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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"><HTML><HEAD> <META NAME="GENERATOR" CONTENT="SGML-Tools 1.0.9"> <TITLE>GTK v1.2 Tutorial: Text Widget</TITLE> <LINK HREF="gtk_tut-15.html" REL=next> <LINK HREF="gtk_tut-13.html" REL=previous> <LINK HREF="gtk_tut.html#toc14" REL=contents></HEAD><BODY BGCOLOR="#FFFFFF"><A HREF="gtk_tut-15.html">Next</A><A HREF="gtk_tut-13.html">Previous</A><A HREF="gtk_tut.html#toc14">Contents</A><HR NOSHADE><H2><A NAME="s14">14. Text Widget</A></H2><P>The Text widget allows multiple lines of text to be displayed andedited. It supports both multi-colored and multi-font text, allowingthem to be mixed in any way we wish. It also has a wide set of keybased text editing commands, which are compatible with Emacs.<P>The text widget supports full cut-and-paste facilities, including theuse of double- and triple-click to select a word and a whole line,respectively.<P><H2><A NAME="ss14.1">14.1 Creating and Configuring a Text box</A></H2><P>There is only one function for creating a new Text widget.<P><BLOCKQUOTE><CODE><PRE>GtkWidget *gtk_text_new( GtkAdjustment *hadj, GtkAdjustment *vadj );</PRE></CODE></BLOCKQUOTE><P>The arguments allow us to give the Text widget pointers to Adjustmentsthat can be used to track the viewing position of the widget. PassingNULL values to either or both of these arguments will cause thegtk_text_new function to create its own.<P><BLOCKQUOTE><CODE><PRE>void gtk_text_set_adjustments( GtkText *text, GtkAdjustment *hadj, GtkAdjustment *vadj );</PRE></CODE></BLOCKQUOTE><P>The above function allows the horizontal and vertical adjustments of atext widget to be changed at any time.<P>The text widget will not automatically create its own scrollbars whenthe amount of text to be displayed is too long for the displaywindow. We therefore have to create and add them to the display layoutourselves.<P><BLOCKQUOTE><CODE><PRE> vscrollbar = gtk_vscrollbar_new (GTK_TEXT(text)->vadj); gtk_box_pack_start(GTK_BOX(hbox), vscrollbar, FALSE, FALSE, 0); gtk_widget_show (vscrollbar);</PRE></CODE></BLOCKQUOTE><P>The above code snippet creates a new vertical scrollbar, and attachesit to the vertical adjustment of the text widget, <CODE>text</CODE>. It thenpacks it into a box in the normal way.<P>Note, currently the GtkText widget does not support horizontalscrollbars.<P>There are two main ways in which a Text widget can be used: to allowthe user to edit a body of text, or to allow us to display multiplelines of text to the user. In order for us to switch between thesemodes of operation, the text widget has the following function:<P><BLOCKQUOTE><CODE><PRE>void gtk_text_set_editable( GtkText *text, gint editable );</PRE></CODE></BLOCKQUOTE><P>The <CODE>editable</CODE> argument is a TRUE or FALSE value that specifieswhether the user is permitted to edit the contents of the Textwidget. When the text widget is editable, it will display a cursor atthe current insertion point.<P>You are not, however, restricted to just using the text widget inthese two modes. You can toggle the editable state of the text widgetat any time, and can insert text at any time.