Allow configuring output mode in rootston

Fixes #336

include/rootston/config.h

@@ -9,6 +9,10 @@ struct output_config {
 	enum wl_output_transform transform;
 	int x, y;
 	struct wl_list link;
+	struct {
+		int width, height;
+		float refresh_rate;
+	} mode;
 };
 
 struct device_config {

rootston/config.c

@@ -1,6 +1,7 @@
 #ifndef _POSIX_C_SOURCE
 #define _POSIX_C_SOURCE 200809L
 #endif
+#include <assert.h>
 #include <stdlib.h>
 #include <limits.h>
 #include <getopt.h>
@@ -244,6 +245,21 @@ static int config_ini_handler(void *user, const char *section, const char *name,
 			} else {
 				wlr_log(L_ERROR, "got unknown transform value: %s", value);
 			}
+		} else if (strcmp(name, "mode") == 0) {
+			char *end;
+			oc->mode.width = strtol(value, &end, 10);
+			assert(*end == 'x');
+			++end;
+			oc->mode.height = strtol(end, &end, 10);
+			if (*end) {
+				assert(*end == '@');
+				++end;
+				oc->mode.refresh_rate = strtof(end, &end);
+				assert(strcmp("Hz", end) == 0);
+			}
+			wlr_log(L_DEBUG, "Configured output %s with mode %dx%d@%f",
+					oc->name, oc->mode.width, oc->mode.height,
+					oc->mode.refresh_rate);
 		}
 	} else if (strcmp(section, "cursor") == 0) {
 		if (strcmp(name, "map-to-output") == 0) {

rootston/output.c

@@ -165,6 +165,26 @@ static void output_frame_notify(struct wl_listener *listener, void *data) {
 	output->last_frame = desktop->last_frame = now;
 }
 
+static void set_mode(struct wlr_output *output, struct output_config *oc) {
+	struct wlr_output_mode *mode, *best = NULL;
+	int mhz = (int)(oc->mode.refresh_rate * 1000);
+	wl_list_for_each(mode, &output->modes, link) {
+		if (mode->width == oc->mode.width && mode->height == oc->mode.height) {
+			if (mode->refresh == mhz) {
+				best = mode;
+				break;
+			}
+			best = mode;
+		}
+	}
+	if (!best) {
+		wlr_log(L_ERROR, "Configured mode for %s not available", output->name);
+	} else {
+		wlr_log(L_DEBUG, "Assigning configured mode to %s", output->name);
+		wlr_output_set_mode(output, best);
+	}
+}
+
 void output_add_notify(struct wl_listener *listener, void *data) {
 	struct wlr_output *wlr_output = data;
 	struct roots_desktop *desktop = wl_container_of(listener, desktop, output_add);
@@ -191,6 +211,9 @@ void output_add_notify(struct wl_listener *listener, void *data) {
 
 	struct output_config *output_config = config_get_output(config, wlr_output);
 	if (output_config) {
+		if (output_config->mode.width) {
+			set_mode(wlr_output, output_config);
+		}
 		wlr_output_transform(wlr_output, output_config->transform);
 		wlr_output_layout_add(desktop->layout,
 				wlr_output, output_config->x, output_config->y);