feat(whitespace): show whitespace in editor views

This commit adds a new Settings entry "ShowWhitespaceinEditor"
("editor/view/showWhitespace") to the Settings class, and a new checkbox
in the Editor settings dialog.

This setting defaults to off/false, preserving the current behaviour of
the application.

If this setting is toggled to on, whitespace is rendered in the HunkWidget
and BlameEditor views.

conf/editor.lua

@@ -14,6 +14,9 @@ return {
     family = family,
     size = size
   },
+  view = {
+    showWhitespace = false
+  },
   indent = {
     tabs = true,
     width = 4,

src/conf/Setting.cpp

@@ -12,6 +12,7 @@ void Setting::initialize(QMap<Id, QString> &keys) {
   keys[Id::IndentWidth] = "editor/indent/width";
   keys[Id::TabWidth] = "editor/indent/tabwidth";
   keys[Id::ShowHeatmapInBlameMargin] = "editor/blame/heatmap";
+  keys[Id::ShowWhitespaceInEditor] = "editor/view/showWhitespace";
   keys[Id::ColorTheme] = "window/theme";
   keys[Id::ShowFullRepoPath] = "window/path/full";
   keys[Id::HideLogAutomatically] = "window/log/hide";

src/conf/Setting.h

@@ -36,6 +36,7 @@ public:
     IndentWidth,
     TabWidth,
     ShowHeatmapInBlameMargin,
+    ShowWhitespaceInEditor,
     ColorTheme,
     ShowFullRepoPath,
     HideLogAutomatically,

src/dialogs/SettingsDialog.cpp

@@ -661,6 +661,14 @@ public:
       Settings::instance()->setValue(Setting::Id::FontSize, i);
     });
 
+    QCheckBox *showWhitespace = new QCheckBox(tr("Show whitespace"), this);
+    showWhitespace->setChecked(
+        settings->value(Setting::Id::ShowWhitespaceInEditor).toBool());
+    connect(showWhitespace, &QCheckBox::toggled, [](bool checked) {
+      Settings::instance()->setValue(Setting::Id::ShowWhitespaceInEditor,
+                                     checked);
+    });
+
     QComboBox *indent = new QComboBox(this);
     indent->addItem(tr("Tabs"));
     indent->addItem(tr("Spaces"));
@@ -695,6 +703,7 @@ public:
     QFormLayout *layout = new QFormLayout(this);
     layout->addRow(tr("Font:"), font);
     layout->addRow(tr("Font size:"), fontSize);
+    layout->addRow(tr("Whitespace:"), showWhitespace);
     layout->addRow(tr("Indent using:"), indent);
     layout->addRow(tr("Indent width:"), indentWidth);
     layout->addRow(tr("Tab width:"), tabWidth);

src/editor/TextEditor.cpp

@@ -182,6 +182,7 @@ void TextEditor::applySettings() {
   setUseTabs(settings->value(Setting::Id::UseTabsForIndent).toBool());
   setIndent(settings->value(Setting::Id::IndentWidth).toInt());
   setTabWidth(settings->value(Setting::Id::TabWidth).toInt());
+  setViewWS(settings->value(Setting::Id::ShowWhitespaceInEditor).toBool());
 
   if (Settings::instance()->isTextEditorWrapLines()) {
     setWrapMode(SC_WRAP_WORD);