* generic/tkCanvText.c (DisplayCanvText): Fix text

	rendering problem with canvas text items that
	have a selected region. The previous implementation
	would render the whole line and then redraw the
	selected text if it was a different color. This caused
	problems when the selected text foreground differs
	from the normal text foreground, the anti-aliasing
	alpha pixels for the two text strings would blend
	together resulting in strange looking text. The
	fix is to draw the normal text and the selected text
	separately. This problem has only been observed
	under Windows, with anti-aliased text. [Patch 968725]

1 files changed, 16 insertions, 7 deletions

diff --git a/generic/tkCanvText.c b/generic/tkCanvText.c
index ee3ad22..5122fff 100644
--- a/generic/tkCanvText.c
+++ b/generic/tkCanvText.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: tkCanvText.c,v 1.16 2004/01/13 02:06:00 davygrvy Exp $
+ * RCS: @(#) $Id: tkCanvText.c,v 1.17 2004/06/08 20:25:04 mdejong Exp $
  */
 
 #include <stdio.h>
@@ -853,21 +853,30 @@ DisplayCanvText(canvas, itemPtr, display, drawable, x, y, width, height)
 
 
     /*
-     * Display the text in two pieces: draw the entire text item, then
-     * draw the selected text on top of it.  The selected text then
-     * will only need to be drawn if it has different attributes (such
-     * as foreground color) than regular text.
+     * If there is no selected text or the selected text foreground
+     * is the same as the regular text foreground, then draw one
+     * text string. If there is selected text and the foregrounds
+     * differ, draw the regular text up to the selection, draw
+     * the selection, then draw the rest of the regular text.
+     * Drawing the regular text and then the selected text over
+     * it would causes problems with anti-aliased text because the
+     * two anti-aliasing colors would blend together.
      */
 
     Tk_CanvasDrawableCoords(canvas, (double) textPtr->leftEdge,
 	    (double) textPtr->header.y1, &drawableX, &drawableY);
-    Tk_DrawTextLayout(display, drawable, textPtr->gc, textPtr->textLayout,
-	    drawableX, drawableY, 0, -1);
 
     if ((selFirstChar >= 0) && (textPtr->selTextGC != textPtr->gc)) {
+	Tk_DrawTextLayout(display, drawable, textPtr->gc, textPtr->textLayout,
+	    drawableX, drawableY, 0, selFirstChar);
 	Tk_DrawTextLayout(display, drawable, textPtr->selTextGC,
 	    textPtr->textLayout, drawableX, drawableY, selFirstChar,
 	    selLastChar + 1);
+	Tk_DrawTextLayout(display, drawable, textPtr->gc, textPtr->textLayout,
+	    drawableX, drawableY, selLastChar + 1, -1);
+    } else {
+	Tk_DrawTextLayout(display, drawable, textPtr->gc, textPtr->textLayout,
+	    drawableX, drawableY, 0, -1);
     }
 
     if (stipple != None) {