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[Plplot-cvs] SF.net SVN: plplot:[11781] trunk/drivers/cairo.c
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From: <ai...@us...> - 2011-06-22 20:45:46
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Revision: 11781
http://plplot.svn.sourceforge.net/plplot/?rev=11781&view=rev
Author: airwin
Date: 2011-06-22 20:45:39 +0000 (Wed, 22 Jun 2011)
Log Message:
-----------
I have discovered experimentally that contrary to the documentation at
http://developer.gnome.org/pango/unstable/PangoMarkupFormat.html, rise
is in units of 1024th of a point (i.e., a real distance unit) rather
than in units of the (variable) font size. Implement a correction the
accounts properly for the real units of rise. The result is the actual
superscript/subscript vertical offsets that are rendered by cairo
devices now is (correctly) proportional to the font size (as opposed
to being fixed in size before). This correction solves the second
issue noted in the previous commit.
The cairo and PLplot character coordinate system have vertical zero
points of respectively the baseline of the fonts and the middle of the
vertical dimension of the fonts. This mismatch in coordinate systems
means the superscript/subscript offsets appear asymmetrical for cairo
devices compared to -dev xwin (i.e., issue 1 noted in the previous
commit message). An approximation for this coordinate shift has been
implemented, and the asymmetry appears to be greatly reduced as a
result.
Modified Paths:
--------------
trunk/drivers/cairo.c
Modified: trunk/drivers/cairo.c
===================================================================
--- trunk/drivers/cairo.c 2011-06-22 19:40:38 UTC (rev 11780)
+++ trunk/drivers/cairo.c 2011-06-22 20:45:39 UTC (rev 11781)
@@ -240,7 +240,7 @@
static char *ucs4_to_pango_markup_format( PLUNICODE *, int, float );
static void open_span_tag( char *, PLUNICODE, float, int );
static void close_span_tag( char *, int );
-static char *rise_span_tag( int, int );
+static char *rise_span_tag( int, int, float );
// Graphics
@@ -651,7 +651,8 @@
aStream = (PLCairo *) pls->dev;
aStream->upDown = 0;
aStream->pangoMarkupString = (char *) malloc( sizeof ( char ) * MAX_MARKUP_LEN );
- aStream->fontSize = pls->chrht * DPI / 25.4;
+ // Calculate the font size (in points since DPI = 72).
+ aStream->fontSize = pls->chrht * DPI / 25.4;
for ( i = 0; i < MAX_MARKUP_LEN; i++ )
{
aStream->pangoMarkupString[i] = 0;
@@ -717,7 +718,7 @@
}
else
{
- strncat( aStream->pangoMarkupString, rise_span_tag( aStream->upDown, 1 ), MAX_MARKUP_LEN - 1 - strlen( aStream->pangoMarkupString ) );
+ strncat( aStream->pangoMarkupString, rise_span_tag( aStream->upDown, 1, aStream->fontSize ), MAX_MARKUP_LEN - 1 - strlen( aStream->pangoMarkupString ) );
}
aStream->upDown++;
break;
@@ -728,7 +729,7 @@
}
else
{
- strncat( aStream->pangoMarkupString, rise_span_tag( aStream->upDown, -1 ), MAX_MARKUP_LEN - 1 - strlen( aStream->pangoMarkupString ) );
+ strncat( aStream->pangoMarkupString, rise_span_tag( aStream->upDown, -1, aStream->fontSize ), MAX_MARKUP_LEN - 1 - strlen( aStream->pangoMarkupString ) );
}
aStream->upDown--;
break;
@@ -866,7 +867,7 @@
return;
}
- // Calculate the font size (in pixels)
+ // Calculate the font size (in points since DPI = 72).
