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Add screen orientation support for Linux frame buffer and DRM applications.

This commit introduces support for screen orientation across various components by adding a new Orientation property of type SurfaceOrientation in DrmOutputOptions and FbDevOutputOptions. The IScreenInfoProvider interface is updated to inherit from ISurfaceOrientation, ensuring consistent orientation management.

Key changes include:

  • Enhanced FramebufferToplevelImpl to handle orientation in size calculations.
  • Updated LibInputBackend for device input coordinate rotation based on screen orientation.
  • Implemented ISurfaceOrientation in DrmOutput and FbdevOutput classes.
  • Modified DrawingContextImpl to support canvas rotation based on orientation.
  • Improved FramebufferRenderTarget and PixelFormatConversionShim to respect framebuffer orientation during surface creation and pixel format conversions.
  • Streamlined rendering methods to ensure drawing operations align with the current surface orientation.

What does the pull request do?

Implement screen rotation for Linux kiosk applications for situations where the Linux drivers do not support all orientations of the display screen.
Supports 0, 90, 180 and 270 degree rotation of the display.
The touch screen input coordinates are also rotated to match the screen orientation.
Implemented in the output backend for both DRM and frame buffer.
Supports dynamic orientation change via the UI without requiring a restart.

What is the current behavior?

See #18535 and #14241
Attempts to implement display rotation at the application level using RotateTransform on the MainView or EmbeddedRoutControl fail as any Combo and Popup menus appear unrotated and in the wrong position. Also, scrolling via touch input does not work for rotated views.

What is the updated/expected behavior with this PR?

Create a kiosk app with FbDevOutputOptions or DrmOutputOptions Orientation set to one of the four SurfaceOrientation enum values to rotate the display output and touch input.
Alternatively, set the orientation dynamically during operation via the ISurfaceOrientation interface if supported by the application lifetime (both DRM and FBDev LinuxFrameBufferLifetime support this) ; e.g.:

                SurfaceOrientation orientation = SurfaceOrientation.Rotated270;
                if (Application.ApplicationLifetime is ISingleTopLevelApplicationLifetime singleView)
                {
                    TopLevel topLevel = singleView.TopLevel;
                    var platformImpl = topLevel?.PlatformImpl;
                    if (platformImpl is ISurfaceOrientation orientation)
                    {
                        // update the orientation
                        orientation.Orientation = orientation;
                    }
                }

This has been tested on a RPI4B running Bookworm with a 7" 720x1280 pixel display. The Linux drivers only support portrait orientation for this display.

How was the solution implemented (if it's not obvious)?

Rotation of the display surface is implemented using SkiaSharp, SKSurface and SKCanvas.

Framebuffer rotation is implemented by buffering the rotated output using the pre-existing PixelFormatConversionShim.
A copy of the rotated screen is rotated back to the native frame buffer orientation and written to the frame buffer.
There may be a more efficient way to do this but it works well enough with a RPI4B and 7" 1280x720 display.

DRM rotation is implemented using a Rotate and Translate transform on the SKCanvas created in the GlRenderTarget.
This should make use of the GPU to accelerate the rendering.
I had to remove some code that appeared redundant from SurfaceRenderTarget to make the rotation work.
I also had to ensure the screen rotation transform was retained in DrawingContextImpl.

Checklist

Breaking changes

None that I am aware of.

Obsoletions / Deprecations

None

Fixed issues

Fixes #18535 and #14241

… frame buffer and DRM applications.

This commit introduces support for screen orientation across various components by adding a new `Orientation` property of type `SurfaceOrientation` in `DrmOutputOptions` and `FbDevOutputOptions`. The `IScreenInfoProvider` interface is updated to inherit from `ISurfaceOrientation`, ensuring consistent orientation management.

Key changes include:
- Enhanced `FramebufferToplevelImpl` to handle orientation in size calculations.
- Updated `LibInputBackend` for device input coordinate rotation based on screen orientation.
- Implemented `ISurfaceOrientation` in `DrmOutput` and `FbdevOutput` classes.
- Modified `DrawingContextImpl` to support canvas rotation based on orientation.
- Improved `FramebufferRenderTarget` and `PixelFormatConversionShim` to respect framebuffer orientation during surface creation and pixel format conversions.
- Streamlined rendering methods to ensure drawing operations align with the current surface orientation.
- Removed redundant code related to framebuffer handling.
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cla-avalonia commented Apr 15, 2025

@aguahombre,

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@aguahombre
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aguahombre commented Apr 15, 2025 via email

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jmacato commented Apr 15, 2025

@aguahombre I think the CLA bot can't recognize the additional content after the "agree" word. Please comment without the additional details first then comment the company details in separate comment :)

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@aguahombre
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aguahombre commented Apr 15, 2025 via email

Comment on lines +246 to +255
if (Orientation == SurfaceOrientation.Rotated180)
{
width = snapshot.Width;
height = snapshot.Height;
}
else
{
width = snapshot.Height;
height = snapshot.Width;
}
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Should the Unknown Orientation swap the width and height?

