DisplayConfig: Make supported scales per mode

This changes the API to pass supported scales per mode instead of
providing a global list. This allows for more flexible scaling
scenarious, where a scale compatible with one mode can still be made
available even though another mode is incompatible.

https://bugzilla.gnome.org/show_bug.cgi?id=765011

src/backends/meta-monitor-config-manager.c

@@ -950,16 +950,6 @@ meta_verify_logical_monitor_config (MetaLogicalMonitorConfig    *logical_monitor
   int expected_mode_width = 0;
   int expected_mode_height = 0;
 
-  if (!meta_monitor_manager_is_scale_supported (monitor_manager,
-                                                layout_mode,
-                                                logical_monitor_config->scale))
-    {
-      g_set_error (error, G_IO_ERROR, G_IO_ERROR_FAILED,
-                   "Invalid logical monitor config scale %g",
-                   logical_monitor_config->scale);
-      return FALSE;
-    }
-
   if (logical_monitor_config->layout.x < 0 ||
       logical_monitor_config->layout.y < 0)
     {

src/backends/meta-monitor-manager-dummy.c

@@ -31,6 +31,7 @@
 
 #include <meta/util.h>
 #include "backends/meta-backend-private.h"
+#include "backends/meta-monitor.h"
 #include "backends/meta-monitor-config-manager.h"
 
 #define ALL_TRANSFORMS ((1 << (META_MONITOR_TRANSFORM_FLIPPED_270 + 1)) - 1)
@@ -40,17 +41,6 @@
 #define MAX_CRTCS (MAX_MONITORS * 2)
 #define MAX_MODES (MAX_MONITORS * 4)
 
-static float supported_scales_dummy_logical[] = {
-  1.0,
-  1.5,
-  2.0
-};
-
-static float supported_scales_dummy_physical[] = {
-  1.0,
-  2.0
-};
-
 struct _MetaMonitorManagerDummy
 {
   MetaMonitorManager parent_instance;
@@ -320,12 +310,8 @@ meta_monitor_manager_dummy_read_current (MetaMonitorManager *manager)
       for (i = 0; i < num_monitors && scales_str_list[i]; i++)
         {
           float scale = g_ascii_strtod (scales_str_list[i], NULL);
-          if (meta_monitor_manager_is_scale_supported (manager,
+
-                                                       manager->layout_mode,
-                                                       scale))
           monitor_scales[i] = scale;
-          else
-            meta_warning ("Invalid dummy monitor scale\n");
         }
       g_strfreev (scales_str_list);
     }
@@ -614,23 +600,28 @@ meta_monitor_manager_dummy_calculate_monitor_mode_scale (MetaMonitorManager *man
   return output_dummy->scale;
 }
 
-static void
+static float *
-meta_monitor_manager_dummy_get_supported_scales (MetaMonitorManager          *manager,
+meta_monitor_manager_dummy_calculate_supported_scales (MetaMonitorManager          *manager,
                                                        MetaLogicalMonitorLayoutMode layout_mode,
-                                                 float                      **scales,
+                                                       MetaMonitor                 *monitor,
-                                                 int                         *n_scales)
+                                                       MetaMonitorMode             *monitor_mode,
+                                                       int                         *n_supported_scales)
 {
+  MetaMonitorScalesConstraint constraints =
+    META_MONITOR_SCALES_CONSTRAINT_NONE;
+
   switch (layout_mode)
     {
     case META_LOGICAL_MONITOR_LAYOUT_MODE_LOGICAL:
-      *scales = supported_scales_dummy_logical;
-      *n_scales = G_N_ELEMENTS (supported_scales_dummy_logical);
       break;
     case META_LOGICAL_MONITOR_LAYOUT_MODE_PHYSICAL:
-      *scales = supported_scales_dummy_physical;
+      constraints |= META_MONITOR_SCALES_CONSTRAINT_NO_FRAC;
-      *n_scales = G_N_ELEMENTS (supported_scales_dummy_physical);
       break;
     }
+
+  return meta_monitor_calculate_supported_scales (monitor, monitor_mode,
+                                                  constraints,
+                                                  n_supported_scales);
 }
 
