move shaders into .glsl files and add #include feature

src/shader.h

@@ -40,6 +40,7 @@ enum class kShaderUniform : uint16_t
     PatternScale = const_hash("pattern_scale"),
     PatternBright = const_hash("pattern_bright"),
     PatternContrast = const_hash("pattern_contr"),
+    PatternDepth = const_hash("pattern_depth"),
     Colorize = const_hash("colorize"),
     DualAlpha = const_hash("dual_alpha"),
 };
@@ -73,10 +74,14 @@ enum class kShader : uint16_t
 
 class Shader
 {
+    std::string m_path;
     std::map<kShaderUniform, GLuint> m_umap;
     GLuint prog;
+    std::string read(const std::string& path);
 public:
     kShader name;
+    void parse_error(const char* msg, const char* code);
+    bool load(const std::string& path);
     bool create(const char* vertex, const char* fragment);
     void use();
     void u_vec4(kShaderUniform id, const glm::vec4& v);
@@ -94,6 +99,7 @@ class ShaderManager
     static Shader* m_current;
 public:
     static bool ext_framebuffer_fetch;
+    static bool load(kShader id, const std::string& path);
     static bool create(kShader id, const char* vertex, const char* fragment);
     static void use(kShader id);
     static void use(const char* name);