outputs: Pass output updates

Introduce a callback in `outputs::Outputs` that calls on every `wl_output.done`, and a dummy consumer in `ui_manager`.

This is sufficient to detect display height changes.

src/outputs.rs

@@ -1,5 +1,10 @@
+/* Copyright (C) 2019-2020 Purism SPC
+ * SPDX-License-Identifier: GPL-3.0+
+ */
+
 /*! Managing Wayland outputs */
 
+use std::cell::RefCell;
 use std::vec::Vec;
 use ::logging;
 
@@ -103,7 +108,7 @@ pub mod c {
         ) -> i32;
     }
 
-    type COutputs = ::util::c::Wrapped<Outputs>;
+    pub type COutputs = ::util::c::Wrapped<Outputs>;
 
     /// A stable reference to an output.
     #[derive(Clone)]
@@ -202,11 +207,12 @@ pub mod c {
     }
 
     extern fn outputs_handle_done(
-        outputs: COutputs,
+        outputs_raw: COutputs,
         wl_output: WlOutput,
     ) {
-        let outputs = outputs.clone_ref();
+        let outputs = outputs_raw.clone_ref();
-        let mut collection = outputs.borrow_mut();
+        {
+            let mut collection = RefCell::borrow_mut(&outputs);
             let output = find_output_mut(&mut collection, wl_output);
             match output {
                 Some(output) => { output.current = output.pending.clone(); }
@@ -216,6 +222,13 @@ pub mod c {
                 ),
             };
         }
+        let collection = RefCell::borrow(&outputs);
+        if let Some(ref cb) = &collection.update_cb {
+            let mut cb = RefCell::borrow_mut(cb);
+            let cb = Box::as_mut(&mut cb);
+            cb(OutputHandle { wl_output, outputs: outputs_raw });
+        }
+    }
 
     extern fn outputs_handle_scale(
         outputs: COutputs,
@@ -239,7 +252,10 @@ pub mod c {
     #[no_mangle]
     pub extern "C"
     fn squeek_outputs_new() -> COutputs {
-        COutputs::new(Outputs { outputs: Vec::new() })
+        COutputs::new(Outputs {
+            outputs: Vec::new(),
+            update_cb: None,
+        })
     }
 
     #[no_mangle]
@@ -308,7 +324,7 @@ pub mod c {
 }
 
 /// Generic size
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 pub struct Size {
     pub width: u32,
     pub height: u32,
@@ -413,6 +429,38 @@ pub struct Output {
     current: OutputState,
 }
 
+/// The manager of all outputs.
+// This is the target of several callbacks,
+// so it should only be used with a stable place in memory, like `Rc<RefCell>`.
+// It should not be instantiated externally or copied,
+// or it will not receive those callbacks and be somewhat of an empty shell.
+// It should be safe to use as long as the fields are not `pub`,
+// and there's no `Clone`, and this module's API only ever gives out
+// references wrapped in `Rc<RefCell>`.
+// For perfectness, it would only ever give out immutable opaque references,
+// but that's not practical at the moment.
+// `mem::swap` could replace the value inside,
+// but as long as the swap is atomic,
+// that should not cause an inconsistent state.
 pub struct Outputs {
     outputs: Vec<Output>,
+    // The RefCell is here to let the function be called
+    // while holding only a read-reference to `Outputs`.
+    // Otherwise anything trying to get useful data from OutputHandle
+    // will fail to acquire reference to Outputs.
+    // TODO: Maybe pass only current state along with Outputs and Output hash.
+    // The only reason a full OutputHandle is here
+    // is to be able to track the right Output.
+    update_cb: Option<RefCell<Box<dyn FnMut(c::OutputHandle)>>>,
+}
+
+impl Outputs {
+    /// The function will get called whenever
+    /// any output changes or is removed or created.
+    /// If output handle doesn't return state, the output just went down.
+    /// It cannot modify anything in Outputs.
+    // FIXME: handle output destruction
+    pub fn set_update_cb(&mut self, callback: Box<dyn FnMut(c::OutputHandle)>) {
+        self.update_cb = Some(RefCell::new(callback));
+    }
 }

src/server-main.c

@@ -203,7 +203,7 @@ main (int argc, char **argv)
         g_warning("Wayland input method interface not available");
     }
 
