Merge #2070: [GUI] coin-control: remove column checkbox extra white space in tree-mode

fe4f556 GUI: ccontrol: remove column checkbox extra whitespace in tree mode (random-zebra)

Pull request description:

  Addresses the comment in #2033 (review)

  Always use the minimum width in list-mode.
  Save the current width when switching from tree-mode to list-mode, and restore it switching back.

ACKs for top commit:
  furszy:
    ACK fe4f556
  Fuzzbawls:
    ACK fe4f556

Tree-SHA512: cc9d7ab0124fbcc7d9074aca1404b39a6afe26ac422a58a4f91c2f59f6f59b8fd800df4691b2f8ba058862c14a7657102a42df02ab3a16b997fc96236d48fcfb

Author: random-zebra

src/qt/coincontroldialog.cpp

@@ -165,7 +165,7 @@ CoinControlDialog::CoinControlDialog(QWidget* parent, bool _forDelegation) : QDi
     // Toggle lock state
     connect(ui->pushButtonToggleLock, &QPushButton::clicked, this, &CoinControlDialog::buttonToggleLockClicked);
 
-    ui->treeWidget->setColumnWidth(COLUMN_CHECKBOX, 100);
+    ui->treeWidget->setColumnWidth(COLUMN_CHECKBOX, colCheckBoxWidth_treeMode);
     ui->treeWidget->setColumnWidth(COLUMN_AMOUNT, 110);
     ui->treeWidget->setColumnWidth(COLUMN_LABEL, 160);
     ui->treeWidget->setColumnWidth(COLUMN_ADDRESS, 310);
@@ -795,6 +795,13 @@ void CoinControlDialog::updateView()
         for (int i = 0; i < ui->treeWidget->topLevelItemCount(); i++)
             if (ui->treeWidget->topLevelItem(i)->checkState(COLUMN_CHECKBOX) == Qt::PartiallyChecked)
                 ui->treeWidget->topLevelItem(i)->setExpanded(true);
+        // restore saved width for COLUMN_CHECKBOX
+        ui->treeWidget->setColumnWidth(COLUMN_CHECKBOX, colCheckBoxWidth_treeMode);
+    } else {
+        // save COLUMN_CHECKBOX width for tree-mode
+        colCheckBoxWidth_treeMode = std::max(110, ui->treeWidget->columnWidth(COLUMN_CHECKBOX));
+        // minimize COLUMN_CHECKBOX width in list-mode (need to display only the check box)
+        ui->treeWidget->resizeColumnToContents(COLUMN_CHECKBOX);
     }
 
     // sort view

src/qt/coincontroldialog.h

@@ -64,6 +64,7 @@ class CoinControlDialog : public QDialog
     int sortColumn;
     Qt::SortOrder sortOrder;
     bool forDelegation;
+    int colCheckBoxWidth_treeMode{110};
     // pair (recipient amount, ishielded recipient)
     std::vector<std::pair<CAmount, bool>> payAmounts{};
     unsigned int nSelectableInputs{0};