From 84e7e5e4994ff233d82ddcc3ce8284299a93e181 Mon Sep 17 00:00:00 2001
From: Ian Douglas Scott <idscott@system76.com>
Date: Mon, 23 Dec 2024 15:19:09 -0800
Subject: [PATCH] Use untransformed texture in
 `MirroringState::new_with_renderer`

Apply inverse of output transform to mode to get render size, and apply
no transform during rendering. The transform of the output being
mirrored from shouldn't affect the final render.

Fixes issues when source output for mirroring has a transform, and also
fixes issues in https://github.com/pop-os/cosmic-comp/pull/1058
when this code is used for postprocessing, where this resulted in the
same transform being applied twice.
---
 src/backend/kms/surface/mod.rs | 31 +++++++++++++++++++------------
 1 file changed, 19 insertions(+), 12 deletions(-)

diff --git a/src/backend/kms/surface/mod.rs b/src/backend/kms/surface/mod.rs
index 0f361bc18..37b27f70c 100644
--- a/src/backend/kms/surface/mod.rs
+++ b/src/backend/kms/surface/mod.rs
@@ -159,25 +159,32 @@ impl MirroringState {
         format: Fourcc,
         output: &Output,
     ) -> Result<Self> {
-        let size = output
-            .current_mode()
-            .map(|mode| mode.size)
-            .unwrap_or_default()
-            .to_logical(1)
-            .to_buffer(1, Transform::Normal);
-        let opaque_regions = vec![Rectangle::from_size(size)];
-
-        let texture = Offscreen::<GlesTexture>::create_buffer(renderer, format, size)?;
-        let transform = output.current_transform();
+        // Apply inverse of output transform to mode size to get correct size
+        // for an untransformed render.
+        let size = output.current_transform().invert().transform_size(
+            output
+                .current_mode()
+                .map(|mode| mode.size)
+                .unwrap_or_default(),
+        );
+        let buffer_size = size.to_logical(1).to_buffer(1, Transform::Normal);
+        let opaque_regions = vec![Rectangle::from_size(buffer_size)];
+
+        let texture = Offscreen::<GlesTexture>::create_buffer(renderer, format, buffer_size)?;
         let texture_buffer = TextureRenderBuffer::from_texture(
             renderer,
             texture,
             1,
-            transform,
+            Transform::Normal,
             Some(opaque_regions),
         );
 
-        let damage_tracker = OutputDamageTracker::from_output(output);
+        // Don't use `from_output` to avoid applying output transform
+        let damage_tracker = OutputDamageTracker::new(
+            size,
+            output.current_scale().fractional_scale(),
+            Transform::Normal,
+        );
 
         Ok(MirroringState {
             texture: texture_buffer,