Print a warning when importing a repeating NPOT texture in a GLES2 project

Repeating NPOT textures are not guaranteed to be displayed correctly
in GLES2, since the specification does not mandate support for it.

The warning is also displayed in GLES3 projects that are configured
to allow falling back to GLES2.

editor/import/resource_importer_texture.cpp

@@ -393,6 +393,21 @@ Error ResourceImporterTexture::import(const String &p_source_file, const String
 	int tex_flags = 0;
 	if (repeat > 0) {
 		tex_flags |= Texture::FLAG_REPEAT;
+
+		const bool min_gles3 = GLOBAL_GET("rendering/quality/driver/driver_name") == "GLES3" &&
+							   !GLOBAL_GET("rendering/quality/driver/fallback_to_gles2");
+		if (!min_gles3 && !image->is_size_po2()) {
+			// The project can be run using GLES2. GLES2 does not guarantee that
+			// repeating textures with a non-power-of-two size will be displayed
+			// without artifacts (due to upscaling to the nearest power of 2).
+			if (GLOBAL_GET("rendering/quality/driver/fallback_to_gles2")) {
+				WARN_PRINT(vformat("%s: Imported a repeating texture with a size of %dx%d, but the project is configured to allow falling back to GLES2.\nNon-power-of-2 repeating textures may not display correctly on some platforms such as HTML5. This is because GLES2 does not mandate support for non-power-of-2 repeating textures.",
+						p_source_file, image->get_width(), image->get_height()));
+			} else {
+				WARN_PRINT(vformat("%s: Imported a repeating texture with a size of %dx%d, but the project is configured to use GLES2.\nNon-power-of-2 repeating textures may not display correctly on some platforms such as HTML5. This is because GLES2 does not mandate support for non-power-of-2 repeating textures.",
+						p_source_file, image->get_width(), image->get_height()));
+			}
+		}
 	}
 	if (repeat == 2) {
 		tex_flags |= Texture::FLAG_MIRRORED_REPEAT;