 static gboolean
@@ -699,7 +690,7 @@ meta_monitor_manager_dummy_class_init (MetaMonitorManagerDummyClass *klass)
   manager_class->apply_configuration = meta_monitor_manager_dummy_apply_config;
   manager_class->is_transform_handled = meta_monitor_manager_dummy_is_transform_handled;
   manager_class->calculate_monitor_mode_scale = meta_monitor_manager_dummy_calculate_monitor_mode_scale;
-  manager_class->get_supported_scales = meta_monitor_manager_dummy_get_supported_scales;
+  manager_class->calculate_supported_scales = meta_monitor_manager_dummy_calculate_supported_scales;
   manager_class->get_capabilities = meta_monitor_manager_dummy_get_capabilities;
   manager_class->get_max_screen_size = meta_monitor_manager_dummy_get_max_screen_size;
   manager_class->get_default_layout_mode = meta_monitor_manager_dummy_get_default_layout_mode;

src/backends/meta-monitor-manager-private.h

@@ -394,9 +394,10 @@ struct _MetaMonitorManagerClass
                                          MetaMonitor        *,
                                          MetaMonitorMode    *);
 
-  void (*get_supported_scales) (MetaMonitorManager          *,
+  float * (*calculate_supported_scales) (MetaMonitorManager          *,
                                          MetaLogicalMonitorLayoutMode ,
-                                float                      **,
+                                         MetaMonitor                 *,
+                                         MetaMonitorMode             *,
                                          int                         *);
 
   MetaMonitorManagerCapability (*get_capabilities) (MetaMonitorManager *);
@@ -509,8 +510,16 @@ float              meta_monitor_manager_calculate_monitor_mode_scale (MetaMonito
                                                                       MetaMonitor        *monitor,
                                                                       MetaMonitorMode    *monitor_mode);
 
+float *            meta_monitor_manager_calculate_supported_scales (MetaMonitorManager          *,
+                                                                    MetaLogicalMonitorLayoutMode ,
+                                                                    MetaMonitor                 *,
+                                                                    MetaMonitorMode             *,
+                                                                    int                         *);
+
 gboolean           meta_monitor_manager_is_scale_supported (MetaMonitorManager          *manager,
                                                             MetaLogicalMonitorLayoutMode layout_mode,
+                                                            MetaMonitor                 *monitor,
+                                                            MetaMonitorMode             *monitor_mode,
                                                             float                        scale);
 
 MetaMonitorManagerCapability

src/backends/meta-monitor-manager.c

@@ -406,16 +406,21 @@ meta_monitor_manager_calculate_monitor_mode_scale (MetaMonitorManager *manager,
                                                       monitor_mode);
 }
 
-static void
+float *
-meta_monitor_manager_get_supported_scales (MetaMonitorManager          *manager,
+meta_monitor_manager_calculate_supported_scales (MetaMonitorManager          *manager,
                                                  MetaLogicalMonitorLayoutMode layout_mode,
-                                           float                      **scales,
+                                                 MetaMonitor                 *monitor,
-                                           int                         *n_scales)
+                                                 MetaMonitorMode             *monitor_mode,
+                                                 int                         *n_supported_scales)
 {
   MetaMonitorManagerClass *manager_class =
     META_MONITOR_MANAGER_GET_CLASS (manager);
 
-  manager_class->get_supported_scales (manager, layout_mode, scales, n_scales);
+  return manager_class->calculate_supported_scales (manager,
+                                                    layout_mode,
+                                                    monitor,
+                                                    monitor_mode,
+                                                    n_supported_scales);
 }
 
 MetaMonitorManagerCapability
@@ -1487,7 +1492,7 @@ meta_monitor_manager_legacy_handle_apply_configuration  (MetaDBusDisplayConfig *
 #define META_DISPLAY_CONFIG_MODE_FLAGS_PREFERRED (1 << 0)
 #define META_DISPLAY_CONFIG_MODE_FLAGS_CURRENT (1 << 1)
 
-#define MODE_FORMAT "(iiddu)"
+#define MODE_FORMAT "(iiddadu)"
 #define MODES_FORMAT "a" MODE_FORMAT
 #define MONITOR_SPEC_FORMAT "(ssss)"
 #define MONITOR_FORMAT "(" MONITOR_SPEC_FORMAT MODES_FORMAT "a{sv})"
@@ -1504,11 +1509,8 @@ meta_monitor_manager_handle_get_current_state (MetaDBusDisplayConfig *skeleton,
   MetaMonitorManager *manager = META_MONITOR_MANAGER (skeleton);
   GVariantBuilder monitors_builder;
   GVariantBuilder logical_monitors_builder;
-  GVariantBuilder supported_scales_builder;
   GVariantBuilder properties_builder;
   GList *l;
-  float *supported_scales;
-  int n_supported_scales;
   int i;
   MetaMonitorManagerCapability capabilities;
   int max_screen_width, max_screen_height;
@@ -1546,8 +1548,11 @@ meta_monitor_manager_handle_get_current_state (MetaDBusDisplayConfig *skeleton,
       for (k = meta_monitor_get_modes (monitor); k; k = k->next)
         {
           MetaMonitorMode *monitor_mode = k->data;
+          GVariantBuilder supported_scales_builder;
           MetaMonitorModeSpec *monitor_mode_spec;
-          int preferred_scale;
+          float preferred_scale;
+          float *supported_scales;
+          int n_supported_scales;
           uint32_t flags = 0;
 
           monitor_mode_spec = meta_monitor_mode_get_spec (monitor_mode);
@@ -1555,6 +1560,20 @@ meta_monitor_manager_handle_get_current_state (MetaDBusDisplayConfig *skeleton,
             meta_monitor_manager_calculate_monitor_mode_scale (manager,
                                                                monitor,
                                                                monitor_mode);
+
+          g_variant_builder_init (&supported_scales_builder,
+                                  G_VARIANT_TYPE ("ad"));
+          supported_scales =
+            meta_monitor_manager_calculate_supported_scales (manager,
+                                                             manager->layout_mode,
+                                                             monitor,
+                                                             monitor_mode,
+                                                             &n_supported_scales);
+          for (i = 0; i < n_supported_scales; i++)
+            g_variant_builder_add (&supported_scales_builder, "d",
+                                   (double) supported_scales[i]);
+          g_free (supported_scales);
+
           if (monitor_mode == current_mode)
             flags |= META_DISPLAY_CONFIG_MODE_FLAGS_CURRENT;
           if (monitor_mode == preferred_mode)
@@ -1565,6 +1584,7 @@ meta_monitor_manager_handle_get_current_state (MetaDBusDisplayConfig *skeleton,
                                  monitor_mode_spec->height,
                                  monitor_mode_spec->refresh_rate,
                                  (double) preferred_scale,
+                                 &supported_scales_builder,
                                  flags);
         }
 
@@ -1632,14 +1652,6 @@ meta_monitor_manager_handle_get_current_state (MetaDBusDisplayConfig *skeleton,
                              NULL);
     }
 
-  g_variant_builder_init (&supported_scales_builder, G_VARIANT_TYPE ("ad"));
-  meta_monitor_manager_get_supported_scales (manager,
-                                             manager->layout_mode,
-                                             &supported_scales,
-                                             &n_supported_scales);
-  for (i = 0; i < n_supported_scales; i++)
-    g_variant_builder_add (&supported_scales_builder, "d", supported_scales[i]);
-
   g_variant_builder_init (&properties_builder, G_VARIANT_TYPE ("a{sv}"));
   capabilities = meta_monitor_manager_get_capabilities (manager);
   if ((capabilities & META_MONITOR_MANAGER_CAPABILITY_MIRRORING) == 0)
@@ -1690,7 +1702,6 @@ meta_monitor_manager_handle_get_current_state (MetaDBusDisplayConfig *skeleton,
     manager->serial,
     g_variant_builder_end (&monitors_builder),
     g_variant_builder_end (&logical_monitors_builder),
-    g_variant_builder_end (&supported_scales_builder),
     g_variant_builder_end (&properties_builder));
 
   return TRUE;
@@ -1708,15 +1719,19 @@ meta_monitor_manager_handle_get_current_state (MetaDBusDisplayConfig *skeleton,
 gboolean
 meta_monitor_manager_is_scale_supported (MetaMonitorManager          *manager,
                                          MetaLogicalMonitorLayoutMode layout_mode,
+                                         MetaMonitor                 *monitor,
+                                         MetaMonitorMode             *monitor_mode,
                                          float                        scale)
 {
-  float *supported_scales;
+  g_autofree float *supported_scales = NULL;
   int n_supported_scales;
   int i;
 
-  meta_monitor_manager_get_supported_scales (manager,
+  supported_scales =
+    meta_monitor_manager_calculate_supported_scales (manager,
                                                      layout_mode,
-                                             &supported_scales,
+                                                     monitor,
+                                                     monitor_mode,
                                                      &n_supported_scales);
   for (i = 0; i < n_supported_scales; i++)
     {
@@ -1740,15 +1755,6 @@ meta_monitor_manager_is_config_applicable (MetaMonitorManager *manager,
       float scale = logical_monitor_config->scale;
       GList *k;
 
-      if (!meta_monitor_manager_is_scale_supported (manager,
-                                                    config->layout_mode,
-                                                    scale))
-        {
-          g_set_error (error, G_IO_ERROR, G_IO_ERROR_FAILED,
-                       "Scale not supported by backend");
-          return FALSE;
-        }
-
       for (k = logical_monitor_config->monitor_configs; k; k = k->next)
         {
           MetaMonitorConfig *monitor_config = k->data;
@@ -1773,6 +1779,18 @@ meta_monitor_manager_is_config_applicable (MetaMonitorManager *manager,
                            "Specified monitor mode not available");
               return FALSE;
             }
+
+          if (!meta_monitor_manager_is_scale_supported (manager,
+                                                        config->layout_mode,
+                                                        monitor,
+                                                        monitor_mode,
+                                                        scale))
+            {
+              g_set_error (error, G_IO_ERROR, G_IO_ERROR_FAILED,
+                           "Scale not supported by backend");
+              return FALSE;
+            }
+
         }
     }
 

src/backends/meta-monitor.c

@@ -1336,6 +1336,43 @@ meta_monitor_calculate_mode_scale (MetaMonitor     *monitor,
   return calculate_scale (monitor, monitor_mode);
 }
 
+float *
+meta_monitor_calculate_supported_scales (MetaMonitor                *monitor,
+                                         MetaMonitorMode            *monitor_mode,
+                                         MetaMonitorScalesConstraint constraints,
+                                         int                        *n_supported_scales)
+{
+  unsigned int i;
+  int width, height;
+  GArray *supported_scales;
+  static const float all_scales[] = {
+    1.0,
+    1.5,
+    2.0
+  };
+
+  meta_monitor_mode_get_resolution (monitor_mode, &width, &height);
+
+  supported_scales = g_array_new (FALSE, FALSE, sizeof (float));
+
+  for (i = 0; i < G_N_ELEMENTS (all_scales); i++)
+    {
+      float scale = all_scales[i];
+
+      if ((constraints & META_MONITOR_SCALES_CONSTRAINT_NO_FRAC) &&
+          fmodf (scale, 1.0) != 0.0)
+        continue;
+
+      if (fmodf (width, scale) != 0.0 || fmodf (height, scale) != 0.0)
+        continue;
+
+      g_array_append_val (supported_scales, scale);
+    }
+
+  *n_supported_scales = supported_scales->len;
+  return (float *) g_array_free (supported_scales, FALSE);
+}
+
 MetaMonitorModeSpec *
 meta_monitor_mode_get_spec (MetaMonitorMode *monitor_mode)
 {

src/backends/meta-monitor.h

@@ -53,6 +53,12 @@ typedef gboolean (* MetaMonitorModeFunc) (MetaMonitor         *monitor,
                                           gpointer             user_data,
                                           GError             **error);
 
+typedef enum _MetaMonitorScalesConstraint
+{
+  META_MONITOR_SCALES_CONSTRAINT_NONE = 0,
+  META_MONITOR_SCALES_CONSTRAINT_NO_FRAC = (1 << 0),
+} MetaMonitorScalesConstraint;
+
 #define META_TYPE_MONITOR (meta_monitor_get_type ())
 G_DECLARE_DERIVABLE_TYPE (MetaMonitor, meta_monitor, META, MONITOR, GObject)
 
@@ -163,6 +169,11 @@ void meta_monitor_calculate_crtc_pos (MetaMonitor         *monitor,
 float meta_monitor_calculate_mode_scale (MetaMonitor     *monitor,
                                          MetaMonitorMode *monitor_mode);
 
+float * meta_monitor_calculate_supported_scales (MetaMonitor                *monitor,
+                                                 MetaMonitorMode            *monitor_mode,
+                                                 MetaMonitorScalesConstraint constraints,
+                                                 int                        *n_supported_scales);
+
 MetaMonitorModeSpec * meta_monitor_mode_get_spec (MetaMonitorMode *monitor_mode);
 
 void meta_monitor_mode_get_resolution (MetaMonitorMode *monitor_mode,

src/backends/native/meta-monitor-manager-kms.c

@@ -52,17 +52,6 @@
 #define ALL_TRANSFORMS_MASK ((1 << ALL_TRANSFORMS) - 1)
 #define SYNC_TOLERANCE 0.01    /* 1 percent */
 
-static float supported_scales_kms_logical[] = {
-  1.0,
-  1.5,
-  2.0
-};
-
-static float supported_scales_kms_physical[] = {
-  1.0,
-  2.0
-};
-
 typedef struct
 {
   drmModeConnector *connector;
@@ -1852,23 +1841,28 @@ meta_monitor_manager_kms_calculate_monitor_mode_scale (MetaMonitorManager *manag
   return meta_monitor_calculate_mode_scale (monitor, monitor_mode);
 }
 
-static void
+static float *
-meta_monitor_manager_kms_get_supported_scales (MetaMonitorManager          *manager,
+meta_monitor_manager_kms_calculate_supported_scales (MetaMonitorManager          *manager,
                                                      MetaLogicalMonitorLayoutMode layout_mode,
-                                               float                      **scales,
+                                                     MetaMonitor                 *monitor,
-                                               int                         *n_scales)
+                                                     MetaMonitorMode             *monitor_mode,
+                                                     int                         *n_supported_scales)
 {
+  MetaMonitorScalesConstraint constraints =
+    META_MONITOR_SCALES_CONSTRAINT_NONE;
+
   switch (layout_mode)
     {
     case META_LOGICAL_MONITOR_LAYOUT_MODE_LOGICAL:
-      *scales = supported_scales_kms_logical;
-      *n_scales = G_N_ELEMENTS (supported_scales_kms_logical);
       break;
     case META_LOGICAL_MONITOR_LAYOUT_MODE_PHYSICAL:
-      *scales = supported_scales_kms_physical;
+      constraints |= META_MONITOR_SCALES_CONSTRAINT_NO_FRAC;
-      *n_scales = G_N_ELEMENTS (supported_scales_kms_physical);
       break;
     }
+
+  return meta_monitor_calculate_supported_scales (monitor, monitor_mode,
+                                                  constraints,
+                                                  n_supported_scales);
 }
 
