SystemService: Persist "wait vsync" setting to disk

This setting has a significant impact on system load, so users may want
xsystem4 to remember their preference.

This implementation uses a JSON format, while the AliceSoft's
implementation saves it to a binary file (WindowSetting.sav).

This only records the wait_vsync setting, since the other fields in
window_settings are currently no-op.

include/savedata.h

@@ -23,6 +23,7 @@
 void json_load_page(struct page *page, cJSON *vars, bool call_dtors);
 
 int save_json(const char *filename, cJSON *json);
+cJSON *load_json(const char *filename);
 int save_globals(const char *keyname, const char *filename, const char *group_name, int *n);
 int load_globals(const char *keyname, const char *filename, const char *group_name, int *n);
 int delete_save_file(const char *filename);

src/hll/SystemService.c

@@ -20,9 +20,11 @@
 #include "system4/ain.h"
 #include "system4/string.h"
 
+#include "cJSON.h"
 #include "input.h"
 #include "gfx/gfx.h"
 #include "mixer.h"
+#include "savedata.h"
 #include "vm.h"
 #include "xsystem4.h"
 #include "hll.h"
@@ -140,6 +142,27 @@ enum window_settings_id {
 	WINDOW_SETTINGS_CLOSE_GAME_CONFIRM = 6,
 };
 
+static void save_window_settings(void)
+{
+	cJSON *root = cJSON_CreateObject();
+	cJSON_AddBoolToObject(root, "wait_vsync", window_settings.wait_vsync);
+	save_json("WindowSetting.json", root);
+	cJSON_Delete(root);
+}
+
+static void load_window_settings(void)
+{
+	cJSON *root = load_json("WindowSetting.json");
+	if (!root)
+		return;
+	cJSON *v;
+	if ((v = cJSON_GetObjectItem(root, "wait_vsync"))) {
+		window_settings.wait_vsync = cJSON_IsTrue(v);
+		gfx_set_wait_vsync(window_settings.wait_vsync);
+	}
+	cJSON_Delete(root);
+}
+
 static bool SystemService_SetWindowSetting(int type, int value)
 {
 	switch (type) {
@@ -169,6 +192,7 @@ static bool SystemService_SetWindowSetting(int type, int value)
 		WARNING("Invalid window setting type: %d", type);
 		return false;
 	}
+	save_window_settings();
 	return true;
 }
 
@@ -275,8 +299,14 @@ static void SystemService_Test(struct string **text)
 
 static void SystemService_PreLink(void);
 
+static void SystemService_ModuleInit(void)
+{
+	load_window_settings();
+}
+
 HLL_LIBRARY(SystemService,
 	    HLL_EXPORT(_PreLink, SystemService_PreLink),
+	    HLL_EXPORT(_ModuleInit, SystemService_ModuleInit),
 	    HLL_EXPORT(GetMixerNumof, mixer_get_numof),
 	    HLL_EXPORT(GetMixerName, SystemService_GetMixerName),
 	    HLL_EXPORT(GetMixerVolume, mixer_get_volume),

src/savedata.c

@@ -67,7 +67,18 @@ int save_json(const char *filename, cJSON *json)
 	}
 	free(str);
 	return 1;
+}
 
+cJSON *load_json(const char *filename)
+{
+	char *path = savedir_path(filename);
+	char *json = file_read(path, NULL);
+	free(path);
+	if (!json)
+		return NULL;
+	cJSON *root = cJSON_Parse(json);
+	free(json);
+	return root;
 }
 
 static int get_group_index(const char *name)

src/video.c

@@ -69,6 +69,7 @@ static struct texture *view = &main_surface;
 static GLint max_texture_size;
 static SDL_Color clear_color = { 0, 0, 0, 255 };
 static float frame_rate;
+static bool wait_vsync = false;
 
 static GLchar *read_shader_file(const char *path)
 {
@@ -267,7 +268,7 @@ int gfx_init(void)
 		ERROR("glewInit failed");
 #endif
 
-	SDL_GL_SetSwapInterval(0);
+	SDL_GL_SetSwapInterval(wait_vsync ? 1 : 0);
 	gl_initialize();
 	gfx_draw_init();
 	gfx_set_window_logical_size(config.view_width, config.view_height);
@@ -353,7 +354,9 @@ void gfx_update_screen_scale(void)
 
 void gfx_set_wait_vsync(bool wait)
 {
-	SDL_GL_SetSwapInterval(wait);
+	wait_vsync = wait;
+	if (gfx_initialized)
+		SDL_GL_SetSwapInterval(wait ? 1 : 0);
 }
 
 void gfx_set_clear_color(int r, int g, int b, int a)