Corrected rounding of coordinates when working with fonts. [Bug 2824916]

6 files changed, 81 insertions, 28 deletions

diff --git a/ChangeLog b/ChangeLog
index 57e3984..c4c9ec2 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,11 +1,21 @@
+2010-01-05  Donal K. Fellows  <dkf@users.sf.net>
+
+	* generic/tkFont.h (ROUND16): [Bug 2824916]: Use a correct rounding
+	* unix/tkUnixFont.c (TkpDrawAngledChars):    macro for converting a
+	* unix/tkUnixRFont.c (TkpDrawAngledChars):   double to a short. This
+	* win/tkWinFont.c (GetScreenFont):	     stops a number of small
+	visual artefacts from happening and reduces the effect of others. The
+	ROUND16 macro is now shared across all the font code (though some
+	platforms do not need it specially).
+
 2010-01-04  Pat Thoyts  <patthoyts@users.sourceforge.net>
 
-	* doc/TkInitStubs.3: [Bug 2192104] Mention USE_TK_STUBS macro.
-	* library/dialog.tcl: [Bug 2811266] <Return> binding should invoke
+	* doc/TkInitStubs.3: [Bug 2192104]: Mention USE_TK_STUBS macro.
+	* library/dialog.tcl: [Bug 2811266]: <Return> binding should invoke
 	the button with the focus.
-	* library/fontchooser.tcl: [Bug 2727476] Fix default size of font
+	* library/fontchooser.tcl: [Bug 2727476]: Fix default size of font
 	chooser dialog and assigned minimum sizes for the lists.
-	* library/console.tcl: [Bug 580361] Fix console <<Cut>> binding.
+	* library/console.tcl: [Bug 580361]: Fix console <<Cut>> binding.
 	* library/console.tcl: Fix keyboard access to console menu.
 	* library/demos/filebox.tcl: Make prettier using ttk.
 	* library/demos/fontchoose.tcl: Fix display of demo code.
diff --git a/generic/tkFont.c b/generic/tkFont.c
index 56018af..54b3afa 100644
--- a/generic/tkFont.c
+++ b/generic/tkFont.c
@@ -10,14 +10,12 @@
  * See the file "license.terms" for information on usage and redistribution of
  * this file, and for a DISCLAIMER OF ALL WARRANTIES.
  *
- * RCS: @(#) $Id: tkFont.c,v 1.64 2010/01/03 21:21:33 patthoyts Exp $
+ * RCS: @(#) $Id: tkFont.c,v 1.65 2010/01/05 08:49:49 dkf Exp $
  */
 
 #include "tkInt.h"
 #include "tkFont.h"
 
-#define ROUND16(x)	((short)((x) + 0.5))
-
 /*
  * The following structure is used to keep track of all the fonts that exist
  * in the current application. It must be stored in the TkMainInfo for the
diff --git a/generic/tkFont.h b/generic/tkFont.h
index 5a16d01..ebf5bca 100644
--- a/generic/tkFont.h
+++ b/generic/tkFont.h
@@ -10,7 +10,7 @@
  * See the file "license.terms" for information on usage and redistribution of
  * this file, and for a DISCLAIMER OF ALL WARRANTIES.
  *
- * RCS: @(#) $Id: tkFont.h,v 1.13 2008/11/05 23:29:58 nijtmans Exp $
+ * RCS: @(#) $Id: tkFont.h,v 1.14 2010/01/05 08:49:49 dkf Exp $
  */
 
 #ifndef _TKFONT
@@ -189,6 +189,12 @@ typedef struct TkXLFDAttributes {
 #define XLFD_NUMFIELDS	    13	/* Number of fields in XLFD. */
 
 /*
+ * Helper macro. How to correctly round a double to a short.
+ */
+
+#define ROUND16(x)	((short) round(x))
+
+/*
  * Low-level API exported by generic code to platform-specific code.
  */
 
diff --git a/unix/tkUnixFont.c b/unix/tkUnixFont.c
index ba78339..3b9beae 100644
--- a/unix/tkUnixFont.c
+++ b/unix/tkUnixFont.c
@@ -9,7 +9,7 @@
  * See the file "license.terms" for information on usage and redistribution of
  * this file, and for a DISCLAIMER OF ALL WARRANTIES.
  *
- * RCS: @(#) $Id: tkUnixFont.c,v 1.40 2009/01/28 20:47:49 nijtmans Exp $
+ * RCS: @(#) $Id: tkUnixFont.c,v 1.41 2010/01/05 08:49:49 dkf Exp $
  */
 
 #include "tkUnixInt.h"
@@ -3010,7 +3010,7 @@ GetEncodingAlias(
     EncodingAlias *aliasPtr;
 
     for (aliasPtr = encodingAliases; aliasPtr->aliasPattern != NULL; ) {
-	if (Tcl_StringMatch((char *) name, aliasPtr->aliasPattern)) {
+	if (Tcl_StringMatch(name, aliasPtr->aliasPattern)) {
 	    return aliasPtr->realName;
 	}
 	aliasPtr++;
@@ -3018,6 +3018,28 @@ GetEncodingAlias(
     return name;
 }
 
+/*
+ *---------------------------------------------------------------------------
+ *
+ * TkpDrawAngledChars --
+ *
+ *	Draw some characters at an angle. This is awkward here because we have
+ *	no reliable way of drawing any characters at an angle in classic X11;
+ *	we have to draw on a Pixmap which is converted to an XImage (from
+ *	helper function GetImageOfText), rotate the image (hokey code!) onto
+ *	another XImage (from helper function InitDestImage), and then use the
+ *	rotated image as a mask when drawing. This is pretty awful; improved
+ *	versions are welcomed!
+ *
+ * Results:
+ *	None.
+ *
+ * Side effects:
+ *	Target drawable is updated.
+ *
+ *---------------------------------------------------------------------------
+ */
+
 static inline XImage *
 GetImageOfText(
     Display *display,		/* Display on which to draw. */
@@ -3179,32 +3201,32 @@ TkpDrawAngledChars(
 	    for (j=0 ; j<srcHeight ; j++) {
 		switch (quadrant) {
 		case Q0:
-		    dx = floor(i*cosA + j*sinA + 0.5);
-		    dy = floor(j*cosA + (srcWidth - i)*sinA + 0.5);
+		    dx = ROUND16(i*cosA + j*sinA);
+		    dy = ROUND16(j*cosA + (srcWidth - i)*sinA);
 		    break;
 		case R1:
 		    dx = j;
 		    dy = srcWidth - i;
 		    break;
 		case Q1:
-		    dx = floor((i - srcWidth)*cosA + j*sinA + 0.5);
-		    dy = floor((srcWidth-i)*sinA + (j-srcHeight)*cosA + 0.5);
+		    dx = ROUND16((i - srcWidth)*cosA + j*sinA);
+		    dy = ROUND16((srcWidth-i)*sinA + (j-srcHeight)*cosA);
 		    break;
 		case R2:
 		    dx = srcWidth - i;
 		    dy = srcHeight - j;
 		    break;
 		case Q2:
-		    dx = floor((i-srcWidth)*cosA + (j-srcHeight)*sinA + 0.5);
-		    dy = floor((j - srcHeight)*cosA - i*sinA + 0.5);
+		    dx = ROUND16((i-srcWidth)*cosA + (j-srcHeight)*sinA);
+		    dy = ROUND16((j - srcHeight)*cosA - i*sinA);
 		    break;
 		case R3:
 		    dx = srcHeight - j;
 		    dy = i;
 		    break;
 		default:
-		    dx = floor(i*cosA + (j - srcHeight)*sinA + 0.5);
-		    dy = floor(j*cosA - i*sinA + 0.5);
+		    dx = ROUND16(i*cosA + (j - srcHeight)*sinA);
+		    dy = ROUND16(j*cosA - i*sinA);
 		}
 
 		if (dx < 0 || dy < 0 || dx >= bufWidth || dy >= bufHeight) {
diff --git a/unix/tkUnixRFont.c b/unix/tkUnixRFont.c
index eef42d5..34f504e 100644
--- a/unix/tkUnixRFont.c
+++ b/unix/tkUnixRFont.c
@@ -8,7 +8,7 @@
  * See the file "license.terms" for information on usage and redistribution of
  * this file, and for a DISCLAIMER OF ALL WARRANTIES.
  *
- * RCS: @(#) $Id: tkUnixRFont.c,v 1.32 2010/01/02 18:40:35 dkf Exp $
+ * RCS: @(#) $Id: tkUnixRFont.c,v 1.33 2010/01/05 08:49:50 dkf Exp $
  */
 
