cairo: Fix handling of font sizes.

Until now this code used pango_font_description_set_absolute_size() to set
the font size.  This sets the font size in device units, e.g. pixels on a
display.  But font sizes are actual specified by the user in points, so
we should instead use pango_font_description_get_size().  This commit
makes that change.

That change is simple, but it necessitates a larger change.
Until now the cairo driver has just assumed that the size of a font is
the size that we assigned it.  But this is no longer the case, since
points and pixels are now different.  So now we measure the actual width
and height of characters and use those as the font size.  At the same
time, the code no longer ignores font sizes included as part of font
description strings, and allows different fonts to have different sizes.

With plenty of help from John Darrington.

diff --git a/src/output/cairo.c b/src/output/cairo.c
index a2b7a2f898178db2ea59f58173b66fb94c695559..d4f31aad6a011f2459f941353c7e8f1a64ca8e4c 100644 (file)
--- a/src/output/cairo.c
+++ b/src/output/cairo.c
@@ -95,10 +95,8 @@ enum xr_font_type
 /* A font for use with Cairo. */
 struct xr_font
   {
-    char *string;
     PangoFontDescription *desc;
     PangoLayout *layout;
-    PangoFontMetrics *metrics;
   };
 
 /* An output item whose rendering is in progress. */
@@ -120,7 +118,6 @@ struct xr_driver
 
     /* User parameters. */
     struct xr_font fonts[XR_N_FONTS];
-    int font_height;            /* In XR units. */
 
     int width;                  /* Page width minus margins. */
     int length;                 /* Page length minus margins and header. */
@@ -136,6 +133,7 @@ struct xr_driver
 
     /* Internal state. */
     struct render_params *params;
+    int char_width, char_height;
     char *command_name;
     char *title;
     char *subtitle;
@@ -150,9 +148,6 @@ static const struct output_driver_class cairo_driver_class;
 static void xr_driver_destroy_fsm (struct xr_driver *);
 static void xr_driver_run_fsm (struct xr_driver *);
 
-static bool load_font (struct xr_driver *, struct xr_font *);
-static void free_font (struct xr_font *);
-
 static void xr_draw_line (void *, int bb[TABLE_N_AXES][2],
                           enum render_line_style styles[TABLE_N_AXES][2]);
 static void xr_measure_cell_width (void *, const struct table_cell *,
@@ -182,23 +177,58 @@ opt (struct output_driver *d, struct string_map *options, const char *key,
   return driver_option_get (d, options, key, default_value);
 }
 
+static PangoFontDescription *
+parse_font (struct output_driver *d, struct string_map *options,
+            const char *key, const char *default_value,
+            int default_points)
+{
+  PangoFontDescription *desc;
+  char *string;
+
+  /* Parse KEY as a font description. */
+  string = parse_string (opt (d, options, key, default_value));
+  desc = pango_font_description_from_string (string);
+  if (desc == NULL)
+    {
+      error (0, 0, _("\"%s\": bad font specification"), string);
+
+      /* Fall back to DEFAULT_VALUE, which had better be a valid font
+         description. */
+      desc = pango_font_description_from_string (default_value);
+      assert (desc != NULL);
+    }
+  free (string);
+
+  /* If the font description didn't include an explicit font size, then set it
+     to DEFAULT_POINTS. */
+  if (!(pango_font_description_get_set_fields (desc) & PANGO_FONT_MASK_SIZE))
+    pango_font_description_set_size (desc,
+                                     default_points / 1000.0 * PANGO_SCALE);
+
+  return desc;
+}
+
 static struct xr_driver *
 xr_allocate (const char *name, int device_type, struct string_map *o)
 {
   int paper_width, paper_length;
   struct output_driver *d;
   struct xr_driver *xr;
+  int font_points;
 
