3 files changed, 43 insertions, 21 deletions
diff --git a/platform/javascript/detect.py b/platform/javascript/detect.py
index 7e6a1518ed..ad6b710382 100644
--- a/platform/javascript/detect.py
+++ b/platform/javascript/detect.py
@@ -65,13 +65,14 @@ def configure(env):
 
     elif (env["target"] == "release_debug"):
         env.Append(CCFLAGS=['-O2', '-DDEBUG_ENABLED'])
-        env.Append(LINKFLAGS=['-O2', '-s', 'ASSERTIONS=1'])
+        env.Append(LINKFLAGS=['-O2'])
         # retain function names at the cost of file size, for backtraces and profiling
         env.Append(LINKFLAGS=['--profiling-funcs'])
 
     elif (env["target"] == "debug"):
         env.Append(CCFLAGS=['-O1', '-D_DEBUG', '-g', '-DDEBUG_ENABLED'])
         env.Append(LINKFLAGS=['-O1', '-g'])
+        env.Append(LINKFLAGS=['-s', 'ASSERTIONS=1'])
 
     ## Compiler configuration
 
@@ -102,7 +103,7 @@ def configure(env):
     ## Compile flags
 
     env.Append(CPPPATH=['#platform/javascript'])
-    env.Append(CPPFLAGS=['-DJAVASCRIPT_ENABLED', '-DUNIX_ENABLED', '-DPTHREAD_NO_RENAME', '-DTYPED_METHOD_BIND', '-DNO_THREADS'])
+    env.Append(CPPFLAGS=['-DJAVASCRIPT_ENABLED', '-DUNIX_ENABLED', '-DTYPED_METHOD_BIND', '-DNO_THREADS'])
     env.Append(CPPFLAGS=['-DGLES3_ENABLED'])
 
     # These flags help keep the file size down
diff --git a/platform/javascript/engine.js b/platform/javascript/engine.js
index bca1851f40..e6fb48d0d2 100644
--- a/platform/javascript/engine.js
+++ b/platform/javascript/engine.js
@@ -138,18 +138,6 @@
 			}
 
 			var actualCanvas = this.rtenv.canvas;
-			var testContext = false;
-			var testCanvas;
-			try {
-				testCanvas = document.createElement('canvas');
-				testContext = testCanvas.getContext('webgl2') || testCanvas.getContext('experimental-webgl2');
-			} catch (e) {}
-			if (!testContext) {
-				throw new Error("WebGL 2 not available");
-			}
-			testCanvas = null;
-			testContext = null;
-
 			// canvas can grab focus on click
 			if (actualCanvas.tabIndex < 0) {
 				actualCanvas.tabIndex = 0;
@@ -273,6 +261,20 @@
 
 	Engine.RuntimeEnvironment = engine.RuntimeEnvironment;
 
+	Engine.isWebGLAvailable = function(majorVersion = 1) {
+
+		var testContext = false;
+		try {
+			var testCanvas = document.createElement('canvas');
+			if (majorVersion === 1) {
+				testContext = testCanvas.getContext('webgl') || testCanvas.getContext('experimental-webgl');
+			} else if (majorVersion === 2) {
+				testContext = testCanvas.getContext('webgl2') || testCanvas.getContext('experimental-webgl2');
+			}
+		} catch (e) {}
+		return !!testContext;
+	};
+
 	Engine.load = function(newBasePath) {
 
 		if (newBasePath !== undefined) basePath = getBasePath(newBasePath);
diff --git a/platform/javascript/os_javascript.cpp b/platform/javascript/os_javascript.cpp
index e226ab6332..cbfe99ba2d 100644
--- a/platform/javascript/os_javascript.cpp
+++ b/platform/javascript/os_javascript.cpp
@@ -33,6 +33,7 @@
 #include "core/engine.h"
 #include "core/io/file_access_buffered_fa.h"
 #include "dom_keys.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"
@@ -57,12 +58,19 @@ static void dom2godot_mod(T emscripten_event_ptr, Ref<InputEventWithModifiers> g
 
 int OS_JavaScript::get_video_driver_count() const {
 
-	return 1;
+	return VIDEO_DRIVER_MAX;
 }
 
 const char *OS_JavaScript::get_video_driver_name(int p_driver) const {
 
-	return "GLES3";
+	switch (p_driver) {
+		case VIDEO_DRIVER_GLES3:
+			return "GLES3";
+		case VIDEO_DRIVER_GLES2:
+			return "GLES2";
+	}
+	ERR_EXPLAIN("Invalid video driver index " + itos(p_driver));
+	ERR_FAIL_V(NULL);
 }
 
 int OS_JavaScript::get_audio_driver_count() const {
@@ -422,8 +430,21 @@ Error OS_JavaScript::initialize(const VideoMode &p_desired, int p_video_driver,
 	emscripten_webgl_init_context_attributes(&attributes);
 	attributes.alpha = false;
 	attributes.antialias = false;
-	attributes.majorVersion = 2;
+	ERR_FAIL_INDEX_V(p_video_driver, VIDEO_DRIVER_MAX, ERR_INVALID_PARAMETER);
+	switch (p_video_driver) {
+		case VIDEO_DRIVER_GLES3:
+			attributes.majorVersion = 2;
+			RasterizerGLES3::register_config();
+			RasterizerGLES3::make_current();
+			break;
+		case VIDEO_DRIVER_GLES2:
+			attributes.majorVersion = 1;
+			RasterizerGLES2::register_config();
+			RasterizerGLES2::make_current();
+			break;
+	}
 	EMSCRIPTEN_WEBGL_CONTEXT_HANDLE ctx = emscripten_webgl_create_context(NULL, &attributes);
+	ERR_EXPLAIN("WebGL " + itos(attributes.majorVersion) + ".0 not available");
 	ERR_FAIL_COND_V(emscripten_webgl_make_context_current(ctx) != EMSCRIPTEN_RESULT_SUCCESS, ERR_UNAVAILABLE);
 
 	video_mode = p_desired;
@@ -447,12 +468,8 @@ Error OS_JavaScript::initialize(const VideoMode &p_desired, int p_video_driver,
 
 	print_line("Init Audio");
 
-	AudioDriverManager::add_driver(&audio_driver_javascript);
 	AudioDriverManager::initialize(p_audio_driver);
 
-	RasterizerGLES3::register_config();
-	RasterizerGLES3::make_current();
-
 	print_line("Init VS");
 
 	visual_server = memnew(VisualServerRaster());
@@ -1012,6 +1029,8 @@ OS_JavaScript::OS_JavaScript(const char *p_execpath, GetUserDataDirFunc p_get_us
 	Vector<Logger *> loggers;
 	loggers.push_back(memnew(StdLogger));
 	_set_logger(memnew(CompositeLogger(loggers)));
+
+	AudioDriverManager::add_driver(&audio_driver_javascript);
 }
 
 OS_JavaScript::~OS_JavaScript() {