Add per-axis scroll speed config for input devices (#2109)

* Add per-axis scroll speed config for input devices.

Accepts negative values to inverse scroll direction.

Properly complements/overrides global `scroll-direction` setting.

Includes docs and tests.

* Update per-axis scroll factor implementation after testing

- Refined configuration structure in niri-config
- Updated input handling to use per-axis scroll factors
- Added comprehensive test snapshots
- Updated documentation with per-axis examples

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

* Simplify per-axis scroll factor implementation per review feedback

- Make documentation concise and clear
- Remove unnecessary comments and test helper functions
- Use inline snapshots for tests
- Rename get_factors() to h_v_factors() for clarity
- Remove unnecessary .clone() calls (ScrollFactor is Copy)
- Reduce test count to essential cases only
- Fix comment about window factor override behavior

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

* Remove unnecessary ScrollFactor::new() helper function

The maintainer prefers minimal code, so removing this helper and
constructing ScrollFactor directly in tests.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

* Fix scroll factor behavior - all settings now multiply with window factor

Per maintainer feedback, both combined and per-axis scroll settings
should multiply with the window-specific scroll factor, not override it.
This ensures consistent behavior regardless of configuration method.

Also removed the now-unused has_per_axis_override() method.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

* Final cleanup: remove redundant comments and unused snapshot files

- Removed unused snapshot files (now using inline snapshots)
- Removed redundant inline comments in tests
- Simplified test descriptions to be more concise

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

* Convert scroll factor parsing tests to use assert_debug_snapshot

Updates parse_scroll_factor_combined, parse_scroll_factor_split, and
parse_scroll_factor_partial tests to use assert_debug_snapshot instead
of manual assert_eq comparisons, as requested in PR review.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

* Convert to inline snapshots as requested

- Convert all scroll factor parsing tests to use inline snapshots instead of external files
- Remove external snapshot files to keep test directory clean
- All tests still pass with inline snapshot assertions

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

* Fix missed assert_eq in parse_scroll_factor_mixed test

Converts the remaining assert_eq calls to assert_debug_snapshot
with inline snapshots in the mixed syntax test function.
Also fixes raw string delimiters from ### to #.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

* Convert scroll_factor_h_v_factors test to use assert_debug_snapshot

Makes all scroll factor tests consistent by using snapshots instead
of assert_eq for better maintainability.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

* fixes

---------

Co-authored-by: Bernardo Kuri <github@bkuri.com>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Ivan Molodetskikh <yalterz@gmail.com>

1 files changed, 24 insertions, 11 deletions

diff --git a/src/input/mod.rs b/src/input/mod.rs
index c2667dfc..cc07aed3 100644
--- a/src/input/mod.rs
+++ b/src/input/mod.rs
@@ -3086,31 +3086,44 @@ impl State {
 
         self.update_pointer_contents();
 
-        let scroll_factor = match source {
-            AxisSource::Wheel => self.niri.config.borrow().input.mouse.scroll_factor,
-            AxisSource::Finger => self.niri.config.borrow().input.touchpad.scroll_factor,
-            _ => None,
+        let device_scroll_factor = {
+            let config = self.niri.config.borrow();
+            match source {
+                AxisSource::Wheel => config.input.mouse.scroll_factor,
+                AxisSource::Finger => config.input.touchpad.scroll_factor,
+                _ => None,
+            }
         };
-        let scroll_factor = scroll_factor.map(|x| x.0).unwrap_or(1.);
 
+        // Get window-specific scroll factor
         let window_scroll_factor = pointer
             .current_focus()
             .map(|focused| self.niri.find_root_shell_surface(&focused))
             .and_then(|root| self.niri.layout.find_window_and_output(&root).unzip().0)
-            .and_then(|window| window.rules().scroll_factor);
-        let scroll_factor = scroll_factor * window_scroll_factor.unwrap_or(1.);
+            .and_then(|window| window.rules().scroll_factor)
+            .unwrap_or(1.);
+
+        // Determine final scroll factors based on configuration
+        let (horizontal_factor, vertical_factor) = device_scroll_factor
+            .map(|x| x.h_v_factors())
+            .unwrap_or((1.0, 1.0));
+        let (horizontal_factor, vertical_factor) = (
+            horizontal_factor * window_scroll_factor,
+            vertical_factor * window_scroll_factor,
+        );
 
         let horizontal_amount = horizontal_amount.unwrap_or_else(|| {
             // Winit backend, discrete scrolling.
             horizontal_amount_v120.unwrap_or(0.0) / 120. * 15.
-        }) * scroll_factor;
+        }) * horizontal_factor;
+
         let vertical_amount = vertical_amount.unwrap_or_else(|| {
             // Winit backend, discrete scrolling.
             vertical_amount_v120.unwrap_or(0.0) / 120. * 15.
-        }) * scroll_factor;
+        }) * vertical_factor;
 
-        let horizontal_amount_v120 = horizontal_amount_v120.map(|x| x * scroll_factor);
-        let vertical_amount_v120 = vertical_amount_v120.map(|x| x * scroll_factor);
+        let horizontal_amount_v120 = horizontal_amount_v120.map(|x| x * horizontal_factor);
+        let vertical_amount_v120 = vertical_amount_v120.map(|x| x * vertical_factor);
 
         let mut frame = AxisFrame::new(event.time_msec()).source(source);
         if horizontal_amount != 0.0 {