only LOG() the DPI when it changes, DLOG() it otherwise (Thanks lkraav)

This avoids flooding stdout every time some text (e.g. a window
decoration) is drawn, yet leaves the message in place when it’s actually
relevant (upon DPI changes).

fixes #1115

i3-config-wizard/main.c

@@ -420,7 +420,7 @@ static char *rewrite_binding(const char *input) {
 
 
 /*
- * Having verboselog() and errorlog() is necessary when using libi3.
+ * Having verboselog(), errorlog() and debuglog() is necessary when using libi3.
  *
  */
 void verboselog(char *fmt, ...) {
@@ -439,6 +439,9 @@ void errorlog(char *fmt, ...) {
     va_end(args);
 }
 
+void debuglog(char *fmt, ...) {
+}
+
 /*
  * This function resolves ~ in pathnames.
  * It may resolve wildcards in the first part of the path, but if no match

i3-input/main.c

@@ -57,7 +57,7 @@ xcb_screen_t *root_screen;
 static xcb_get_input_focus_cookie_t focus_cookie;
 
 /*
- * Having verboselog() and errorlog() is necessary when using libi3.
+ * Having verboselog(), errorlog() and debuglog() is necessary when using libi3.
  *
  */
 void verboselog(char *fmt, ...) {
@@ -76,6 +76,9 @@ void errorlog(char *fmt, ...) {
     va_end(args);
 }
 
+void debuglog(char *fmt, ...) {
+}
+
 /*
  * Restores the X11 input focus to whereever it was before.
  * This is necessary because i3-input’s window has override_redirect=1

i3-nagbar/main.c

@@ -61,7 +61,7 @@ xcb_connection_t *conn;
 xcb_screen_t *root_screen;
 
 /*
- * Having verboselog() and errorlog() is necessary when using libi3.
+ * Having verboselog(), errorlog() and debuglog() is necessary when using libi3.
  *
  */
 void verboselog(char *fmt, ...) {
@@ -80,6 +80,9 @@ void errorlog(char *fmt, ...) {
     va_end(args);
 }
 
+void debuglog(char *fmt, ...) {
+}
+
 /*
  * Starts the given application by passing it through a shell. We use double fork
  * to avoid zombie processes. As the started application’s parent exits (immediately),

i3bar/include/util.h

@@ -48,6 +48,9 @@
     } \
 } while (0)
 
+#if defined(DLOG)
+#undef DLOG
+#endif
 /* Use cool logging-macros */
 #define DLOG(fmt, ...) do { \
     if (config.verbose) { \

i3bar/src/main.c

@@ -18,7 +18,7 @@
 #include "common.h"
 
 /*
- * Having verboselog() and errorlog() is necessary when using libi3.
+ * Having verboselog(), errorlog() and debuglog() is necessary when using libi3.
  *
  */
 void verboselog(char *fmt, ...) {
@@ -37,6 +37,9 @@ void errorlog(char *fmt, ...) {
     va_end(args);
 }
 
+void debuglog(char *fmt, ...) {
+}
+
 /*
  * Glob path, i.e. expand ~
  *

include/libi3.h

@@ -72,13 +72,20 @@ struct Font {
 /* Since this file also gets included by utilities which don’t use the i3 log
  * infrastructure, we define a fallback. */
 #if !defined(LOG)
-void verboselog(char *fmt, ...);
+void verboselog(char *fmt, ...)
+    __attribute__ ((format (printf, 1, 2)));
 #define LOG(fmt, ...) verboselog("[libi3] " __FILE__ " " fmt, ##__VA_ARGS__)
 #endif
 #if !defined(ELOG)
-void errorlog(char *fmt, ...);
+void errorlog(char *fmt, ...)
+    __attribute__ ((format (printf, 1, 2)));
 #define ELOG(fmt, ...) errorlog("[libi3] ERROR: " fmt, ##__VA_ARGS__)
 #endif
+#if !defined(DLOG)
+void debuglog(char *fmt, ...)
+    __attribute__ ((format (printf, 1, 2)));
+#define DLOG(fmt, ...) debuglog("%s:%s:%d - " fmt, I3__FILE__, __FUNCTION__, __LINE__, ##__VA_ARGS__)
+#endif
 
 /**
  * Try to get the contents of the given atom (for example I3_SOCKET_PATH) from

include/log.h

@@ -21,6 +21,9 @@
 #if defined(ELOG)
 #undef ELOG
 #endif
+#if defined(DLOG)
+#undef DLOG
+#endif
 /** ##__VA_ARGS__ means: leave out __VA_ARGS__ completely if it is empty, that
    is, delete the preceding comma */
 #define LOG(fmt, ...) verboselog(fmt, ##__VA_ARGS__)

libi3/font.c

@@ -30,6 +30,10 @@ static double pango_font_red;
 static double pango_font_green;
 static double pango_font_blue;
 
+/* Necessary to track whether the dpi changes and trigger a LOG() message,
+ * which is more easily visible to users. */
+static double logged_dpi = 0.0;
+
 static PangoLayout *create_layout_with_dpi(cairo_t *cr) {
     PangoLayout *layout;
     PangoContext *context;
@@ -37,7 +41,12 @@ static PangoLayout *create_layout_with_dpi(cairo_t *cr) {
     context = pango_cairo_create_context(cr);
     const double dpi = (double)root_screen->height_in_pixels * 25.4 /
                        (double)root_screen->height_in_millimeters;
+    if (logged_dpi != dpi) {
+        logged_dpi = dpi;
         LOG("X11 root window dictates %f DPI\n", dpi);
+    } else {
+        DLOG("X11 root window dictates %f DPI\n", dpi);
+    }
     pango_cairo_context_set_resolution(context, dpi);
     layout = pango_layout_new(context);
     g_object_unref(context);