issuecomment-514486077):
  > the monospace font looks a bit weird no macOS

  ... because it is _not_ monospaced.
  Also some discrepancies I've noted on Windows while testing Qt 5.15 ([#19716](https://github.com/bitcoin/bitcoin/pull/19716)).

  Of course, we could check the actual font with `QFontInfo`, and try to choose another font.
  But this PR suggests to just embed a monospaced font, and get the GUI look (partially) independent from a platform.

  [Roboto Mono](https://fonts.google.com/specimen/Roboto+Mono) was chosen after discussion with Bitcoin Design community, and due to its [Apache License, Version 2.0](https://fonts.google.com/specimen/Roboto+Mono#license).

  Changes are scoped to the Overview page only.

  ---

  Screenshots on macOS 10.15.6 (images are simulated by code patching):

  - master (ca30d34cf94b7797272ef1920ca4b48716e7f999)
  ![Screenshot from 2020-09-03 14-10-03](https://user-images.githubusercontent.com/32963518/92107902-30357d80-edef-11ea-8a4f-b4c758eebf66.png)

  - this PR (3fdd5b6bd17a679d6e3876682266092159c52d59)
  ![Screenshot from 2020-09-03 15-41-36](https://user-images.githubusercontent.com/32963518/92116277-4b5aba00-edfc-11ea-8cb9-22fc44460bfb.png)

  ---

  More screenshots added after https://github.com/bitcoin-core/gui/pull/79#issuecomment-782909149:

  - Linux Mint 20.1 + Cinnamon DE

  ![DeepinScreenshot_select-area_20210221205410](https://user-images.githubusercontent.com/32963518/108635739-b327be80-7489-11eb-8851-ac89f61199ee.png)

  - Windows 10 (with depends)

  ![DeepinScreenshot_select-area_20210221205056](https://user-images.githubusercontent.com/32963518/108635741-b6bb4580-7489-11eb-8b6b-66be5551eb8c.png)

  - macOS Big Sur (with depends)

  ![DeepinScreenshot_select-area_20210221202917](https://user-images.githubusercontent.com/32963518/108635746-bd49bd00-7489-11eb-8cd2-cf4bb2273a6d.png)

ACKs for top commit:
  laanwj:
    Tested ACK 67f26319a0ca7e34e3db17d9330133622a40de09

Tree-SHA512: a59775570b8ce314669ede50a0b69f53e8a47a41e7eea428835013240f0ce9afcff6e4c258895455b56806417ed877e5b7a9522f1904e95a5f435db8ccf6078c

12 files changed, 160 insertions, 58 deletions

diff --git a/src/qt/bitcoin.cpp b/src/qt/bitcoin.cpp
index d6d5ba6968..bad74fcbcc 100644
--- a/src/qt/bitcoin.cpp
+++ b/src/qt/bitcoin.cpp
@@ -44,6 +44,7 @@
 
 #include <QApplication>
 #include <QDebug>
+#include <QFontDatabase>
 #include <QLibraryInfo>
 #include <QLocale>
 #include <QMessageBox>
@@ -475,6 +476,7 @@ int GuiMain(int argc, char* argv[])
 #endif
 
     BitcoinApplication app;
+    QFontDatabase::addApplicationFont(":/fonts/monospace");
 
     /// 2. Parse command-line options. We do this after qt in order to show an error if there are problems parsing these
     // Command-line options take precedence:
diff --git a/src/qt/bitcoin.qrc b/src/qt/bitcoin.qrc
index 7115459808..fed373e551 100644
--- a/src/qt/bitcoin.qrc
+++ b/src/qt/bitcoin.qrc
@@ -83,4 +83,7 @@
         <file alias="spinner-034">res/animation/spinner-034.png</file>
         <file alias="spinner-035">res/animation/spinner-035.png</file>
     </qresource>
+    <qresource prefix="/fonts">
+        <file alias="monospace">res/fonts/RobotoMono-Bold.ttf</file>
+    </qresource>
 </RCC>
diff --git a/src/qt/forms/optionsdialog.ui b/src/qt/forms/optionsdialog.ui
index 8181cc47e2..6d279540e9 100644
--- a/src/qt/forms/optionsdialog.ui
+++ b/src/qt/forms/optionsdialog.ui
@@ -706,6 +706,106 @@
         </layout>
        </item>
        <item>
+        <widget class="QGroupBox" name="font_groupBox">
+         <property name="title">
+          <string>Monospaced font in the Overview tab:</string>
+         </property>
+         <layout class="QVBoxLayout" name="font_verticalLayout">
+          <item>
+           <layout class="QHBoxLayout" name="embeddedFont_horizontalLayout">
+            <item>
+             <widget class="QRadioButton" name="embeddedFont_radioButton">
+              <property name="text">
+               <string>embedded &quot;%1&quot;</string>
+              </property>
+             </widget>
+            </item>
+            <item>
+             <spacer name="embeddedFont_horizontalSpacer">
+              <property name="orientation">
+               <enum>Qt::Horizontal</enum>
+              </property>
+              <property name="sizeHint" stdset="0">
+               <size>
+                <width>40</width>
+                <height>20</height>
+               </size>
+              </property>
+             </spacer>
+            </item>
+            <item>
+             <layout class="QVBoxLayout" name="embeddedFont_verticalLayout">
+              <item>
+               <widget class="QLabel" name="embeddedFont_label_1">
+                <property name="text">
+                 <string>111.11111111 BTC</string>
+                </property>
+               </widget>
+              </item>
+              <item>
+               <widget class="QLabel" name="embeddedFont_label_9">
+                <property name="text">
+                 <string>909.09090909 BTC</string>
+                </property>
+               </widget>
+              </item>
+             </layout>
+            </item>
+           </layout>
+          </item>
+          <item>
+           <widget class="Line" name="font_line">
+            <property name="orientation">
+             <enum>Qt::Horizontal</enum>
+            </property>
+           </widget>
+          </item>
+          <item>
+           <layout class="QHBoxLayout" name="systemFont_horizontalLayout">
+            <item>
+             <widget class="QRadioButton" name="systemFont_radioButton">
+              <property name="text">
+               <string>closest matching &quot;%1&quot;</string>
+              </property>
+             </widget>
+            </item>
+            <item>
+             <spacer name="systemFont_horizontalSpacer">
+              <property name="orientation">
+               <enum>Qt::Horizontal</enum>
+              </property>
+              <property name="sizeHint" stdset="0">
+               <size>
+                <width>40</width>
+                <height>20</height>
+               </size>
+              </property>
+             </spacer>
+            </item>
+            <item>
+             <layout class="QVBoxLayout" name="systemFont_verticalLayout">
+              <item>
+               <widget class="QLabel" name="systemFont_label_1">
+                <property name="text">
+                 <string>111.11111111 BTC</string>
+                </property>
+               </widget>
+              </item>
+              <item>
+               <widget class="QLabel" name="systemFont_label_9">
+                <property name="text">
+                 <string>909.09090909 BTC</string>
+                </property>
+               </widget>
+              </item>
+             </layout>
+            </item>
+           </layout>
+          </item>
+         </layout>
+        </widget>
+       </item>
+       <item>
         <spacer name="verticalSpacer_Display">
