Add warning for missing characters in label font

scene/gui/label.cpp

@@ -288,6 +288,36 @@ void Label::_update_theme_item_cache() {
 	theme_cache.font_shadow_outline_size = get_theme_constant(SNAME("shadow_outline_size"));
 }
 
+PackedStringArray Label::get_configuration_warnings() const {
+	PackedStringArray warnings = Control::get_configuration_warnings();
+
+	// Ensure that the font can render all of the required glyphs.
+	Ref<Font> font;
+	if (settings.is_valid()) {
+		font = settings->get_font();
+	}
+	if (font.is_null()) {
+		font = theme_cache.font;
+	}
+
+	if (font.is_valid()) {
+		if (dirty || font_dirty || lines_dirty) {
+			const_cast<Label *>(this)->_shape();
+		}
+
+		const Glyph *glyph = TS->shaped_text_get_glyphs(text_rid);
+		int64_t glyph_count = TS->shaped_text_get_glyph_count(text_rid);
+		for (int64_t i = 0; i < glyph_count; i++) {
+			if (glyph[i].font_rid == RID()) {
+				warnings.push_back(RTR("The current font does not support rendering one or more characters used in this Label's text."));
+				break;
+			}
+		}
+	}
+
+	return warnings;
+}
+
 void Label::_notification(int p_what) {
 	switch (p_what) {
 		case NOTIFICATION_TRANSLATION_CHANGED: {
@@ -302,6 +332,7 @@ void Label::_notification(int p_what) {
 			dirty = true;
 
 			queue_redraw();
+			update_configuration_warnings();
 		} break;
 
 		case NOTIFICATION_LAYOUT_DIRECTION_CHANGED: {
@@ -674,6 +705,7 @@ void Label::set_text(const String &p_string) {
 	}
 	queue_redraw();
 	update_minimum_size();
+	update_configuration_warnings();
 }
 
 void Label::_invalidate() {

scene/gui/label.h

@@ -93,6 +93,7 @@ protected:
 
 public:
 	virtual Size2 get_minimum_size() const override;
+	virtual PackedStringArray get_configuration_warnings() const override;
 
 	void set_horizontal_alignment(HorizontalAlignment p_alignment);
 	HorizontalAlignment get_horizontal_alignment() const;