dpi.c - i3lock-color - The world's most popular non-default computer lockscreen.

dpi.c (2914B)
Line numbers
   1 /*
   2  * vim:ts=4:sw=4:expandtab
   3  *
   4  * i3 - an improved dynamic tiling window manager
   5  * © 2009 Michael Stapelberg and contributors (see also: LICENSE)
   6  *
   7  */
   8 #include "dpi.h"
   9 
  10 #include <math.h>
  11 #include <stdlib.h>
  12 #include <stdio.h>
  13 #include <xcb/xcb_xrm.h>
  14 #include "xcb.h"
  15 #include "i3lock.h"
  16 
  17 extern bool debug_mode;
  18 
  19 static long dpi;
  20 
  21 extern xcb_screen_t *screen;
  22 
  23 static long init_dpi_fallback(void) {
  24     return (double)screen->height_in_pixels * 25.4 / (double)screen->height_in_millimeters;
  25 }
  26 
  27 /*
  28  * Initialize the DPI setting.
  29  * This will use the 'Xft.dpi' X resource if available and fall back to
  30  * guessing the correct value otherwise.
  31  */
  32 void init_dpi(void) {
  33     xcb_xrm_database_t *database = NULL;
  34     char *resource = NULL;
  35 
  36     if (conn == NULL) {
  37         goto init_dpi_end;
  38     }
  39 
  40     database = xcb_xrm_database_from_default(conn);
  41     if (database == NULL) {
  42         DEBUG("Failed to open the resource database.\n");
  43         goto init_dpi_end;
  44     }
  45 
  46     xcb_xrm_resource_get_string(database, "Xft.dpi", NULL, &resource);
  47     if (resource == NULL) {
  48         DEBUG("Resource Xft.dpi not specified, skipping.\n");
  49         goto init_dpi_end;
  50     }
  51 
  52     char *endptr;
  53     double in_dpi = strtod(resource, &endptr);
  54     if (in_dpi == HUGE_VAL || dpi < 0 || *endptr != '\0' || endptr == resource) {
  55         DEBUG("Xft.dpi = %s is an invalid number and couldn't be parsed.\n", resource);
  56         dpi = 0;
  57         goto init_dpi_end;
  58     }
  59     dpi = (long)round(in_dpi);
  60 
  61     DEBUG("Found Xft.dpi = %ld.\n", dpi);
  62 
  63 init_dpi_end:
  64     if (resource != NULL) {
  65         free(resource);
  66     }
  67 
  68     if (database != NULL) {
  69         xcb_xrm_database_free(database);
  70     }
  71 
  72     if (dpi == 0) {
  73         DEBUG("Using fallback for calculating DPI.\n");
  74         dpi = init_dpi_fallback();
  75         DEBUG("Using dpi = %ld\n", dpi);
  76     }
  77 }
  78 
  79 /*
  80  * This function returns the value of the DPI setting.
  81  *
  82  */
  83 long get_dpi_value(void) {
  84     return dpi;
  85 }
  86 
  87 /*
  88  * Convert a logical amount of pixels (e.g. 2 pixels on a “standard” 96 DPI
  89  * screen) to a corresponding amount of physical pixels on a standard or retina
  90  * screen, e.g. 5 pixels on a 227 DPI MacBook Pro 13" Retina screen.
  91  *
  92  */
  93 int logical_px(const int logical) {
  94     if (screen == NULL) {
  95         /* Dpi info may not be available when parsing a config without an X
  96          * server, such as for config file validation. */
  97         return logical;
  98     }
  99 
 100     /* There are many misconfigurations out there, i.e. systems with screens
 101      * whose dpi is in fact higher than 96 dpi, but not significantly higher,
 102      * so software was never adapted. We could tell people to reconfigure their
 103      * systems to 96 dpi in order to get the behavior they expect/are used to,
 104      * but since we can easily detect this case in code, let’s do it for them.
 105      */
 106     if ((dpi / 96.0) < 1.25)
 107         return logical;
 108     return ceil((dpi / 96.0) * logical);
 109 }