Add box to float custom column creation to specify the number of decimal digits allowed when editing.

src/calibre/gui2/custom_column_widgets.py

@@ -286,7 +286,7 @@ class Float(Int):
         self.widgets = [QLabel(label_string(self.col_metadata['name']), parent)]
         self.finish_ui_setup(parent, ClearingDoubleSpinBox)
         self.editor.setRange(-1000000., float(100000000))
-        self.editor.setDecimals(2)
+        self.editor.setDecimals(self.col_metadata['display'].get('decimals', 2))
 
 
 class Rating(Base):
@@ -1098,7 +1098,7 @@ class BulkFloat(BulkInt):
     def setup_ui(self, parent):
         self.make_widgets(parent, QDoubleSpinBox)
         self.main_widget.setRange(-1000000., float(100000000))
-        self.main_widget.setDecimals(2)
+        self.main_widget.setDecimals(self.col_metadata['display'].get('decimals', 2))
         self.finish_ui_setup(parent)
 
     def set_to_undefined(self):

src/calibre/gui2/library/delegates.py

@@ -553,7 +553,7 @@ class CcNumberDelegate(QStyledItemDelegate, UpdateEditorGeometry):  # {{{
             editor = ClearingDoubleSpinBox(parent)
             editor.setSpecialValueText(_('Undefined'))
             editor.setRange(-1000000., 100000000.)
-            editor.setDecimals(2)
+            editor.setDecimals(m.custom_columns[col]['display'].get('decimals', 2))
         return editor
 
     def setModelData(self, editor, model, index):

src/calibre/gui2/preferences/create_custom_column.py

@@ -13,7 +13,7 @@ from functools import partial
 from qt.core import (
     QDialog, Qt, QColor, QIcon, QVBoxLayout, QLabel, QGridLayout,
     QDialogButtonBox, QWidget, QLineEdit, QHBoxLayout, QComboBox,
-    QCheckBox
+    QCheckBox, QSpinBox
 )
 
 from calibre.gui2 import error_dialog
@@ -197,6 +197,7 @@ class CreateCustomColumn(QDialog):
         elif ct == '*text':
             self.is_names.setChecked(c['display'].get('is_names', False))
         self.description_box.setText(c['display'].get('description', ''))
+        self.decimals_box.setValue(min(9, max(1, c['display'].get('decimals', 2))))
 
         all_colors = [str(s) for s in list(QColor.colorNames())]
         self.enum_colors_label.setToolTip('<p>' + ', '.join(all_colors) + '</p>')
@@ -323,6 +324,19 @@ class CreateCustomColumn(QDialog):
         h.addWidget(la)
         self.format_label = add_row('', h)
 
+        # Float number of decimal digits
+        h = QHBoxLayout()
+        self.decimals_box = fb = QSpinBox(self)
+        fb.setRange(1, 9)
+        h.addWidget(fb)
+        self.decimals_default_label = la = QLabel(_('This controls the number of decimal '
+                                                    'digits you can enter when editing '
+                                                    'this column using the GUI. The '
+                                                    'value can be between 1 and 9'))
+        la.setWordWrap(True)
+        h.addWidget(la)
+        self.decimals_label = add_row(_('Decimals when editing'), h)
+
         # Template
         self.composite_box = cb = TemplateLineEditor(self)
         self.composite_default_label = cdl = QLabel(_("Default: (nothing)"))
@@ -420,6 +434,7 @@ class CreateCustomColumn(QDialog):
         needs_format = col_type in ('datetime', 'int', 'float')
         for x in ('box', 'default_label', 'label'):
             getattr(self, 'format_'+x).setVisible(needs_format)
+            getattr(self, 'decimals_'+x).setVisible(col_type == 'float')
         if needs_format:
             if col_type == 'datetime':
                 l, dl = _('&Format for dates'), _('Default: dd MMM yyyy.')
@@ -591,6 +606,8 @@ class CreateCustomColumn(QDialog):
                 display_dict = {'number_format':str(self.format_box.text()).strip()}
             else:
                 display_dict = {'number_format': None}
+            if col_type == 'float':
+                display_dict['decimals'] = self.decimals_box.value()
             if default_val:
                 try:
                     if col_type == 'int':
@@ -743,8 +760,10 @@ class CreateNewCustomColumn:
         'enum_values': a string containing comma-separated valid values for an enumeration
         'enum_colors': a string containing comma-separated colors for an enumeration
         'use_decorations': True or False -- should check marks be displayed
+      float columns:
+        'decimals': the number of decimal digits to allow when editing (int). Range: 1 - 9
       float and int columns:
-        'number_format': the format to apply for the column
+        'number_format': the format to apply when displaying the column
       rating columns:
         'allow_half_stars': True or False -- are half-stars allowed
       text columns: