Highlight alignment column

Fixes DistributedProofreaders#43

src/guiguts/application.py

@@ -22,6 +22,7 @@
     highlight_double_quotes,
     remove_highlights,
     highlight_quotbrac_callback,
+    highlight_aligncol_callback,
 )
 from guiguts.maintext import maintext
 from guiguts.mainwindow import (
@@ -591,6 +592,12 @@ def init_search_menu(self) -> None:
             "Highlight S~urrounding Quotes & Brackets",
             root().highlight_quotbrac,
         )
+        menu_search.add_checkbox(
+            "Highlight Al~ignment Column",
+            root().highlight_aligncol,
+            lambda: highlight_aligncol_callback(True),
+            lambda: highlight_aligncol_callback(False),
+        )
         menu_search.add_button(
             "~Remove Highlights",
             remove_highlights,

src/guiguts/highlight.py

@@ -4,6 +4,7 @@
 
 from guiguts.maintext import maintext
 from guiguts.preferences import preferences, PrefKey
+from guiguts.root import root
 from guiguts.utilities import IndexRange
 
 
@@ -19,6 +20,7 @@ class HighlightTag(StrEnum):
     CURLY_DOUBLE_QUOTE = auto()
     STRAIGHT_SINGLE_QUOTE = auto()
     CURLY_SINGLE_QUOTE = auto()
+    ALIGNCOL = auto()
 
 
 class HighlightColors:
@@ -88,6 +90,12 @@ class HighlightColors:
         "Default": {"bg": "dodgerblue", "fg": "white"},
     }
 
+    ALIGNCOL = {
+        "Light": {"bg": "greenyellow", "fg": "black"},
+        "Dark": {"bg": "greenyellow", "fg": "black"},
+        "Default": {"bg": "greenyellow", "fg": "black"},
+    }
+
 
 def highlight_selection(
     pat: str,
@@ -433,3 +441,42 @@ def remove_highlights_quotbrac() -> None:
         HighlightTag.CURLY_SINGLE_QUOTE,
     ):
         maintext().tag_delete(tag)
+
+
+def highlight_aligncol_callback(value: bool) -> None:
+    """Callback when highlight_aligncol active state is changed."""
+    if value:
+        root().highlight_aligncol.set(True)
+        root().aligncol = maintext().get_insert_index().col
+        highlight_aligncol()
+    else:
+        root().highlight_aligncol.set(False)
+        root().aligncol = -1
+        remove_highlights_aligncol()
+
+
+def highlight_aligncol() -> None:
+    """Add a highlight to all characters in the alignment column."""
+    if root().highlight_aligncol.get() and root().aligncol:
+        (top_index, bot_index) = get_screen_window_coordinates()
+
+        col = root().aligncol
+        row = int(top_index.split(".")[0])
+        end_row = int(bot_index.split(".")[0])
+
+        maintext().tag_delete(HighlightTag.ALIGNCOL)
+        _highlight_configure_tag(HighlightTag.ALIGNCOL, HighlightColors.ALIGNCOL)
+        while row <= end_row:
+            # find length of row; don't highlight if row is too short to contain col
+            rowlen = int(maintext().index(f"{row}.0 lineend").split(".")[1])
+            if 0 < col < rowlen:
+                maintext().tag_add(HighlightTag.ALIGNCOL, f"{row}.{col}")
+            row += 1
+
+        # TODO: refactor to use on_change like quotbrac does
+        root().after(500, highlight_aligncol)
+
+
+def remove_highlights_aligncol() -> None:
+    """Remove highlights for alignment column"""
+    maintext().tag_delete(HighlightTag.ALIGNCOL)

src/guiguts/root.py

@@ -45,6 +45,8 @@ def __init__(self, **kwargs: Any) -> None:
         self.allow_config_saves = False
         self.split_text_window = PersistentBoolean(PrefKey.SPLIT_TEXT_WINDOW)
         self.highlight_quotbrac = PersistentBoolean(PrefKey.HIGHLIGHT_QUOTBRAC)
+        self.highlight_aligncol = tk.BooleanVar()
+        self.aligncol = -1
 
         self.option_add("*tearOff", preferences.get(PrefKey.TEAROFF_MENUS))
         self.rowconfigure(0, weight=1)