Add GLSL toggle

With the environment variable PROTON_NO_GLSL=1 you can tell wine to
disable GLSL shaders and use ARB shaders instead which might reduce
stuttering in games with wined3d. Usually favours nvidia graphics
drivers.

README.md

@@ -213,5 +213,6 @@ the Wine prefix. Removing the option will revert to the previous behavior.
 | <tt>forcelgadd</tt>   | <tt>PROTON_FORCE_LARGE_ADDRESS_AWARE</tt> | Force Wine to enable the LARGE_ADDRESS_AWARE flag for all executables. |
 | <tt>galliumnine</tt>  | <tt>PROTON_USE_GALLIUM_NINE</tt> | Use Gallium Nine (can also be enabled on the staging tab in winecfg). |
 |                       | <tt>PROTON_GALLIUM_NINE_MODULEPATH</tt> | Set the modulepath for `d3dadapter9.so.1`. By default `/usr/lib32/d3d/d3dadapter9.so.1:/usr/lib64/d3d/d3dadapter9.so.1` |
+| <tt>noglsl</tt>       | <tt>PROTON_NO_GLSL</tt> | Disable GLSL shaders and use ARB shaders instead. Can reduce stuttering when using wined3d. |
 
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proton

@@ -454,6 +454,19 @@ else:
         "/v", "d3d9",
         "/f"], env=env, stdout=DEVNULL, stderr=DEVNULL)
 
+check_environment("PROTON_NO_GLSL", "noglsl")
+subprocess.call([wine_path, "reg", "add",
+    "HKEY_CURRENT_USER\\Software\\Wine\\Direct3D",
+    "/v", "UseGLSL",
+    "/d", "disabled" if "noglsl" in config_opts else "enabled",
+    "/f"], env=env, stdout=DEVNULL, stderr=DEVNULL)
+subprocess.call([wine_path, "reg", "add",
+    "HKEY_CURRENT_USER\\Software\\Wine\\Direct3D",
+    "/v", "MaxVersionGL",
+    "/t", "REG_DWORD",
+    "/d", "0x00030001" if "noglsl" in config_opts else "0",
+    "/f"], env=env, stdout=DEVNULL, stderr=DEVNULL)
+
 ARCH_UNKNOWN=0
 ARCH_I386=1
 ARCH_X86_64=2

user_settings.sample.py

@@ -23,4 +23,7 @@
 
     #Specify d3dadapter9.so.1 path
 #    "PROTON_GALLIUM_NINE_MODULEPATH": "/usr/lib32/d3d/d3dadapter9.so.1:/usr/lib64/d3d/d3dadapter9.so.1",
+
+    #Disable GLSL shaders and use ARB shaders instead
+#    "PROTON_NO_GLSL": "1",
 }