Opengles texture upside-down in ImageFilter.compose golden tests #177611

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1. gaaclarke

   added

   e: impellerImpeller rendering backend issues and features requestsImpeller rendering backend issues and features requests

   team-engineOwned by Engine teamOwned by Engine team

   on Oct 27, 2025
2. jason-simmons commented on Oct 27, 2025

   

   jason-simmons

   on Oct 27, 2025

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   Does this work as intended if the shader adjusts the y-axis direction for OpenGL as described in https://github.com/flutter/flutter/blob/master/engine/src/flutter/lib/ui/painting.dart#L4265?
3. gaaclarke commented on Oct 27, 2025

   

   gaaclarke

   on Oct 27, 2025

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   Does this work as intended if the shader adjusts the y-axis direction for OpenGL as described in https://github.com/flutter/flutter/blob/master/engine/src/flutter/lib/ui/painting.dart#L4265?

   No, it doesn't fix it unfortunately. I messed up in the description. I'll update it.

   Without any change ComposePaintRuntimeInner renders right side up, but ComposePaintRuntimeOuter renders upside down.

   Adding the flip like in the linked document fixes ComposePaintRuntimeOuter but flops ComposePaintRuntimeInner.
4. gaaclarke commented on Oct 27, 2025

   

   gaaclarke

   on Oct 27, 2025

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   The shader with the documented y flip:

   #include <flutter/runtime_effect.glsl>
   
   uniform vec2 u_size;
   uniform sampler2D u_texture;
   
   out vec4 frag_color;
   
   void main() {
     vec2 uv = FlutterFragCoord().xy / u_size;
   #ifdef IMPELLER_TARGET_OPENGLES
    uv.y = 1.0 - uv.y;
   #endif
     frag_color = texture(u_texture, uv +
       vec2(0.0, 0.1 * sin(FlutterFragCoord().x / u_size.x * 3.14 * 5.0)));
   }
5. gaaclarke commented on Oct 27, 2025

   

   gaaclarke

   on Oct 27, 2025

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   The workaround for this is to just use 2 different shaders. One with the y coordinate swap in it, one without it.
6. gaaclarke

   self-assigned this

   on Oct 29, 2025
7. github-merge-queue

   added a commit that references this issue on Oct 30, 2025

   Fixes RuntimeEffect when used with ImageFilter.compose and gaussian b…

   ...

   c089837
8. auto-submit

   closed this as completedin #177687on Oct 30, 2025
9. github-actions commented on Nov 13, 2025

   

   github-actionsbot

   on Nov 13, 2025 – with GitHub Actions

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   This thread has been automatically locked since there has not been any recent activity after it was closed. If you are still experiencing a similar issue, please open a new bug, including the output of flutter doctor -v and a minimal reproduction of the issue.
10. github-actions

    locked as resolved and limited conversation to collaborators on Nov 13, 2025
11. reidbaker

    added a commit that references this issue on Dec 10, 2025

    Fixes RuntimeEffect when used with ImageFilter.compose and gaussian b…

    ...

    84ed97f
12. Nakiha

    added a commit that references this issue on Sep 28, 2026

    Fixes RuntimeEffect when used with ImageFilter.compose and gaussian b…

    ...

    24d7873