          <property name="orientation">
           <enum>Qt::Vertical</enum>
diff --git a/src/qt/forms/overviewpage.ui b/src/qt/forms/overviewpage.ui
index ee9d4a113c..b82143e1ba 100644
--- a/src/qt/forms/overviewpage.ui
+++ b/src/qt/forms/overviewpage.ui
@@ -116,13 +116,6 @@
             </property>
             <item row="2" column="2">
              <widget class="QLabel" name="labelWatchPending">
-              <property name="font">
-               <font>
-                <family>Monospace</family>
-                <weight>75</weight>
-                <bold>true</bold>
-               </font>
-              </property>
               <property name="cursor">
                <cursorShape>IBeamCursor</cursorShape>
               </property>
@@ -142,13 +135,6 @@
             </item>
             <item row="2" column="1">
              <widget class="QLabel" name="labelUnconfirmed">
-              <property name="font">
-               <font>
-                <family>Monospace</family>
-                <weight>75</weight>
-                <bold>true</bold>
-               </font>
-              </property>
               <property name="cursor">
                <cursorShape>IBeamCursor</cursorShape>
               </property>
@@ -168,13 +154,6 @@
             </item>
             <item row="3" column="2">
              <widget class="QLabel" name="labelWatchImmature">
-              <property name="font">
-               <font>
-                <family>Monospace</family>
-                <weight>75</weight>
-                <bold>true</bold>
-               </font>
-              </property>
               <property name="cursor">
                <cursorShape>IBeamCursor</cursorShape>
               </property>
@@ -227,13 +206,6 @@
             </item>
             <item row="3" column="1">
              <widget class="QLabel" name="labelImmature">
-              <property name="font">
-               <font>
-                <family>Monospace</family>
-                <weight>75</weight>
-                <bold>true</bold>
-               </font>
-              </property>
               <property name="cursor">
                <cursorShape>IBeamCursor</cursorShape>
               </property>
@@ -273,13 +245,6 @@
             </item>
             <item row="5" column="1">
              <widget class="QLabel" name="labelTotal">
-              <property name="font">
-               <font>
-                <family>Monospace</family>
-                <weight>75</weight>
-                <bold>true</bold>
-               </font>
-              </property>
               <property name="cursor">
                <cursorShape>IBeamCursor</cursorShape>
               </property>
@@ -299,13 +264,6 @@
             </item>
             <item row="5" column="2">
              <widget class="QLabel" name="labelWatchTotal">
-              <property name="font">
-               <font>
-                <family>Monospace</family>
-                <weight>75</weight>
-                <bold>true</bold>
-               </font>
-              </property>
               <property name="cursor">
                <cursorShape>IBeamCursor</cursorShape>
               </property>
@@ -342,13 +300,6 @@
             </item>
             <item row="1" column="1">
              <widget class="QLabel" name="labelBalance">
-              <property name="font">
-               <font>
-                <family>Monospace</family>
-                <weight>75</weight>
-                <bold>true</bold>
-               </font>
-              </property>
               <property name="cursor">
                <cursorShape>IBeamCursor</cursorShape>
               </property>
@@ -368,13 +319,6 @@
             </item>
             <item row="1" column="2">
              <widget class="QLabel" name="labelWatchAvailable">
-              <property name="font">
-               <font>
-                <family>Monospace</family>
-                <weight>75</weight>
-                <bold>true</bold>
-               </font>
-              </property>
               <property name="cursor">
                <cursorShape>IBeamCursor</cursorShape>
               </property>
diff --git a/src/qt/guiutil.cpp b/src/qt/guiutil.cpp
index d72ed0c3ff..c70bd9f418 100644
--- a/src/qt/guiutil.cpp
+++ b/src/qt/guiutil.cpp
@@ -78,8 +78,11 @@ QString dateTimeStr(qint64 nTime)
     return dateTimeStr(QDateTime::fromTime_t((qint32)nTime));
 }
 
