tk8.5.8-src.tar.gz

/* * tkTextDisp.c -- * * This module provides facilities to display text widgets. It is the * only place where information is kept about the screen layout of text * widgets. (Well, strictly, each TkTextLine and B-tree node caches its * last observed pixel height, but that information originates here). * * Copyright (c) 1992-1994 The Regents of the University of California. * Copyright (c) 1994-1997 Sun Microsystems, Inc. * * 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 1.68.2.1 2009/08/04 21:46:03 dkf Exp $ */ #include "tkInt.h" #include "tkText.h" #ifdef __WIN32__ #include "tkWinInt.h" #endif #ifdef MAC_OSX_TK #include "tkMacOSXInt.h" #endif /* * "Calculations of line pixel heights and the size of the vertical * scrollbar." * * Given that tag, font and elide changes can happen to large numbers of * diverse chunks in a text widget containing megabytes of text, it is not * possible to recalculate all affected height information immediately any * such change takes place and maintain a responsive user-experience. Yet, for * an accurate vertical scrollbar to be drawn, we must know the total number * of vertical pixels shown on display versus the number available to be * displayed. * * The way the text widget solves this problem is by maintaining cached line * pixel heights (in the BTree for each logical line), and having asynchronous * timer callbacks (i) to iterate through the logical lines recalculating * their heights, and (ii) to recalculate the vertical scrollbar's position * and size. * * Typically this works well but there are some situations where the overall * functional design of this file causes some problems. These problems can * only arise because the calculations used to display lines on screen are not * connected to those in the iterating-line- recalculation-process. * * The reason for this disconnect is that the display calculations operate in * display lines, and the iteration and cache operates in logical lines. * Given that the display calculations both need not contain complete logical * lines (at top or bottom of display), and that they do not actually keep * track of logical lines (for simplicity of code and historical design), this * means a line may be known and drawn with a different pixel height to that * which is cached in the BTree, and this might cause some temporary * undesirable mismatch between display and the vertical scrollbar. * * All such mismatches should be temporary, however, since the asynchronous * height calculations will always catch up eventually. * * For further details see the comments before and within the following * functions below: LayoutDLine, AsyncUpdateLineMetrics, GetYView, * GetYPixelCount, TkTextUpdateOneLine, TkTextUpdateLineMetrics. * * For details of the way in which the BTree keeps track of pixel heights, see * tkTextBTree.c. Basically the BTree maintains two pieces of information: the * logical line indices and the pixel height cache. */ /* * TK_LAYOUT_WITH_BASE_CHUNKS: * * With this macro set, collect all char chunks that have no holes * between them, that are on the same line and use the same font and font * size. Allocate the chars of all these chunks, the so-called "stretch", * in a DString in the first chunk, the so-called "base chunk". Use the * base chunk string for measuring and drawing, so that these actions are * always performed with maximum context. * * This is necessary for text rendering engines that provide ligatures * and sub-pixel layout, like ATSU on Mac. If we don't do this, the * measuring will change all the time, leading to an ugly "tremble and * shiver" effect. This is because of the continuous splitting and * re-merging of chunks that goes on in a text widget, when the cursor or * the selection move. * * Side effects: * * Memory management changes. Instead of attaching the character data to * the clientData structures of the char chunks, an additional DString is * used. The collection process will even lead to resizing this DString * for large stretches (> TCL_DSTRING_STATIC_SIZE == 200). We could * reduce the overall memory footprint by copying the result to a plain * char array after the line breaking process, but that would complicate * the code and make performance even worse speedwise. See also TODOs. * * TODOs: * * - Move the character collection process from the LayoutProc into * LayoutDLine(), so that the collection can be done before actual * layout. In this way measuring can look at the following text, too, * right from the beginning. Memory handling can also be improved with * this. Problem: We don't easily know which chunks are adjacent until * all the other chunks have calculated their width. Apparently marks * would return width==0. A separate char collection loop would have to * know these things. * * - Use a new context parameter to pass the context from LayoutDLine() to * the LayoutProc instead of using a global variable like now. Not * pressing until the previous point gets implemented. */ /* * The following structure describes how to display a range of characters. * The information is generated by scanning all of the tags associated with * the characters and combining that with default information for the overall * widget. These structures form the hash keys for dInfoPtr->styleTable. */ typedef struct StyleValues { Tk_3DBorder border; /* Used for drawing background under text. * NULL means use widget background. */ int borderWidth; /* Width of 3-D border for background. */ int relief; /* 3-D relief for background. */ Pixmap bgStipple; /* Stipple bitmap for background. None means * draw solid. */ XColor *fgColor; /* Foreground color for text. */ Tk_Font tkfont; /* Font for displaying text. */ Pixmap fgStipple; /* Stipple bitmap for text and other * foreground stuff. None means draw solid.*/ int justify; /* Justification style for text. */ int lMargin1; /* Left margin, in pixels, for first display * line of each text line. */ int lMargin2; /* Left margin, in pixels, for second and * later display lines of each text line. */ int offset; /* Offset in pixels of baseline, relative to * baseline of line. */ int overstrike; /* Non-zero means draw overstrike through * text. */ int rMargin; /* Right margin, in pixels. */ int spacing1; /* Spacing above first dline in text line. */ int spacing2; /* Spacing between lines of dline. */ int spacing3; /* Spacing below last dline in text line. */ TkTextTabArray *tabArrayPtr;/* Locations and types of tab stops (may be * NULL). */ int tabStyle; /* One of TABULAR or WORDPROCESSOR. */ int underline; /* Non-zero means draw underline underneath * text. */ int elide; /* Zero means draw text, otherwise not. */ TkWrapMode wrapMode; /* How to handle wrap-around for this tag. * One of TEXT_WRAPMODE_CHAR, * TEXT_WRAPMODE_NONE or TEXT_WRAPMODE_WORD.*/ } StyleValues; /* * The following structure extends the StyleValues structure above with * graphics contexts used to actually draw the characters. The entries in * dInfoPtr->styleTable point to structures of this type. */ typedef struct TextStyle { int refCount; /* Number of times this structure is * referenced in Chunks. */ GC bgGC; /* Graphics context for background. None means * use widget background. */ GC fgGC; /* Graphics context for foreground. */ StyleValues *sValuePtr; /* Raw information from which GCs were * derived. */ Tcl_HashEntry *hPtr; /* Pointer to entry in styleTable. Used to * delete entry. */ } TextStyle; /* * The following macro determines whether two styles have the same background * so that, for example, no beveled border