anvil: add BufferUtils

A helper struct which currently contains only a method for retrieving
buffer dimensions. Will be used for getting the buffer dimensions early,
before rendering, to always have up-to-date size which is not zero.

anvil/src/buffer_utils.rs

@@ -0,0 +1,59 @@
+use std::{cell::RefCell, rc::Rc};
+
+use slog::Logger;
+
+#[cfg(feature = "egl")]
+use smithay::backend::egl::{BufferAccessError, EGLDisplay};
+use smithay::{
+    reexports::wayland_server::protocol::wl_buffer::WlBuffer,
+    wayland::shm::with_buffer_contents as shm_buffer_contents,
+};
+
+/// Utilities for working with `WlBuffer`s.
+#[derive(Clone)]
+pub struct BufferUtils {
+    #[cfg(feature = "egl")]
+    egl_display: Rc<RefCell<Option<EGLDisplay>>>,
+    log: Logger,
+}
+
+impl BufferUtils {
+    /// Creates a new `BufferUtils`.
+    #[cfg(feature = "egl")]
+    pub fn new(egl_display: Rc<RefCell<Option<EGLDisplay>>>, log: Logger) -> Self {
+        Self { egl_display, log }
+    }
+
+    /// Creates a new `BufferUtils`.
+    #[cfg(not(feature = "egl"))]
+    pub fn new(log: Logger) -> Self {
+        Self { log }
+    }
+
+    /// Returns the dimensions of an image stored in the buffer.
+    #[cfg(feature = "egl")]
+    pub fn dimensions(&self, buffer: &WlBuffer) -> Option<(i32, i32)> {
+        // Try to retrieve the EGL dimensions of this buffer, and, if that fails, the shm dimensions.
+        self.egl_display
+            .borrow()
+            .as_ref()
+            .and_then(|display| display.egl_buffer_dimensions(buffer))
+            .or_else(|| self.shm_buffer_dimensions(buffer))
+    }
+
+    /// Returns the dimensions of an image stored in the buffer.
+    #[cfg(not(feature = "egl"))]
+    pub fn dimensions(&self, buffer: &WlBuffer) -> Option<(i32, i32)> {
+        self.shm_buffer_dimensions(buffer)
+    }
+
+    /// Returns the dimensions of an image stored in the shm buffer.
+    fn shm_buffer_dimensions(&self, buffer: &WlBuffer) -> Option<(i32, i32)> {
+        shm_buffer_contents(buffer, |_, data| (data.width, data.height))
+            .map_err(|err| {
+                warn!(self.log, "Unable to load buffer contents"; "err" => format!("{:?}", err));
+                err
+            })
+            .ok()
+    }
+}

anvil/src/main.rs

@@ -12,6 +12,7 @@ use smithay::reexports::{calloop::EventLoop, wayland_server::Display};
 
 #[macro_use]
 mod shaders;
+mod buffer_utils;
 mod glium_drawer;
 mod input_handler;
 mod shell;