image-source: Check for file changes

Polls for file changes like the text plugin does.  This is an interim
solution; both the text plugin and image source should use a file
monitoring API, preferably implemented through libobs.

Closes jp9000/obs-studio#482

plugins/image-source/image-source.c

@@ -1,4 +1,6 @@
 #include <obs-module.h>
+#include <util/platform.h>
+#include <sys/stat.h>
 
 #define blog(log_level, format, ...) \
 	blog(log_level, "[image_source: '%s'] " format, \
@@ -16,12 +18,22 @@ struct image_source {
 
 	char         *file;
 	bool         persistent;
+	time_t       file_timestamp;
+	float        update_time_elapsed;
 
 	gs_texture_t *tex;
 	uint32_t     cx;
 	uint32_t     cy;
 };
 
+
+static time_t get_modified_timestamp(const char *filename)
+{
+	struct stat stats;
+	stat(filename, &stats);
+	return stats.st_mtime;
+}
+
 static const char *image_source_get_name(void *unused)
 {
 	UNUSED_PARAMETER(unused);
@@ -40,8 +52,10 @@ static void image_source_load(struct image_source *context)
 
 	if (file && *file) {
 		debug("loading texture '%s'", file);
-
+		context->file_timestamp = get_modified_timestamp(file);
 		context->tex = gs_texture_create_from_file(file);
+		context->update_time_elapsed = 0;
+
 		if (context->tex) {
 			context->cx = gs_texture_get_width(context->tex);
 			context->cy = gs_texture_get_height(context->tex);
@@ -150,6 +164,26 @@ static void image_source_render(void *data, gs_effect_t *effect)
 	gs_draw_sprite(context->tex, 0, context->cx, context->cy);
 }
 
+static void image_source_tick(void *data, float seconds)
+{
+	struct image_source *context = data;
+	uint64_t now = os_gettime_ns();
+
+	if (!obs_source_showing(context->source)) return;
+
+	context->update_time_elapsed += seconds;
+
+	if (context->update_time_elapsed >= 1.0f) {
+		time_t t = get_modified_timestamp(context->file);
+		context->update_time_elapsed = 0.0f;
+
+		if (context->file_timestamp < t) {
+			image_source_load(context);
+		}
+	}
+}
+
+
 static const char *image_filter =
 	"All formats (*.bmp *.tga *.png *.jpeg *.jpg *.gif);;"
 	"BMP Files (*.bmp);;"
@@ -187,6 +221,7 @@ static struct obs_source_info image_source_info = {
 	.get_width      = image_source_getwidth,
 	.get_height     = image_source_getheight,
 	.video_render   = image_source_render,
+	.video_tick     = image_source_tick,
 	.get_properties = image_source_properties
 };