[pango/fix-spaceless-fonts] Fix handling of space-less fonts

[Matthias Clasen <matthiasc src gnome org>]

commit b420d022a2979c2e86b465bca0c7d603dd136108
Author: Matthias Clasen <mclasen redhat com>
Date:   Thu Dec 16 08:40:07 2021 -0500

    Fix handling of space-less fonts
    
    HarfBuzz knows how to synthesize spaces, we just
    need to tickle it in the right way.
    
    Test included.
    
    Update affected tests.
    
    Fixes: #641

 pango/shape.c                   |  10 ++-
 tests/fonts/README              |   1 +
 tests/fonts/fa-regular-f2db.ttf | Bin 0 -> 912 bytes
 tests/fonts/fa-solid-f2db.ttf   | Bin 0 -> 1320 bytes
 tests/layouts/no-space.layout   | 142 ++++++++++++++++++++++++++++++++++++++++
 tests/layouts/valid-14.layout   |  20 ++----
 tests/meson.build               |   1 +
 7 files changed, 160 insertions(+), 14 deletions(-)
---
diff --git a/pango/shape.c b/pango/shape.c
index 45c979f2..d0140d5e 100644
--- a/pango/shape.c
+++ b/pango/shape.c
@@ -137,10 +137,18 @@ pango_hb_font_get_nominal_glyph (hb_font_t      *font,
   if (hb_font_get_nominal_glyph (context->parent, unicode, glyph))
     return TRUE;
 
+  /* HarfBuzz knows how to synthesize spaces, so never replace them
+   * with unknown glyphs, but we do need to tell HarfBuzz that the
+   * font does not have a glyph.
+   */
+  if (g_unichar_type (unicode) == G_UNICODE_SPACE_SEPARATOR)
+    return FALSE;
+
   *glyph = PANGO_GET_UNKNOWN_GLYPH (unicode);
 
   /* We draw our own invalid-Unicode shape, so prevent HarfBuzz
-   * from using REPLACEMENT CHARACTER. */
+   * from using REPLACEMENT CHARACTER.
+   */
   if (unicode > 0x10FFFF)
     return TRUE;
 