-QFont fixedPitchFont()
+QFont fixedPitchFont(bool use_embedded_font)
 {
+    if (use_embedded_font) {
+        return {"Roboto Mono"};
+    }
     return QFontDatabase::systemFont(QFontDatabase::FixedFont);
 }
 
diff --git a/src/qt/guiutil.h b/src/qt/guiutil.h
index 3134c98429..7984aa1141 100644
--- a/src/qt/guiutil.h
+++ b/src/qt/guiutil.h
@@ -53,7 +53,7 @@ namespace GUIUtil
     QString dateTimeStr(qint64 nTime);
 
     // Return a monospace font
-    QFont fixedPitchFont();
+    QFont fixedPitchFont(bool use_embedded_font = false);
 
     // Set up widget for address
     void setupAddressWidget(QValidatedLineEdit *widget, QWidget *parent);
diff --git a/src/qt/optionsdialog.cpp b/src/qt/optionsdialog.cpp
index 7b8d7871ec..e6b9488344 100644
--- a/src/qt/optionsdialog.cpp
+++ b/src/qt/optionsdialog.cpp
@@ -144,6 +144,20 @@ OptionsDialog::OptionsDialog(QWidget *parent, bool enableWallet) :
         ui->minimizeToTray->setEnabled(false);
     }
 
+    QFont embedded_font{GUIUtil::fixedPitchFont(true)};
+    ui->embeddedFont_radioButton->setText(ui->embeddedFont_radioButton->text().arg(QFontInfo(embedded_font).family()));
+    embedded_font.setWeight(QFont::Bold);
+    ui->embeddedFont_label_1->setFont(embedded_font);
+    ui->embeddedFont_label_9->setFont(embedded_font);
+
+    QFont system_font{GUIUtil::fixedPitchFont(false)};
+    ui->systemFont_radioButton->setText(ui->systemFont_radioButton->text().arg(QFontInfo(system_font).family()));
+    system_font.setWeight(QFont::Bold);
+    ui->systemFont_label_1->setFont(system_font);
+    ui->systemFont_label_9->setFont(system_font);
+    // Checking the embeddedFont_radioButton automatically unchecks the systemFont_radioButton.
+    ui->systemFont_radioButton->setChecked(true);
+
     GUIUtil::handleCloseWindowShortcut(this);
 }
 
@@ -246,6 +260,7 @@ void OptionsDialog::setMapper()
     mapper->addMapping(ui->lang, OptionsModel::Language);
     mapper->addMapping(ui->unit, OptionsModel::DisplayUnit);
     mapper->addMapping(ui->thirdPartyTxUrls, OptionsModel::ThirdPartyTxUrls);
+    mapper->addMapping(ui->embeddedFont_radioButton, OptionsModel::UseEmbeddedMonospacedFont);
 }
 
 void OptionsDialog::setOkButtonState(bool fState)
diff --git a/src/qt/optionsmodel.cpp b/src/qt/optionsmodel.cpp
index 1e0391a35c..d51a5b06ff 100644
--- a/src/qt/optionsmodel.cpp
+++ b/src/qt/optionsmodel.cpp
@@ -163,6 +163,12 @@ void OptionsModel::Init(bool resetSettings)
         addOverriddenOption("-lang");
 
     language = settings.value("language").toString();
+
+    if (!settings.contains("UseEmbeddedMonospacedFont")) {
+        settings.setValue("UseEmbeddedMonospacedFont", "true");
+    }
+    m_use_embedded_monospaced_font = settings.value("UseEmbeddedMonospacedFont").toBool();
+    Q_EMIT useEmbeddedMonospacedFontChanged(m_use_embedded_monospaced_font);
 }
 
 /** Helper function to copy contents from one QSettings to another.
@@ -326,6 +332,8 @@ QVariant OptionsModel::data(const QModelIndex & index, int role) const
             return strThirdPartyTxUrls;
         case Language:
             return settings.value("language");
+        case UseEmbeddedMonospacedFont:
+            return m_use_embedded_monospaced_font;
         case CoinControlFeatures:
             return fCoinControlFeatures;
         case Prune:
@@ -453,6 +461,11 @@ bool OptionsModel::setData(const QModelIndex & index, const QVariant & value, in
                 setRestartRequired(true);
             }
             break;
+        case UseEmbeddedMonospacedFont:
+            m_use_embedded_monospaced_font = value.toBool();
+            settings.setValue("UseEmbeddedMonospacedFont", m_use_embedded_monospaced_font);
+            Q_EMIT useEmbeddedMonospacedFontChanged(m_use_embedded_monospaced_font);
+            break;
         case CoinControlFeatures:
             fCoinControlFeatures = value.toBool();
             settings.setValue("fCoinControlFeatures", fCoinControlFeatures);
diff --git a/src/qt/optionsmodel.h b/src/qt/optionsmodel.h
index f7171951a1..4d012a9b8f 100644
--- a/src/qt/optionsmodel.h
+++ b/src/qt/optionsmodel.h
@@ -59,6 +59,7 @@ public:
         DisplayUnit,            // BitcoinUnits::Unit
         ThirdPartyTxUrls,       // QString
         Language,               // QString
+        UseEmbeddedMonospacedFont, // bool
         CoinControlFeatures,    // bool
         ThreadsScriptVerif,     // int
         Prune,                  // bool
@@ -84,6 +85,7 @@ public:
     bool getMinimizeOnClose() const { return fMinimizeOnClose; }
     int getDisplayUnit() const { return nDisplayUnit; }
     QString getThirdPartyTxUrls() const { return strThirdPartyTxUrls; }
+    bool getUseEmbeddedMonospacedFont() const { return m_use_embedded_monospaced_font; }
     bool getCoinControlFeatures() const { return fCoinControlFeatures; }
     const QString& getOverriddenByCommandLine() { return strOverriddenByCommandLine; }
 
