[pango/fix-tabs-nowrap: 2/2] Fix line width computation

[Matthias Clasen <matthiasc src gnome org>]

commit 21d02db53e740ee37c0aedbf0bf8a92e528036a0
Author: Matthias Clasen <mclasen redhat com>
Date:   Mon Dec 6 22:57:27 2021 -0500

    Fix line width computation
    
    We an only use the line_width - remaining_width
    shortcut if we are actually maintaining remaining_width,
    i.e. not if we don't wrap lines.
    
    Testcase included.
    
    Fixes: #635

 pango/pango-layout.c             |  27 ++-
 tests/layouts/tabs-nowrap.layout | 363 +++++++++++++++++++++++++++++++++++++++
 tests/meson.build                |   1 +
 3 files changed, 390 insertions(+), 1 deletion(-)
---
diff --git a/pango/pango-layout.c b/pango/pango-layout.c
index ed46d57a..a495596c 100644
--- a/pango/pango-layout.c
+++ b/pango/pango-layout.c
@@ -3662,6 +3662,31 @@ get_decimal_prefix_width (PangoItem        *item,
   g_free (log_widths);
 }
 
+static int
+line_width (ParaBreakState  *state,
+            PangoLayoutLine *line)
+{
+  GSList *l;
+  int i;
+  int width = 0;
+
+  if (state->remaining_width > -1)
+    return state->line_width - state->remaining_width;
+
+  /* Compute the width of the line currently - inefficient, but easier
+   * than keeping the current width of the line up to date everywhere
+   */
+  for (l = line->runs; l; l = l->next)
+    {
+      PangoLayoutRun *run = l->data;
+
+      for (i = 0; i < run->glyphs->num_glyphs; i++)
+        width += run->glyphs->glyphs[i].geometry.width;
+    }
+
+  return width;
+}
+
 static PangoGlyphString *
 shape_run (PangoLayoutLine *line,
            ParaBreakState  *state,
@@ -3671,7 +3696,7 @@ shape_run (PangoLayoutLine *line,
   PangoGlyphString *glyphs = pango_glyph_string_new ();
 
