From 46a58b926866a523a37d0e8505a7ac301baac237 Mon Sep 17 00:00:00 2001
From: Roman Sorokin <sorok-roma@yandex.ru>
Date: Mon, 25 Aug 2014 14:50:37 +0300
Subject: [PATCH] Added functions to process shaders

---
 drape/shader.cpp | 63 +++++++++++++++++++++++++++++++++++++++++++++---
 drape/shader.hpp |  8 +++++-
 2 files changed, 67 insertions(+), 4 deletions(-)

diff --git a/drape/shader.cpp b/drape/shader.cpp
index ed27bdbdc6..a6b64ede32 100644
--- a/drape/shader.cpp
+++ b/drape/shader.cpp
@@ -1,14 +1,26 @@
 #include "shader.hpp"
-#include "glfunctions.hpp"
 
 #include "../base/assert.hpp"
+#include "../base/string_utils.hpp"
+
 
 namespace dp
 {
 
+#if defined(OMIM_OS_DESKTOP) && !defined(COMPILER_TESTS)
+  #define LOW_P string("")
+  #define MEDIUM_P string("")
+  #define HIGH_P string("")
+#else
+  #define LOW_P string("lowp")
+  #define MEDIUM_P string("mediump")
+  #define HIGH_P string("highp")
+#endif
+
+using strings::to_string;
+
 namespace
 {
-
 glConst convert(Shader::Type t)
 {
   if (t == Shader::VertexShader)
@@ -17,7 +29,51 @@ glConst convert(Shader::Type t)
   return gl_const::GLFragmentShader;
 }
 
-} // namespace
+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";
+
+  for (int i = 0; i < count; ++i)
+  {
+    result += "const int " + index + to_string(i) + " = " + to_string(i) + ";\n";
+  }
+  result += "\n";
+
+  result += "uniform sampler2D u_textures[" + to_string(count) + "];\n";
+
+  //Head
+  result += MEDIUM_P + " vec4 getTexel(int " + texindex + ", " + LOW_P + " vec2 " + texcoord + ") \n";
+  result += "{\n";
+  result += "  " + MEDIUM_P + " vec4 " + answer + "; \n";
+  //Body
+  result += "  if (" + texindex + " == " + index + "0) \n";
+  result += "    " + answer + " = texture2D(" + sampler + "[" + index + "0], " + texcoord + "); \n";
+  for (int i = 1; i < count; ++i)
+  {
+    string num = to_string(i);
+    result += "  else if (" + texindex + " == " + index + num + ") \n";
+    result += "    " + answer + " = texture2D(" + sampler + "[" + index + num + "], " + texcoord + "); \n";
+  }
+  //Tail
+  result += "  return " + answer + ";\n";
+  result += "}\n";
+}
+}
+
+void sh::Inject(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, Type type)
   : m_source(shaderSource)
@@ -25,6 +81,7 @@ Shader::Shader(string const & shaderSource, Type type)
   , m_glID(0)
 {
   m_glID = GLFunctions::glCreateShader(convert(m_type));
+  sh::Inject(m_source);
   GLFunctions::glShaderSource(m_glID, m_source);
   string errorLog;
   bool result = GLFunctions::glCompileShader(m_glID, errorLog);
diff --git a/drape/shader.hpp b/drape/shader.hpp
index 31cdf02638..157e9a0fcf 100644
--- a/drape/shader.hpp
+++ b/drape/shader.hpp
@@ -1,4 +1,5 @@
 #pragma once
+#include "glfunctions.hpp"
 
 #include "../std/string.hpp"
 #include "../std/stdint.hpp"
@@ -21,9 +22,14 @@ public:
   int GetID() const;
 
 private:
-  string const m_source;
+  string m_source;
   Type m_type;
   uint32_t m_glID;
 };
 
+namespace sh
+{
+  void Inject(string & src);
+}
+
 } // namespace dp