From 7d795eede96e08bf7673a3264648b33693adea21 Mon Sep 17 00:00:00 2001
From: Federico Angelilli <code@fedang.net>
Date: Wed, 15 Nov 2023 20:55:54 +0100
Subject: Fix dpi calculation

---
 x11.c | 40 +++++++++++++++++++++-------------------
 1 file changed, 21 insertions(+), 19 deletions(-)

diff --git a/x11.c b/x11.c
index ac1d858..beb65b8 100644
--- a/x11.c
+++ b/x11.c
@@ -22,6 +22,7 @@
 struct Window {
     xcb_connection_t *connection;
     xcb_screen_t *screen;
+    xcb_randr_screen_size_t *screen_size;
     xcb_xrm_database_t *database;
     xcb_errors_context_t *errors;
     xcb_drawable_t window;
@@ -30,8 +31,6 @@ struct Window {
     cairo_surface_t *surface;
     cairo_t *cr;
     double dpi;
-    uint16_t screen_width;
-    uint16_t screen_height;
     int x, y;
     int width, height;
     GSource *source;
@@ -151,6 +150,17 @@ static void attach_source(Window *win)
     g_source_attach(win->source, NULL);
 }
 
+static bool query_xrm(Window *win, const char *res, char **value)
+{
+    if (xcb_xrm_resource_get_string(win->database,res, res, value) >= 0) {
+        log_debug("Xrm query '%s' found '%s'", res, *value);
+        return true;
+    }
+
+    log_debug("Xrm query '%s' not found", res);
+    return false;
+}
+
 static xcb_atom_t intern_atom(Window *win, const char *atom)
 {
     xcb_generic_error_t *error;
@@ -277,11 +287,9 @@ Window *window_create(void)
     xcb_randr_get_screen_info_reply_t *info_reply = xcb_randr_get_screen_info_reply(win->connection, cookie, &error);
     g_assert_null(error);
 
-    xcb_randr_screen_size_t *screen_size = xcb_randr_get_screen_info_sizes(info_reply);
-    log_debug("Screen size [width=%d, height=%d]", screen_size->width, screen_size->height);
-
-    win->screen_width  = screen_size->width;
-    win->screen_height = screen_size->height;
+    win->screen_size = xcb_randr_get_screen_info_sizes(info_reply);
+    g_assert_nonnull(win->screen_size);
+    log_debug("Screen size [width=%d, height=%d]", win->screen_size->width, win->screen_size->height);
 
     win->width = win->height = 0;
     win->x = win->y = 0;
@@ -367,8 +375,8 @@ found_visual:
     win->surface = cairo_xcb_surface_create(win->connection,
                                             win->window,
                                             win->visual_type,
-                                            screen_size->width,
-                                            screen_size->height);
+                                            win->screen_size->width,
+                                            win->screen_size->height);
 
     g_assert_cmpint(cairo_surface_status(win->surface), ==, CAIRO_STATUS_SUCCESS);
     log_debug("Cairo surface created");
@@ -394,17 +402,11 @@ void window_update_scale(Window *win)
     const char *dpi_res = "Xft.dpi";
     char *dpi_value;
 
-    if (xcb_xrm_resource_get_string(win->database, dpi_res, dpi_res, &dpi_value) >= 0) {
-        log_debug("Xrm query '%s' found '%s'", dpi_res, dpi_value);
+    if (query_xrm(win, dpi_res, &dpi_value)) {
         win->dpi = strtod(dpi_value, NULL);
         g_free(dpi_value);
     } else {
-        log_debug("Xrm query '%s' not found", dpi_res);
-
-        win->dpi = 96.0;
-        // TODO: Should we actually calculate the dpi depending on the screen size?
-        //win->dpi = (double)screen_size->height * 25.4 / (double)screen_size->mheight;
-
+        win->dpi = (double)win->screen_size->height * 25.4 / (double)win->screen_size->mheight;
         log_debug("Fallback dpi value '%.2lf'", win->dpi);
     }
 }
@@ -416,8 +418,8 @@ double window_get_scale(Window *win)
 
 void window_get_screen_size(Window *win, int *width, int *height)
 {
-    *width = win->screen_width;
-    *height = win->screen_height;
+    *width = win->screen_size->width;
+    *height = win->screen_size->height;
 }
 
 void window_set_opacity(Window *win, double alpha)
-- 
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