fontSize = pls->chrht * DPI / 25.4;
// Convert the escape characters into the appropriate Pango markup
@@ -1019,7 +1020,7 @@
}
else
{
- strncat( pangoMarkupString, rise_span_tag( upDown, 1 ), MAX_MARKUP_LEN - 1 - strlen( pangoMarkupString ) );
+ strncat( pangoMarkupString, rise_span_tag( upDown, 1, fontSize ), MAX_MARKUP_LEN - 1 - strlen( pangoMarkupString ) );
}
upDown++;
}
@@ -1031,7 +1032,7 @@
}
else
{
- strncat( pangoMarkupString, rise_span_tag( upDown, -1 ), MAX_MARKUP_LEN - 1 - strlen( pangoMarkupString ) );
+ strncat( pangoMarkupString, rise_span_tag( upDown, -1, fontSize ), MAX_MARKUP_LEN - 1 - strlen( pangoMarkupString ) );
}
upDown--;
}
@@ -1090,7 +1091,7 @@
while ( upDown > 0 )
{
upDown--;
- strncat( pangoMarkupString, rise_span_tag( upDown, 1 ), MAX_MARKUP_LEN - 1 - strlen( pangoMarkupString ) );
+ strncat( pangoMarkupString, rise_span_tag( upDown, 1, fontSize ), MAX_MARKUP_LEN - 1 - strlen( pangoMarkupString ) );
}
}
if ( upDown < 0 )
@@ -1098,7 +1099,7 @@
while ( upDown < 0 )
{
upDown++;
- strncat( pangoMarkupString, rise_span_tag( upDown, -1 ), MAX_MARKUP_LEN - 1 - strlen( pangoMarkupString ) );
+ strncat( pangoMarkupString, rise_span_tag( upDown, -1, fontSize ), MAX_MARKUP_LEN - 1 - strlen( pangoMarkupString ) );
}
}
}
@@ -1131,33 +1132,59 @@
strncat( pangoMarkupString, "</span>", MAX_MARKUP_LEN - 1 - strlen( pangoMarkupString ) );
}
+// Use 16/20ths to mimic what plstr in plsym.c does for first level
+// of superscripts/subscripts.
+# define RISE_FACTOR 0.8
+
+// Experimental correction to help account for difference between
+// cairo and PLplot character coordinate systems.
+# define OFFSET_FACTOR 1.0
+
//--------------------------------------------------------------------------
// rise_span_tag
//
// Create a rise span tag w/ appropriate font size & baseline offset
//--------------------------------------------------------------------------
-#define STEPSIZE 15000.0
-
-char *rise_span_tag( int level, int direction )
+char *rise_span_tag( int level, int direction, float fontSize )
{
int i;
float multiplier = 1.0;
- float rise = STEPSIZE;
+ float rise = RISE_FACTOR;
+ float offset;
static char tag[100];
for ( i = 0; i < abs( level ); i++ )
{
multiplier = multiplier * 0.75;
- rise += STEPSIZE * multiplier;
+ rise += RISE_FACTOR * multiplier;
}
+ // http://developer.gnome.org/pango/unstable/PangoMarkupFormat.html says
+ // rise should be in units of 10000 em's, but empricial evidence shows
+ // it is in units of 1024th of a point. Therefore, since FontSize
+ // is in points, a rise of 1024. * fontSize corresponds a rise of
+ // a full character height.
+ rise = 1024. * fontSize * rise;
+
+ // This is the correction for the difference between baseline and
+ // middle coordinate systems. Theoretically this offset should be
+ // 0.5*(fontSize - superscript/subscript fontSize). We make the
+ // assumption that the "smaller" fonts below are close to 0.75*
+ // multiplier * fontSize in size, where the "extra" factor of 0.75
+ // corrects for an off-by-one issue in the termination of
+ // the multiplier calculation in the above loop. OFFSET_FACTOR
+ // is an empirical correction.
+ offset = 1024. * 0.5 * fontSize * ( 1.0 - 0.75 * multiplier * OFFSET_FACTOR );
+
if ( direction > 0 )
{
- sprintf( tag, "<span rise=\"%d\" size=\"smaller\">", (int) rise );
+ sprintf( tag, "<span rise=\"%d\" size=\"smaller\">",
+ (int) ( rise + offset ) );
}
else
{
- sprintf( tag, "<span rise=\"%d\" size=\"smaller\">", (int) -rise );
+ sprintf( tag, "<span rise=\"%d\" size=\"smaller\">",
+ (int) -( rise - offset ) );
}
return ( tag );
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