   if (layout->text[item->offset] == '\t')
-    shape_tab (line, &state->last_tab, &state->properties, state->line_width - state->remaining_width, item, 
glyphs);
+    shape_tab (line, &state->last_tab, &state->properties, line_width (state, line), item, glyphs);
   else
     {
       PangoShapeFlags shape_flags = PANGO_SHAPE_NONE;
diff --git a/tests/layouts/tabs-nowrap.layout b/tests/layouts/tabs-nowrap.layout
new file mode 100644
index 00000000..4a1d40b5
--- /dev/null
+++ b/tests/layouts/tabs-nowrap.layout
@@ -0,0 +1,363 @@
+{
+  "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" : "A case where tabs were broken if line wrapping is disabled.",
+  "text" : "123\t9\n123456789",
+  "attributes" : [
+    {
+      "type" : "font-features",
+      "value" : "tnum=1"
+    }
+  ],
+  "font" : "DejaVu Sans Mono 32",
+  "output" : {
+    "is-wrapped" : false,
+    "is-ellipsized" : false,
+    "unknown-glyphs" : 0,
+    "width" : 239616,
+    "height" : 239616,
+    "log-attrs" : [
+      {
+        "char-break" : true,
+        "cursor-position" : true,
+        "word-start" : true,
+        "sentence-boundary" : true,
+        "sentence-start" : true,
+        "backspace-deletes-character" : true,
+        "word-boundary" : true
+      },
+      {
+        "char-break" : true,
+        "cursor-position" : true
+      },
+      {
+        "char-break" : true,
+        "cursor-position" : true
+      },
+      {
+        "char-break" : true,
+        "white" : true,
+        "cursor-position" : true,
+        "word-end" : true,
+        "word-boundary" : true
+      },
+      {
+        "line-break" : true,
+        "char-break" : true,
+        "cursor-position" : true,
+        "word-start" : true,
+        "backspace-deletes-character" : true,
+        "word-boundary" : true
+      },
+      {
+        "char-break" : true,
+        "white" : true,
+        "cursor-position" : true,
+        "word-end" : true,
+        "sentence-end" : true,
+        "word-boundary" : true
+      },
+      {
+        "line-break" : true,
+        "mandatory-break" : true,
+        "char-break" : true,
+        "cursor-position" : true,
+        "word-start" : true,
+        "sentence-boundary" : true,
+        "sentence-start" : true,
+        "backspace-deletes-character" : true,
+        "word-boundary" : true
+      },
+      {
+        "char-break" : true,
+        "cursor-position" : true
+      },
+      {
+        "char-break" : true,
+        "cursor-position" : true
+      },
+      {
+        "char-break" : true,
+        "cursor-position" : true
+      },
+      {
+        "char-break" : true,
+        "cursor-position" : true
+      },
+      {
+        "char-break" : true,
+        "cursor-position" : true
+      },
+      {
+        "char-break" : true,
+        "cursor-position" : true
+      },
+      {
+        "char-break" : true,
+        "cursor-position" : true
+      },
+      {
+        "char-break" : true,
+        "cursor-position" : true
+      },
+      {
+        "line-break" : true,
+        "mandatory-break" : true,
+        "char-break" : true,
+        "white" : true,
+        "cursor-position" : true,
+        "word-end" : true,
+        "sentence-boundary" : true,
+        "sentence-end" : true,
+        "word-boundary" : true
+      }
+    ],
+    "lines" : [
+      {
+        "start-index" : 0,
+        "length" : 5,
+        "paragraph-start" : true,
+        "direction" : "ltr",
+        "runs" : [
+          {
+            "offset" : 0,
+            "length" : 3,
+            "text" : "123",
+            "bidi-level" : 0,
+            "gravity" : "south",
+            "language" : "en-us",
+            "script" : "common",
+            "font" : {
+              "description" : "DejaVu Sans Mono 32",
+              "checksum" : "84c5467cadd1f6f23db0d9fbb6377e0d301334d3b5f36e6d5acebd34d0857d3a",
+              "matrix" : [
+                1,
+                -0,
+                -0,
+                1,
+                0,
+                0
+              ]
+            },
+            "flags" : 0,
+            "extra-attributes" : [
+              {
+                "type" : "font-features",
+                "value" : "tnum=1"
+              }
+            ],
+            "y-offset" : 0,
+            "start-x-offset" : 0,
+            "end-x-offset" : 0,
+            "glyphs" : [
+              {
+                "glyph" : 20,
+                "width" : 26624,
+                "is-cluster-start" : true,
+                "log-cluster" : 0
+              },
+              {
+                "glyph" : 21,
+                "width" : 26624,
+                "is-cluster-start" : true,
+                "log-cluster" : 1
+              },
+              {
+                "glyph" : 22,
+                "width" : 26624,
+                "is-cluster-start" : true,
+                "log-cluster" : 2
+              }
+            ]
+          },
+          {
+            "offset" : 3,
+            "length" : 1,
+            "text" : "\t",
+            "bidi-level" : 0,
+            "gravity" : "south",
+            "language" : "en-us",
