Skia shader cause a compilation error #487
Description
I'm trying to use Skia library with GL4ES. If shaders are not involved everything seems to work while once a shader is involved an compilation error occur. This is the shader created by GL4ES:
#version 110
#extension GL_EXT_shader_non_constant_global_initializers : enable
precision highp float;
float dFdx(float p) {return 0.0001;}
vec2 dFdx(vec2 p) {return vec2(0.0001);}
float clamp(float f, int a, int b) {
return clamp(f, float(a), float(b));
}
float clamp(float f, float a, int b) {
return clamp(f, a, float(b));
}
float clamp(float f, int a, float b) {
return clamp(f, float(a), b);
}
vec2 clamp(vec2 f, int a, int b) {
return clamp(f, float(a), float(b));
}
vec2 clamp(vec2 f, float a, int b) {
return clamp(f, a, float(b));
}
vec2 clamp(vec2 f, int a, float b) {
return clamp(f, float(a), b);
}
vec3 clamp(vec3 f, int a, int b) {
return clamp(f, float(a), float(b));
}
vec3 clamp(vec3 f, float a, int b) {
return clamp(f, a, float(b));
}
vec3 clamp(vec3 f, int a, float b) {
return clamp(f, float(a), b);
}
vec4 clamp(vec4 f, int a, int b) {
return clamp(f, float(a), float(b));
}
vec4 clamp(vec4 f, float a, int b) {
return clamp(f, a, float(b));
}
vec4 clamp(vec4 f, int a, float b) {
return clamp(f, float(a), b);
}
vec3 dFdx(vec3 p) {return vec3(0.0001);}
float dFdy(float p) {return 0.0001;}
vec2 dFdy(vec2 p) {return vec2(0.0001);}
vec3 dFdy(vec3 p) {return vec3(0.0001);}
float fwidth(float p) {return abs(dFdx(p))+abs(dFdy(p));}
vec2 fwidth(vec2 p) {return abs(dFdx(p))+abs(dFdy(p));}
vec3 fwidth(vec3 p) {return abs(dFdx(p))+abs(dFdy(p));}
#define GL4ES
precision highp int;
varying vec4 vcolor_S0;
varying vec2 varccoord_S0;
void main() {
vec4 outputColor_S0 = vcolor_S0;
float x_plus_1 = varccoord_S0.x;
float y = varccoord_S0.y;
float coverage;
if (0.00000 == x_plus_1) {
coverage = y;
} else {
float fn = x_plus_1 * (x_plus_1 - 2.00000);
fn = ((y) * (y) + (fn));
float fnwidth = fwidth(fn);
coverage = 0.500000 - fn / fnwidth;
coverage = clamp(coverage, 0.00000, 1.00000);
}
coverage = float(coverage >= 0.500000);
vec4 outputCoverage_S0 = vec4(coverage);
{
gl_FragColor = outputColor_S0 * outputCoverage_S0;
}
}
You can try it here:
https://shader-playground.timjones.io/82f451461cb682120eece7c3aa6094f7
This is the code i'm using as test:
#include "GLFW/glfw3.h"
#define SK_GANESH
#define SK_GL
#include "include/gpu/ganesh/GrBackendSurface.h"
#include "include/gpu/ganesh/GrDirectContext.h"
#include "include/gpu/ganesh/gl/GrGLDirectContext.h"
#include "include/gpu/ganesh/gl/GrGLInterface.h"
#include "include/gpu/ganesh/gl/GrGLAssembleInterface.h"
#include "include/gpu/ganesh/SkSurfaceGanesh.h"
#include "include/gpu/ganesh/gl/GrGLBackendSurface.h"
#include "include/core/SkCanvas.h"
#include "include/core/SkColorSpace.h"
#include "include/core/SkSurface.h"
#include "include/core/SkFont.h"
#include <stdio.h>
#include <stdlib.h>
//uncomment the two lines below to enable correct color spaces
//#define GL_FRAMEBUFFER_SRGB 0x8DB9
//#define GL_SRGB8_ALPHA8 0x8C43
GrDirectContext* sContext = nullptr;
SkSurface* sSurface = nullptr;
void error_callback(int error, const char* description) {
