Show backend messages similarly to the keyboard layout

cairo.c

@@ -5,6 +5,10 @@
 #include <gdk-pixbuf/gdk-pixbuf.h>
 #endif
 
+uint32_t color_with_alpha(uint32_t color, uint8_t alpha) {
+	return (color & 0xFFFFFF00) | alpha;
+}
+
 void cairo_set_source_u32(cairo_t *cairo, uint32_t color) {
 	cairo_set_source_rgba(cairo,
 			(color >> (3*8) & 0xFF) / 255.0,

include/cairo.h

@@ -9,6 +9,7 @@
 #include <gdk-pixbuf/gdk-pixbuf.h>
 #endif
 
+uint32_t color_with_alpha(uint32_t color, uint8_t alpha);
 void cairo_set_source_u32(cairo_t *cairo, uint32_t color);
 cairo_subpixel_order_t to_cairo_subpixel_order(enum wl_output_subpixel subpixel);
 

include/swaylock.h

@@ -77,6 +77,12 @@ struct swaylock_password {
 	char *buffer;
 };
 
+struct swaylock_backend_message_list {
+	size_t num_messages;
+	size_t max_num_messages;
+	char **messages;
+};
+
 struct swaylock_state {
 	struct loop *eventloop;
 	struct loop_timer *input_idle_timer; // timer to reset input state to IDLE
@@ -90,6 +96,7 @@ struct swaylock_state {
 	struct wl_list images;
 	struct swaylock_args args;
 	struct swaylock_password password;
+	struct swaylock_backend_message_list backend_message_list; // backend messages displayed in the UI
 	struct swaylock_xkb xkb;
 	cairo_surface_t *test_surface;
 	cairo_t *test_cairo; // used to estimate font/text sizes
@@ -144,4 +151,8 @@ void initialize_pw_backend(int argc, char **argv);
 void run_pw_backend_child(void);
 void clear_buffer(char *buf, size_t size);
 
+// Add a message to the list of displayed backend messages. Creates a copy of
+// the string, it can be freed after calling this function.
+void add_backend_message(struct swaylock_state *state, char *msg);
+
 #endif

main.c

@@ -1034,9 +1034,24 @@ static void display_in(int fd, short mask, void *data) {
 	}
 }
 
+void add_backend_message(struct swaylock_state *state, char *msg) {
+	size_t n_max = state->backend_message_list.max_num_messages;
+	char **messages = state->backend_message_list.messages;
+	if (state->backend_message_list.num_messages == n_max) {
+		free(messages[n_max - 1]);
+	} else {
+		state->backend_message_list.num_messages += 1;
+	}
+	for (int i = n_max - 1; i > 0; i--) {
+		messages[i] = messages[i - 1];
+	}
+	messages[0] = strdup(msg);
+}
+
 static void handle_backend_text_message(char *msg) {
-	//TODO: show message in UI
-	swaylock_log(LOG_DEBUG, "Received text message from backend: %s", msg);
+	//TODO: schedule old messages to be hidden after a timeout?
+	add_backend_message(&state, msg);
+	damage_state(&state);
 }
 
 static void handle_auth_result(bool success) {
@@ -1067,7 +1082,7 @@ static void comm_in(int fd, short mask, void *data) {
 	switch(msg_type){
 	case BACKEND_MESSAGE_TYPE_TEXT:
 		handle_backend_text_message((char *) comm_data);
-		//TODO: memory leak; where to free comm_data?
+		free(comm_data);
 		break;
 	case BACKEND_MESSAGE_TYPE_AUTH_RESULT:
 		handle_auth_result(*(bool *) comm_data);
@@ -1178,6 +1193,16 @@ int main(int argc, char **argv) {
 		return EXIT_FAILURE;
 	}
 
+	state.backend_message_list = (struct swaylock_backend_message_list){
+		.num_messages = 0,
+		//TODO: make configurable?
+		.max_num_messages = 4,
+	};
+	state.backend_message_list.messages = malloc(state.backend_message_list.max_num_messages * sizeof(char *));
+	for (size_t i = 0; i < state.backend_message_list.max_num_messages; i++) {
+		state.backend_message_list.messages[i] = NULL;
+	}
+
 	if (pipe(sigusr_fds) != 0) {
 		swaylock_log(LOG_ERROR, "Failed to pipe");
 		return EXIT_FAILURE;

render.c

@@ -189,6 +189,7 @@ static bool render_frame(struct swaylock_surface *surface) {
 	int buffer_diameter = (arc_radius + arc_thickness) * 2;
 	int buffer_width = buffer_diameter;
 	int buffer_height = buffer_diameter;
+	double box_padding = 4.0 * surface->scale;
 
