Right align the left editor

TODO

@@ -1,5 +1,4 @@
 Todo:
-- Right align the left editor.
 - Keyboard shortcuts for resolving differences.
 - How to handle tabs?
 - Colourise file name.
@@ -29,6 +28,7 @@ Done:
 - Fix coast scrolling.
 - Put it on github.
 - tab key should align code.
+- Right align the left editor.
 
 
 Shelved:

diff_edit/__init__.py

@@ -128,7 +128,7 @@ def draw_connector(columns, color, left_y, right_y):
 class DiffEditor:
 
     def __init__(self, left_path, right_path):
-        self.left_editor = editor.Editor()
+        self.left_editor = editor.Editor(is_right_aligned=True)
         self.left_editor.load(left_path)
         self.left_editor.view_widget.is_scrollbar_right = False
         self.right_editor = editor.Editor()
@@ -370,6 +370,7 @@ def main():
     if path_b is None:
         editor_ = editor.Editor(path_a)
         editor_.load(path_a)
+        editor_.is_right_aligned = True
     else:
         editor_ = DiffEditor(path_a, path_b)
     asyncio.run(fill3.tui(PROJECT_NAME, editor_))

diff_edit/editor.py

@@ -184,7 +184,7 @@ class Editor:
     THEMES = [pygments.styles.get_style_by_name(style)
               for style in ["monokai", "fruity", "native"]] + [None]
 
-    def __init__(self, text="", path="Untitled"):
+    def __init__(self, text="", path="Untitled", is_right_aligned=False):
         self.path = os.path.normpath(path)
         self.set_text(text)
         self.mark = None
@@ -195,6 +195,7 @@ class Editor:
         self.theme_index = 0
         self.previous_term_code = None
         self.history = []
+        self.is_right_aligned = is_right_aligned
 
     @property
     def cursor_x(self):
@@ -626,6 +627,13 @@ class Editor:
 
     def appearance_for(self, dimensions):
         width, height = dimensions
+        text_width = self.text_widget.max_line_length
+        if self.is_right_aligned and text_width < width:
+            x, y = self.view_widget.position
+            new_x = text_width - width
+            if self.cursor_x == text_width:
+                new_x += 1
+            self.view_widget.position = new_x, y
         is_changed = self.text_widget.actual_text != self.original_text
         header = self.get_header(self.path, width, self.cursor_x, self.cursor_y, is_changed)
         self.last_width = width

setup.py

@@ -18,4 +18,4 @@ setup(name="diff-edit",
       entry_points={"console_scripts": ["diff-edit=diff_edit:main"]},
       install_requires=[
           "pygments==2.10.0", "docopt==0.6.2",
-          "fill3 @ git+https://github.com/ahamilton/eris@v2022.01.18#subdirectory=fill3"])
+          "fill3 @ git+https://github.com/ahamilton/eris@v2022.01.21#subdirectory=fill3"])