detect multiple touch inputs

crates/rnote-ui/src/canvas/input.rs

@@ -1,5 +1,6 @@
 // Imports
 use super::RnCanvas;
+use adw::glib::subclass::types::ObjectSubclassIsExt;
 use gtk4::{gdk, glib, graphene, prelude::*, Native};
 use rnote_compose::penevent::{KeyboardKey, ModifierKey, PenEvent, PenState, ShortcutKey};
 use rnote_compose::penpath::Element;
@@ -28,7 +29,7 @@ pub(crate) fn handle_pointer_controller_event(
     //std::thread::sleep(std::time::Duration::from_millis(100));
     //super::input::debug_gdk_event(event);
 
-    if reject_pointer_input(event, touch_drawing) {
+    if reject_pointer_input(event, touch_drawing, canvas) {
         return (glib::Propagation::Proceed, pen_state);
     }
 
@@ -294,10 +295,34 @@ fn debug_gdk_event(event: &gdk::Event) {
 }
 
 /// Returns true if input should be rejected
-fn reject_pointer_input(event: &gdk::Event, touch_drawing: bool) -> bool {
+fn reject_pointer_input(event: &gdk::Event, touch_drawing: bool, canvas: &RnCanvas) -> bool {
     if touch_drawing {
-        if event.device().unwrap().num_touches() > 1 {
-            return true;
+        let sequence = event.event_sequence().as_ptr() as usize;
+        let event_type = event.event_type();
+        let status_tid = canvas.imp().touch_id.get();
+
+        match event_type {
+            gdk::EventType::TouchBegin => {
+                if status_tid.is_none() {
+                    canvas.imp().touch_id.set(Some(sequence));
+                    return false;
+                } else {
+                    return true;
+                }
+            }
+            gdk::EventType::TouchUpdate => {
+                return Some(sequence) != status_tid;
+                // reject if the sequence is not the same as the one in store
+            }
+            gdk::EventType::TouchEnd | gdk::EventType::TouchCancel => {
+                if Some(sequence) == status_tid {
+                    canvas.imp().touch_id.set(None);
+                    return false;
+                } else {
+                    return false;
+                }
+            }
+            _ => return false,
         }
     } else {
         let event_type = event.event_type();

crates/rnote-ui/src/canvas/mod.rs

@@ -15,7 +15,7 @@ use gettextrs::gettext;
 use gtk4::{
     gdk, gio, glib, glib::clone, graphene, prelude::*, subclass::prelude::*, Adjustment,
     DropTarget, EventControllerKey, EventControllerLegacy, IMMulticontext, PropagationPhase,
-    Scrollable, ScrollablePolicy, Widget,
+    Scrollable, ScrollablePolicy, Widget
 };
 use notify_debouncer_full::notify::{self, Watcher};
 use once_cell::sync::Lazy;
@@ -80,6 +80,7 @@ mod imp {
         pub(crate) unsaved_changes: Cell<bool>,
         pub(crate) empty: Cell<bool>,
         pub(crate) touch_drawing: Cell<bool>,
+        pub(crate) touch_id: Cell<Option<usize>>, // we need to extract the memory value ...
         pub(crate) show_drawing_cursor: Cell<bool>,
 
         pub(crate) last_export_dir: RefCell<Option<gio::File>>,
@@ -174,6 +175,7 @@ mod imp {
                 unsaved_changes: Cell::new(false),
                 empty: Cell::new(true),
                 touch_drawing: Cell::new(false),
+                touch_id: Cell::new(None),
                 show_drawing_cursor: Cell::new(false),
 
                 last_export_dir: RefCell::new(None),