fix(kms): run modesetting after the surface is resized

examples/drm.rs

@@ -3,7 +3,7 @@
 #[cfg(kms_platform)]
 mod imple {
     use drm::control::{connector, Device as CtrlDevice, Event, ModeTypeFlags, PlaneType};
-    use drm::Device;
+    use drm::{ClientCapability, Device};
 
     use raw_window_handle::{DisplayHandle, DrmDisplayHandle, DrmWindowHandle, WindowHandle};
     use softbuffer::{Context, Surface};
@@ -16,6 +16,7 @@ mod imple {
     pub(super) fn entry() -> Result<(), Box<dyn std::error::Error>> {
         // Open a new device.
         let device = Card::find()?;
+        device.set_client_capability(ClientCapability::UniversalPlanes, true)?;
 
         // Create the softbuffer context.
         let context = unsafe {

src/backends/kms.rs

@@ -224,6 +224,29 @@ impl<D: HasDisplayHandle + ?Sized, W: HasWindowHandle> SurfaceInterface<D, W> fo
         let front_buffer = SharedBuffer::new(&self.display, width, height)?;
         let back_buffer = SharedBuffer::new(&self.display, width, height)?;
 
+        // Iterate over all modes of all the connectors,
+        // and pick one that is compatible with the size given by the user.
+        let mode = self
+            .connectors
+            .iter()
+            .flat_map(|con| self.display.get_modes(*con).unwrap())
+            .find(|mode| {
+                mode.size().0 as u32 == u32::from(width)
+                    && mode.size().1 as u32 == u32::from(height)
+            })
+            .swbuf_err("No mode found")?;
+
+        // When changing the display resolution, we need to modeset
+        self.display
+            .set_crtc(
+                self.crtc.handle(),
+                Some(front_buffer.fb),
+                (0, 0),
+                &self.connectors,
+                Some(mode),
+            )
+            .swbuf_err("Failed to modeset")?;
+
         self.buffer = Some(Buffers {
             first_is_front: true,
             buffers: [front_buffer, back_buffer],