 #include "tkUnixInt.h"
@@ -16,8 +16,6 @@
 #include <X11/Xft/Xft.h>
 #include <ctype.h>
 
-#define ROUND16(x) ((short)((x) + 0.5))
-
 typedef struct {
     XftFont *ftFont;
     XftFont *ft0Font;
@@ -827,6 +825,25 @@ Tk_DrawChars(
     }
 }
 
+/*
+ *---------------------------------------------------------------------------
+ *
+ * TkpDrawAngledChars --
+ *
+ *	Draw some characters at an angle. This would be simple code, except
+ *	Xft has bugs with cumulative errors in character positioning which are
+ *	caused by trying to perform all calculations internally with integers.
+ *	So we have to do the work ourselves with floating-point math.
+ *
+ * Results:
+ *	None.
+ *
+ * Side effects:
+ *	Target drawable is updated.
+ *
+ *---------------------------------------------------------------------------
+ */
+
 void
 TkpDrawAngledChars(
     Display *display,		/* Display on which to draw. */
@@ -923,8 +940,8 @@ TkpDrawAngledChars(
 		XftDrawGlyphs(fontPtr->ftDraw, &fontPtr->color, currentFtFont,
 			originX, originY, glyphs, nglyph);
 	    }
-	    originX = (int) floor(x + 0.5);
-	    originY = (int) floor(y + 0.5);
+	    originX = ROUND16(x);
+	    originY = ROUND16(y);
 	    if (nglyph) {
 		XftGlyphExtents(fontPtr->display, currentFtFont, glyphs,
 			nglyph, &metrics);
@@ -993,8 +1010,8 @@ TkpDrawAngledChars(
 	if (ftFont && ft0Font) {
 	    specs[nspec].font = ftFont;
 	    specs[nspec].glyph = XftCharIndex(fontPtr->display, ftFont, c);
-	    specs[nspec].x = (int) floor(x + 0.5);
-	    specs[nspec].y = (int) floor(y + 0.5);
+	    specs[nspec].x = ROUND16(x);
+	    specs[nspec].y = ROUND16(y);
 	    XftGlyphExtents(fontPtr->display, ft0Font, &specs[nspec].glyph, 1,
 		    &metrics);
 	    x += metrics.xOff*cosA + metrics.yOff*sinA;
diff --git a/win/tkWinFont.c b/win/tkWinFont.c
index 79df98c..715228b 100644
--- a/win/tkWinFont.c
+++ b/win/tkWinFont.c
@@ -11,7 +11,7 @@
  * See the file "license.terms" for information on usage and redistribution of
  * this file, and for a DISCLAIMER OF ALL WARRANTIES.
  *
- * RCS: @(#) $Id: tkWinFont.c,v 1.47 2009/10/29 09:44:55 patthoyts Exp $
+ * RCS: @(#) $Id: tkWinFont.c,v 1.48 2010/01/05 08:49:50 dkf Exp $
  */
 
 #include "tkWinInt.h"
@@ -2500,8 +2500,8 @@ GetScreenFont(
     memset(&lf, 0, sizeof(lf));
     lf.lfHeight		= -pixelSize;
     lf.lfWidth		= 0;
-    lf.lfEscapement	= (int) floor(angle * 10 + 0.5);
-    lf.lfOrientation	= (int) floor(angle * 10 + 0.5);
+    lf.lfEscapement	= ROUND16(angle * 10);
+    lf.lfOrientation	= ROUND16(angle * 10);
     lf.lfWeight = (faPtr->weight == TK_FW_NORMAL) ? FW_NORMAL : FW_BOLD;
     lf.lfItalic		= faPtr->slant;
     lf.lfUnderline	= faPtr->underline;