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Maybe the Unknown value should not be exposed in the API...
The default orientation is intended to be Normal.
The Unknown value was not intended to be used other than internally; e.g, to force an initial update as used in LibinputBackend.cs:36

@JaggerJo
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Looking forward to this 👍 Quite handy with devices like the seed studio reTerminal that make native rotation almost impossible..

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You can test this PR using the following package version. 12.0.999-cibuild0056164-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

@MrJul MrJul added the needs-api-review The PR adds new public APIs that should be reviewed. label May 31, 2025
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MrJul commented Jun 8, 2025

Public API for review:

 namespace Avalonia.Skia
 {
+    public enum SurfaceOrientation
+    {
+        Normal,
+        Rotated90,
+        Rotated180,
+        Rotated270,
+        Unknown,
+    }
 
+    public interface ISurfaceOrientation
+    {
+        SurfaceOrientation Orientation { get; set; }
+    }
}

 namespace Avalonia.LinuxFramebuffer
 {
     public class DrmOutputOptions
     {
+        public SurfaceOrientation Orientation { get; set; }
     }
 }
 
 namespace Avalonia.LinuxFramebuffer.Input
 {
     public interface IScreenInfoProvider
+        : ISurfaceOrientation;
 }

 
 namespace Avalonia.LinuxFramebuffer.Output
 {
     public class DrmOutputOptions
     {
+        public SurfaceOrientation Orientation { get; set; }
     }
 
     public interface IOutputBackend 
+        : ISurfaceOrientation;

     public class FbDevOutputOptions
     {
+        public SurfaceOrientation Orientation { get; set; }
     }
     
     public sealed class FbdevOutput : IFramebufferPlatformSurface, IDisposable, IOutputBackend
     {
+        public SurfaceOrientation Orientation { get; set; }
     }
 }

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What is the point of ISurfaceOrientation interface?

Also, Unknown as a requested orientation.

@aguahombre
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What is the point of ISurfaceOrientation interface?

Also, Unknown as a requested orientation.

You can use ISurfaceOrientation to allow runtime changes to the orientation through the UI; e.g.

                if (ApplicationLifetime is ISingleTopLevelApplicationLifetime singleView)
                {
                    TopLevel topLevel = singleView.TopLevel;
                    var platformImpl = topLevel?.PlatformImpl;
                    if (platformImpl is ISurfaceOrientation orientation)
                    {
                        // update the orientation
                        orientation.Orientation = x.Orientation;
                    }
                }

It is also used in the DRM and frame buffer implementation to obtain the orientation without needing to know which type of output backend is in use.

The Unknown should not be for application use. It is used in some places as an initial value for variables to allow some code to run once on the first pass. It could be removed and replace with a cast value e.g. Unknown = (SurfaceOrientation)-1

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Exposing interfaces from TopLevel.PlatformImpl to be used from user code is an API design we are trying to avoid. It should be some kind of a TopLevel property, especially since it's possible to control orientation for mobile platforms too.

@aguahombre
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Exposing interfaces from TopLevel.PlatformImpl to be used from user code is an API design we are trying to avoid. It should be some kind of a TopLevel property, especially since it's possible to control orientation for mobile platforms too.

Yes, I think Avalonia could expose a TopLevel property that uses the interface to read and write the orientation and then make the interface internal.

@MrJul
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MrJul commented Jun 24, 2025

Notes from the API review:

  • Remove SurfaceOrientation.Unknown. Internally, a nullable value can be used instead when the orientation is effectively unknown.
  • Move SurfaceOrientation and ISurfaceOrientation from the Avalonia.Skia namespace/project to the Avalonia.Platform namespace in the Avalonia.Base project.
  • FramebufferRenderTarget._orientation should be renamed to Orientation since it's a property. It can also be made private since it's an implementation detail.
  • ISurfaceOrientation should be internal. We can add the Orientation property directly to the TopLevel as suggested in Add screen orientation support for Linux frame buffer and DRM applications. #18658 (comment).

Additional thoughts I had while I'm writing this: since the orientation won't work everywhere maybe it should be a hint? In that case I question whether we should have it both on the FB/DRM options and the TopLevel. We'll very likely do another review pass to validate the whole design once the requested changes are in place and things are clearer.

@MrJul MrJul added api-change-requested The new public APIs need some changes. and removed needs-api-review The PR adds new public APIs that should be reviewed. labels Jun 24, 2025
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