Scroll sensitivity

CHANGELOG.md

@@ -11,6 +11,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 - Added the coroutines `Animator.wait_until_complete` and `pilot.wait_for_scheduled_animations` that allow waiting for all current and scheduled animations https://github.com/Textualize/textual/issues/1658
 - Added the method `Animator.is_being_animated` that checks if an attribute of an object is being animated or is scheduled for animation
+- Added App.scroll_sensitivity_x and App.scroll_sensitivity_y to adjust how many lines the scroll wheel moves the scroll position https://github.com/Textualize/textual/issues/928
+- Added Shift+scroll wheel and ctrl+scroll wheel to scroll horizontally
 
 ### Changed
 

src/textual/app.py

@@ -370,6 +370,13 @@ def __init__(
         self.css_path = css_paths
         self._registry: WeakSet[DOMNode] = WeakSet()
 
+        # Sensitivity on X is double the sensitivity on Y to account for
+        # cells being twice as tall as wide
+        self.scroll_sensitivity_x: float = 4.0
+        """Number of columns to scroll in the X direction with wheel or trackpad."""
+        self.scroll_sensitivity_y: float = 2.0
+        """Number of lines to scroll in the Y direction with wheel or trackpad."""
+
         self._installed_screens: WeakValueDictionary[
             str, Screen | Callable[[], Screen]
         ] = WeakValueDictionary()

src/textual/widget.py

@@ -1577,7 +1577,7 @@ def scroll_left(
 
         """
         return self.scroll_to(
-            x=self.scroll_target_x - 1,
+            x=self.scroll_target_x - self.app.scroll_sensitivity_x,
             animate=animate,
             speed=speed,
             duration=duration,
@@ -1609,7 +1609,7 @@ def scroll_right(
 
         """
         return self.scroll_to(
-            x=self.scroll_target_x + 1,
+            x=self.scroll_target_x + self.app.scroll_sensitivity_x,
             animate=animate,
             speed=speed,
             duration=duration,
@@ -1641,7 +1641,7 @@ def scroll_down(
 
         """
         return self.scroll_to(
-            y=self.scroll_target_y + 1,
+            y=self.scroll_target_y + self.app.scroll_sensitivity_y,
             animate=animate,
             speed=speed,
             duration=duration,
@@ -1673,7 +1673,7 @@ def scroll_up(
 
         """
         return self.scroll_to(
-            y=self.scroll_target_y - 1,
+            y=self.scroll_target_y - +self.app.scroll_sensitivity_y,
             animate=animate,
             speed=speed,
             duration=duration,
@@ -2480,15 +2480,25 @@ def _on_descendant_focus(self, event: events.DescendantBlur) -> None:
         if self._has_focus_within:
             self.app.update_styles(self)
 
-    def _on_mouse_scroll_down(self, event) -> None:
-        if self.allow_vertical_scroll:
-            if self.scroll_down(animate=False):
-                event.stop()
-
-    def _on_mouse_scroll_up(self, event) -> None:
-        if self.allow_vertical_scroll:
-            if self.scroll_up(animate=False):
-                event.stop()
+    def _on_mouse_scroll_down(self, event: events.MouseScrollDown) -> None:
+        if event.ctrl or event.shift:
+            if self.allow_horizontal_scroll:
+                if self.scroll_right(animate=False):
+                    event.stop()
+        else:
+            if self.allow_vertical_scroll:
+                if self.scroll_down(animate=False):
+                    event.stop()
+
+    def _on_mouse_scroll_up(self, event: events.MouseScrollUp) -> None:
+        if event.ctrl or event.shift:
+            if self.allow_horizontal_scroll:
+                if self.scroll_left(animate=False):
+                    event.stop()
+        else:
+            if self.allow_vertical_scroll:
+                if self.scroll_up(animate=False):
+                    event.stop()
 
     def _on_scroll_to(self, message: ScrollTo) -> None:
         if self._allow_scroll: