Check only for WebGL 1.0, move test to HTML file

Whether to use WebGL 1.0 or 2.0 can only be determined at runtime after
reading project settings, so check for the lower version.

The test is now in the HTML file, so if desired WebGL 2.0 can be
checked early by changing the behaviour there.

3 files changed, 32 insertions, 23 deletions

diff --git a/misc/dist/html/default.html b/misc/dist/html/default.html
index a1a4e89d02..4e3515a7b6 100644
--- a/misc/dist/html/default.html
+++ b/misc/dist/html/default.html
@@ -244,9 +244,6 @@ $GODOT_HEAD_INCLUDE
 			var statusMode = 'hidden';
 			var indeterminiateStatusAnimationId = 0;
 
-			setStatusMode('indeterminate');
-			engine.setCanvas(canvas);
-
 			function setStatusMode(mode) {
 
 				if (statusMode === mode || !initializing)
@@ -367,18 +364,27 @@ $GODOT_HEAD_INCLUDE
 				});
 			}
 
-			engine.startGame(BASENAME + '.pck').then(() => {
-				setStatusMode('hidden');
-				initializing = false;
-			}, err => {
+			function displayFailureNotice(err) {
+				var msg = err.message || err;
 				if (DEBUG_ENABLED) {
-					printError(err.message);
-					console.warn(err);
+					printError(msg);
 				}
-				setStatusNotice(err.message);
+				console.error(msg);
+				setStatusNotice(msg);
 				setStatusMode('notice');
 				initializing = false;
-			});
+			};
+
+			if (!Engine.isWebGLAvailable()) {
+				displayFailureNotice("WebGL not available");
+			} else {
+				setStatusMode('indeterminate');
+				engine.setCanvas(canvas);
+				engine.startGame(BASENAME + '.pck').then(() => {
+					setStatusMode('hidden');
+					initializing = false;
+				}, displayFailureNotice);
+			}
 		})();
 	//]]></script>
 </body>
diff --git a/platform/javascript/engine.js b/platform/javascript/engine.js
index bca1851f40..8f22e41660 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.getContet('experimental-webgl');
+			} else if (majorVersion === 2) {
+				testContext = testCanvas.getContext('webgl2') || testCanvas.getContet('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 ace0bdad60..cbfe99ba2d 100644
--- a/platform/javascript/os_javascript.cpp
+++ b/platform/javascript/os_javascript.cpp
@@ -444,6 +444,7 @@ Error OS_JavaScript::initialize(const VideoMode &p_desired, int p_video_driver,
 			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;