Add touch pressure information for touch events on iOS (#1090)

* Add touch pressure information for touch events on iOS

* Add a variant for calibrated touch pressure

src/platform_impl/ios/ffi.rs

@@ -70,6 +70,24 @@ pub enum UITouchPhase {
     Cancelled,
 }
 
+#[derive(Debug, PartialEq)]
+#[allow(dead_code)]
+#[repr(isize)]
+pub enum UIForceTouchCapability {
+    Unknown = 0,
+    Unavailable,
+    Available,
+}
+
+#[derive(Debug, PartialEq)]
+#[allow(dead_code)]
+#[repr(isize)]
+pub enum UITouchType {
+    Direct = 0,
+    Indirect,
+    Pencil,
+}
+
 #[repr(C)]
 #[derive(Debug, Clone)]
 pub struct UIEdgeInsets {

src/platform_impl/ios/view.rs

@@ -6,13 +6,14 @@ use objc::{
 };
 
 use crate::{
-    event::{DeviceId as RootDeviceId, Event, Touch, TouchPhase, WindowEvent},
+    event::{DeviceId as RootDeviceId, Event, Force, Touch, TouchPhase, WindowEvent},
     platform::ios::MonitorHandleExtIOS,
     platform_impl::platform::{
         app_state::AppState,
         event_loop,
         ffi::{
-            id, nil, CGFloat, CGPoint, CGRect, UIInterfaceOrientationMask, UIRectEdge, UITouchPhase,
+            id, nil, CGFloat, CGPoint, CGRect, UIForceTouchCapability, UIInterfaceOrientationMask,
+            UIRectEdge, UITouchPhase, UITouchType,
         },
         window::PlatformSpecificWindowBuilderAttributes,
         DeviceId,
@@ -218,6 +219,27 @@ unsafe fn get_window_class() -> &'static Class {
                         break;
                     }
                     let location: CGPoint = msg_send![touch, locationInView: nil];
+                    let touch_type: UITouchType = msg_send![touch, type];
+                    let trait_collection: id = msg_send![object, traitCollection];
+                    let touch_capability: UIForceTouchCapability =
+                        msg_send![trait_collection, forceTouchCapability];
+                    let force = if touch_capability == UIForceTouchCapability::Available {
+                        let force: CGFloat = msg_send![touch, force];
+                        let max_possible_force: CGFloat = msg_send![touch, maximumPossibleForce];
+                        let altitude_angle: Option<f64> = if touch_type == UITouchType::Pencil {
+                            let angle: CGFloat = msg_send![touch, altitudeAngle];
+                            Some(angle as _)
+                        } else {
+                            None
+                        };
+                        Some(Force::Calibrated {
+                            force: force as _,
+                            max_possible_force: max_possible_force as _,
+                            altitude_angle,
+                        })
+                    } else {
+                        None
+                    };
                     let touch_id = touch as u64;
                     let phase: UITouchPhase = msg_send![touch, phase];
                     let phase = match phase {
@@ -235,6 +257,7 @@ unsafe fn get_window_class() -> &'static Class {
                             device_id: RootDeviceId(DeviceId { uiscreen }),
                             id: touch_id,
                             location: (location.x as f64, location.y as f64).into(),
+                            force,
                             phase,
                         }),
                     });