add follow tail feature

src/ui/ScaledScrollBar.py

@@ -18,6 +18,9 @@ class ScaledScrollBar(QScrollBar):
         code involved. We work around this by converting the python int 
         into a string."""
 
+    scrolled_to_end = Signal(bool)
+    """Signal emitted when the scroll bar value is set."""
+
     def __init__(self):
         super(ScaledScrollBar, self).__init__()
         self.real_maximum = self.maximum()
@@ -46,6 +49,7 @@ class ScaledScrollBar(QScrollBar):
             super().setMaximum(maximum)
 
     def _valueChanged(self, value: int):
+        self.scrolled_to_end.emit(value == self.maximum() and value > 0)
         if self.is_huge:
             real_value = (value / self.maximum()) * self.real_maximum
             # print("scaled value changed: %d -> %d (%f)" % (value, real_value, value / self.maximum()))

src/ui/bigtext/bigtext.py

@@ -66,10 +66,6 @@ class BigText(QWidget):
 
         self.model = model
 
-        self.watchdog = FileWatchdogThread(self, model.get_file())
-        QThreadPool.globalInstance().start(self.watchdog)
-        self.trigger_update.connect(self.update)
-
         self.grid = QGridLayout()
         self.grid.setContentsMargins(0, 0, 0, 0)
         self.grid.setHorizontalSpacing(0)
@@ -87,11 +83,16 @@ class BigText(QWidget):
         self.v_scroll_bar = ScaledScrollBar()
         # self.v_scroll_bar.setPageStep(1)
         self.v_scroll_bar.scaledValueChanged.connect(self.big_text.v_scroll_event)
+        self.v_scroll_bar.scrolled_to_end.connect(self.big_text.v_scroll_update_follow_tail)
 
         self.grid.addWidget(self.big_text, 0, 0)
         self.grid.addWidget(self.h_scroll_bar, 1, 0)
         self.grid.addWidget(self.v_scroll_bar, 0, 1)
 
+        self.watchdog = FileWatchdogThread(self, model.get_file())
+        QThreadPool.globalInstance().start(self.watchdog)
+        self.trigger_update.connect(self.big_text._file_changed)
+
     def get_file(self):
         return self.model.get_file()
 
@@ -137,6 +138,8 @@ class InnerBigText(QWidget):
         self._last_double_click_time = 0
         self._last_double_click_line_number = -1
 
+        self._follow_tail = False
+
         self.highlight_selected_text = HighlightRegex(
             "",
             is_regex=False,
@@ -306,6 +309,10 @@ class InnerBigText(QWidget):
         self._byte_offset = int(byte_offset)
         self.update()
 
+    @Slot()
+    def v_scroll_update_follow_tail(self, scrolled_to_end: bool):
+        self._follow_tail = scrolled_to_end
+
     def update_longest_line(self, length: int):
         width_in_chars = self.width() / self.char_width
         # print("width_in_chars: %d" % width_in_chars)
@@ -369,7 +376,6 @@ class InnerBigText(QWidget):
 
                 if you_sure.clickedButton() != copy_btn:
                     # abort
-                    print("abort")
                     return
 
             selected_text = self.model.read_range(start, end)
@@ -409,7 +415,14 @@ class InnerBigText(QWidget):
 
         self.highlight_selected_text.set_query("")
 
+    def _file_changed(self):
+        if self._follow_tail:
+            self.scroll_to_byte(self.model.byte_count())
+        self.update()
+
     def paintEvent(self, event: QPaintEvent) -> None:
+        start_ns = time.process_time_ns()
+        print(f"paint {self.model.get_file()} at {self._byte_offset} with follow_tail={self._follow_tail}")
         painter = QPainter(self)
         # font = "Courier New" if sys.platform == 'win32' or sys.platform == 'cygwin' else "Monospace"
         painter.setFont(QFont("Courier New", self.model.settings.getint_session('general', "font_size")))
@@ -458,6 +471,8 @@ class InnerBigText(QWidget):
             y_line_offset = y_line_offset + self.char_height
 
         painter.end()
+        end_ns = time.process_time_ns()
+        print(f"paint took {(end_ns - start_ns) / 1000000.0}")
 
     def draw_highlights(self, highlights: [HighlightedRange], painter: QPainter, y_line_offset: int):