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#include "drape/shader.hpp"
#include "drape/shader_def.hpp"
#include "base/assert.hpp"
#include "base/string_utils.hpp"
namespace dp
{
using strings::to_string;
namespace
{
glConst convert(Shader::Type t)
{
if (t == Shader::VertexShader)
return gl_const::GLVertexShader;
return gl_const::GLFragmentShader;
}
void ResolveGetTexel(string & result, string const & sampler, int count)
{
string const index = "index";
string const answer = "answer";
string const texIndex = "texIndex";
string const texCoord = "texCoord";
result.reserve(250 + 130 * count);
for (int i = 0; i < count; ++i)
{
string const number = to_string(i);
result.append("const int ").append(index).append(number).append(" = ").append(number).append(";\n");
}
result.append("uniform sampler2D u_textures[").append(to_string(count)).append("];\n");
// Function signature
result.append(LOW_P).append(" vec4 getTexel(int ").append(texIndex).append(", ")
.append(MAXPREC_P).append(" vec2 ").append(texCoord).append("){ \n");
// Declare result var;
result.append(LOW_P).append(" vec4 ").append(answer).append(";\n");
for (uint32_t i = 0; i < count; ++i)
{
string constIndex = index + to_string(i);
if (i != 0)
result.append("else ");
result.append("if (").append(texIndex).append("==").append(constIndex).append(")\n");
result.append(answer).append("=texture2D(")
.append(sampler).append("[").append(constIndex).append("],")
.append(texCoord).append(");\n");
}
result.append("return ").append(answer).append(";}");
}
}
void PreprocessShaderSource(string & src)
{
string const replacement("~getTexel~");
int const pos = src.find(replacement);
if (pos == string::npos)
return;
string injector = "";
int const count = min(8, GLFunctions::glGetInteger(gl_const::GLMaxFragmentTextures));
ResolveGetTexel(injector, "u_textures", count);
src.replace(pos, replacement.length(), injector);
}
Shader::Shader(string const & shaderSource, string const & defines, Type type)
: m_glID(0)
{
m_glID = GLFunctions::glCreateShader(convert(type));
string source = shaderSource;
PreprocessShaderSource(source);
GLFunctions::glShaderSource(m_glID, source, defines);
string errorLog;
bool result = GLFunctions::glCompileShader(m_glID, errorLog);
CHECK(result, ("Shader compile error : ", errorLog));
}
Shader::~Shader()
{
GLFunctions::glDeleteShader(m_glID);
}
int Shader::GetID() const
{
return m_glID;
}
} // namespace dp
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