ecore-drm2: Add API to get/set which output is relative to another

In order to know which output we should clone, we need a way to
store/retrieve the output which should be cloned. This patch adds a
small api we can use in randr config dialog to get/set that value.

@feature

Signed-off-by: Chris Michael <cp.michael@samsung.com>

src/lib/ecore_drm2/Ecore_Drm2.h

@@ -824,6 +824,29 @@ EAPI void ecore_drm2_output_relative_mode_set(Ecore_Drm2_Output *output, Ecore_D
  */
 EAPI Ecore_Drm2_Relative_Mode ecore_drm2_output_relative_mode_get(Ecore_Drm2_Output *output);
 
+/**
+ * Set which output a given output is relative to
+ *
+ * @param output The output for which to set relative
+ * @param relative The output for which the first output is relative to
+ *
+ * @ingroup Ecore_Drm2_Output_Group
+ * @since 1.21
+ */
+EAPI void ecore_drm2_output_relative_to_set(Ecore_Drm2_Output *output, const char *relative);
+
+/**
+ * Get which output is relative to a given output
+ *
+ * @param output The output for which to retrieve relative
+ *
+ * @return The name of the output which is relative to the given output or NULL
+ *
+ * @ingroup Ecore_Drm2_Output_Group
+ * @since 1.21
+ */
+EAPI const char *ecore_drm2_output_relative_to_get(Ecore_Drm2_Output *output);
+
 /**
  * @defgroup Ecore_Drm2_Fb_Group Drm framebuffer functions
  *

src/lib/ecore_drm2/ecore_drm2_outputs.c

@@ -1668,3 +1668,17 @@ ecore_drm2_output_relative_mode_get(Ecore_Drm2_Output *output)
    EINA_SAFETY_ON_NULL_RETURN_VAL(output, ECORE_DRM2_RELATIVE_MODE_UNKNOWN);
    return output->relative.mode;
 }
+
+EAPI void
+ecore_drm2_output_relative_to_set(Ecore_Drm2_Output *output, const char *relative)
+{
+   EINA_SAFETY_ON_NULL_RETURN(output);
+   eina_stringshare_replace(&output->relative.to, relative);
+}
+
+EAPI const char *
+ecore_drm2_output_relative_to_get(Ecore_Drm2_Output *output)
+{
+   EINA_SAFETY_ON_NULL_RETURN_VAL(output, NULL);
+   return output->relative.to;
+}

src/lib/ecore_drm2/ecore_drm2_private.h

@@ -234,6 +234,7 @@ struct _Ecore_Drm2_Output
 
    struct
      {
+        const char *to;
         Ecore_Drm2_Relative_Mode mode;
      } relative;