backend: fix bug that mistakeningly selected wrong render device

src/backend.rs

@@ -585,6 +585,9 @@ pub trait BackendDrmDevice {
     fn direct_scanout_enabled(&self) -> bool {
         false
     }
+    fn gfx_fast_ram_access(&self) -> bool {
+        false
+    }
     fn create_lease(
         self: Rc<Self>,
         lessee: Rc<dyn BackendDrmLessee>,

src/backends/metal/video.rs

@@ -189,6 +189,10 @@ impl BackendDrmDevice for MetalDrmDevice {
             .unwrap_or(self.backend.state.direct_scanout_enabled.get())
     }
 
+    fn gfx_fast_ram_access(&self) -> bool {
+        self.ctx.get().gfx.fast_ram_access()
+    }
+
     fn create_lease(
         self: Rc<Self>,
         lessee: Rc<dyn BackendDrmLessee>,

src/state.rs

@@ -637,6 +637,9 @@ impl State {
                 {
                     continue;
                 }
+                if dev.dev.gfx_fast_ram_access() {
+                    continue;
+                }
                 dev.make_render_device();
                 if self.render_ctx.is_some() {
                     break;