<P>The text widget wraps lines of text that are too long to fit onto asingle line of the display window. Its default behaviour is to breakwords across line breaks. This can be changed using the next function:<P><BLOCKQUOTE><CODE><PRE>void gtk_text_set_word_wrap( GtkText *text, gint word_wrap );</PRE></CODE></BLOCKQUOTE><P>Using this function allows us to specify that the text widget shouldwrap long lines on word boundaries. The <CODE>word_wrap</CODE> argument is aTRUE or FALSE value.<P><H2><A NAME="ss14.2">14.2 Text Manipulation</A></H2><P>The current insertion point of a Text widget can be set using<BLOCKQUOTE><CODE><PRE>void gtk_text_set_point( GtkText *text, guint index );</PRE></CODE></BLOCKQUOTE><P>where <CODE>index</CODE> is the position to set the insertion point.<P>Analogous to this is the function for getting the current insertionpoint:<P><BLOCKQUOTE><CODE><PRE>guint gtk_text_get_point( GtkText *text );</PRE></CODE></BLOCKQUOTE><P>A function that is useful in combination with the above two functionsis<P><BLOCKQUOTE><CODE><PRE>guint gtk_text_get_length( GtkText *text );</PRE></CODE></BLOCKQUOTE><P>which returns the current length of the Text widget. The length is thenumber of characters that are within the text block of the widget,including characters such as carriage-return, which marks the end oflines.<P>In order to insert text at the current insertion point of a Textwidget, the function gtk_text_insert is used, which also allows us tospecify background and foreground colors and a font for the text.<P><BLOCKQUOTE><CODE><PRE>void gtk_text_insert( GtkText *text, GdkFont *font, GdkColor *fore, GdkColor *back, const char *chars, gint length );</PRE></CODE></BLOCKQUOTE><P>Passing a value of <CODE>NULL</CODE> in as the value for the foreground color,background colour or font will result in the values set within thewidget style to be used. Using a value of <CODE>-1</CODE> for the lengthparameter will result in the whole of the text string given beinginserted.<P>The text widget is one of the few within GTK that redraws itselfdynamically, outside of the gtk_main function. This means that allchanges to the contents of the text widget take effectimmediately. This may be undesirable when performing multiple changesto the text widget. In order to allow us to perform multiple updatesto the text widget without it continuously redrawing, we can freezethe widget, which temporarily stops it from automatically redrawingitself every time it is changed. We can then thaw the widget after ourupdates are complete.<P>The following two functions perform this freeze and thaw action:<P><BLOCKQUOTE><CODE><PRE>void gtk_text_freeze( GtkText *text );void gtk_text_thaw( GtkText *text ); </PRE></CODE></BLOCKQUOTE><P>Text is deleted from the text widget relative to the current insertionpoint by the following two functions. The return value is a TRUE orFALSE indicator of whether the operation was successful.<P><BLOCKQUOTE><CODE><PRE>gint gtk_text_backward_delete( GtkText *text, guint nchars );gint gtk_text_forward_delete ( GtkText *text, guint nchars );</PRE></CODE></BLOCKQUOTE><P>If you want to retrieve the contents of the text widget, then themacro <CODE>GTK_TEXT_INDEX(t, index)</CODE> allows you to retrieve thecharacter at position <CODE>index</CODE> within the text widget <CODE>t</CODE>.<P>To retrieve larger blocks of text, we can use the function<P><BLOCKQUOTE><CODE><PRE>gchar *gtk_editable_get_chars( GtkEditable *editable, gint start_pos, gint end_pos ); </PRE></CODE></BLOCKQUOTE><P>This is a function of the parent class of the text widget. A value of-1 as <CODE>end_pos</CODE> signifies the end of the text. The index of thetext starts at 0.