Remove obsolete GLES2 backend code

This code currently isn't compiled (and cannot compile).

We plan to re-add OpenGL ES-based renderer(s) in Godot 4.0 alongside Vulkan
(probably ES 3.0, possibly also a low-end ES 2.0), but the code will be quite
different so it's not relevant to keep this old Godot 3.2 code.

The `drivers/gles2` code from the `3.2` branch can be used as a reference for
a potential new implementation.

glsl_builders.py

@@ -0,0 +1,224 @@
+"""Functions used to generate source files during build time
+
+All such functions are invoked in a subprocess on Windows to prevent build flakiness.
+
+"""
+from platform_methods import subprocess_main
+
+
+class RDHeaderStruct:
+    def __init__(self):
+        self.vertex_lines = []
+        self.fragment_lines = []
+        self.compute_lines = []
+
+        self.vertex_included_files = []
+        self.fragment_included_files = []
+
+        self.reading = ""
+        self.line_offset = 0
+        self.vertex_offset = 0
+        self.fragment_offset = 0
+        self.compute_offset = 0
+
+
+def include_file_in_rd_header(filename, header_data, depth):
+    fs = open(filename, "r")
+    line = fs.readline()
+
+    while line:
+
+        if line.find("#[vertex]") != -1:
+            header_data.reading = "vertex"
+            line = fs.readline()
+            header_data.line_offset += 1
+            header_data.vertex_offset = header_data.line_offset
+            continue
+
+        if line.find("#[fragment]") != -1:
+            header_data.reading = "fragment"
+            line = fs.readline()
+            header_data.line_offset += 1
+            header_data.fragment_offset = header_data.line_offset
+            continue
+
+        if line.find("#[compute]") != -1:
+            header_data.reading = "compute"
+            line = fs.readline()
+            header_data.line_offset += 1
+            header_data.compute_offset = header_data.line_offset
+            continue
+
+        while line.find("#include ") != -1:
+            includeline = line.replace("#include ", "").strip()[1:-1]
+
+            import os.path
+
+            included_file = os.path.relpath(os.path.dirname(filename) + "/" + includeline)
+            if not included_file in header_data.vertex_included_files and header_data.reading == "vertex":
+                header_data.vertex_included_files += [included_file]
+                if include_file_in_rd_header(included_file, header_data, depth + 1) is None:
+                    print("Error in file '" + filename + "': #include " + includeline + "could not be found!")
+            elif not included_file in header_data.fragment_included_files and header_data.reading == "fragment":
+                header_data.fragment_included_files += [included_file]
+                if include_file_in_rd_header(included_file, header_data, depth + 1) is None:
+                    print("Error in file '" + filename + "': #include " + includeline + "could not be found!")
+            elif not included_file in header_data.compute_included_files and header_data.reading == "compute":
+                header_data.compute_included_files += [included_file]
+                if include_file_in_rd_header(included_file, header_data, depth + 1) is None:
+                    print("Error in file '" + filename + "': #include " + includeline + "could not be found!")
+
+            line = fs.readline()
+
+        line = line.replace("\r", "")
+        line = line.replace("\n", "")
+
+        if header_data.reading == "vertex":
+            header_data.vertex_lines += [line]
+        if header_data.reading == "fragment":
+            header_data.fragment_lines += [line]
+        if header_data.reading == "compute":
+            header_data.compute_lines += [line]
+
+        line = fs.readline()
+        header_data.line_offset += 1
+
+    fs.close()
+
+    return header_data
+
+
+def build_rd_header(filename):
+    header_data = RDHeaderStruct()
+    include_file_in_rd_header(filename, header_data, 0)