 static MetaMonitorManagerCapability
@@ -1973,7 +1967,7 @@ meta_monitor_manager_kms_class_init (MetaMonitorManagerKmsClass *klass)
   manager_class->set_crtc_gamma = meta_monitor_manager_kms_set_crtc_gamma;
   manager_class->is_transform_handled = meta_monitor_manager_kms_is_transform_handled;
   manager_class->calculate_monitor_mode_scale = meta_monitor_manager_kms_calculate_monitor_mode_scale;
-  manager_class->get_supported_scales = meta_monitor_manager_kms_get_supported_scales;
+  manager_class->calculate_supported_scales = meta_monitor_manager_kms_calculate_supported_scales;
   manager_class->get_capabilities = meta_monitor_manager_kms_get_capabilities;
   manager_class->get_max_screen_size = meta_monitor_manager_kms_get_max_screen_size;
   manager_class->get_default_layout_mode = meta_monitor_manager_kms_get_default_layout_mode;

src/backends/x11/meta-monitor-manager-xrandr.c

@@ -54,10 +54,6 @@
  * for the reasoning */
 #define DPI_FALLBACK 96.0
 
-static float supported_scales_xrandr[] = {
-  1.0, 2.0
-};
-
 struct _MetaMonitorManagerXrandr
 {
   MetaMonitorManager parent_instance;
@@ -1799,14 +1795,19 @@ meta_monitor_manager_xrandr_calculate_monitor_mode_scale (MetaMonitorManager *ma
   return meta_monitor_calculate_mode_scale (monitor, monitor_mode);
 }
 
-static void
+static float *
-meta_monitor_manager_xrandr_get_supported_scales (MetaMonitorManager          *manager,
+meta_monitor_manager_xrandr_calculate_supported_scales (MetaMonitorManager          *manager,
                                                         MetaLogicalMonitorLayoutMode layout_mode,
-                                                  float                      **scales,
+                                                        MetaMonitor                 *monitor,
-                                                  int                         *n_scales)
+                                                        MetaMonitorMode             *monitor_mode,
+                                                        int                         *n_supported_scales)
 {
-  *scales = supported_scales_xrandr;
+  MetaMonitorScalesConstraint constraints;
-  *n_scales = G_N_ELEMENTS (supported_scales_xrandr);
+
+  constraints = META_MONITOR_SCALES_CONSTRAINT_NO_FRAC;
+  return meta_monitor_calculate_supported_scales (monitor, monitor_mode,
+                                                  constraints,
+                                                  n_supported_scales);
 }
 
 static MetaMonitorManagerCapability
@@ -1913,7 +1914,7 @@ meta_monitor_manager_xrandr_class_init (MetaMonitorManagerXrandrClass *klass)
 #endif
   manager_class->is_transform_handled = meta_monitor_manager_xrandr_is_transform_handled;
   manager_class->calculate_monitor_mode_scale = meta_monitor_manager_xrandr_calculate_monitor_mode_scale;
-  manager_class->get_supported_scales = meta_monitor_manager_xrandr_get_supported_scales;
+  manager_class->calculate_supported_scales = meta_monitor_manager_xrandr_calculate_supported_scales;
   manager_class->get_capabilities = meta_monitor_manager_xrandr_get_capabilities;
   manager_class->get_max_screen_size = meta_monitor_manager_xrandr_get_max_screen_size;
   manager_class->get_default_layout_mode = meta_monitor_manager_xrandr_get_default_layout_mode;

src/org.gnome.Mutter.DisplayConfig.xml

@@ -307,7 +307,6 @@
 	@serial: configuration serial
 	@monitors: available monitors
 	@logical_monitors: current logical monitor configuration
-	@supported_scales: scaling factors supported by the display server
 	@properties: display configuration properties
 
 	@monitors represent connected physical monitors
@@ -316,11 +315,12 @@
 	* s vendor: vendor name
 	* s product: product name
 	* s serial: product serial
-	* a(iidu) modes: available modes
+	* a(iiddadu) modes: available modes
 	    * i width: width in physical pixels
 	    * i height: height in physical pixels
 	    * d refresh rate: refresh rate
 	    * d preferred scale: scale preferred as per calculations
+	    * ad supported scales: scales supported by this mode
 	    * u flags: mode flags (see below)
 	* a{sv} properties: optional properties, including:
 	    - "width-mm" (i): physical width of monitor in millimeters
@@ -366,10 +366,6 @@
 	  7: 270° flipped
 
