gri3-wm/libi3/dpi.c

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/*
* 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>
#include <stdlib.h>
#include <xcb/xcb_xrm.h>
static long dpi;
static long init_dpi_fallback(void) {
return (double)root_screen->height_in_pixels * 25.4 / (double)root_screen->height_in_millimeters;
}
/*
* Initialize the DPI setting.
* This will use the 'Xft.dpi' X resource if available and fall back to
* guessing the correct value otherwise.
*/
void init_dpi(void) {
xcb_xrm_database_t *database = NULL;
char *resource = NULL;
if (conn == NULL) {
goto init_dpi_end;
}
database = xcb_xrm_database_from_default(conn);
if (database == NULL) {
ELOG("Failed to open the resource database.\n");
goto init_dpi_end;
}
xcb_xrm_resource_get_string(database, "Xft.dpi", NULL, &resource);
if (resource == NULL) {
DLOG("Resource Xft.dpi not specified, skipping.\n");
goto init_dpi_end;
}
char *endptr;
double in_dpi = strtod(resource, &endptr);
if (in_dpi == HUGE_VAL || dpi < 0 || *endptr != '\0' || endptr == resource) {
ELOG("Xft.dpi = %s is an invalid number and couldn't be parsed.\n", resource);
dpi = 0;
goto init_dpi_end;
}
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dpi = lround(in_dpi);
DLOG("Found Xft.dpi = %ld.\n", dpi);
init_dpi_end:
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free(resource);
if (database != NULL) {
xcb_xrm_database_free(database);
}
if (dpi == 0) {
DLOG("Using fallback for calculating DPI.\n");
dpi = init_dpi_fallback();
DLOG("Using dpi = %ld\n", dpi);
}
}
/*
* This function returns the value of the DPI setting.
*
*/
long get_dpi_value(void) {
return dpi;
}
/*
* 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
* screen, e.g. 5 pixels on a 227 DPI MacBook Pro 13" Retina 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;
}
/* 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, lets do it for them.
*/
if ((dpi / 96.0) < 1.25)
return logical;
return ceil((dpi / 96.0) * logical);
}