fputs(description, stderr);
}
void key_callback(GLFWwindow* window, int key, int scancode, int action, int mods) {
if (key == GLFW_KEY_ESCAPE && action == GLFW_PRESS)
glfwSetWindowShouldClose(window, GL_TRUE);
}
void init_skia(int w, int h) {
auto interface = GrGLMakeNativeInterface();
if (interface == nullptr) {
//backup plan. see https://gist.github.com/ad8e/dd150b775ae6aa4d5cf1a092e4713add?permalink_comment_id=4680136#gistcomment-4680136
interface = GrGLMakeAssembledInterface(
nullptr, (GrGLGetProc) * [](void*, const char* p) -> void* { return (void*)glfwGetProcAddress(p); });
}
sContext = GrDirectContexts::MakeGL(interface).release();
GrGLFramebufferInfo framebufferInfo;
framebufferInfo.fFBOID = 0; // assume default framebuffer
// We are always using OpenGL and we use RGBA8 internal format for both RGBA and BGRA configs in OpenGL.
//(replace line below with this one to enable correct color spaces) framebufferInfo.fFormat = GL_SRGB8_ALPHA8;
framebufferInfo.fFormat = GL_RGBA8;
SkColorType colorType = kRGBA_8888_SkColorType;
GrBackendRenderTarget backendRenderTarget = GrBackendRenderTargets::MakeGL(w, h,
0, // sample count
0, // stencil bits
framebufferInfo);
//(replace line below with this one to enable correct color spaces) sSurface = SkSurfaces::WrapBackendRenderTarget(sContext, backendRenderTarget>
sSurface = SkSurfaces::WrapBackendRenderTarget(sContext, backendRenderTarget, kBottomLeft_GrSurfaceOrigin, colorType, nullptr, nullptr).release(>
if (sSurface == nullptr) abort();
}
void cleanup_skia() {
delete sSurface;
delete sContext;
}
const int kWidth = 960;
const int kHeight = 640;
int main(void) {
GLFWwindow* window;
glfwSetErrorCallback(error_callback);
if (!glfwInit()) {
exit(EXIT_FAILURE);
}
//glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
//glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 2);
//glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
//glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
//(uncomment to enable correct color spaces) glfwWindowHint(GLFW_SRGB_CAPABLE, GL_TRUE);
glfwWindowHint(GLFW_STENCIL_BITS, 0);
//glfwWindowHint(GLFW_ALPHA_BITS, 0);
glfwWindowHint(GLFW_DEPTH_BITS, 0);
window = glfwCreateWindow(kWidth, kHeight, "Simple example", NULL, NULL);
if (!window) {
glfwTerminate();
exit(EXIT_FAILURE);
}
glfwMakeContextCurrent(window);
//(uncomment to enable correct color spaces) glEnable(GL_FRAMEBUFFER_SRGB);
init_skia(kWidth, kHeight);
glfwSwapInterval(1);
glfwSetKeyCallback(window, key_callback);
// Draw to the surface via its SkCanvas.
SkCanvas* canvas = sSurface->getCanvas(); // We don't manage this pointer's lifetime.
SkFont font;
font.setSize(24);
while (!glfwWindowShouldClose(window)) {
glfwWaitEvents();
SkPaint paint;
paint.setColor(SK_ColorWHITE);
canvas->drawPaint(paint);
paint.setColor(SK_ColorBLUE);
canvas->drawRect({100, 200, 300, 500}, paint);
canvas->drawCircle(100, 100, 64, paint);
canvas->drawString("Hello AmigaOS4! We are working hard!", 10, 20, font, paint);
sContext->flush();
glfwSwapBuffers(window);
}
cleanup_skia();
glfwDestroyWindow(window);
glfwTerminate();
exit(EXIT_SUCCESS);
}
If you comment the drawString you will not have any error