+            "script" : "common",
+            "font" : {
+              "description" : "DejaVu Sans Mono 32",
+              "checksum" : "84c5467cadd1f6f23db0d9fbb6377e0d301334d3b5f36e6d5acebd34d0857d3a",
+              "matrix" : [
+                1,
+                -0,
+                -0,
+                1,
+                0,
+                0
+              ]
+            },
+            "flags" : 0,
+            "extra-attributes" : [
+              {
+                "type" : "font-features",
+                "value" : "tnum=1"
+              }
+            ],
+            "y-offset" : 0,
+            "start-x-offset" : 0,
+            "end-x-offset" : 0,
+            "glyphs" : [
+              {
+                "glyph" : 268435455,
+                "width" : 133120,
+                "is-cluster-start" : true,
+                "log-cluster" : 0
+              }
+            ]
+          },
+          {
+            "offset" : 4,
+            "length" : 1,
+            "text" : "9",
+            "bidi-level" : 0,
+            "gravity" : "south",
+            "language" : "en-us",
+            "script" : "common",
+            "font" : {
+              "description" : "DejaVu Sans Mono 32",
+              "checksum" : "84c5467cadd1f6f23db0d9fbb6377e0d301334d3b5f36e6d5acebd34d0857d3a",
+              "matrix" : [
+                1,
+                -0,
+                -0,
+                1,
+                0,
+                0
+              ]
+            },
+            "flags" : 0,
+            "extra-attributes" : [
+              {
+                "type" : "font-features",
+                "value" : "tnum=1"
+              }
+            ],
+            "y-offset" : 0,
+            "start-x-offset" : 0,
+            "end-x-offset" : 0,
+            "glyphs" : [
+              {
+                "glyph" : 28,
+                "width" : 26624,
+                "is-cluster-start" : true,
+                "log-cluster" : 0
+              }
+            ]
+          }
+        ]
+      },
+      {
+        "start-index" : 6,
+        "length" : 9,
+        "paragraph-start" : true,
+        "direction" : "ltr",
+        "runs" : [
+          {
+            "offset" : 6,
+            "length" : 9,
+            "text" : "123456789",
+            "bidi-level" : 0,
+            "gravity" : "south",
+            "language" : "en-us",
+            "script" : "common",
+            "font" : {
+              "description" : "DejaVu Sans Mono 32",
+              "checksum" : "84c5467cadd1f6f23db0d9fbb6377e0d301334d3b5f36e6d5acebd34d0857d3a",
+              "matrix" : [
+                1,
+                -0,
+                -0,
+                1,
+                0,
+                0
+              ]
+            },
+            "flags" : 0,
+            "extra-attributes" : [
+              {
+                "type" : "font-features",
+                "value" : "tnum=1"
+              }
+            ],
+            "y-offset" : 0,
+            "start-x-offset" : 0,
+            "end-x-offset" : 0,
+            "glyphs" : [
+              {
+                "glyph" : 20,
+                "width" : 26624,
+                "is-cluster-start" : true,
+                "log-cluster" : 0
+              },
+              {
+                "glyph" : 21,
+                "width" : 26624,
+                "is-cluster-start" : true,
+                "log-cluster" : 1
+              },
+              {
+                "glyph" : 22,
+                "width" : 26624,
+                "is-cluster-start" : true,
+                "log-cluster" : 2
+              },
+              {
+                "glyph" : 23,
+                "width" : 26624,
+                "is-cluster-start" : true,
+                "log-cluster" : 3
+              },
+              {
+                "glyph" : 24,
+                "width" : 26624,
+                "is-cluster-start" : true,
+                "log-cluster" : 4
+              },
+              {
+                "glyph" : 25,
+                "width" : 26624,
+                "is-cluster-start" : true,
+                "log-cluster" : 5
+              },
+              {
+                "glyph" : 26,
+                "width" : 26624,
+                "is-cluster-start" : true,
+                "log-cluster" : 6
+              },
+              {
+                "glyph" : 27,
+                "width" : 26624,
+                "is-cluster-start" : true,
+                "log-cluster" : 7
+              },
+              {
+                "glyph" : 28,
+                "width" : 26624,
+                "is-cluster-start" : true,
+                "log-cluster" : 8
+              }
+            ]
+          }
+        ]
+      }
+    ]
+  }
+}
diff --git a/tests/meson.build b/tests/meson.build
index 2acf0def..b15c7291 100644
--- a/tests/meson.build
+++ b/tests/meson.build
@@ -96,6 +96,7 @@ installed_test_layouts_data = [
   'layouts/effigy.layout',
   'layouts/kebab.layout',
   'layouts/tabs.layout',
+  'layouts/tabs-nowrap.layout',
   'layouts/valid-1.layout',
   'layouts/valid-2.layout',
   'layouts/valid-3.layout',