meta-gpu-xrandr: Account for the current user text scale factor

when calculating the crtc scale based on Xft.dpi.

- cinnamon-settings-daemon retrieves the global scale from muffin,
  and the text scale from gsettings, calculates the dpi and sets
  it on the server.
- muffin retrieves the dpi from the server and calculates the global
  scale from that *rounding to the nearest integer*. A text factor
  of >= 1.5 causes a higher global scale to be assumed each time
  muffin restarts. Muffin triggers a dbus signal, and cinnamon-
  settings-daemon does its thing over again.

ref: linuxmint/mint21.1-beta#43

Author: mtwebster

Diff for: src/backends/meta-settings-private.h

@@ -58,6 +58,8 @@ void meta_settings_update_ui_scaling_factor (MetaSettings *settings);
 gboolean meta_settings_get_global_scaling_factor (MetaSettings *settings,
                                                   int          *scaing_factor);
 
+double meta_settings_get_font_scaling_factor (MetaSettings *settings);
+
 META_EXPORT_TEST
 gboolean meta_settings_is_experimental_feature_enabled (MetaSettings           *settings,
                                                         MetaExperimentalFeature feature);

Diff for: src/backends/meta-settings.c

@@ -223,6 +223,12 @@ meta_settings_update_font_dpi (MetaSettings *settings)
     g_signal_emit (settings, signals[FONT_DPI_CHANGED], 0);
 }
 
+double
+meta_settings_get_font_scaling_factor(MetaSettings *settings)
+{
+    return g_settings_get_double (settings->interface_settings, "text-scaling-factor");
+}
+
 int
 meta_settings_get_font_dpi (MetaSettings *settings)
 {

Diff for: src/backends/x11/meta-gpu-xrandr.c

@@ -98,6 +98,10 @@ static int
 get_current_dpi_scale (MetaMonitorManagerXrandr *manager_xrandr,
                        MetaGpuXrandr            *gpu_xrandr)
 {
+  MetaMonitorManager *monitor_manager = META_MONITOR_MANAGER (manager_xrandr);
+  MetaBackend *backend = meta_monitor_manager_get_backend (monitor_manager);
+  MetaSettings *settings = meta_backend_get_settings (backend);
+
   Atom actual;
   int result, format;
   unsigned long n, left;
@@ -109,10 +113,6 @@ get_current_dpi_scale (MetaMonitorManagerXrandr *manager_xrandr,
   if (gpu_xrandr->resources->timestamp ==
       meta_monitor_manager_xrandr_get_config_timestamp (manager_xrandr))
     {
-      MetaMonitorManager *monitor_manager = META_MONITOR_MANAGER (manager_xrandr);
-      MetaBackend *backend = meta_monitor_manager_get_backend (monitor_manager);
-      MetaSettings *settings = meta_backend_get_settings (backend);
-
       return meta_settings_get_ui_scaling_factor (settings);
     }
 
@@ -139,7 +139,10 @@ get_current_dpi_scale (MetaMonitorManagerXrandr *manager_xrandr,
               dpi = g_ascii_strtoull (res[1], NULL, 10);
 
               if (dpi > 0 && dpi < 96 * 10)
-                return MAX (1, roundf ((float) dpi / 96.0f));
+                {
+                  double factor = meta_settings_get_font_scaling_factor (settings);
+                  return MAX (1, roundf ((float) dpi / 96.0f / factor));
+                }
             }
         }
     }