+
+    out_file = filename + ".gen.h"
+    fd = open(out_file, "w")
+
+    enum_constants = []
+
+    fd.write("/* WARNING, THIS FILE WAS GENERATED, DO NOT EDIT */\n")
+
+    out_file_base = out_file
+    out_file_base = out_file_base[out_file_base.rfind("/") + 1 :]
+    out_file_base = out_file_base[out_file_base.rfind("\\") + 1 :]
+    out_file_ifdef = out_file_base.replace(".", "_").upper()
+    fd.write("#ifndef " + out_file_ifdef + "_RD\n")
+    fd.write("#define " + out_file_ifdef + "_RD\n")
+
+    out_file_class = out_file_base.replace(".glsl.gen.h", "").title().replace("_", "").replace(".", "") + "ShaderRD"
+    fd.write("\n")
+    fd.write('#include "servers/rendering/rasterizer_rd/shader_rd.h"\n\n')
+    fd.write("class " + out_file_class + " : public ShaderRD {\n\n")
+    fd.write("public:\n\n")
+
+    fd.write("\t" + out_file_class + "() {\n\n")
+
+    if len(header_data.compute_lines):
+
+        fd.write("\t\tstatic const char _compute_code[] = {\n")
+        for x in header_data.compute_lines:
+            for c in x:
+                fd.write(str(ord(c)) + ",")
+            fd.write(str(ord("\n")) + ",")
+        fd.write("\t\t0};\n\n")
+
+        fd.write('\t\tsetup(nullptr, nullptr, _compute_code, "' + out_file_class + '");\n')
+        fd.write("\t}\n")
+
+    else:
+
+        fd.write("\t\tstatic const char _vertex_code[] = {\n")
+        for x in header_data.vertex_lines:
+            for c in x:
+                fd.write(str(ord(c)) + ",")
+            fd.write(str(ord("\n")) + ",")
+        fd.write("\t\t0};\n\n")
+
+        fd.write("\t\tstatic const char _fragment_code[]={\n")
+        for x in header_data.fragment_lines:
+            for c in x:
+                fd.write(str(ord(c)) + ",")
+            fd.write(str(ord("\n")) + ",")
+        fd.write("\t\t0};\n\n")
+
+        fd.write('\t\tsetup(_vertex_code, _fragment_code, nullptr, "' + out_file_class + '");\n')
+        fd.write("\t}\n")
+
+    fd.write("};\n\n")
+
+    fd.write("#endif\n")
+    fd.close()
+
+
+def build_rd_headers(target, source, env):
+    for x in source:
+        build_rd_header(str(x))
+
+
+class RAWHeaderStruct:
+    def __init__(self):
+        self.code = ""
+
+
+def include_file_in_raw_header(filename, header_data, depth):
+    fs = open(filename, "r")
+    line = fs.readline()
+    text = ""
+
+    while line:
+
+        while line.find("#include ") != -1:
+            includeline = line.replace("#include ", "").strip()[1:-1]
+
+            import os.path
+
+            included_file = os.path.relpath(os.path.dirname(filename) + "/" + includeline)
+            include_file_in_raw_header(included_file, header_data, depth + 1)
+
+            line = fs.readline()
+
+        header_data.code += line
+        line = fs.readline()
+
+    fs.close()
+
+
+def build_raw_header(filename):
+    header_data = RAWHeaderStruct()
+    include_file_in_raw_header(filename, header_data, 0)
+
+    out_file = filename + ".gen.h"
+    fd = open(out_file, "w")
+
+    enum_constants = []
+
+    fd.write("/* WARNING, THIS FILE WAS GENERATED, DO NOT EDIT */\n")
+
+    out_file_base = out_file.replace(".glsl.gen.h", "_shader_glsl")
+    out_file_base = out_file_base[out_file_base.rfind("/") + 1 :]
+    out_file_base = out_file_base[out_file_base.rfind("\\") + 1 :]
+    out_file_ifdef = out_file_base.replace(".", "_").upper()
+    fd.write("#ifndef " + out_file_ifdef + "_RAW_H\n")
+    fd.write("#define " + out_file_ifdef + "_RAW_H\n")
+    fd.write("\n")
+    fd.write("static const char " + out_file_base + "[] = {\n")
+    for c in header_data.code:
+        fd.write(str(ord(c)) + ",")
+    fd.write("\t\t0};\n\n")
+    fd.write("#endif\n")
+    fd.close()
+
+
+def build_rd_headers(target, source, env):
+    for x in source:
+        build_rd_header(str(x))
+
+
+def build_raw_headers(target, source, env):
+    for x in source:
+        build_raw_header(str(x))
+
+
+if __name__ == "__main__":
+    subprocess_main(globals())