Disable driver fallback to GLES2 by default

GLES2 is not designed to be a drop-in replacement for the GLES3 backend,
so the fallback mode has to be used knowingly. It *can* make sense for
simple projects which make sure to handle the differences between both
rendering backends, but most users should stick to one supported backend.

By making it opt-in, we can now use this parameter to define whether to
export ETC textures to Android and iOS when using GLES3 + Fallback.

When using GLES3 without Fallback on Android, set the proper min GLES
version in the AndroidManifest.

Also made the option boolean and renamed it for clarity and to avoid
conflict with the previous String option (which would always evaluate as
"true" otherwise).

Fixes #26569.

12 files changed, 43 insertions, 18 deletions

diff --git a/doc/classes/ProjectSettings.xml b/doc/classes/ProjectSettings.xml
index 1782edf25d..1fec737642 100644
--- a/doc/classes/ProjectSettings.xml
+++ b/doc/classes/ProjectSettings.xml
@@ -688,10 +688,13 @@
 		</member>
 		<member name="rendering/quality/directional_shadow/size.mobile" type="int" setter="" getter="">
 		</member>
-		<member name="rendering/quality/driver/driver_fallback" type="String" setter="" getter="">
-			Whether to allow falling back to other graphics drivers if the preferred driver is not available. Best means use the best working driver (this is the default). Never means never fall back to another driver even if it does not work. This means the project will not run if the preferred driver does not function.
-		</member>
 		<member name="rendering/quality/driver/driver_name" type="String" setter="" getter="">
+			Name of the configured video driver ("GLES2" or "GLES3").
+			Note that the backend in use can be overridden at runtime via the [code]--video-driver[/code] command line argument, or by the [member rendering/quality/driver/fallback_to_gles2] option if the target system does not support GLES3 and falls back to GLES2. In such cases, this property is not updated, so use [method OS.get_current_video_driver] to query it at runtime.
+		</member>
+		<member name="rendering/quality/driver/fallback_to_gles2" type="bool" setter="" getter="">
+			Whether to allow falling back to the GLES2 driver if the GLES3 driver is not supported. Default value: [code]false[/code].
+			Note that the two video drivers are not drop-in replacements for each other, so a game designed for GLES3 might not work properly when falling back to GLES2. In particular, some features of the GLES3 backend are not available in GLES2. Enabling this setting also means that both ETC and ETC2 VRAM-compressed textures will be exported on Android and iOS, increasing the size of the game data pack.
 		</member>
 		<member name="rendering/quality/filters/anisotropic_filter_level" type="int" setter="" getter="">
 			Maximum Anisotropic filter level used for textures when anisotropy enabled.
diff --git a/editor/editor_export.cpp b/editor/editor_export.cpp
index 75708431ec..0423fdf4db 100644
--- a/editor/editor_export.cpp
+++ b/editor/editor_export.cpp
@@ -1163,13 +1163,23 @@ void EditorExport::add_export_preset(const Ref<EditorExportPreset> &p_preset, in
 String EditorExportPlatform::test_etc2() const {
 
 	String driver = ProjectSettings::get_singleton()->get("rendering/quality/driver/driver_name");
+	bool driver_fallback = ProjectSettings::get_singleton()->get("rendering/quality/driver/fallback_to_gles2");
 	bool etc_supported = ProjectSettings::get_singleton()->get("rendering/vram_compression/import_etc");
 	bool etc2_supported = ProjectSettings::get_singleton()->get("rendering/vram_compression/import_etc2");
 
 	if (driver == "GLES2" && !etc_supported) {
-		return TTR("Target platform requires 'ETC' texture compression for GLES2. Enable 'rendering/vram_compression/import_etc' in Project Settings.");
-	} else if (driver == "GLES3" && !etc2_supported) {
-		return TTR("Target platform requires 'ETC2' texture compression for GLES3. Enable 'rendering/vram_compression/import_etc2' in Project Settings.");
+		return TTR("Target platform requires 'ETC' texture compression for GLES2. Enable 'Import Etc' in Project Settings.");
+	} else if (driver == "GLES3") {
+		String err;
+		if (!etc2_supported) {
+			err += TTR("Target platform requires 'ETC2' texture compression for GLES3. Enable 'Import Etc 2' in Project Settings.");
+		}
+		if (driver_fallback && !etc_supported) {
+			if (err != String())
+				err += "\n";
+			err += TTR("Target platform requires 'ETC' texture compression for the driver fallback to GLES2.\nEnable 'Import Etc' in Project Settings, or disable 'Driver Fallback Enabled'.");
+		}
+		return err;
 	}
 	return String();
 }
diff --git a/main/main.cpp b/main/main.cpp
index 9b062d3951..1ef8491a60 100644
--- a/main/main.cpp
+++ b/main/main.cpp
@@ -880,8 +880,7 @@ Error Main::setup(const char *execpath, int argc, char *argv[], bool p_second_ph
 		video_driver = GLOBAL_GET("rendering/quality/driver/driver_name");
 	}
 
