Use output subpixel when rendering text

Fixes #63

include/wayland.h

@@ -2,6 +2,7 @@
 #define _MAKO_WAYLAND_H
 
 #include <stdbool.h>
+#include <wayland-client-protocol.h>
 
 struct mako_state;
 
@@ -21,6 +22,7 @@ struct mako_output {
 	struct wl_list link; // mako_state::outputs
 
 	char *name;
+	enum wl_output_subpixel subpixel;
 	int32_t scale;
 };
 

render.c

@@ -37,11 +37,43 @@ static void set_rectangle(cairo_t *cairo, int x, int y, int width, int height,
 	cairo_rectangle(cairo, x * scale, y * scale, width * scale, height * scale);
 }
 
+static cairo_subpixel_order_t get_cairo_subpixel_order(
+		enum wl_output_subpixel subpixel) {
+	switch (subpixel) {
+	case WL_OUTPUT_SUBPIXEL_UNKNOWN:
+	case WL_OUTPUT_SUBPIXEL_NONE:
+		return CAIRO_SUBPIXEL_ORDER_DEFAULT;
+	case WL_OUTPUT_SUBPIXEL_HORIZONTAL_RGB:
+		return CAIRO_SUBPIXEL_ORDER_RGB;
+	case WL_OUTPUT_SUBPIXEL_HORIZONTAL_BGR:
+		return CAIRO_SUBPIXEL_ORDER_BGR;
+	case WL_OUTPUT_SUBPIXEL_VERTICAL_RGB:
+		return CAIRO_SUBPIXEL_ORDER_VRGB;
+	case WL_OUTPUT_SUBPIXEL_VERTICAL_BGR:
+		return CAIRO_SUBPIXEL_ORDER_VBGR;
+	}
+}
+
+static void set_font_options(cairo_t *cairo, struct mako_state *state) {
+	if (state->surface_output == NULL) {
+		return;
+	}
+
+	cairo_font_options_t *fo = cairo_font_options_create();
+	cairo_font_options_set_antialias(fo, CAIRO_ANTIALIAS_SUBPIXEL);
+	cairo_font_options_set_subpixel_order(fo,
+		get_cairo_subpixel_order(state->surface_output->subpixel));
+	cairo_set_font_options(cairo, fo);
+	cairo_font_options_destroy(fo);
+}
+
 static int render_notification(cairo_t *cairo, struct mako_state *state,
 		struct mako_style *style, const char *text, int offset_y, int scale) {
 	int border_size = 2 * style->border_size;
 	int padding_size = 2 * style->padding;
 
+	set_font_options(cairo, state);
+
 	PangoLayout *layout = pango_cairo_create_layout(cairo);
 	set_layout_size(layout,
 		state->width - border_size - padding_size,

wayland.c

@@ -40,14 +40,22 @@ static void get_xdg_output(struct mako_output *output) {
 		output);
 }
 
+static void output_handle_geometry(void *data, struct wl_output *wl_output,
+		int32_t x, int32_t y, int32_t phy_width, int32_t phy_height,
+		int32_t subpixel, const char *make, const char *model,
+		int32_t transform) {
+	struct mako_output *output = data;
+	output->subpixel = subpixel;
+}
+
 static void output_handle_scale(void *data, struct wl_output *wl_output,
 		int32_t factor) {
 	struct mako_output *output = data;
 	output->scale = factor;
 }
 
 static const struct wl_output_listener output_listener = {
-	.geometry = noop,
+	.geometry = output_handle_geometry,
 	.mode = noop,
 	.done = noop,
 	.scale = output_handle_scale,