336996c7ab
and errors reported by HTML Tidy. git-svn-id: file:///fltk/svn/fltk/branches/branch-1.0@1454 ea41ed52-d2ee-0310-a9c1-e6b18d33e121
558 lines
16 KiB
HTML
558 lines
16 KiB
HTML
<HTML><BODY>
|
|
<H1 ALIGN=RIGHT><A NAME=editor>4 - Designing a Simple Text Editor</A></H1>
|
|
This chapter takes you through the design of a simple FLTK-based text
|
|
editor.
|
|
<H2>Determining the Goals of the Text Editor</H2>
|
|
Since this will be the first big project you'll be doing with FLTK,
|
|
lets define what we want our text editor to do:
|
|
<OL>
|
|
<LI>Menubar/menus for all functions. </LI>
|
|
<LI>Edit a single text file. </LI>
|
|
<LI>Load from a file. </LI>
|
|
<LI>Save to a file. </LI>
|
|
<LI>Cut/copy/delete/paste functions. </LI>
|
|
<LI>Search and replace functions. </LI>
|
|
<LI>Keep track of when the file has been changed. </LI>
|
|
</OL>
|
|
<H2>Designing the Main Window</H2>
|
|
Now that we've outlined the goals for our editor, we can begin with
|
|
the design of our GUI. Obviously the first thing that we need is a
|
|
window:
|
|
<UL>
|
|
<PRE>
|
|
Fl_Window *window;
|
|
|
|
window = new Fl_Window(640, 480, "Text Editor");
|
|
</PRE>
|
|
</UL>
|
|
<H2>Variables</H2>
|
|
Our text editor will need some global variables to keep track of
|
|
things:
|
|
<UL>
|
|
<PRE>
|
|
Fl_Window *window;
|
|
Fl_Menu_Bar *menubar;
|
|
Fl_Multiline_Input *input;
|
|
Fl_Window *replace_dlg;
|
|
Fl_Input *replace_find;
|
|
Fl_Input *replace_with;
|
|
Fl_Button *replace_all;
|
|
Fl_Return_Button *replace_next;
|
|
Fl_Button *replace_cancel;
|
|
|
|
int changed = 0;
|
|
char filename[1024] = "";
|
|
char search[256] = "";
|
|
</PRE>
|
|
</UL>
|
|
The <TT>window</TT> variable is our top-level window described
|
|
previously. We'll cover the other variables as we build the
|
|
application.
|
|
<H2>Menubars and Menus</H2>
|
|
The first goal requires us to use a menubar and menus that define each
|
|
function the editor needs to perform. The <A href=Fl_Menu_Item.html#Fl_Menu_Item>
|
|
<TT>Fl_Menu_Item</TT></A> structure is used to define the menus and
|
|
items in a menubar:
|
|
<UL>
|
|
<PRE>
|
|
Fl_Menu_Item menuitems[] = {
|
|
{ "&File", 0, 0, 0, FL_SUBMENU },
|
|
{ "&New", FL_ALT + 'n', (Fl_Callback *)new_cb },
|
|
{ "&Open...", FL_ALT + 'o', (Fl_Callback *)open_cb, 0, FL_MENU_DIVIDER },
|
|
{ "&Save", FL_ALT + 's', (Fl_Callback *)save_cb },
|
|
{ "Save &As...", FL_ALT + FL_SHIFT + 's', (Fl_Callback *)saveas_cb, 0, FL_MENU_DIVIDER },
|
|
{ "&Quit", FL_ALT + 'q', (Fl_Callback *)quit_cb },
|
|
{ 0 },
|
|
|
|
{ "&Edit", 0, 0, 0, FL_SUBMENU },
|
|
{ "&Undo", FL_ALT + 'z', (Fl_Callback *)undo_cb, 0, FL_MENU_DIVIDER },
|
|
{ "Cu&t", FL_ALT + 'x', (Fl_Callback *)cut_cb },
|
|
{ "&Copy", FL_ALT + 'c', (Fl_Callback *)copy_cb },
|
|
{ "&Paste", FL_ALT + 'v', (Fl_Callback *)paste_cb },
|
|
{ "&Delete", 0, (Fl_Callback *)delete_cb },
|
|
{ 0 },
|
|
|
|
{ "&Search", 0, 0, 0, FL_SUBMENU },
|
|
{ "&Find...", FL_ALT + 'f', (Fl_Callback *)find_cb },
|
|
{ "F&ind Again", FL_ALT + 'g', (Fl_Callback *)find2_cb },
|
|
{ "&Replace...", FL_ALT + 'r', (Fl_Callback *)replace_cb },
|
|
{ "Re&place Again", FL_ALT + 't', (Fl_Callback *)replace2_cb },
|
|
{ 0 },
|
|
|
|
{ 0 }
|
|
};
|
|
</PRE>
|
|
</UL>
|
|
Once we have the menus defined we can create the <TT>Fl_Menu_Bar</TT>
|
|
widget and assign the menus to it with:
|
|
<UL>
|
|
<PRE>
|
|
Fl_Menu_Bar *menubar = new Fl_Menu_Bar(0, 0, 640, 30);
|
|
menubar->menu(menuitems);
|
|
</PRE>
|
|
</UL>
|
|
We'll define the callback functions later.
