Do a better job at finding a crtc in the example

examples/drm.rs

@@ -16,12 +16,10 @@ mod helpers;
 
 use drm::control::{Device as ControlDevice, ResourceInfo};
 use drm::control::connector::{Info as ConnectorInfo, State as ConnectorState};
-
+use drm::control::encoder::Info as EncoderInfo;
 use glium::Surface;
-
 use helpers::GliumDrawer;
 use slog::*;
-
 use smithay::backend::drm::{DrmBackend, DrmDevice, DrmHandler, Id};
 use smithay::backend::graphics::egl::EGLGraphicsBackend;
 use smithay::backend::graphics::glium::{GliumGraphicsBackend, IntoGlium};
@@ -30,14 +28,11 @@ use smithay::compositor::roles::Role;
 use smithay::shell::{self, PopupConfigure, PopupSurface, ShellClient, ShellHandler, ShellSurfaceRole,
                      ToplevelConfigure, ToplevelSurface};
 use smithay::shm::{ShmGlobal, ShmToken};
-
 use std::fs::OpenOptions;
 use std::io::Error as IoError;
 use std::os::unix::io::AsRawFd;
 use std::time::Duration;
-
 use wayland_protocols::unstable::xdg_shell::server::{zxdg_shell_v6, zxdg_toplevel_v6};
-
 use wayland_server::{Client, EventLoopHandle};
 use wayland_server::protocol::{wl_callback, wl_compositor, wl_output, wl_seat, wl_shell, wl_shm,
                                wl_subcompositor, wl_surface};
@@ -204,8 +199,17 @@ fn main() {
         .find(|conn| conn.connection_state() == ConnectorState::Connected)
         .unwrap();
 
-    // Use the first crtc (should be successful in most cases)
+    // Use the first encoder
-    let crtc = res_handles.crtcs()[0];
+    let encoder_info = EncoderInfo::load_from_device(&device, connector_info.encoders()[0]).unwrap();
+
+    // use the connected crtc if any
+    let crtc = encoder_info.current_crtc()
+        // or use the first one that is compatible with the encoder
+        .unwrap_or_else(||
+            *res_handles.crtcs()
+            .iter()
+            .find(|crtc| encoder_info.supports_crtc(**crtc))
+            .unwrap());
 
     // Assuming we found a good connector and loaded the info into `connector_info`
     let mode = connector_info.modes()[0]; // Use first mode (usually highest resoltion, but in reality you should filter and sort and check and match with other connectors, if you use more then one.)

src/backend/drm/mod.rs

@@ -39,15 +39,20 @@
 //! You will need to use the `drm` crate to provide the required types to create
 //! a backend.
 //!
-//! ```rust,ignore
+//! ```rust,no_run
 //! extern crate drm;
 //! extern crate smithay;
 //! # extern crate wayland_server;
 //!
 //! use drm::control::{Device as ControlDevice, ResourceInfo};
 //! use drm::control::connector::{Info as ConnectorInfo, State as ConnectorState};
+//! use drm::control::encoder::{Info as EncoderInfo};
+//! # use std::io::Error as IoError;
 //! use std::fs::OpenOptions;
+//! # use std::time::Duration;
 //! use smithay::backend::drm::DrmDevice;
+//! # use smithay::backend::drm::{DrmHandler, Id};
+//! # use wayland_server::EventLoopHandle;
 //!
 //! # fn main() {
 //! // Open the drm device
@@ -68,8 +73,17 @@
 //!     .find(|conn| conn.connection_state() == ConnectorState::Connected)
 //!     .unwrap();
 //!
-//! // Use first crtc (should be successful in most cases)
+//! // Use the first encoder
-//! let crtc = res_handles.crtcs()[0];
+//! let encoder_info = EncoderInfo::load_from_device(&device, connector_info.encoders()[0]).unwrap();
+//!
+//! // use the connected crtc if any
+//! let crtc = encoder_info.current_crtc()
+//!     // or use the first one that is compatible with the encoder
+//!     .unwrap_or_else(||
+//!         *res_handles.crtcs()
+//!         .iter()
+//!         .find(|crtc| encoder_info.supports_crtc(**crtc))
+//!         .unwrap());
 //!
 //! // Use first mode (usually the highest resolution)
 //! let mode = connector_info.modes()[0];
@@ -80,6 +94,14 @@
 //!         mode,
 //!         vec![connector_info.handle()]
 //!     ).unwrap();
+//! # struct MyDrmHandler;
+//! #
+//! # impl DrmHandler for MyDrmHandler {
+//! #    fn ready(&mut self, _: &mut EventLoopHandle, id: Id, _frame: u32, _duration: Duration) {}
+//! #    fn error(&mut self, _: &mut EventLoopHandle, error: IoError) {}
+//! # }
+//! #
+//! # device.set_handler(MyDrmHandler);
 //! # }
 //! ```
 //!
@@ -123,6 +145,7 @@
 //! #     options.open("/dev/dri/card0").unwrap(), // try to detect it properly
 //! #     None /*put a logger here*/
 //! # ).unwrap();
+//! #
 //! # let res_handles = device.resource_handles().unwrap();
 //! # let connector_info = res_handles.connectors().iter()
 //! #     .map(|conn| ConnectorInfo::load_from_device(&device, *conn).unwrap())