<P>The function allocates a new chunk of memory for the text block, sodon't forget to free it with a call to g_free when you have finishedwith it.<P><H2><A NAME="ss14.3">14.3 Keyboard Shortcuts</A></H2><P>The text widget has a number of pre-installed keyboard shortcuts forcommon editing, motion and selection functions. These are accessedusing Control and Alt key combinations.<P>In addition to these, holding down the Control key whilst using cursorkey movement will move the cursor by words rather thancharacters. Holding down Shift whilst using cursor movement willextend the selection.<P><H3>Motion Shortcuts</H3><P><UL><LI> Ctrl-A Beginning of line</LI><LI> Ctrl-E End of line</LI><LI> Ctrl-N Next Line</LI><LI> Ctrl-P Previous Line</LI><LI> Ctrl-B Backward one character</LI><LI> Ctrl-F Forward one character</LI><LI> Alt-B Backward one word</LI><LI> Alt-F Forward one word</LI></UL><P><H3>Editing Shortcuts</H3><P><UL><LI> Ctrl-H Delete Backward Character (Backspace)</LI><LI> Ctrl-D Delete Forward Character (Delete)</LI><LI> Ctrl-W Delete Backward Word</LI><LI> Alt-D Delete Forward Word</LI><LI> Ctrl-K Delete to end of line</LI><LI> Ctrl-U Delete line</LI></UL><P><H3>Selection Shortcuts</H3><P><UL><LI> Ctrl-X Cut to clipboard</LI><LI> Ctrl-C Copy to clipboard</LI><LI> Ctrl-V Paste from clipboard</LI></UL><P><H2><A NAME="ss14.4">14.4 A GtkText Example</A></H2><P><BLOCKQUOTE><CODE><PRE>/* example-start text text.c *//* text.c */#include <stdio.h>#include <gtk/gtk.h>void text_toggle_editable (GtkWidget *checkbutton, GtkWidget *text){ gtk_text_set_editable(GTK_TEXT(text), GTK_TOGGLE_BUTTON(checkbutton)->active);}void text_toggle_word_wrap (GtkWidget *checkbutton, GtkWidget *text){ gtk_text_set_word_wrap(GTK_TEXT(text), GTK_TOGGLE_BUTTON(checkbutton)->active);}void close_application( GtkWidget *widget, gpointer data ){ gtk_main_quit();}int main (int argc, char *argv[]){ GtkWidget *window; GtkWidget *box1; GtkWidget *box2; GtkWidget *hbox; GtkWidget *button; GtkWidget *check; GtkWidget *separator; GtkWidget *table; GtkWidget *vscrollbar; GtkWidget *text; GdkColormap *cmap; GdkColor colour; GdkFont *fixed_font; FILE *infile; gtk_init (&argc, &argv); window = gtk_window_new (GTK_WINDOW_TOPLEVEL); gtk_widget_set_usize (window, 600, 500); gtk_window_set_policy (GTK_WINDOW(window), TRUE, TRUE, FALSE); gtk_signal_connect (GTK_OBJECT (window), "destroy", GTK_SIGNAL_FUNC(close_application), NULL); gtk_window_set_title (GTK_WINDOW (window), "Text Widget Example"); gtk_container_set_border_width (GTK_CONTAINER (window), 0); box1 = gtk_vbox_new (FALSE, 0); gtk_container_add (GTK_CONTAINER (window), box1); gtk_widget_show (box1); box2 = gtk_vbox_new (FALSE, 10); gtk_container_set_border_width (GTK_CONTAINER (box2), 10); gtk_box_pack_start (GTK_BOX (box1), box2, TRUE, TRUE, 0); gtk_widget_show (box2); table = gtk_table_new (2, 2, FALSE); gtk_table_set_row_spacing (GTK_TABLE (table), 0, 2); gtk_table_set_col_spacing (GTK_TABLE (table), 0, 2); gtk_box_pack_start (GTK_BOX (box2), table, TRUE, TRUE, 0); gtk_widget_show (table); /* Create the GtkText widget */ text = gtk_text_new (NULL, NULL); gtk_text_set_editable (GTK_TEXT (text), TRUE); gtk_table_attach (GTK_TABLE (table), text, 0, 1, 0, 1, GTK_EXPAND | GTK_SHRINK | GTK_FILL, GTK_EXPAND | GTK_SHRINK | GTK_FILL, 0, 0); gtk_widget_show (text); /* Add a vertical scrollbar to the GtkText widget */ vscrollbar = gtk_vscrollbar_new (GTK_TEXT (text)->vadj); gtk_table_attach (GTK_TABLE (table), vscrollbar, 1, 2, 0, 1, GTK_FILL, GTK_EXPAND | GTK_SHRINK | GTK_FILL, 0, 0); gtk_widget_show (vscrollbar); /* Get the system colour map and allocate the colour red */ cmap = gdk_colormap_get_system(); colour.red = 0xffff; colour.green = 0; colour.blue = 0; if (!gdk_color_alloc(cmap, &colour)) { g_error("couldn't allocate colour"); } /* Load a fixed font */ fixed_font = gdk_font_load ("-misc-fixed-medium-r-*-*-*-140-*-*-*-*-*-*"); /* Realizing a widget creates a window for it, * ready for us to insert some text */ gtk_widget_realize (text); /* Freeze the text widget, ready for multiple updates */ gtk_text_freeze (GTK_TEXT (text)); /* Insert some coloured text */ gtk_text_insert (GTK_TEXT (text), NULL, &text->style->black, NULL, "Supports ", -1); gtk_text_insert (GTK_TEXT (text), NULL, &colour, NULL, "colored ", -1); gtk_text_insert (GTK_TEXT (text), NULL, &text->style->black, NULL, "text and different ", -1); gtk_text_insert (GTK_TEXT (text), fixed_font, &text->style->black, NULL, "fonts\n\n", -1); /* Load the file text.c into the text window */ infile = fopen("text.c", "r"); if (infile) { char buffer[1024]; int nchars; while (1) { nchars = fread(buffer, 1, 1024, infile); gtk_text_insert (GTK_TEXT (text), fixed_font, NULL, NULL, buffer, nchars); if (nchars < 1024) break; } fclose (infile); } /* Thaw the text widget, allowing the updates to become visible */ gtk_text_thaw (GTK_TEXT (text)); hbox = gtk_hbutton_box_new (); gtk_box_pack_start (GTK_BOX (box2), hbox, FALSE, FALSE, 0); gtk_widget_show (hbox); check = gtk_check_button_new_with_label("Editable"); gtk_box_pack_start (GTK_BOX (hbox), check, FALSE, FALSE, 0); gtk_signal_connect (GTK_OBJECT(check), "toggled", GTK_SIGNAL_FUNC(text_toggle_editable), text); gtk_toggle_button_set_active(GTK_TOGGLE_BUTTON(check), TRUE); gtk_widget_show (check); check = gtk_check_button_new_with_label("Wrap Words"); gtk_box_pack_start (GTK_BOX (hbox), check, FALSE, TRUE, 0); gtk_signal_connect (GTK_OBJECT(check), "toggled", GTK_SIGNAL_FUNC(text_toggle_word_wrap), text); gtk_toggle_button_set_active(GTK_TOGGLE_BUTTON(check), FALSE); gtk_widget_show (check); separator = gtk_hseparator_new (); gtk_box_pack_start (GTK_BOX (box1), separator, FALSE, TRUE, 0); gtk_widget_show (separator); box2 = gtk_vbox_new (FALSE, 10); gtk_container_set_border_width (GTK_CONTAINER (box2), 10); gtk_box_pack_start (GTK_BOX (box1), box2, FALSE, TRUE, 0); gtk_widget_show (box2); button = gtk_button_new_with_label ("close"); gtk_signal_connect (GTK_OBJECT (button), "clicked", GTK_SIGNAL_FUNC(close_application), NULL); gtk_box_pack_start (GTK_BOX (box2), button, TRUE, TRUE, 0); GTK_WIDGET_SET_FLAGS (button, GTK_CAN_DEFAULT); gtk_widget_grab_default (button); gtk_widget_show (button); gtk_widget_show (window); gtk_main (); return(0); }/* example-end */</PRE></CODE></BLOCKQUOTE><P><P><HR NOSHADE><A HREF="gtk_tut-15.html">Next</A><A HREF="gtk_tut-13.html">Previous</A><A HREF="gtk_tut.html#toc14">Contents</A></BODY></HTML>⌨️ 快捷键说明
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