diff options
Diffstat (limited to 'generic')
| -rw-r--r-- | generic/tkTextDisp.c | 140 |
1 files changed, 74 insertions, 66 deletions
diff --git a/generic/tkTextDisp.c b/generic/tkTextDisp.c index 85a160d..ee1e40b 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 1.25 2003/11/08 17:22:46 vincentdarley Exp $ + * RCS: @(#) $Id: tkTextDisp.c,v 1.26 2003/11/10 14:37:33 vincentdarley Exp $ */ #include "tkPort.h" @@ -5352,76 +5352,84 @@ GetYView(interp, textPtr, report) totalPixels = TkBTreeNumPixels(textPtr->tree); - /* - * Get the pixel count for the first display visible pixel of the - * first visible line. If the first visible line is only partially - * visible, then we use 'topPixelOffset' to get the difference. - */ - count = GetPixelCount(textPtr, dlPtr); - first = ((double) (count + dInfoPtr->topPixelOffset))/((double)totalPixels); - - /* - * Add on the total number of visible pixels to get the count to - * the last visible pixel. - */ - while (1) { - int extra; - count += dlPtr->height; + if (totalPixels == 0) { + first = 0.0; + last = 1.0; + } else { + /* + * Get the pixel count for the first display visible pixel of the + * first visible line. If the first visible line is only + * partially visible, then we use 'topPixelOffset' to get the + * difference. + */ + count = GetPixelCount(textPtr, dlPtr); + first = ((double) (count + dInfoPtr->topPixelOffset)) + /((double)totalPixels); - extra = dlPtr->y + dlPtr->height - dInfoPtr->maxY; - if (extra > 0) { - /* - * This much of the last line is not visible, so don't - * count these pixels. Since we've reached the bottom - * of the window, we break out of the loop. - */ - count -= extra; - break; - } - if (dlPtr->nextPtr == NULL) { - break; - } - dlPtr = dlPtr->nextPtr; - } - - if (count > totalPixels) { /* - * It can be possible, if we do not update each line's - * pixelHeight cache when we lay out individual DLines that - * the count generated here is more up-to-date than that - * maintained by the BTree. In such a case, the best we can - * do here is to fix up 'count' and continue, which might - * result in small, temporary perturbations to the size of - * the scrollbar. This is basically harmless, but in a - * perfect world we would not have this problem. - * - * For debugging purposes, if anyone wishes to improve the text - * widget further, the following 'panic' can be activated. In - * principle it should be possible to ensure the BTree is always - * at least as up to date as the display, so in the future we - * might be able to leave the 'panic' in permanently when we - * believe we have resolved the cache synchronisation issue. - * - * However, to achieve that goal would, I think, require a - * fairly substantial refactorisation of the code in this - * file so that there is much more obvious and explicit - * coordination between calls to LayoutDLine and updating - * of each TkTextLine's pixelHeight. The complicated bit - * is that LayoutDLine deals with individual display lines, - * but pixelHeight is for a logical line. + * Add on the total number of visible pixels to get the count to + * the last visible pixel. */ -#if 0 - char buffer[200]; + while (1) { + int extra; + count += dlPtr->height; - sprintf(buffer, - "Counted more pixels (%d) than expected (%d) total pixels in text widget scroll bar calculation.", - count, totalPixels); - panic(buffer); -#endif - count = totalPixels; + extra = dlPtr->y + dlPtr->height - dInfoPtr->maxY; + if (extra > 0) { + /* + * This much of the last line is not visible, so don't + * count these pixels. Since we've reached the bottom + * of the window, we break out of the loop. + */ + count -= extra; + break; + } + if (dlPtr->nextPtr == NULL) { + break; + } + dlPtr = dlPtr->nextPtr; + } + + if (count > totalPixels) { + /* + * It can be possible, if we do not update each line's + * pixelHeight cache when we lay out individual DLines that + * the count generated here is more up-to-date than that + * maintained by the BTree. In such a case, the best we can + * do here is to fix up 'count' and continue, which might + * result in small, temporary perturbations to the size of + * the scrollbar. This is basically harmless, but in a + * perfect world we would not have this problem. + * + * For debugging purposes, if anyone wishes to improve the + * text widget further, the following 'panic' can be + * activated. In principle it should be possible to ensure + * the BTree is always at least as up to date as the display, + * so in the future we might be able to leave the 'panic' in + * permanently when we believe we have resolved the cache + * synchronisation issue. + * + * However, to achieve that goal would, I think, require a + * fairly substantial refactorisation of the code in this + * file so that there is much more obvious and explicit + * coordination between calls to LayoutDLine and updating of + * each TkTextLine's pixelHeight. The complicated bit is + * that LayoutDLine deals with individual display lines, but + * pixelHeight is for a logical line. + */ + #if 0 + char buffer[200]; + + sprintf(buffer, + "Counted more pixels (%d) than expected (%d) total pixels in text widget scroll bar calculation.", + count, totalPixels); + panic(buffer); + #endif + count = totalPixels; + } + + last = ((double) (count))/((double)totalPixels); } - - last = ((double) (count))/((double)totalPixels); if (!report) { listObj = Tcl_NewListObj(0,NULL); |