-	GLOBAL_DEF("rendering/quality/driver/driver_fallback", "Best");
-	ProjectSettings::get_singleton()->set_custom_property_info("rendering/quality/driver/driver_fallback", PropertyInfo(Variant::STRING, "rendering/quality/driver/driver_fallback", PROPERTY_HINT_ENUM, "Best,Never"));
+	GLOBAL_DEF("rendering/quality/driver/fallback_to_gles2", false);
 
 	// Assigning here even though it's GLES2-specific, to be sure that it appears in docs
 	GLOBAL_DEF("rendering/quality/2d/gles2_use_nvidia_rect_flicker_workaround", false);
diff --git a/platform/android/export/export.cpp b/platform/android/export/export.cpp
index 8ffd355219..aab4bc3883 100644
--- a/platform/android/export/export.cpp
+++ b/platform/android/export/export.cpp
@@ -658,6 +658,8 @@ class EditorExportPlatformAndroid : public EditorExportPlatform {
 
 		int orientation = p_preset->get("screen/orientation");
 
+		bool min_gles3 = ProjectSettings::get_singleton()->get("rendering/quality/driver/driver_name") == "GLES3" &&
+						 !ProjectSettings::get_singleton()->get("rendering/quality/driver/fallback_to_gles2");
 		bool screen_support_small = p_preset->get("screen/support_small");
 		bool screen_support_normal = p_preset->get("screen/support_normal");
 		bool screen_support_large = p_preset->get("screen/support_large");
@@ -815,6 +817,11 @@ class EditorExportPlatformAndroid : public EditorExportPlatform {
 							}
 						}
 
+						if (tname == "uses-feature" && attrname == "glEsVersion") {
+
+							encode_uint32(min_gles3 ? 0x00030000 : 0x00020000, &p_manifest.write[iofs + 16]);
+						}
+
 						iofs += 20;
 					}
 
@@ -1119,6 +1126,9 @@ public:
 			r_features->push_back("etc");
 		} else if (driver == "GLES3") {
 			r_features->push_back("etc2");
+			if (ProjectSettings::get_singleton()->get("rendering/quality/driver/fallback_to_gles2")) {
+				r_features->push_back("etc");
+			}
 		}
 
 		Vector<String> abis = get_enabled_abis(p_preset);
diff --git a/platform/android/os_android.cpp b/platform/android/os_android.cpp
index b86976843c..8c4531213f 100644
--- a/platform/android/os_android.cpp
+++ b/platform/android/os_android.cpp
@@ -131,7 +131,7 @@ Error OS_Android::initialize(const VideoMode &p_desired, int p_video_driver, int
 				RasterizerGLES3::make_current();
 				break;
 			} else {
-				if (GLOBAL_GET("rendering/quality/driver/driver_fallback") == "Best") {
+				if (GLOBAL_GET("rendering/quality/driver/fallback_to_gles2")) {
 					p_video_driver = VIDEO_DRIVER_GLES2;
 					use_gl3 = false;
 					continue;
diff --git a/platform/iphone/export/export.cpp b/platform/iphone/export/export.cpp
index 67034388b9..f25c8a4a22 100644
--- a/platform/iphone/export/export.cpp
+++ b/platform/iphone/export/export.cpp
@@ -201,6 +201,9 @@ void EditorExportPlatformIOS::get_preset_features(const Ref<EditorExportPreset>
 		r_features->push_back("etc");
 	} else if (driver == "GLES3") {
 		r_features->push_back("etc2");
+		if (ProjectSettings::get_singleton()->get("rendering/quality/driver/fallback_to_gles2")) {
+			r_features->push_back("etc");
+		}
 	}
 