 
-	@supported_scales is an ordered list of floating point numbers representing
-	scale factors of logical monitors supported by the display server.
-
-
 	@layout_mode current layout mode represents the way logical monitors
 	are layed out on the screen. Possible modes include:
 
@@ -408,9 +404,8 @@
     -->
     <method name="GetCurrentState">
       <arg name="serial" direction="out" type="u" />
-      <arg name="monitors" direction="out" type="a((ssss)a(iiddu)a{sv})" />
+      <arg name="monitors" direction="out" type="a((ssss)a(iiddadu)a{sv})" />
       <arg name="logical_monitors" direction="out" type="a(iiduba(ssss)a{sv})" />
-      <arg name="supported_scales" direction="out" type="ad" />
       <arg name="properties" direction="out" type="a{sv}" />
     </method>
 

src/tests/meta-monitor-manager-test.c

@@ -24,17 +24,6 @@
 #include "backends/meta-backend-private.h"
 #include "backends/meta-monitor-config-manager.h"
 
-static float supported_scales_test_logical[] = {
-  1.0,
-  1.5,
-  2.0
-};
-
-static float supported_scales_test_physical[] = {
-  1.0,
-  2.0
-};
-
 struct _MetaMonitorManagerTest
 {
   MetaMonitorManager parent;
@@ -420,23 +409,28 @@ meta_monitor_manager_test_calculate_monitor_mode_scale (MetaMonitorManager *mana
   return output_test->scale;
 }
 
-static void
+static float *
-meta_monitor_manager_test_get_supported_scales (MetaMonitorManager          *manager,
+meta_monitor_manager_test_calculate_supported_scales (MetaMonitorManager          *manager,
                                                       MetaLogicalMonitorLayoutMode layout_mode,
-                                                float                      **scales,
+                                                      MetaMonitor                 *monitor,
-                                                int                         *n_scales)
+                                                      MetaMonitorMode             *monitor_mode,
+                                                      int                         *n_supported_scales)
 {
+  MetaMonitorScalesConstraint constraints =
+    META_MONITOR_SCALES_CONSTRAINT_NONE;
+
   switch (layout_mode)
     {
     case META_LOGICAL_MONITOR_LAYOUT_MODE_LOGICAL:
-      *scales = supported_scales_test_logical;
-      *n_scales = G_N_ELEMENTS (supported_scales_test_logical);
       break;
     case META_LOGICAL_MONITOR_LAYOUT_MODE_PHYSICAL:
-      *scales = supported_scales_test_physical;
+      constraints |= META_MONITOR_SCALES_CONSTRAINT_NO_FRAC;
-      *n_scales = G_N_ELEMENTS (supported_scales_test_physical);
       break;
     }
+
+  return meta_monitor_calculate_supported_scales (monitor, monitor_mode,
+                                                  constraints,
+                                                  n_supported_scales);
 }
 
 static gboolean
@@ -525,7 +519,7 @@ meta_monitor_manager_test_class_init (MetaMonitorManagerTestClass *klass)
   manager_class->tiled_monitor_removed = meta_monitor_manager_test_tiled_monitor_removed;
   manager_class->is_transform_handled = meta_monitor_manager_test_is_transform_handled;
   manager_class->calculate_monitor_mode_scale = meta_monitor_manager_test_calculate_monitor_mode_scale;
-  manager_class->get_supported_scales = meta_monitor_manager_test_get_supported_scales;
+  manager_class->calculate_supported_scales = meta_monitor_manager_test_calculate_supported_scales;
   manager_class->get_capabilities = meta_monitor_manager_test_get_capabilities;
   manager_class->get_max_screen_size = meta_monitor_manager_test_get_max_screen_size;
   manager_class->get_default_layout_mode = meta_monitor_manager_test_get_default_layout_mode;