better Mac support (#32)

- If dark mode is enabled on your machine, you get white text on a black background, and the highlighting color should change from light to dark to match (so the highlighted token is either black text on a yellow-instead-of-white background, or white text on a grey-instead-of-black background).
- Two-finger scrolling on a touchpad uses the new-in-9.0.0 Tcl/Tk event TouchpadScroll.
- Scrolling with a mouse wheel on a Mac seems to set the `delta` to +/-120 instead of +/-1, so just take the sign before zooming by that amount.

* support dark mode when relevant

* add support for touchpad scrolling

* fix scroll-to-zoom on Mac

* tweak: pre-compute the highlight color only once

* linux uses a version of Tcl/Tk that doesn't have TouchpadScroll

* update readme to be more confident of how to install it

* tweak: make the touchpad zooming less twitchy

* tweak: in dark mode, highlight with grey, not dimgrey

* tweak: make zooming on a touchpad slightly more responsive

Author: penguinland

README.md

@@ -32,10 +32,8 @@ for Python. This might require installing something outside of your virtual
 environment: you'll know it's set up right if you can run `python3 -m tkinter`
 and get a little interactive window to pop up.
 
-- On Mac, try `brew install python-tk` to install that.
-- On Ubuntu, you might try `sudo apt-get install python3-pil.imagetk` to get
-Tcl/Tk set up correctly. I don't remember exactly what I did that finally
-worked, but that was one of the things I tried.
+- On Mac: `brew install python-tk`
+- On Ubuntu: `sudo apt-get install python3-pil.imagetk`
 
 After that, just `pip3 install -r requirements.txt`, and you should be good!
 

gui.py

@@ -1,3 +1,4 @@
+import darkdetect
 from math import ceil
 import numpy
 import numpy.typing
@@ -57,6 +58,7 @@ def __init__(
         self._lines = data.lines
         self._boundaries = data.boundaries
         self._zoom_map = zoom_map
+        self._highlight_color = "grey" if darkdetect.isDark() else "yellow"
 
     def _snip_line(self, i: int) -> str:
         """
@@ -114,7 +116,7 @@ def display(self, pixel: int) -> None:
                                     ac + self.PRELUDE_WIDTH),
                      "{}.{}".format(self.CONTEXT_COUNT + 1 + br - ar,
                                     bc + self.PRELUDE_WIDTH))
-        self.tag_config("token", background="yellow")
+        self.tag_config("token", background=self._highlight_color)
 
         # ...but don't highlight the line numbers on multi-line tokens.
         for i in range(self.CONTEXT_COUNT):

requirements.txt

@@ -4,6 +4,7 @@ code_ast==0.1.0
 code_tokenize==0.2.0
 contourpy==1.3.0
 cycler==0.12.1
+darkdetect==0.8.0
 fonttools==4.54.1
 gitdb==4.0.11
 GitPython==3.1.43

zoom_map.py

@@ -3,6 +3,7 @@
 import numpy.typing
 import PIL.Image
 import PIL.ImageTk
+import platform
 import tkinter as tk
 from typing import Optional
 
@@ -44,6 +45,11 @@ def __init__(
             # every function will be Callable: some are methods and some are
             # functools.partial objects.
             self.bind(button_name, function)  # type: ignore
+        if platform.system() == "Darwin":
+            # Macs use Tcl/Tk version 9.0.0 or later to get touchpad support,
+            # whereas (as of January 2025) Ubuntu uses Tcl/Tk version 8.6.14,
+            # which lacks this event type.
+            self.bind("<TouchpadScroll>", self._zoom_touchpad)
 
     def _set_image(self) -> None:
         """
@@ -82,11 +88,31 @@ def _set_image(self) -> None:
                                            image=self._cached_image)
 
     def _zoom_mac(self, event: tk.Event) -> None:
-        self._zoom(-event.delta, event)
+        sign = 1 if event.delta > 0 else -1
+        self._zoom(-sign, event)
+
+    _zoom_touchpad_amount: int = 0
+    def _zoom_touchpad(self, event: tk.Event) -> None:
+        # The event's delta is two 2-byte signed words packed together.
+        delta_x = (event.delta >> 16) & 0xFFFF
+        delta_y = (event.delta >>  0) & 0xFFFF
+        if delta_x >= 2 ** 15:
+            delta_x -= 2 ** 16
+        if delta_y >= 2 ** 15:
+            delta_y -= 2 ** 16
+
+        # We get lots of events about tiny movements. Sum them up and only
+        # change zoom levels if there have been a bunch all in the same
+        # direction.
+        self._zoom_touchpad_amount += delta_x + delta_y
+        if abs(self._zoom_touchpad_amount) > 20:
+            sign = 1 if self._zoom_touchpad_amount > 0 else -1
+            self._zoom_touchpad_amount = 0
+            self._zoom(-sign, event)
 
     def _zoom(self, amount: int, event: tk.Event) -> None:
         if not self._pyramid.zoom(amount):
-            return
+            return  # We're at an extreme level, and didn't actually zoom.
 
         # Otherwise, we changed zoom levels, so adjust everything accordingly.
         # We need to move the map so the pixels that started under the mouse are