-    instance.ui_manager = squeek_uiman_new();
+    instance.ui_manager = squeek_uiman_new(instance.wayland.outputs);
 
     instance.settings_context = eekboard_context_service_new(&instance.layout_choice);
 

src/ui_manager.h

@@ -7,7 +7,7 @@
 
 struct ui_manager;
 
-struct ui_manager *squeek_uiman_new();
+struct ui_manager *squeek_uiman_new(struct squeek_outputs *outputs);
 void squeek_uiman_set_output(struct ui_manager *uiman, struct squeek_output_handle output);
 uint32_t squeek_uiman_get_perceptual_height(struct ui_manager *uiman);
 

src/ui_manager.rs

@@ -7,20 +7,30 @@
  * Coordinates this based on information collated from all possible sources.
  */
 
+use std::cell::RefCell;
 use std::cmp::min;
+use std::rc::Rc;
 
 use ::logging;
-use ::outputs::OutputState;
+use ::outputs::{ Outputs, OutputState};
 use ::outputs::c::OutputHandle;
 
 mod c {
     use super::*;
+    use ::outputs::c::COutputs;
     use ::util::c::Wrapped;
 
     #[no_mangle]
     pub extern "C"
-    fn squeek_uiman_new() -> Wrapped<Manager> {
+    fn squeek_uiman_new(outputs: COutputs) -> Wrapped<Manager> {
-        Wrapped::new(Manager { output: None })
+        let uiman_raw = Wrapped::new(Manager { output: None });
+        if !outputs.is_null() {
+            let uiman = uiman_raw.clone_ref();
+            let outputs = outputs.clone_ref();
+            let mut outputs = outputs.borrow_mut();
+            register_output_man(uiman, &mut outputs);
+        }
+        uiman_raw
     }
 
     /// Used to size the layer surface containing all the OSK widgets.
@@ -43,7 +53,7 @@ mod c {
     ) {
         let uiman = uiman.clone_ref();
         let mut uiman = uiman.borrow_mut();
-        uiman.output = Some(output);
+        uiman.set_output(output)
     }
 }
 
@@ -123,4 +133,30 @@ impl Manager {
             None => None,
         }
     }
+    
+    fn set_output(&mut self, output: OutputHandle) {
+        self.output = Some(output);
+    }
+
+    fn handle_output_change(&mut self, output: OutputHandle) {
+        match output.get_state() {
+            Some(os) => {
+                println!("{:?}", os.get_pixel_size());
+            }
+            None => {
+                println!("gone");
+            }
+        }
+    }
+}
+
+fn register_output_man(
+    ui_man: Rc<RefCell<Manager>>,
+    output_man: &mut Outputs,
+) {
+    let ui_man = ui_man.clone();
+    output_man.set_update_cb(Box::new(move |output: OutputHandle| {
+        let mut ui_man = ui_man.borrow_mut();
+        ui_man.handle_output_change(output)
+    }))
 }

src/util.rs

@@ -94,6 +94,7 @@ pub mod c {
         }
         /// Extracts the reference to the data.
         /// It may cause problems if attempted in more than one place
+        // FIXME: check for null
         pub unsafe fn unwrap(self) -> Rc<RefCell<T>> {
             Rc::from_raw(self.0)
         }
@@ -107,6 +108,10 @@ pub mod c {
             Rc::into_raw(used_rc); // prevent dropping the original reference
             rc
         }
+
+        pub fn is_null(&self) -> bool {
+            self.0.is_null()
+        }
     }
     
     impl<T> Clone for Wrapped<T> {