diff --git a/ChangeLog b/ChangeLog
index 9a5796e92..3c935647d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,22 @@
+2020-12-16  Chris Liddell  <chris.liddell@artifex.com>
+
+	[truetype] Fix incremental metrics (#59503).
+
+	* src/truetype/ttgload.c (tt_get_metrics, load_truetype_glyph):
+	Previously, the code would populate the phantom points before
+	calling the `get_glyph_metrics` callback.  For formats like PCL XL
+	format 1, class 2 downloaded fonts (where metrics are removed from
+	the TTF header), this causes problems when the hinting program uses
+	the phantom points (misplaced and distorted glyphs) due to the
+	metrics being unset (all zeros).
+	(tt_get_metrics_incr_overrides): Renamed to...
+	(tt_get_metrics_incremental): ... this.  Updated caller
+
+	* include/freetype/ftincrem.h: Update the documentation to make it
+	clearer that `get_glyph_metrics` is to retrieve metrics from a
+	non-standard source, but *not* for the purpose of imposing custom
+	metrics.
+
 2020-12-14  Werner Lemberg  <wl@gnu.org>
 
 	[type42] Pacify static analysis tools (#59682).
diff --git a/include/freetype/ftincrem.h b/include/freetype/ftincrem.h
index f67655eda..54145c1d1 100644
--- a/include/freetype/ftincrem.h
+++ b/include/freetype/ftincrem.h
@@ -213,9 +213,14 @@ FT_BEGIN_HEADER
    *
    * @description:
    *   A function used to retrieve the basic metrics of a given glyph index
-   *   before accessing its data.  This is necessary because, in certain
-   *   formats like TrueType, the metrics are stored in a different place
-   *   from the glyph images proper.
+   *   before accessing its data.  This allows for handling font types such
+   *   as PCL~XL Format~1, Class~2 downloaded TrueType fonts, where the glyph
+   *   metrics (`hmtx` and `vmtx` tables) are permitted to be omitted from
+   *   the font, and the relevant metrics included in the header of the glyph
+   *   outline data.  Importantly, this is not intended to allow custom glyph
+   *   metrics (for example, Postscript Metrics dictionaries), because that
+   *   conflicts with the requirements of outline hinting.  Such custom
+   *   metrics must be handled separately, by the calling application.
    *
    * @input:
    *   incremental ::
@@ -235,7 +240,7 @@ FT_BEGIN_HEADER
    *
    * @output:
    *   ametrics ::
-   *     The replacement glyph metrics in font units.
+   *     The glyph metrics in font units.
    *
    */
   typedef FT_Error
@@ -264,7 +269,7 @@ FT_BEGIN_HEADER
    *
    *   get_glyph_metrics ::
    *     The function to get glyph metrics.  May be null if the font does not
-   *     provide overriding glyph metrics.
+   *     require it.
    *
    */
   typedef struct  FT_Incremental_FuncsRec_
diff --git a/src/truetype/ttgload.c b/src/truetype/ttgload.c
index d08a97565..81cecbb85 100644
--- a/src/truetype/ttgload.c
+++ b/src/truetype/ttgload.c
@@ -197,10 +197,17 @@
     }
 #endif /* TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY */
 
-    if ( !loader->linear_def )
+#ifdef FT_CONFIG_OPTION_INCREMENTAL
+    /* With the incremental interface, these values are set by  */
+    /* a call to `tt_get_metrics_incremental'.                  */
+    if ( face->root.internal->incremental_interface == NULL )
+#endif
     {
-      loader->linear_def = 1;
-      loader->linear     = advance_width;
+      if ( !loader->linear_def )
+      {
+        loader->linear_def = 1;
+        loader->linear     = advance_width;
+      }
     }
 
     return FT_Err_Ok;
@@ -210,8 +217,8 @@
 #ifdef FT_CONFIG_OPTION_INCREMENTAL
 
   static void
-  tt_get_metrics_incr_overrides( TT_Loader  loader,
-                                 FT_UInt    glyph_index )
+  tt_get_metrics_incremental( TT_Loader  loader,
+                              FT_UInt    glyph_index )
   {
     TT_Face  face = loader->face;
 
@@ -1741,13 +1748,11 @@
 
     if ( loader->byte_len == 0 || loader->n_contours == 0 )
     {
-      /* must initialize points before (possibly) overriding */
-      /* glyph metrics from the incremental interface        */
+#ifdef FT_CONFIG_OPTION_INCREMENTAL
+      tt_get_metrics_incremental( loader, glyph_index );
+#endif
       tt_loader_set_pp( loader );
 
-#ifdef FT_CONFIG_OPTION_INCREMENTAL
-      tt_get_metrics_incr_overrides( loader, glyph_index );
-#endif
 
 #ifdef TT_CONFIG_OPTION_GX_VAR_SUPPORT
 
@@ -1830,13 +1835,11 @@
       goto Exit;
     }
 
-    /* must initialize phantom points before (possibly) overriding */
-    /* glyph metrics from the incremental interface                */
+#ifdef FT_CONFIG_OPTION_INCREMENTAL
+    tt_get_metrics_incremental( loader, glyph_index );
+#endif
     tt_loader_set_pp( loader );
 
-#ifdef FT_CONFIG_OPTION_INCREMENTAL
-    tt_get_metrics_incr_overrides( loader, glyph_index );
-#endif
 
     /***********************************************************************/
     /***********************************************************************/