impeller/entity/shaders/blending/porter_duff_blend.frag

// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

precision mediump float;

#include <impeller/blending.glsl>
#include <impeller/color.glsl>
#include <impeller/texture.glsl>
#include <impeller/types.glsl>

uniform f16sampler2D texture_sampler_dst;

uniform FragInfo {
  float16_t src_coeff;
  float16_t src_coeff_dst_alpha;
  float16_t dst_coeff;
  float16_t dst_coeff_src_alpha;
  float16_t dst_coeff_src_color;
  float16_t input_alpha;
  float16_t output_alpha;
  float supports_decal_sampler_address_mode;
}
frag_info;

in vec2 v_texture_coords;
in f16vec4 v_color;

out f16vec4 frag_color;

f16vec4 Sample(f16sampler2D texture_sampler, vec2 texture_coords) {
#ifdef IMPELLER_TARGET_OPENGLES
  if (frag_info.supports_decal_sampler_address_mode > 0.0) {
    return texture(texture_sampler, texture_coords);
  } else {
    return IPHalfSampleDecal(texture_sampler, texture_coords);
  }
#else
  return texture(texture_sampler, texture_coords);
#endif
}

void main() {
  f16vec4 dst =
      texture(texture_sampler_dst, v_texture_coords) * frag_info.input_alpha;
  f16vec4 src = v_color;
  frag_color =
      src * (frag_info.src_coeff + dst.a * frag_info.src_coeff_dst_alpha) +
      dst * (frag_info.dst_coeff + src.a * frag_info.dst_coeff_src_alpha +
             src * frag_info.dst_coeff_src_color);
  frag_color *= frag_info.output_alpha;
}