travis: ubuntu: install autoconf (for autoreconf)

[i3/i3] / libi3 / dpi.c

diff --git a/libi3/dpi.c b/libi3/dpi.c
index 090a65600004dbdd83b80edea8379de4419b5b95..897e6e4016a362645f96ee84bd032b577ed0015f 100644 (file)
--- a/libi3/dpi.c
+++ b/libi3/dpi.c
@@ -1,8 +1,13 @@
+/*
+ * vim:ts=4:sw=4:expandtab
+ *
+ * i3 - an improved dynamic tiling window manager
+ * © 2009 Michael Stapelberg and contributors (see also: LICENSE)
+ *
+ */
 #include "libi3.h"
 #include <math.h>
 
-extern xcb_screen_t *root_screen;
-
 /*
  * Convert a logical amount of pixels (e.g. 2 pixels on a “standard” 96 DPI
  * screen) to a corresponding amount of physical pixels on a standard or retina
@@ -10,7 +15,21 @@ extern xcb_screen_t *root_screen;
  *
  */
 int logical_px(const int logical) {
+    if (root_screen == NULL) {
+        /* Dpi info may not be available when parsing a config without an X
+         * server, such as for config file validation. */
+        return logical;
+    }
+
     const int dpi = (double)root_screen->height_in_pixels * 25.4 /
                     (double)root_screen->height_in_millimeters;
+    /* There are many misconfigurations out there, i.e. systems with screens
+     * whose dpi is in fact higher than 96 dpi, but not significantly higher,
+     * so software was never adapted. We could tell people to reconfigure their
+     * systems to 96 dpi in order to get the behavior they expect/are used to,
+     * but since we can easily detect this case in code, let’s do it for them.
+     */
+    if ((dpi / 96.0) < 1.25)
+        return logical;
     return ceil((dpi / 96.0) * logical);
 }