@@ -107,6 +109,7 @@ private:
     QString language;
     int nDisplayUnit;
     QString strThirdPartyTxUrls;
+    bool m_use_embedded_monospaced_font;
     bool fCoinControlFeatures;
     /* settings that were overridden by command-line */
     QString strOverriddenByCommandLine;
@@ -120,6 +123,7 @@ Q_SIGNALS:
     void displayUnitChanged(int unit);
     void coinControlFeaturesChanged(bool);
     void showTrayIconChanged(bool);
+    void useEmbeddedMonospacedFontChanged(bool);
 };
 
 #endif // BITCOIN_QT_OPTIONSMODEL_H
diff --git a/src/qt/overviewpage.cpp b/src/qt/overviewpage.cpp
index bc542a0833..7f12b1d2b5 100644
--- a/src/qt/overviewpage.cpp
+++ b/src/qt/overviewpage.cpp
@@ -257,6 +257,9 @@ void OverviewPage::setClientModel(ClientModel *model)
         // Show warning, for example if this is a prerelease version
         connect(model, &ClientModel::alertsChanged, this, &OverviewPage::updateAlerts);
         updateAlerts(model->getStatusBarWarnings());
+
+        connect(model->getOptionsModel(), &OptionsModel::useEmbeddedMonospacedFontChanged, this, &OverviewPage::setMonospacedFont);
+        setMonospacedFont(model->getOptionsModel()->getUseEmbeddedMonospacedFont());
     }
 }
 
@@ -321,3 +324,17 @@ void OverviewPage::showOutOfSyncWarning(bool fShow)
     ui->labelWalletStatus->setVisible(fShow);
     ui->labelTransactionsStatus->setVisible(fShow);
 }
+
+void OverviewPage::setMonospacedFont(bool use_embedded_font)
+{
+    QFont f = GUIUtil::fixedPitchFont(use_embedded_font);
+    f.setWeight(QFont::Bold);
+    ui->labelBalance->setFont(f);
+    ui->labelUnconfirmed->setFont(f);
+    ui->labelImmature->setFont(f);
+    ui->labelTotal->setFont(f);
+    ui->labelWatchAvailable->setFont(f);
+    ui->labelWatchPending->setFont(f);
+    ui->labelWatchImmature->setFont(f);
+    ui->labelWatchTotal->setFont(f);
+}
diff --git a/src/qt/overviewpage.h b/src/qt/overviewpage.h
index 578ef601fb..5158c81678 100644
--- a/src/qt/overviewpage.h
+++ b/src/qt/overviewpage.h
@@ -61,6 +61,7 @@ private Q_SLOTS:
     void updateAlerts(const QString &warnings);
     void updateWatchOnlyLabels(bool showWatchOnly);
     void handleOutOfSyncWarningClicks();
+    void setMonospacedFont(bool use_embedded_font);
 };
 
 #endif // BITCOIN_QT_OVERVIEWPAGE_H
diff --git a/src/qt/res/fonts/RobotoMono-Bold.ttf b/src/qt/res/fonts/RobotoMono-Bold.ttf
new file mode 100644
index 0000000000..900fce6848
--- /dev/null
+++ b/src/qt/res/fonts/RobotoMono-Bold.ttf