[goffice] GOFormat: minor speed improvement.

[Morten Welinder <mortenw src gnome org>]

commit 55427945f5e0b82606924cc049f9892bdd59d7fd
Author: Morten Welinder <terra gnome org>
Date:   Wed Apr 9 11:10:13 2014 -0400

    GOFormat: minor speed improvement.

 ChangeLog                 |    3 +
 goffice/utils/go-format.c |  113 ++++++++++++++++++++++++++++++++++++++------
 2 files changed, 100 insertions(+), 16 deletions(-)
---
diff --git a/ChangeLog b/ChangeLog
index 2e5025b..3f3cff1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,8 @@
 2014-04-09  Morten Welinder  <terra gnome org>
 
+       * goffice/utils/go-format.c (go_render_general): Drop a decimal by
+       double-rounding the decimal string unless the string ends in '5'.
+
        * goffice/math/go-dtoa.c (go_dtoa): Improve long-double handling.
 
 2014-04-07  Morten Welinder  <terra gnome org>
diff --git a/goffice/utils/go-format.c b/goffice/utils/go-format.c
index 9ac3a68..2b3ac71 100644
--- a/goffice/utils/go-format.c
+++ b/goffice/utils/go-format.c
@@ -52,6 +52,8 @@
 #include <errno.h>
 #include <stdlib.h>
 
+#undef DEBUG_GENERAL
+
 /**
  * GOFormatFamily:
  * @GO_FORMAT_UNKNOWN: unknown ,should not occur.
@@ -491,6 +493,14 @@ typedef struct {
 #define UTF8_FULLWIDTH_MINUS "\357\274\215"
 #define UTF8_FULLWIDTH_PLUS  "\357\274\213"
 
+/* Number of digits required for roundtrip of DOUBLE.  */
+#ifdef DEFINE_COMMON
+static int go_format_roundtrip_digits;
+#ifdef GOFFICE_WITH_LONG_DOUBLE
+static int go_format_roundtrip_digitsl;
+#endif
+#endif
+
 gboolean
 go_format_allow_ee_markup (void)
 {
@@ -4756,7 +4766,7 @@ go_format_measure_pango (G_GNUC_UNUSED const GString *str,
        int w;
        pango_layout_get_size (layout, &w, NULL);
 #ifdef DEBUG_GENERAL
-       g_print ("[%s] --> %d\n", str->str, w);
+       g_printerr ("[%s] --> %d\n", str->str, w);
 #endif
        return w;
 }
@@ -4810,6 +4820,46 @@ drop_zeroes (GString *str, int *prec)
                g_string_truncate (str, dot - str->str);
        }
 }
+
+static gboolean
+cheap_drop_decimal (GString *str, size_t pos)
+{
+       char l = str->str[pos];
+       int carry;
+
+       if (!g_ascii_isdigit (l) || l == '5')
+               return FALSE;
+
+       g_string_erase (str, pos, 1);
+       pos--;
+
+       carry = (l > '5');
+       if (!carry && !g_ascii_isdigit (str->str[pos])) {
+               const char *dot = g_utf8_prev_char (str->str + pos + 1);
+               g_string_erase (str, dot - str->str, str->str + pos + 1 - dot);
+#ifdef DEBUG_GENERAL
+               g_printerr ("Removing decimal cheaply\n");
+#endif
+       }
+
+       while (carry) {
+               l = str->str[pos];
+               if (!g_ascii_isdigit (l))
+                       return FALSE;
+
+               if (l < '9') {
+                       str->str[pos] = l + 1;
+                       carry = 0;
+               } else
+                       str->str[pos] = '0';
+               pos--;
+       }
+
+#ifdef DEBUG_GENERAL
+       g_printerr ("Cheaply dropped decimal\n");
+#endif
+       return TRUE;
+}
 #endif
 
 static int
@@ -4870,7 +4920,8 @@ SUFFIX(go_render_general) (PangoLayout *layout, GString *str,
                           guint shape_flags)
 {
        DOUBLE aval;
-       int prec, safety, digs, digs_as_int, maxdigits = PREFIX(DIG);
+       int prec, safety, digs, digs_as_int;
+       int maxdigits = SUFFIX(go_format_roundtrip_digits) - 1;
        size_t epos;
        gboolean rounds_to_0;
        int sign_width;
@@ -4901,7 +4952,7 @@ SUFFIX(go_render_general) (PangoLayout *layout, GString *str,
        }
 
 #ifdef DEBUG_GENERAL
-       g_print ("Rendering %" FORMAT_G " to width %d (<=%d digits)\n",
+       g_printerr ("Rendering %" FORMAT_G " to width %d (<=%d digits)\n",
                 val, col_width, maxdigits);
 #endif
        if (val == 0)
@@ -4919,15 +4970,18 @@ SUFFIX(go_render_general) (PangoLayout *layout, GString *str,
 
