1 files changed, 109 insertions, 0 deletions

diff --git a/dpi.c b/dpi.c
new file mode 100644
index 0000000..3cb08ee
--- /dev/null
+++ b/dpi.c
@@ -0,0 +1,109 @@
+/*
+ * vim:ts=4:sw=4:expandtab
+ *
+ * i3 - an improved dynamic tiling window manager
+ * © 2009 Michael Stapelberg and contributors (see also: LICENSE)
+ *
+ */
+#include "dpi.h"
+
+#include <math.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <xcb/xcb_xrm.h>
+#include "xcb.h"
+#include "i3lock.h"
+
+extern bool debug_mode;
+
+static long dpi;
+
+extern xcb_screen_t *screen;
+
+static long init_dpi_fallback(void) {
+    return (double)screen->height_in_pixels * 25.4 / (double)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) {
+        DEBUG("Failed to open the resource database.\n");
+        goto init_dpi_end;
+    }
+
+    xcb_xrm_resource_get_string(database, "Xft.dpi", NULL, &resource);
+    if (resource == NULL) {
+        DEBUG("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) {
+        DEBUG("Xft.dpi = %s is an invalid number and couldn't be parsed.\n", resource);
+        dpi = 0;
+        goto init_dpi_end;
+    }
+    dpi = (long)round(in_dpi);
+
+    DEBUG("Found Xft.dpi = %ld.\n", dpi);
+
+init_dpi_end:
+    if (resource != NULL) {
+        free(resource);
+    }
+
+    if (database != NULL) {
+        xcb_xrm_database_free(database);
+    }
+
+    if (dpi == 0) {
+        DEBUG("Using fallback for calculating DPI.\n");
+        dpi = init_dpi_fallback();
+        DEBUG("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 (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, let’s do it for them.
+     */
+    if ((dpi / 96.0) < 1.25)
+        return logical;
+    return ceil((dpi / 96.0) * logical);
+}