Add timeout option for image info block

Create a new timer in viewer to hide image info blocks on trigger; when
set, image info will be displayed on screen until the timeout expires.
When the timeout expires, the UI will redraw and hide info blocks.

The timeout is disabled by default (info block shown forever) but a user
may override it to a fixed time (in seconds) or to a percentage of a
frame time in slideshow mode (eg if slideshow_time=10 and
image_info_timeout=50%, the info block will be hidden after 5 seconds).

extra/swayimgrc

@@ -42,6 +42,8 @@ background = none
 slideshow = no
 # Slideshow image display time (seconds)
 slideshow_time = 3
+# Hide image information after a timeout (seconds e.g. `5`, or percent of slideshow_time e.g. `50%`)
+image_info_timeout = 50%
 
 ################################################################################
 # Image list configuration

extra/swayimgrc.5

@@ -95,6 +95,9 @@ Run slideshow at startup, \fIno\fR by default.
 .IP "\fBslideshow_time\fR = \fISECONDS\fR"
 Set slideshow image duration in seconds, default is \fI3\fR.
 .\" ----------------------------------------------------------------------------
+.IP "\fBimage_info_timeout\fR = \fISECONDS|PERCENT\fR"
+Set timeout of image information displayed on screen. Value is in seconds (e.g. `5`) or in percentage of slideshow_time (e.g. `50%`). `image_info_timeout=0` disables the timeout (info block is shown forever). If set as a percentage of the slideshow time, but slideshow is disabled, this timeout will be disabled too. Default is \fI0\fR.
+.\" ----------------------------------------------------------------------------
 .IP "\fBapp_id\fR = \fINAME\fR"
 Set a constant window class/app_id. Setting this may break the window layout.
 .\" ****************************************************************************

src/info.c

@@ -107,6 +107,7 @@ struct info_block {
 /** Info data context. */
 struct info_context {
     enum info_mode mode;
+    int timeout;
     const char* file;
     struct info_line* exif_lines;
     size_t exif_num;
@@ -207,6 +208,24 @@ static enum config_status load_config(const char* key, const char* value)
     size_t scheme_sz = 0;
     ssize_t index;
 
+    if (strcmp(key, VIEWER_CFG_INFO_TIMEOUT) == 0) {
+        size_t val_sz = strlen(value);
+        bool timeout_is_rel = false;
+        if (value[val_sz - 1] == '%') {
+            val_sz = val_sz - 1;
+            timeout_is_rel = true;
+        }
+
+        ssize_t num;
+        const ssize_t maxVal = timeout_is_rel ? 100 : 86400;
+        if (str_to_num(value, val_sz, &num, 0) && num != 0 && num <= maxVal) {
+            ctx.timeout = num * (timeout_is_rel ? -1 : 1);
+            return cfgst_ok;
+        } else {
+            return cfgst_invalid_value;
+        }
+    }
+
     if (strcmp(key, "mode") == 0) {
         index = str_index(mode_names, value, 0);
         if (index < 0) {
@@ -274,6 +293,7 @@ void info_create(void)
 {
     // set defaults
     ctx.mode = info_mode_full;
+    ctx.timeout = 0;
     ctx.frame = UINT32_MAX;
     ctx.index = UINT32_MAX;
     SET_DEFAULT(info_mode_full, info_top_left, default_full_top_left);
@@ -530,3 +550,8 @@ const struct info_line* info_lines(enum info_position pos)
 
     return block->lines;
 }
+
+int info_timeout(void)
+{
+    return ctx.timeout;
+}

src/info.h

@@ -6,6 +6,9 @@
 
 #include "font.h"
 
