input: Add screenshotting shortcut

src/state.rs

@@ -8,7 +8,7 @@ use crate::{
     wayland::protocols::{
         drm::WlDrmState, output_configuration::OutputConfigurationState,
         workspace::WorkspaceClientState,
-    },
+    }, utils::prelude::OutputExt,
 };
 use smithay::{
     backend::drm::DrmNode,
@@ -199,6 +199,61 @@ impl BackendData {
             _ => unreachable!("No backend was initialized"),
         }
     }
+
+    pub fn offscreen_for_output(
+        &mut self,
+        output: &Output,
+        state: &mut Common,
+    ) -> anyhow::Result<image::ImageBuffer<image::Rgba<u8>, Vec<u8>>> {
+        use anyhow::Context;
+        use smithay::{
+            backend::{
+                drm::NodeType,
+                renderer::{
+                    Bind, Offscreen, ExportMem,
+                    gles2::Gles2Renderbuffer,
+                },
+            },
+            utils::Rectangle,
+        };
+        use crate::backend::render::render_output;
+
+        let mut _tmp_multirenderer = None;
+        let (node, renderer) = match self {
+            BackendData::Winit(winit) => (None, winit.backend.renderer()),
+            BackendData::X11(x11) => (None, &mut x11.renderer),
+            BackendData::Kms(kms) => {
+                let node = kms.target_node_for_output(output)
+                    .unwrap_or(kms.primary)
+                    .node_with_type(NodeType::Render)
+                    .with_context(|| "Unable to find node")??;
+                _tmp_multirenderer = Some(kms.api.renderer::<Gles2Renderbuffer>(&node, &node)?);
+                (Some(node), _tmp_multirenderer.as_mut().map(|x| x.as_mut()).unwrap())
+            },
+            BackendData::Unset => unreachable!(),
+        };
+
+        let size = output.geometry().size.to_f64().to_buffer(
+            output.current_scale().fractional_scale(),
+            output.current_transform().into()
+        ).to_i32_round();
+        let buffer = Offscreen::<Gles2Renderbuffer>::create_buffer(renderer, size)?;
+        renderer.bind(buffer)?;
+        render_output(
+            node.as_ref(),
+            renderer,
+            0,
+            state,
+            output,
+            false,
+            #[cfg(feature = "debug")]
+            None,
+        )?;
+        let mapping = renderer.copy_framebuffer(Rectangle::from_loc_and_size((0, 0), size))?;
+        let data = Vec::from(renderer.map_texture(&mapping)?);
+
+        Ok(image::ImageBuffer::from_raw(size.w as u32, size.h as u32, data).with_context(|| "buffer smaller then dimensions")?)
+    }
 }
 
 impl State {