Change the "slow-down-camera" modifier to Alt on non-Mac (#3051)

This Fixes #1867. Setting Alt as the slowdown behaviour for the camera
movement. Note, that this also sets it to alt for wasm architecture, let
me know if you wish for an extra check for wasm (and leave it as alt).

Thanks.

### What

### Checklist
* [X] I have read and agree to [Contributor
Guide](https://github.com/rerun-io/rerun/blob/main/CONTRIBUTING.md) and
the [Code of
Conduct](https://github.com/rerun-io/rerun/blob/main/CODE_OF_CONDUCT.md)
* [X] I've included a screenshot or gif (if applicable)
* [X] I have tested [demo.rerun.io](https://demo.rerun.io/pr/{{
pr.number }}) (if applicable)

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- [Wasm size tracking](https://ref.rerun.io/dev/sizes/)

---------

Co-authored-by: hemosphere <hemosphere@proton.me>
Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>

crates/re_space_view/src/controls.rs

@@ -1,3 +1,5 @@
+use egui::{os::OperatingSystem, Modifiers};
+
 /// Modifier to press for scroll to zoom.
 pub const ZOOM_SCROLL_MODIFIER: egui::Modifiers = egui::Modifiers::COMMAND;
 
@@ -35,11 +37,19 @@ pub const ROLL_MOUSE_MODIFIER: egui::Modifiers = egui::Modifiers::ALT;
 /// Which modifier speeds up the 3D camera movement.
 pub const SPEED_UP_3D_MODIFIER: egui::Modifiers = egui::Modifiers::SHIFT;
 
-/// Which modifier slows down the 3D camera movement.
-pub const SLOW_DOWN_3D_MODIFIER: egui::Modifiers = egui::Modifiers::CTRL;
-
 /// Key to restore the camera.
 pub const TRACKED_CAMERA_RESTORE_KEY: egui::Key = egui::Key::Escape;
 
 /// Description text for which action resets a space view.
 pub const RESET_VIEW_BUTTON_TEXT: &str = "double click";
+
+pub struct RuntimeModifiers {}
+
+impl RuntimeModifiers {
+    pub fn slow_down(os: &OperatingSystem) -> Modifiers {
+        match os {
+            egui::os::OperatingSystem::Mac => egui::Modifiers::CTRL,
+            _ => egui::Modifiers::ALT,
+        }
+    }
+}

crates/re_space_view_spatial/src/eye.rs

@@ -3,8 +3,8 @@ use glam::Affine3A;
 use macaw::{vec3, BoundingBox, IsoTransform, Mat4, Quat, Vec3};
 
 use re_space_view::controls::{
-    DRAG_PAN3D_BUTTON, ROLL_MOUSE, ROLL_MOUSE_ALT, ROLL_MOUSE_MODIFIER, ROTATE3D_BUTTON,
-    SLOW_DOWN_3D_MODIFIER, SPEED_UP_3D_MODIFIER,
+    RuntimeModifiers, DRAG_PAN3D_BUTTON, ROLL_MOUSE, ROLL_MOUSE_ALT, ROLL_MOUSE_MODIFIER,
+    ROTATE3D_BUTTON, SPEED_UP_3D_MODIFIER,
 };
 
 use crate::space_camera_3d::SpaceCamera3D;
@@ -389,7 +389,10 @@ impl OrbitEye {
                 } else {
                     1.0
                 })
-                * (if input.modifiers.contains(SLOW_DOWN_3D_MODIFIER) {
+                * (if input
+                    .modifiers
+                    .contains(RuntimeModifiers::slow_down(&egui_ctx.os()))
+                {
                     0.1
                 } else {
                     1.0

crates/re_space_view_spatial/src/ui_3d.rs

@@ -10,8 +10,8 @@ use re_renderer::{
     LineStripSeriesBuilder, Size,
 };
 use re_space_view::controls::{
-    DRAG_PAN3D_BUTTON, RESET_VIEW_BUTTON_TEXT, ROLL_MOUSE, ROLL_MOUSE_ALT, ROLL_MOUSE_MODIFIER,
-    ROTATE3D_BUTTON, SLOW_DOWN_3D_MODIFIER, SPEED_UP_3D_MODIFIER, TRACKED_CAMERA_RESTORE_KEY,
+    RuntimeModifiers, DRAG_PAN3D_BUTTON, RESET_VIEW_BUTTON_TEXT, ROLL_MOUSE, ROLL_MOUSE_ALT,
+    ROLL_MOUSE_MODIFIER, ROTATE3D_BUTTON, SPEED_UP_3D_MODIFIER, TRACKED_CAMERA_RESTORE_KEY,
 };
 use re_viewer_context::{
     gpu_bridge, HoveredSpace, Item, SpaceViewSystemExecutionError, ViewContextCollection,
@@ -291,10 +291,10 @@ pub fn help_text(re_ui: &re_ui::ReUi) -> egui::WidgetText {
     layout.add_button_text("QE");
     layout.add(".\n");
 
+    layout.add(RuntimeModifiers::slow_down(&re_ui.egui_ctx.os()));
+    layout.add(" slows down, ");
     layout.add(SPEED_UP_3D_MODIFIER);
-    layout.add(" speeds up, ");
-    layout.add(SLOW_DOWN_3D_MODIFIER);
-    layout.add(" slows down.\n\n");
+    layout.add(" speeds up\n\n");
 
     layout.add_button_text("double-click");
     layout.add(" an object to focus the view on it.\n");