        if (digs_as_int * min_digit_width > col_width) {
 #ifdef DEBUG_GENERAL
-               g_print ("No room for whole part.\n");
+               g_printerr ("No room for whole part.\n");
 #endif
                goto e_notation;
        } else if (digs_as_int * metrics->max_digit_width + safety <
                   col_width - (val > 0 ? 0 : sign_width)) {
 #ifdef DEBUG_GENERAL
-               g_print ("Room for whole part.\n");
+               g_printerr ("Room for whole part.\n");
 #endif
                if (val == SUFFIX(floor) (val) || digs_as_int == maxdigits) {
+#ifdef DEBUG_GENERAL
+                       g_printerr ("Integer or room for nothing else.\n");
+#endif
                        go_dtoa (str, "=^.0" FORMAT_f, val);
                        HANDLE_NUMERAL_SHAPE;
                        HANDLE_SIGN (0);
@@ -4937,7 +4991,7 @@ SUFFIX(go_render_general) (PangoLayout *layout, GString *str,
        } else {
                int w;
 #ifdef DEBUG_GENERAL
-               g_print ("Maybe room for whole part.\n");
+               g_printerr ("Maybe room for whole part.\n");
 #endif
 
                go_dtoa (str, "=^.0" FORMAT_f, val);
@@ -4948,14 +5002,21 @@ SUFFIX(go_render_general) (PangoLayout *layout, GString *str,
                if (w > col_width)
                        goto e_notation;
 
-               if (val == SUFFIX(floor) (val) || digs_as_int == maxdigits)
+               if (val == SUFFIX(floor) (val) || digs_as_int == maxdigits) {
+#ifdef DEBUG_GENERAL
+                       g_printerr ("Integer or room for nothing else.\n");
+#endif
                        return;
+               }
        }
 
        /* Number of digits in [aval].  */
        digs = (aval >= 10 ? 1 + SUFFIX(ilog10) (aval) : 1);
 
        prec = maxdigits - digs;
+#ifdef DEBUG_GENERAL
+       g_printerr ("Starting with with %d decimals\n", prec);
+#endif
        go_dtoa (str, "=^.*" FORMAT_f, prec, val);
        if (check_val) {
                /*
@@ -4974,22 +5035,35 @@ SUFFIX(go_render_general) (PangoLayout *layout, GString *str,
        while (prec > 0) {
                int w;
 
+#ifdef DEBUG_GENERAL
+               g_printerr ("Trying with %d decimals\n", prec);
+#endif
                SETUP_LAYOUT;
                w = measure (str, layout);
-               if (w <= col_width)
+               if (w <= col_width) {
+#ifdef DEBUG_GENERAL
+                       g_printerr ("Success\n");
+#endif
                        return;
+               }
 
                prec--;
-               go_dtoa (str, "=^.*" FORMAT_f, prec, val);
-               drop_zeroes (str, &prec);
-               HANDLE_NUMERAL_SHAPE;
-               HANDLE_SIGN (0);
+               if (num_shape > 1 || !cheap_drop_decimal (str, str->len - 1)) {
+                       go_dtoa (str, "=^.*" FORMAT_f, prec, val);
+                       drop_zeroes (str, &prec);
+                       HANDLE_NUMERAL_SHAPE;
+                       HANDLE_SIGN (0);
+               } else
+                       drop_zeroes (str, &prec);
        }
 
        SETUP_LAYOUT;
        return;
 
  e_notation:
+#ifdef DEBUG_GENERAL
+       g_printerr ("Trying E-notation\n");
+#endif
        rounds_to_0 = (aval < 0.5);
        prec = (col_width -
                (val >= 0 ? 0 : sign_width) -
@@ -4998,9 +5072,9 @@ SUFFIX(go_render_general) (PangoLayout *layout, GString *str,
        if (prec <= 0) {
 #ifdef DEBUG_GENERAL
                if (prec == 0)
-                       g_print ("Maybe room for E notation with no decimals.\n");
+                       g_printerr ("Maybe room for E notation with no decimals.\n");
                else
-                       g_print ("No room for E notation.\n");
+                       g_printerr ("No room for E notation.\n");
 #endif
                /* Certainly too narrow for precision.  */
                if (prec == 0 || !rounds_to_0) {
@@ -5068,7 +5142,7 @@ SUFFIX(go_render_general) (PangoLayout *layout, GString *str,
 
  zero:
 #ifdef DEBUG_GENERAL
-       g_print ("Zero.\n");
+       g_printerr ("Zero.\n");
 #endif
        g_string_assign (str, "0");
        SETUP_LAYOUT;
@@ -5287,6 +5361,14 @@ SUFFIX(go_format_value) (GOFormat const *fmt, DOUBLE val)
 void
 _go_number_format_init (void)
 {
+       double l10 = log10 (FLT_RADIX);
+       go_format_roundtrip_digits =
+               (int)ceil (DBL_MANT_DIG * l10) + (l10 != (int)l10);
+#ifdef GOFFICE_WITH_LONG_DOUBLE
+       go_format_roundtrip_digitsl =
+               (int)ceil (LDBL_MANT_DIG * l10) + (l10 != (int)l10);
+#endif
+
        style_format_hash = g_hash_table_new_full (g_str_hash, g_str_equal,
                NULL, (GDestroyNotify) go_format_unref);
 }
@@ -8967,7 +9049,6 @@ go_format_output_conditional_to_odf (GsfXMLOut *xout, gboolean with_extension,
                g_free (partname);
                g_string_free (condition, TRUE);
        }
-       /* Do we need to add a catch-all General?  */
 
        gsf_xml_out_end_element (xout); /* </number:text-style> or </number:number-style> */
 }