+// Config key for info block timeout
+#define VIEWER_CFG_INFO_TIMEOUT "timeout"
+
 /** Info block position. */
 enum info_position {
     info_top_left,
@@ -69,3 +72,10 @@ size_t info_height(enum info_position pos);
  * @return pointer to the lines array
  */
 const struct info_line* info_lines(enum info_position pos);
+
+/**
+ * Get info display timeout.
+ * @return 0 if timeout disabled, positive number for absolute time in second,
+ * or negative number for slideshow relative percents.
+ */
+int info_timeout(void);

src/viewer.c

@@ -76,6 +76,9 @@ struct viewer {
     bool slideshow_enable; ///< Slideshow enable/disable
     int slideshow_fd;      ///< Slideshow timer
     size_t slideshow_time; ///< Slideshow image display time (seconds)
+
+    bool info_timedout; ///< Indicates info block shouldn't be displayed anymore
+    int info_timeout_fd; ///< Info timer
 };
 
 static struct viewer ctx = {
@@ -87,6 +90,8 @@ static struct viewer ctx = {
     .slideshow_enable = false,
     .slideshow_fd = -1,
     .slideshow_time = 3,
+    .info_timedout = false,
+    .info_timeout_fd = -1,
 };
 
 /**
@@ -340,12 +345,30 @@ static void reset_state(void)
     ctx.img_x = 0;
     ctx.img_y = 0;
     ctx.scale = 0;
+    ctx.info_timedout = false;
     scale_image(ctx.scale_init);
     fixup_position(true);
 
     ui_set_title(entry.image->file_name);
     animation_ctl(true);
     slideshow_ctl(ctx.slideshow_enable);
+
+    // Expire info block after timeout
+    const int timeout = info_timeout();
+    if (timeout != 0) {
+        struct itimerspec info_ts = { 0 };
+        if (!ctx.slideshow_enable && timeout < 0) {
+            // If timeout is relative to slideshow, but slideshow is not
+            // enabled, then disable info timeout too
+            info_ts.it_value.tv_sec = 0;
+        } else if (timeout < 0) {
+            // If timeout < 0 => it's relative to slideshow time
+            info_ts.it_value.tv_sec = ctx.slideshow_time * -1 * timeout / 100;
+        } else {
+            info_ts.it_value.tv_sec = timeout;
+        }
+        timerfd_settime(ctx.info_timeout_fd, 0, &info_ts, NULL);
+    }
 }
 
 /**
@@ -408,6 +431,18 @@ static void on_slideshow_timer(void)
     ui_redraw();
 }
 
+/**
+ * Info block timer event handler.
+ */
+static void on_info_block_timeout(void)
+{
+    // Reset timer to 0, so it won't fire again
+    struct itimerspec info_ts = { 0 };
+    timerfd_settime(ctx.info_timeout_fd, 0, &info_ts, NULL);
+    ctx.info_timedout = true;
+    ui_redraw();
+}
+
 /**
  * Execute system command for the current image.
  * @param expr command expression
@@ -588,6 +623,13 @@ void viewer_init(void)
         ui_add_event(ctx.slideshow_fd, on_slideshow_timer);
     }
 
+    // setup info block timer
+    ctx.info_timeout_fd =
+        timerfd_create(CLOCK_MONOTONIC, TFD_CLOEXEC | TFD_NONBLOCK);
+    if (ctx.info_timeout_fd != -1) {
+        ui_add_event(ctx.info_timeout_fd, on_info_block_timeout);
+    }
+
     // register configuration loader
     config_add_loader(GENERAL_CONFIG_SECTION, load_config);
 }
@@ -603,6 +645,9 @@ void viewer_free(void)
     if (ctx.slideshow_fd != -1) {
         close(ctx.slideshow_fd);
     }
+    if (ctx.info_timeout_fd != -1) {
+        close(ctx.info_timeout_fd);
+    }
 }
 
 bool viewer_reload(void)
@@ -628,12 +673,14 @@ void viewer_on_redraw(struct pixmap* window)
     draw_image(window);
 
     // put text info blocks on window surface
-    for (size_t i = 0; i < INFO_POSITION_NUM; ++i) {
-        const size_t lines_num = info_height(i);
-        if (lines_num) {
-            const enum info_position pos = (enum info_position)i;
-            const struct info_line* lines = info_lines(pos);
-            text_print(window, pos, lines, lines_num);
+    if (!ctx.info_timedout) {
+        for (size_t i = 0; i < INFO_POSITION_NUM; ++i) {
+            const size_t lines_num = info_height(i);
+            if (lines_num) {
+                const enum info_position pos = (enum info_position)i;
+                const struct info_line* lines = info_lines(pos);
+                text_print(window, pos, lines, lines_num);
+            }
         }
     }
     if (ctx.help) {