FragmentProgram.fromAsset on skia fails to compile a for loop #116850
Description
FragmentProgram.fromAsset on skia fails to compile a for loop.
This only happens on skia renderer, works fine on impeller, but I'm not sure if it's possible to do flutter test with impeller on.
Steps to Reproduce
- Execute
flutter teston the code sample.
Expected results:
Mandelbrot image gets rendered into mandelbrot.png.
Actual results:
Test fails because shader fails to compile.
SkSL Error:
error: 20: missing init declaration
for (; i < 100; i++)
^
1 error
dart:ui FragmentProgram.fromAsset
package:fractal/main.dart 7:26 fromAsset
test/shader_test.dart 25:25 renderShader
test/shader_test.dart 21:28 main.<fn>
Code sample
The failing shader:
#version 320 es
precision highp float;
const int iter = 100;
layout(location = 0) uniform vec2 center;
layout(location = 2) uniform vec2 size;
layout(location = 4) uniform float scale;
layout(location = 0) out vec4 oColor;
void main() {
vec2 coord = gl_FragCoord.xy / size;
float aspectRatio = size.x / size.y;
vec2 z, c;
c.x = aspectRatio * (coord.x - 0.5) * scale - center.x;
c.y = (coord.y - 0.5) * scale - center.y;
int i;
for(i=0; i< iter; i++) {
float x = (z.x * z.x - z.y * z.y) + c.x;
float y = (z.y * z.x + z.x * z.y) + c.y;
if((x * x + y * y) > 4.0) {
break;
}
z.x = x;
z.y = y;
}
oColor.r = i == iter ? 0.0 : float(i) / float(iter);
oColor.a = 1.0;
}Logs
szotp@MacBook-Pro-Pawel mandelbrot_minimal % flutter test
00:01 +1 -1: mandelbrot [E]
Exception: Invalid SkSL:
// This SkSL shader is autogenerated by spirv-cross.
float4 flutter_FragCoord;
uniform vec2 center;
uniform vec2 size;
uniform float scale;
vec4 oColor;
void FLT_main()
{
vec2 coord = flutter_FragCoord.xy / size;
float aspectRatio = size.x / size.y;
vec2 c;
c.x = ((aspectRatio * (coord.x - 0.5)) * scale) - center.x;
c.y = ((coord.y - 0.5) * scale) - center.y;
int i = 0;
vec2 z;
for (; i < 100; i++)
{
float x = ((z.x * z.x) - (z.y * z.y)) + c.x;
float y = ((z.y * z.x) + (z.x * z.y)) + c.y;
if (((x * x) + (y * y)) > 4.0)
{
break;
}
z.x = x;
z.y = y;
}
float _122;
if (i == 100)
{
_122 = 0.0;
}
else
{
_122 = float(i) / 100.0;
}
oColor.x = _122;
oColor.w = 1.0;
}
half4 main(float2 iFragCoord)
{
flutter_FragCoord = float4(iFragCoord, 0, 0);
FLT_main();
return oColor;
}
SkSL Error:
error: 20: missing init declaration
for (; i < 100; i++)
^
1 error
dart:ui FragmentProgram.fromAsset
test/shader_test.dart 53:41 renderShader
test/shader_test.dart 21:28 main.<fn>
To run this test again: /Users/szotp/flutter-sdk/bin/cache/dart-sdk/bin/dart test /Users/szotp/Projects/mandelbrot_minimal/test/shader_test.dart -p vm --plain-name 'mandelbrot'
00:01 +1 -1: Some tests failed.
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