diff --git a/tests/fonts/README b/tests/fonts/README
index 9cc88ca7..ca56ca40 100644
--- a/tests/fonts/README
+++ b/tests/fonts/README
@@ -7,3 +7,4 @@ DejaVSansMono.ttf: DejaVu Sans Mono
 emoji-subset.ttf: subset of Noto Color Emoji
 droid-sans-subset.ttf: subset of Droid Sans Japanese
 amiri-06dd.ttf: subset of Amiri containing U+06dd
+fa-regular-f2db.ttf, fa-solid-f2db.ttf: subset of FontAwesome containing U+f2db
diff --git a/tests/fonts/fa-regular-f2db.ttf b/tests/fonts/fa-regular-f2db.ttf
new file mode 100644
index 00000000..54e0f1fb
Binary files /dev/null and b/tests/fonts/fa-regular-f2db.ttf differ
diff --git a/tests/fonts/fa-solid-f2db.ttf b/tests/fonts/fa-solid-f2db.ttf
new file mode 100644
index 00000000..dc5ef3d7
Binary files /dev/null and b/tests/fonts/fa-solid-f2db.ttf differ
diff --git a/tests/layouts/no-space.layout b/tests/layouts/no-space.layout
new file mode 100644
index 00000000..07f6aa06
--- /dev/null
+++ b/tests/layouts/no-space.layout
@@ -0,0 +1,142 @@
+{
+  "context" : {
+    "font" : "serif 12",
+    "base-gravity" : "south",
+    "gravity-hint" : "natural",
+    "base-dir" : "weak-ltr",
+    "round-glyph-positions" : true,
+    "transform" : [
+      1,
+      0,
+      0,
+      1,
+      0,
+      0
+    ]
+  },
+  "comment" : "Test that we get synthesized spaces\nfrom HarfBuzz.",
+  "text" : "    ",
+  "font" : "Font Awesome 5 Free 32",
+  "output" : {
+    "is-wrapped" : false,
+    "is-ellipsized" : false,
+    "unknown-glyphs" : 0,
+    "width" : 220160,
+    "height" : 220160,
+    "log-attrs" : [
+      {
+        "char-break" : true,
+        "white" : true,
+        "cursor-position" : true,
+        "sentence-boundary" : true,
+        "backspace-deletes-character" : true,
+        "expandable-space" : true,
+        "word-boundary" : true
+      },
+      {
+        "char-break" : true,
+        "white" : true,
+        "cursor-position" : true,
+        "expandable-space" : true
+      },
+      {
+        "line-break" : true,
+        "char-break" : true,
+        "cursor-position" : true,
+        "sentence-start" : true,
+        "word-boundary" : true
+      },
+      {
+        "char-break" : true,
+        "white" : true,
+        "cursor-position" : true,
+        "sentence-end" : true,
+        "backspace-deletes-character" : true,
+        "expandable-space" : true,
+        "word-boundary" : true
+      },
+      {
+        "char-break" : true,
+        "white" : true,
+        "cursor-position" : true,
+        "expandable-space" : true
+      },
+      {
+        "line-break" : true,
+        "mandatory-break" : true,
+        "char-break" : true,
+        "white" : true,
+        "cursor-position" : true,
+        "sentence-boundary" : true,
+        "word-boundary" : true
+      }
+    ],
+    "lines" : [
+      {
+        "start-index" : 0,
+        "length" : 7,
+        "paragraph-start" : true,
+        "direction" : "ltr",
+        "runs" : [
+          {
+            "offset" : 0,
+            "length" : 7,
+            "text" : "    ",
+            "bidi-level" : 0,
+            "gravity" : "south",
+            "language" : "en-us",
+            "script" : "common",
+            "font" : {
+              "description" : "Font Awesome 5 Free Solid Heavy 32",
+              "checksum" : "8fe6cd51391fa6f8c2008609ddd489bb81a6d7674f3a1c8b7fa07efd026a6397",
+              "matrix" : [
+                1,
+                -0,
+                -0,
+                1,
+                0,
+                0
+              ]
+            },
+            "flags" : 0,
+            "y-offset" : 0,
+            "start-x-offset" : 0,
+            "end-x-offset" : 0,
+            "glyphs" : [
+              {
+                "glyph" : 0,
+                "width" : 44032,
+                "is-cluster-start" : true,
+                "log-cluster" : 0
+              },
+              {
+                "glyph" : 0,
+                "width" : 44032,
+                "is-cluster-start" : true,
+                "log-cluster" : 1
+              },
+              {
+                "glyph" : 1,
+                "width" : 44032,
+                "is-cluster-start" : true,
+                "log-cluster" : 2
+              },
+              {
+                "glyph" : 0,
+                "width" : 44032,
+                "is-cluster-start" : true,
+                "log-cluster" : 5
+              },
+              {
+                "glyph" : 0,
+                "width" : 44032,
+                "is-cluster-start" : true,
+                "log-cluster" : 6
+              }
+            ]
+          }
+        ]
+      }
+    ]
+  }
+}
diff --git a/tests/layouts/valid-14.layout b/tests/layouts/valid-14.layout
index ca686814..8cfa62d9 100644
--- a/tests/layouts/valid-14.layout
+++ b/tests/layouts/valid-14.layout
@@ -23,7 +23,7 @@
   "output" : {
     "is-wrapped" : false,
     "is-ellipsized" : true,
-    "unknown-glyphs" : 1,
+    "unknown-glyphs" : 0,
     "width" : 161792,
     "height" : 161792,
     "log-attrs" : [
@@ -189,8 +189,8 @@
         "runs" : [
           {
             "offset" : 0,
-            "length" : 3,
-            "text" : "你",
+            "length" : 6,
+            "text" : "你好",
             "bidi-level" : 0,
             "gravity" : "south",
             "language" : "en-us",
@@ -241,9 +241,9 @@
             ]
           },
           {
-            "offset" : 3,
-            "length" : 4,
-            "text" : "好 ",
+            "offset" : 6,
+            "length" : 1,
+            "text" : " ",
             "bidi-level" : 0,
             "gravity" : "south",
             "language" : "xx",
@@ -266,16 +266,10 @@
             "end-x-offset" : 0,
             "glyphs" : [
               {
-                "glyph" : 1,
+                "glyph" : 0,
                 "width" : 15360,
                 "is-cluster-start" : true,
                 "log-cluster" : 0
-              },
-              {
-                "glyph" : 268435488,
-                "width" : 0,
-                "is-cluster-start" : true,
-                "log-cluster" : 3
               }
             ]
           },
diff --git a/tests/meson.build b/tests/meson.build
index 79510fb6..271d9046 100644
--- a/tests/meson.build
+++ b/tests/meson.build
@@ -122,6 +122,7 @@ installed_test_layouts_data = [
   'layouts/tab-crash.layout',
   'layouts/tab-assert.layout',
   'layouts/arabic-format.layout',
+  'layouts/no-space.layout',
 ]
 
 test_markups_data = [