 	Vector<String> architectures = _get_preset_architectures(p_preset);
diff --git a/platform/iphone/os_iphone.cpp b/platform/iphone/os_iphone.cpp
index b44b3127c7..7d0fdd2078 100644
--- a/platform/iphone/os_iphone.cpp
+++ b/platform/iphone/os_iphone.cpp
@@ -120,7 +120,7 @@ Error OSIPhone::initialize(const VideoMode &p_desired, int p_video_driver, int p
 				RasterizerGLES3::make_current();
 				break;
 			} else {
-				if (GLOBAL_GET("rendering/quality/driver/driver_fallback") == "Best") {
+				if (GLOBAL_GET("rendering/quality/driver/fallback_to_gles2")) {
 					p_video_driver = VIDEO_DRIVER_GLES2;
 					use_gl3 = false;
 					continue;
diff --git a/platform/javascript/os_javascript.cpp b/platform/javascript/os_javascript.cpp
index 57ae1b6e26..34781ce365 100644
--- a/platform/javascript/os_javascript.cpp
+++ b/platform/javascript/os_javascript.cpp
@@ -829,7 +829,7 @@ Error OS_JavaScript::initialize(const VideoMode &p_desired, int p_video_driver,
 				RasterizerGLES3::make_current();
 				break;
 			} else {
-				if (GLOBAL_GET("rendering/quality/driver/driver_fallback") == "Best") {
+				if (GLOBAL_GET("rendering/quality/driver/fallback_to_gles2")) {
 					p_video_driver = VIDEO_DRIVER_GLES2;
 					gles3 = false;
 					continue;
diff --git a/platform/osx/os_osx.mm b/platform/osx/os_osx.mm
index 027a4e76f6..d72e6038d4 100644
--- a/platform/osx/os_osx.mm
+++ b/platform/osx/os_osx.mm
@@ -1420,7 +1420,7 @@ Error OS_OSX::initialize(const VideoMode &p_desired, int p_video_driver, int p_a
 				RasterizerGLES3::make_current();
 				break;
 			} else {
-				if (GLOBAL_GET("rendering/quality/driver/driver_fallback") == "Best" || editor) {
+				if (GLOBAL_GET("rendering/quality/driver/fallback_to_gles2") || editor) {
 					p_video_driver = VIDEO_DRIVER_GLES2;
 					gles3 = false;
 					continue;
diff --git a/platform/uwp/os_uwp.cpp b/platform/uwp/os_uwp.cpp
index 637ef5aaef..bc74da8a1b 100644
--- a/platform/uwp/os_uwp.cpp
+++ b/platform/uwp/os_uwp.cpp
@@ -202,7 +202,7 @@ Error OS_UWP::initialize(const VideoMode &p_desired, int p_video_driver, int p_a
 			memdelete(gl_context);
 			gl_context = NULL;
 
-			if (GLOBAL_GET("rendering/quality/driver/driver_fallback") == "Best") {
+			if (GLOBAL_GET("rendering/quality/driver/fallback_to_gles2")) {
 				if (p_video_driver == VIDEO_DRIVER_GLES2) {
 					gl_initialization_error = true;
 					break;
@@ -224,7 +224,7 @@ Error OS_UWP::initialize(const VideoMode &p_desired, int p_video_driver, int p_a
 				RasterizerGLES3::make_current();
 				break;
 			} else {
-				if (GLOBAL_GET("rendering/quality/driver/driver_fallback") == "Best") {
+				if (GLOBAL_GET("rendering/quality/driver/fallback_to_gles2")) {
 					p_video_driver = VIDEO_DRIVER_GLES2;
 					opengl_api_type = ContextEGL_UWP::GLES_2_0;
 					continue;
diff --git a/platform/windows/os_windows.cpp b/platform/windows/os_windows.cpp
index 1a5e97cfb1..6125455e74 100644
--- a/platform/windows/os_windows.cpp
+++ b/platform/windows/os_windows.cpp
@@ -1290,7 +1290,7 @@ Error OS_Windows::initialize(const VideoMode &p_desired, int p_video_driver, int
 			memdelete(gl_context);
 			gl_context = NULL;
 
-			if (GLOBAL_GET("rendering/quality/driver/driver_fallback") == "Best" || editor) {
+			if (GLOBAL_GET("rendering/quality/driver/fallback_to_gles2") || editor) {
 				if (p_video_driver == VIDEO_DRIVER_GLES2) {
 					gl_initialization_error = true;
 					break;
@@ -1312,7 +1312,7 @@ Error OS_Windows::initialize(const VideoMode &p_desired, int p_video_driver, int
 				RasterizerGLES3::make_current();
 				break;
 			} else {
-				if (GLOBAL_GET("rendering/quality/driver/driver_fallback") == "Best" || editor) {
+				if (GLOBAL_GET("rendering/quality/driver/fallback_to_gles2") || editor) {
 					p_video_driver = VIDEO_DRIVER_GLES2;
 					gles3_context = false;
 					continue;
diff --git a/platform/x11/os_x11.cpp b/platform/x11/os_x11.cpp
index cc4d57ea99..87b63c0982 100644
--- a/platform/x11/os_x11.cpp
+++ b/platform/x11/os_x11.cpp
@@ -299,7 +299,7 @@ Error OS_X11::initialize(const VideoMode &p_desired, int p_video_driver, int p_a
 			memdelete(context_gl);
 			context_gl = NULL;
 
-			if (GLOBAL_GET("rendering/quality/driver/driver_fallback") == "Best" || editor) {
+			if (GLOBAL_GET("rendering/quality/driver/fallback_to_gles2") || editor) {
 				if (p_video_driver == VIDEO_DRIVER_GLES2) {
 					gl_initialization_error = true;
 					break;
@@ -321,7 +321,7 @@ Error OS_X11::initialize(const VideoMode &p_desired, int p_video_driver, int p_a
 				RasterizerGLES3::make_current();
 				break;
 			} else {
-				if (GLOBAL_GET("rendering/quality/driver/driver_fallback") == "Best" || editor) {
+				if (GLOBAL_GET("rendering/quality/driver/fallback_to_gles2") || editor) {
 					p_video_driver = VIDEO_DRIVER_GLES2;
 					opengl_api_type = ContextGL_X11::GLES_2_0_COMPATIBLE;
 					continue;