   xr = xzalloc (sizeof *xr);
   d = &xr->driver;
   output_driver_init (d, &cairo_driver_class, name, device_type);
-  xr->font_height = XR_POINT * 10;
-  xr->fonts[XR_FONT_FIXED].string
-    = parse_string (opt (d, o, "fixed-font", "monospace"));
-  xr->fonts[XR_FONT_PROPORTIONAL].string
-    = parse_string (opt (d, o, "prop-font", "serif"));
-  xr->fonts[XR_FONT_EMPHASIS].string
-    = parse_string (opt (d, o, "emph-font", "serif italic"));
+
+  font_points = parse_int (opt (d, o, "font-size", "10000"),
+                           1000, 1000000);
+  xr->fonts[XR_FONT_FIXED].desc = parse_font (d, o, "fixed-font", "monospace",
+                                              font_points);
+  xr->fonts[XR_FONT_PROPORTIONAL].desc = parse_font (d, o, "prop-font",
+                                                     "serif", font_points);
+  xr->fonts[XR_FONT_EMPHASIS].desc = parse_font (d, o, "emph-font",
+                                                 "serif italic", font_points);
+
   xr->line_gutter = XR_POINT;
   xr->line_space = XR_POINT;
   xr->line_width = XR_POINT / 2;
@@ -216,18 +246,57 @@ xr_allocate (const char *name, int device_type, struct string_map *o)
   return xr;
 }
 
+static bool
+xr_is_72dpi (cairo_t *cr)
+{
+  cairo_surface_type_t type;
+  cairo_surface_t *surface;
+
+  surface = cairo_get_target (cr);
+  type = cairo_surface_get_type (surface);
+  return type == CAIRO_SURFACE_TYPE_PDF || type == CAIRO_SURFACE_TYPE_PS;
+}
+
 static bool
 xr_set_cairo (struct xr_driver *xr, cairo_t *cairo)
 {
+  PangoContext *context;
+  PangoFontMap *map;
   int i;
 
   xr->cairo = cairo;
 
   cairo_set_line_width (xr->cairo, xr_to_pt (xr->line_width));
 
+  map = pango_cairo_font_map_get_default ();
+  context = pango_cairo_font_map_create_context (PANGO_CAIRO_FONT_MAP (map));
+  if (xr_is_72dpi (cairo))
+    {
+      /* Pango seems to always scale fonts according to the DPI specified
+         in the font map, even if the surface has a real DPI.  The default
+         DPI is 96, so on a 72 DPI device fonts end up being 96/72 = 133%
+         of their desired size.  We deal with this by fixing the resolution
+         here.  Presumably there is a better solution, but what? */
+      pango_cairo_context_set_resolution (context, 72.0);
+    }
+
+  xr->char_width = 0;
+  xr->char_height = 0;
   for (i = 0; i < XR_N_FONTS; i++)
-    if (!load_font (xr, &xr->fonts[i]))
-      return false;
+    {
+      struct xr_font *font = &xr->fonts[i];
+      int char_width, char_height;
+
+      font->layout = pango_layout_new (context);
+      pango_layout_set_font_description (font->layout, font->desc);
+
+      pango_layout_set_text (font->layout, "0", 1);
+      pango_layout_get_size (font->layout, &char_width, &char_height);
+      xr->char_width = MAX (xr->char_width, char_width);
+      xr->char_height = MAX (xr->char_height, char_height);
+    }
+
+  g_object_unref (G_OBJECT (context));
 
   if (xr->params == NULL)
     {
@@ -241,8 +310,8 @@ xr_set_cairo (struct xr_driver *xr, cairo_t *cairo)
       xr->params->aux = xr;
       xr->params->size[H] = xr->width;
       xr->params->size[V] = xr->length;
-      xr->params->font_size[H] = xr->font_height / 2; /* XXX */
-      xr->params->font_size[V] = xr->font_height;
+      xr->params->font_size[H] = xr->char_width;
+      xr->params->font_size[V] = xr->char_height;
 
       single_width = 2 * xr->line_gutter + xr->line_width;
       double_width = 2 * xr->line_gutter + xr->line_space + 2 * xr->line_width;
@@ -300,23 +369,23 @@ xr_create (const char *file_name, enum settings_output_devices device_type,
   cairo_save (xr->cairo);
   xr_driver_next_page (xr, xr->cairo);
 
-  if (xr->width / (xr->font_height / 2) < MIN_WIDTH)
+  if (xr->width / xr->char_width < MIN_WIDTH)
     {
       error (0, 0, _("The defined page is not wide enough to hold at least %d "
                      "characters in the default font.  In fact, there's only "
                      "room for %d characters."),
              MIN_WIDTH,
-             xr->width / (xr->font_height / 2));
+             xr->width / xr->char_width);
       goto error;
     }
 
