Remove obsolete GLES3 backend

Due to the port to Vulkan and complete redesign of the rendering backend,
the `drivers/gles3` code is no longer usable in this state and is not
planned to be ported to the new architecture.

The GLES2 backend is kept (while still disabled and non-working) as it
will eventually be ported to serve as the low-end renderer for Godot 4.0.

Some GLES3 features might be selectively ported to the updated GLES2
backend if there's a need for them, and extensions we can use for that.

So long, OpenGL driver bugs!

2 files changed, 10 insertions, 43 deletions

diff --git a/platform/javascript/export/export.cpp b/platform/javascript/export/export.cpp
index 6e1f7d749b..c44a0270ab 100644
--- a/platform/javascript/export/export.cpp
+++ b/platform/javascript/export/export.cpp
@@ -271,11 +271,9 @@ void EditorExportPlatformJavaScript::get_preset_features(const Ref<EditorExportP
 		String driver = ProjectSettings::get_singleton()->get("rendering/quality/driver/driver_name");
 		if (driver == "GLES2") {
 			r_features->push_back("etc");
-		} else if (driver == "GLES3") {
+		} else if (driver == "Vulkan") {
+			// FIXME: Review if this is correct.
 			r_features->push_back("etc2");
-			if (ProjectSettings::get_singleton()->get("rendering/quality/driver/fallback_to_gles2")) {
-				r_features->push_back("etc");
-			}
 		}
 	}
 }
diff --git a/platform/javascript/os_javascript.cpp b/platform/javascript/os_javascript.cpp
index f657ef483e..d22e53e7ea 100644
--- a/platform/javascript/os_javascript.cpp
+++ b/platform/javascript/os_javascript.cpp
@@ -32,7 +32,6 @@
 
 #include "core/io/file_access_buffered_fa.h"
 #include "drivers/gles2/rasterizer_gles2.h"
-#include "drivers/gles3/rasterizer_gles3.h"
 #include "drivers/unix/dir_access_unix.h"
 #include "drivers/unix/file_access_unix.h"
 #include "main/main.h"
@@ -825,8 +824,6 @@ int OS_JavaScript::get_video_driver_count() const {
 const char *OS_JavaScript::get_video_driver_name(int p_driver) const {
 
 	switch (p_driver) {
-		case VIDEO_DRIVER_GLES3:
-			return "GLES3";
 		case VIDEO_DRIVER_GLES2:
 			return "GLES2";
 	}
@@ -908,41 +905,14 @@ Error OS_JavaScript::initialize(const VideoMode &p_desired, int p_video_driver,
 		set_window_per_pixel_transparency_enabled(true);
 	}
 
-	bool gles3 = true;
-	if (p_video_driver == VIDEO_DRIVER_GLES2) {
-		gles3 = false;
-	}
-
 	bool gl_initialization_error = false;
 
-	while (true) {
-		if (gles3) {
-			if (RasterizerGLES3::is_viable() == OK) {
-				attributes.majorVersion = 2;
-				RasterizerGLES3::register_config();
-				RasterizerGLES3::make_current();
-				break;
-			} else {
-				if (GLOBAL_GET("rendering/quality/driver/fallback_to_gles2")) {
-					p_video_driver = VIDEO_DRIVER_GLES2;
-					gles3 = false;
-					continue;
-				} else {
-					gl_initialization_error = true;
-					break;
-				}
-			}
-		} else {
-			if (RasterizerGLES2::is_viable() == OK) {
-				attributes.majorVersion = 1;
-				RasterizerGLES2::register_config();
-				RasterizerGLES2::make_current();
-				break;
-			} else {
-				gl_initialization_error = true;
-				break;
-			}
-		}
+	if (RasterizerGLES2::is_viable() == OK) {
+		attributes.majorVersion = 1;
+		RasterizerGLES2::register_config();
+		RasterizerGLES2::make_current();
+	} else {
+		gl_initialization_error = true;
 	}
 
 	EMSCRIPTEN_WEBGL_CONTEXT_HANDLE ctx = emscripten_webgl_create_context(GODOT_CANVAS_SELECTOR, &attributes);
@@ -951,9 +921,8 @@ Error OS_JavaScript::initialize(const VideoMode &p_desired, int p_video_driver,
 	}
 
 	if (gl_initialization_error) {
-		OS::get_singleton()->alert("Your browser does not support any of the supported WebGL versions.\n"
-								   "Please update your browser version.",
-				"Unable to initialize Video driver");
+		OS::get_singleton()->alert("Your browser does not seem to support WebGL. Please update your browser version.",
+				"Unable to initialize video driver");
 		return ERR_UNAVAILABLE;
 	}