Add HiDPI support

Fixes #3

include/slurp.h

@@ -33,6 +33,7 @@ struct slurp_output {
 	struct wl_list link; // slurp_state::outputs
 
 	struct slurp_box geometry;
+	int32_t scale;
 
 	struct wl_surface *surface;
 	struct zwlr_layer_surface_v1 *layer_surface;

main.c

@@ -150,11 +150,18 @@ static void output_handle_geometry(void *data, struct wl_output *wl_output,
 	output->geometry.y = y;
 }
 
+static void output_handle_scale(void *data, struct wl_output *wl_output,
+		int32_t scale) {
+	struct slurp_output *output = data;
+
+	output->scale = scale;
+}
+
 static const struct wl_output_listener output_listener = {
 	.geometry = output_handle_geometry,
 	.mode = noop,
 	.done = noop,
-	.scale = noop,
+	.scale = output_handle_scale,
 };
 
 static void create_output(struct slurp_state *state,
@@ -166,6 +173,7 @@ static void create_output(struct slurp_state *state,
 	}
 	output->wl_output = wl_output;
 	output->state = state;
+	output->scale = 1;
 	wl_list_insert(&state->outputs, &output->link);
 
 	wl_output_add_listener(wl_output, &output_listener, output);
@@ -192,8 +200,11 @@ static void send_frame(struct slurp_output *output) {
 		return;
 	}
 
+	int32_t buffer_width = output->width * output->scale;
+	int32_t buffer_height = output->height * output->scale;
+
 	output->current_buffer = get_next_buffer(state->shm, output->buffers,
-		output->width, output->height);
+		buffer_width, buffer_height);
 	if (output->current_buffer == NULL) {
 		return;
 	}
@@ -207,6 +218,7 @@ static void send_frame(struct slurp_output *output) {
 
 	wl_surface_attach(output->surface, output->current_buffer->buffer, 0, 0);
 	wl_surface_damage(output->surface, 0, 0, output->width, output->height);
+	wl_surface_set_buffer_scale(output->surface, output->scale);
 	wl_surface_commit(output->surface);
 	output->dirty = false;
 }

render.c

@@ -18,6 +18,10 @@ void render(struct slurp_output *output) {
 	struct slurp_state *state = output->state;
 	struct pool_buffer *buffer = output->current_buffer;
 	cairo_t *cairo = buffer->cairo;
+	int32_t scale = output->scale;
+
+	uint32_t border_color = 0x000000FF;
+	int border_size = 2;
 
 	// Clear
 	cairo_save(cairo);
@@ -37,10 +41,10 @@ void render(struct slurp_output *output) {
 		pointer_get_box(pointer, &x, &y, &width, &height);
 
 		// Draw border
-		int border_size = 2;
-		set_source_u32(cairo, 0x000000FF);
-		cairo_set_line_width(cairo, border_size);
-		cairo_rectangle(cairo, x, y, width, height);
+		set_source_u32(cairo, border_color);
+		cairo_set_line_width(cairo, border_size * scale);
+		cairo_rectangle(cairo, x * scale, y * scale,
+			width * scale, height * scale);
 		cairo_stroke(cairo);
 	}
 }