correct handling of interpolated tabs using fractional pixel widths

3 files changed, 40 insertions, 25 deletions

diff --git a/generic/tkText.c b/generic/tkText.c
index 133d88d..c5c8baa 100644
--- a/generic/tkText.c
+++ b/generic/tkText.c
@@ -14,7 +14,7 @@
  * See the file "license.terms" for information on usage and redistribution
  * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
  *
- * RCS: @(#) $Id: tkText.c,v 1.44 2003/11/15 02:33:50 vincentdarley Exp $
+ * RCS: @(#) $Id: tkText.c,v 1.45 2003/11/21 18:51:18 vincentdarley Exp $
  */
 
 #include "default.h"
@@ -3310,6 +3310,7 @@ TkTextGetTabs(interp, tkwin, stringPtr)
     TkTextTabArray *tabArrayPtr;
     TkTextTab *tabPtr;
     Tcl_UniChar ch;
+    double prevStop, lastStop;
 
     /* Map these strings to TkTextTabAlign values */
     
@@ -3342,6 +3343,8 @@ TkTextGetTabs(interp, tkwin, stringPtr)
     tabArrayPtr = (TkTextTabArray *) ckalloc((unsigned)
 	    (sizeof(TkTextTabArray) + (count-1)*sizeof(TkTextTab)));
     tabArrayPtr->numTabs = 0;
+    prevStop = 0.0;
+    lastStop = 0.0;
     for (i = 0, tabPtr = &tabArrayPtr->tabs[0]; i  < objc; i++, tabPtr++) {
 	int index;
 	
@@ -3349,6 +3352,14 @@ TkTextGetTabs(interp, tkwin, stringPtr)
 		!= TCL_OK) {
 	    goto error;
 	}
+	
+	prevStop = lastStop;
+	if (Tk_GetMMFromObj(interp, tkwin, objv[i], &lastStop) != TCL_OK) {
+	    goto error;
+	}
+	lastStop *= WidthOfScreen(Tk_Screen(tkwin));
+	lastStop /= WidthMMOfScreen(Tk_Screen(tkwin));
+	
 	tabArrayPtr->numTabs++;
 
 	/*
@@ -3373,6 +3384,15 @@ TkTextGetTabs(interp, tkwin, stringPtr)
 	}
 	tabPtr->alignment = ((TkTextTabAlign)index);
     }
+    
+    /*
+     * For when we need to interpolate tab stops, store
+     * these two so we know the tab stop size to very
+     * high precision.
+     */
+    tabArrayPtr->lastTab = lastStop;
+    tabArrayPtr->tabIncrement = lastStop - prevStop;
+    
     return tabArrayPtr;
 
     error:
diff --git a/generic/tkText.h b/generic/tkText.h
index ee19ad2..bf79bc7 100644
--- a/generic/tkText.h
+++ b/generic/tkText.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: tkText.h,v 1.21 2003/11/15 02:33:50 vincentdarley Exp $
+ * RCS: @(#) $Id: tkText.h,v 1.22 2003/11/21 18:51:18 vincentdarley Exp $
  */
 
 #ifndef _TKTEXT
@@ -474,6 +474,12 @@ typedef struct TkTextTab {
 
 typedef struct TkTextTabArray {
     int numTabs;			/* Number of tab stops. */
+    double lastTab;                     /* The accurate fractional pixel 
+                                         * position of the last tab. */
+    double tabIncrement;                /* The accurate fractional pixel
+                                         * increment between interpolated 
+                                         * tabs we have to create when
+                                         * we exceed numTabs. */
     TkTextTab tabs[1];			/* Array of tabs.  The actual size
 					 * will be numTabs.  THIS FIELD MUST
 					 * BE THE LAST IN THE STRUCTURE. */
diff --git a/generic/tkTextDisp.c b/generic/tkTextDisp.c
index 623570a..b218a79 100644
--- a/generic/tkTextDisp.c
+++ b/generic/tkTextDisp.c
@@ -13,7 +13,7 @@
  * See the file "license.terms" for information on usage and redistribution
  * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
  *
- * RCS: @(#) $Id: tkTextDisp.c,v 1.34 2003/11/21 17:29:13 vincentdarley Exp $
+ * RCS: @(#) $Id: tkTextDisp.c,v 1.35 2003/11/21 18:51:18 vincentdarley Exp $
  */
 
 #include "tkPort.h"
@@ -6596,7 +6596,7 @@ AdjustForTab(textPtr, tabArrayPtr, index, chunkPtr)
     int x, desired, delta, width, decimal, i, gotDigit;
     TkTextDispChunk *chunkPtr2, *decimalChunkPtr;
     CharInfo *ciPtr;
-    int tabX, prev, spaceWidth;
+    int tabX, spaceWidth;
     char *p;
     TkTextTabAlign alignment;
 
@@ -6633,15 +6633,10 @@ AdjustForTab(textPtr, tabArrayPtr, index, chunkPtr)
 	 * from the last two tab positions.
 	 */
 
-	if (tabArrayPtr->numTabs > 1) {
-	    prev = tabArrayPtr->tabs[tabArrayPtr->numTabs-2].location;
-	} else {
-	    prev = 0;
-	}
+	tabX = (int) (tabArrayPtr->lastTab 
+		      + (index + 1 - tabArrayPtr->numTabs) 
+		      * tabArrayPtr->tabIncrement + 0.5);
 	alignment = tabArrayPtr->tabs[tabArrayPtr->numTabs-1].alignment;
-	tabX = tabArrayPtr->tabs[tabArrayPtr->numTabs-1].location
-		+ (index + 1 - tabArrayPtr->numTabs)
-		* (tabArrayPtr->tabs[tabArrayPtr->numTabs-1].location - prev);
     }
 
     if (alignment == LEFT) {
@@ -6780,7 +6775,7 @@ SizeOfTab(textPtr, tabArrayPtr, indexPtr, x, maxX)
     int maxX;				/* X-location of pixel just past the
 					 * right edge of the line. */
 {
-    int tabX, prev, result, index, spaceWidth;
+    int tabX, result, index, spaceWidth;
     TkTextTabAlign alignment;
     
     index = *indexPtr;
@@ -6796,7 +6791,7 @@ SizeOfTab(textPtr, tabArrayPtr, indexPtr, x, maxX)
 
     do {
 	/* 
-	 * We were given the count before this tabs, so increment it
+	 * We were given the count before this tab, so increment it
 	 * first.
 	 */
 	index++;
@@ -6805,18 +6800,12 @@ SizeOfTab(textPtr, tabArrayPtr, indexPtr, x, maxX)
 	    alignment = tabArrayPtr->tabs[index].alignment;
 	} else {
 	    /*
-	     * Ran out of tab stops;  compute a tab position by extrapolating
-	     * from the last two tab positions.
+	     * Ran out of tab stops; compute a tab position by
+	     * extrapolating.
 	     */
-	    
-	    if (tabArrayPtr->numTabs > 1) {
-		prev = tabArrayPtr->tabs[tabArrayPtr->numTabs-2].location;
-	    } else {
-		prev = 0;
-	    }
-	    tabX = tabArrayPtr->tabs[tabArrayPtr->numTabs-1].location
-	      + (index + 1 - tabArrayPtr->numTabs)
-	      * (tabArrayPtr->tabs[tabArrayPtr->numTabs-1].location - prev);
+	    tabX = (int) (tabArrayPtr->lastTab 
+			  + (index + 1 - tabArrayPtr->numTabs) 
+			  * tabArrayPtr->tabIncrement + 0.5);
 	    alignment = tabArrayPtr->tabs[tabArrayPtr->numTabs-1].alignment;
 	}
 	/*