-  if (xr->length / xr->font_height < MIN_LENGTH)
+  if (xr->length / xr->char_height < MIN_LENGTH)
     {
       error (0, 0, _("The defined page is not long enough to hold at least %d "
                      "lines in the default font.  In fact, there's only "
                      "room for %d lines."),
              MIN_LENGTH,
-             xr->length / xr->font_height);
+             xr->length / xr->char_height);
       goto error;
     }
 
@@ -371,7 +440,15 @@ xr_destroy (struct output_driver *driver)
 
   free (xr->command_name);
   for (i = 0; i < XR_N_FONTS; i++)
-    free_font (&xr->fonts[i]);
+    {
+      struct xr_font *font = &xr->fonts[i];
+
+      if (font->desc != NULL)
+        pango_font_description_free (font->desc);
+      if (font->layout != NULL)
+        g_object_unref (font->layout);
+    }
+
   free (xr->params);
   free (xr);
 }
@@ -764,45 +841,6 @@ xr_layout_cell (struct xr_driver *xr, const struct table_cell *cell,
     }
 }
 \f
-/* Attempts to load FONT, initializing its other members based on
-   its 'string' member and the information in DRIVER.  Returns true
-   if successful, otherwise false. */
-static bool
-load_font (struct xr_driver *xr, struct xr_font *font)
-{
-  PangoContext *context;
-  PangoLanguage *language;
-
-  font->desc = pango_font_description_from_string (font->string);
-  if (font->desc == NULL)
-    {
-      error (0, 0, _("\"%s\": bad font specification"), font->string);
-      return false;
-    }
-  pango_font_description_set_absolute_size (font->desc, xr->font_height);
-
-  font->layout = pango_cairo_create_layout (xr->cairo);
-  pango_layout_set_font_description (font->layout, font->desc);
-
-  language = pango_language_get_default ();
-  context = pango_layout_get_context (font->layout);
-  font->metrics = pango_context_get_metrics (context, font->desc, language);
-
-  return true;
-}
-
-/* Frees FONT. */
-static void
-free_font (struct xr_font *font)
-{
-  free (font->string);
-  if (font->desc != NULL)
-    pango_font_description_free (font->desc);
-  pango_font_metrics_unref (font->metrics);
-  if (font->layout != NULL)
-    g_object_unref (font->layout);
-}
-
 struct output_driver_factory pdf_driver_factory = { "pdf", xr_pdf_create };
 struct output_driver_factory ps_driver_factory = { "ps", xr_ps_create };
 struct output_driver_factory svg_driver_factory = { "svg", xr_svg_create };
@@ -1097,7 +1135,7 @@ xr_render_table (struct xr_driver *xr, const struct table_item *table_item)
   ts->table_item = table_item_ref (table_item);
 
   if (xr->y > 0)
-    xr->y += xr->font_height;
+    xr->y += xr->char_height;
 
   page = xr_render_table_item (xr, table_item, &ts->caption_height);
   xr->params->size[V] = xr->length - ts->caption_height;
@@ -1212,7 +1250,7 @@ xr_render_text (struct xr_driver *xr, const struct text_item *text_item)
 
     case TEXT_ITEM_BLANK_LINE:
       if (xr->y > 0)
-        xr->y += xr->font_height;
+        xr->y += xr->char_height;
       break;
 
     case TEXT_ITEM_EJECT_PAGE:

diff --git a/tests/output/render-test.c b/tests/output/render-test.c
index 4863eaea91ec9cfcee870f1dddab43990dc585f0..e325dbb16d9ba35fae564bb2a9fb3b7327fb02f9 100644 (file)
--- a/tests/output/render-test.c
+++ b/tests/output/render-test.c
@@ -109,7 +109,7 @@ configure_drivers (int width, int length)
   string_map_insert (&options, "left-margin", "0");
   string_map_insert (&options, "right-margin", "0");
   string_map_insert_nocopy (&options, xstrdup ("paper-size"),
-                            xasprintf ("%dx%dpt", width * 5, length * 6));
+                            xasprintf ("%dx%dpt", width * 5, length * 8));
   driver = output_driver_create (&options);
   if (driver == NULL)
     exit (EXIT_FAILURE);