presses: Move press handling to Rust

This fixes some rendering things which would happen with multiple state-sharing buttons. It also removes some interfaces exposing rows, views, layouts, and buttons, bringing the code closer to removing them from the FFI entirely.

src/submission.rs

@@ -0,0 +1,68 @@
+/*! Managing the events belonging to virtual-keyboard interface. */
+
+use ::keyboard::{ KeyState, PressType };
+
+/// Gathers stuff defined in C or called by C
+pub mod c {
+    use std::os::raw::c_void;
+
+    #[repr(transparent)]
+    #[derive(Clone, Copy)]
+    pub struct ZwpVirtualKeyboardV1(*const c_void);
+
+    #[no_mangle]
+    extern "C" {
+        /// Checks if point falls within bounds,
+        /// which are relative to origin and rotated by angle (I think)
+        pub fn eek_virtual_keyboard_v1_key(
+            virtual_keyboard: ZwpVirtualKeyboardV1,
+            timestamp: u32,
+            keycode: u32,
+            press: u32,
+        );
+    }
+}
+
+pub struct Timestamp(pub u32);
+
+/// Layout-independent backend. TODO: Have one instance per program or seat
+pub struct VirtualKeyboard(pub c::ZwpVirtualKeyboardV1);
+
+impl VirtualKeyboard {
+    // TODO: split out keyboard state management
+    pub fn switch(
+        &self,
+        key: &mut KeyState,
+        action: PressType,
+        timestamp: Timestamp,
+    ) {
+        key.pressed = action.clone();
+
+        let keycodes_count = key.keycodes.len();
+        for keycode in key.keycodes.iter() {
+            let keycode = keycode - 8;
+            match (&key.pressed, keycodes_count) {
+                // Pressing a key made out of a single keycode is simple:
+                // press on press, release on release.
+                (_, 1) => unsafe {
+                    c::eek_virtual_keyboard_v1_key(
+                        self.0, timestamp.0, keycode, action.clone() as u32
+                    );
+                },
+                // A key made of multiple keycodes
+                // has to submit them one after the other
+                (PressType::Pressed, _) => unsafe {
+                    c::eek_virtual_keyboard_v1_key(
+                        self.0, timestamp.0, keycode, PressType::Pressed as u32
+                    );
+                    c::eek_virtual_keyboard_v1_key(
+                        self.0, timestamp.0, keycode, PressType::Released as u32
+                    );
+                },
+                // Design choice here: submit multiple all at press time
+                // and do nothing at release time
+                (PressType::Released, _) => {},
+            }
+        }
+    }
+}