Use class Caption(urwid.Text) to represent the header.

`Caption` will handle the display of header's content, including the
current source filename

Author: qhuy4119

pudb/debugger.py

@@ -858,7 +858,8 @@ def helpside(w, size, key):
                         ],
                     dividechars=1)
 
-        self.caption = urwid.Text("")
+        from pudb.ui_tools import Caption
+        self.caption = Caption("")
         header = urwid.AttrMap(self.caption, "header")
         self.top = SignalWrap(urwid.Frame(
             urwid.AttrMap(self.columns, "background"),
@@ -2618,37 +2619,31 @@ def interaction(self, exc_tuple, show_exc_dialog=True):
 
         from pudb import VERSION
         separator = " - "
-        info_string = separator.join(["PuDB %s" % VERSION, "?:help"])
-
-        def get_source_filename():
-            available_width = self.screen.get_cols_rows(
-            )[0] - (len(info_string) + len(separator))
-            full_filename = self.source_code_provider.get_source_identifier()
-            if (full_filename is None):
-                return "Source filename not available"
-            elif available_width > len(full_filename):
-                return full_filename
-            else:
-                trim_index = len(full_filename) - available_width
-                filename = full_filename[trim_index:]
-                first_dirname_index = filename.find(os.sep)
-                filename = filename[first_dirname_index + 1:]
-                return filename
-
-        caption = [(None, separator.join([info_string, get_source_filename()]))]
+        pudb_version = "PuDB %s" % VERSION
+        hotkey = "?:help"
+        if self.source_code_provider.get_source_identifier():
+            source_filename = self.source_code_provider.get_source_identifier()
+        else:
+            source_filename = "source filename is unavailable"
+        caption = [(None, pudb_version),
+                (None, separator),
+                (None, hotkey),
+                (None, separator),
+                (None, source_filename)
+                ]
 
         if self.debugger.post_mortem:
             if show_exc_dialog and exc_tuple is not None:
                 self.show_exception_dialog(exc_tuple)
 
             caption.extend([
-                (None, " "),
+                (None, separator),
                 ("warning", "[POST-MORTEM MODE]")
                 ])
         elif exc_tuple is not None:
             caption.extend([
-                (None, " "),
-                ("warning", "[PROCESSING EXCEPTION - hit 'e' to examine]")
+                (None, separator),
+                ("warning", "[PROCESSING EXCEPTION, hit 'e' to examine]")
                 ])
 
         self.caption.set_text(caption)

pudb/ui_tools.py

@@ -332,4 +332,61 @@ def keypress(self, size, key):
 
         return result
 
+
+class Caption(urwid.Text):
+    def __init__(self, markup, separator=" - "):
+        self.separator = separator
+        super().__init__(markup)
+
+    def set_text(self, markup):
+        super().set_text(markup)
+        if len(markup) > 0:
+            # Assume the format of caption is:
+            # <PuDB version> <hotkey> <source filename> [optional_alert]
+            caption, _ = self.get_text()
+            caption_elements = caption.split(self.separator)
+            self.pudb_version = caption_elements[0]
+            self.hotkey = caption_elements[1]
+            self.full_source_filename = caption_elements[2]
+            self.optional_alert = caption_elements[3] if len(
+                caption_elements) > 3 else ""
+        else:
+            self.pudb_version = self.hotkey = ""
+            self.full_source_filename = self.optional_alert = ""
+
+    def rows(self, size, focus=False):
+        # Always return 1 to avoid
+        # `assert head.rows() == hrows, "rows, render mismatch")`
+        # in urwid.Frame.render() in urwid/container.py
+        return 1
+
+    def render(self, size, focus=False):
+        maxcol = size[0]
+        if super().rows(size) > 1:
+            filename = self.get_shortened_source_filename(size)
+        else:
+            filename = self.full_source_filename
+        caption = self.separator.join(
+            [self.pudb_version, self.hotkey, filename, self.optional_alert]
+            ).strip(self.separator)
+        if self.optional_alert:
+            attr = [("warning", len(caption))]
+        else:
+            attr = [(None, 0)]
+
+        return make_canvas([caption], [attr], maxcol)
+
+    def get_shortened_source_filename(self, size):
+        import os
+        maxcol = size[0]
+
+        occupied_width = (len(self.pudb_version) + len(self.hotkey)
+                          + len(self.optional_alert) + len(self.separator)*3)
+        available_width = maxcol - occupied_width
+        trim_index = len(self.full_source_filename) - available_width
+        filename = self.full_source_filename[trim_index:]
+        first_dirname_index = filename.find(os.sep)
+        filename = filename[first_dirname_index + 1:]
+
+        return filename
 # }}}