 	if (text || layout_text) {
 		cairo_set_antialias(state->test_cairo, CAIRO_ANTIALIAS_BEST);
@@ -204,7 +205,6 @@ static bool render_frame(struct swaylock_surface *surface) {
 		if (layout_text) {
 			cairo_text_extents_t extents;
 			cairo_font_extents_t fe;
-			double box_padding = 4.0 * surface->scale;
 			cairo_text_extents(state->test_cairo, layout_text, &extents);
 			cairo_font_extents(state->test_cairo, &fe);
 			buffer_height += fe.height + 2 * box_padding;
@@ -213,6 +213,25 @@ static bool render_frame(struct swaylock_surface *surface) {
 			}
 		}
 	}
+	if (state->backend_message_list.num_messages > 0) {
+		cairo_set_antialias(state->test_cairo, CAIRO_ANTIALIAS_BEST);
+		configure_font_drawing(state->test_cairo, state, surface->subpixel, arc_radius);
+
+		buffer_height += 2 * box_padding;
+		for (size_t i = 0; i < state->backend_message_list.num_messages; i++) {
+			cairo_text_extents_t extents;
+			cairo_font_extents_t fe;
+			cairo_text_extents(state->test_cairo, state->backend_message_list.messages[i], &extents);
+			cairo_font_extents(state->test_cairo, &fe);
+			// NOTE: if the indicator is not shown, this results in
+			// unnecessarily large buffer_height, that could be checked here
+			buffer_height += fe.height + 2 * box_padding;
+			if (buffer_width < extents.width + 2 * box_padding) {
+				buffer_width = extents.width + 2 * box_padding;
+			}
+		}
+	}
+
 	// Ensure buffer size is multiple of buffer scale - required by protocol
 	buffer_height += surface->scale - (buffer_height % surface->scale);
 	buffer_width += surface->scale - (buffer_width % surface->scale);
@@ -260,6 +279,8 @@ static bool render_frame(struct swaylock_surface *surface) {
 	float type_indicator_border_thickness =
 		TYPE_INDICATOR_BORDER_THICKNESS * surface->scale;
 
+	float layout_text_box_height = 0;
+
 	if (draw_indicator) {
 		// Fill inner circle
 		cairo_set_line_width(cairo, 0);
@@ -348,17 +369,17 @@ static bool render_frame(struct swaylock_surface *surface) {
 			cairo_text_extents_t extents;
 			cairo_font_extents_t fe;
 			double x, y;
-			double box_padding = 4.0 * surface->scale;
 			cairo_text_extents(cairo, layout_text, &extents);
 			cairo_font_extents(cairo, &fe);
 			// upper left coordinates for box
 			x = (buffer_width / 2) - (extents.width / 2) - box_padding;
 			y = buffer_diameter;
 
 			// background box
+			layout_text_box_height = fe.height + 2.0 * box_padding;
 			cairo_rectangle(cairo, x, y,
 				extents.width + 2.0 * box_padding,
-				fe.height + 2.0 * box_padding);
+				layout_text_box_height);
 			cairo_set_source_u32(cairo, state->args.colors.layout_background);
 			cairo_fill_preserve(cairo);
 			// border
@@ -375,6 +396,61 @@ static bool render_frame(struct swaylock_surface *surface) {
 		}
 	}
 
+	// display messages from backend
+	if (state->backend_message_list.num_messages > 0) {
+		configure_font_drawing(cairo, state, surface->subpixel, arc_radius);
+		for (size_t i = 0; i < state->backend_message_list.num_messages; i++) {
+			char *str = state->backend_message_list.messages[i];
+
+			cairo_text_extents_t extents;
+			cairo_font_extents_t fe;
+			double x, y;
+
+			cairo_text_extents(cairo, str, &extents);
+			cairo_font_extents(cairo, &fe);
+
+			// upper left coordinates for box
+			x = (buffer_width / 2) - (extents.width / 2) - box_padding;
+			if (draw_indicator) {
+				y = buffer_diameter + 2 * box_padding;
+				if (layout_text) {
+					y += layout_text_box_height;
+				}
+			} else {
+				y = (buffer_diameter / 2) - (fe.height / 2) - box_padding;
+			}
+			y += (fe.height + 2 * box_padding) * i;
+
+			// background box
+			cairo_rectangle(cairo, x, y,
+					extents.width + 2.0 * box_padding,
+					fe.height + 2.0 * box_padding);
+			//TODO: make colors customizable
+			cairo_set_source_u32(cairo,
+					color_with_alpha(
+						state->args.colors.layout_background,
+						(uint8_t) (state->args.colors.layout_background & 0xFF) / (i == 0 ? 1 : 2)));
+			cairo_fill_preserve(cairo);
+
+			// border
+			cairo_set_source_u32(cairo,
+					color_with_alpha(
+						state->args.colors.layout_border,
+						(uint8_t) (state->args.colors.layout_border & 0xFF) / (i == 0 ? 1 : 2)));
+			cairo_stroke(cairo);
+
+			cairo_move_to(cairo,
+					x - extents.x_bearing + box_padding,
+					y + (fe.height - fe.descent) + box_padding);
+			cairo_set_source_u32(cairo,
+					color_with_alpha(
+						state->args.colors.layout_text,
+						(uint8_t) (state->args.colors.layout_text & 0xFF) / (i == 0 ? 1 : 2)));
+			cairo_show_text(cairo, str);
+			cairo_new_sub_path(cairo);
+		}
+	}
+
 	// Send Wayland requests
 	wl_subsurface_set_position(surface->subsurface, subsurf_xpos, subsurf_ypos);