|
|
<H2>Editing the Text</H2>
|
|
To keep things simple our text editor will use the <A href=Fl_Multiline_Input.html#Fl_Multiline_Input>
|
|
<TT>Fl_Multiline_Input</TT></A> widget to edit the text:
|
|
<UL>
|
|
<PRE>
|
|
Fl_Multiline_Input *input = new Fl_Multiline_Input(0, 30, 640, 450);
|
|
</PRE>
|
|
</UL>
|
|
So that we can keep track of changes to the file, we also want to add
|
|
a "changed" callback:
|
|
<UL>
|
|
<PRE>
|
|
input->callback(changed_cb);
|
|
input->when(FL_WHEN_CHANGED);
|
|
</PRE>
|
|
</UL>
|
|
Finally, we want to use a mono-spaced font like <TT>FL_COURIER</TT>:
|
|
<UL>
|
|
<PRE>
|
|
input->textfont(FL_COURIER);
|
|
</PRE>
|
|
</UL>
|
|
<H2>The Replace Dialog</H2>
|
|
We can use the FLTK convenience functions for many of the editor's
|
|
dialogs, however the replace dialog needs its own custom window. To
|
|
keep things simple we will have a "find" string, a "replace" string,
|
|
and "replace all", "replace next", and "cancel" buttons. The strings
|
|
are just <TT>Fl_Input</TT> widgets, the "replace all" and "cancel"
|
|
buttons are <TT>Fl_Button</TT> widgets, and the "replace next " button
|
|
is a <TT>Fl_Return_Button</TT> widget:
|
|
<P ALIGN=CENTER><IMG src="editor-replace.gif" ALT="The search and replace dialog."></P>
|
|
<UL>
|
|
<PRE>
|
|
Fl_Window *replace_dlg = new Fl_Window(300, 105, "Replace");
|
|
Fl_Input *replace_find = new Fl_Input(70, 10, 200, 25, "Find:");
|
|
Fl_Input *replace_with = new Fl_Input(70, 40, 200, 25, "Replace:");
|
|
Fl_Button *replace_all = new Fl_Button(10, 70, 90, 25, "Replace All");
|
|
Fl_Button *replace_next = new Fl_Button(105, 70, 120, 25, "Replace Next");
|
|
Fl_Button *replace_cancel = new Fl_Button(230, 70, 60, 25, "Cancel");
|
|
</PRE>
|
|
</UL>
|
|
<H2>Callbacks</H2>
|
|
Now that we've defined the GUI components of our editor, we need to
|
|
define our callback functions.
|
|
<H3>changed_cb()</H3>
|
|
This function will be called whenever the user changes any text in the <TT>
|
|
input</TT> widget:
|
|
<UL>
|
|
<PRE>
|
|
void changed_cb(void) {
|
|
set_changed(1);
|
|
}
|
|
</PRE>
|
|
</UL>
|
|
The <TT>set_changed()</TT> function is one that we will write to set
|
|
the changed status on the current file. We're doing it this way
|
|
because some of the other callbacks will set the changed status to 0,
|
|
and also because we want to show the changed status in the window's
|
|
title bar.
|
|
<H3>copy_cb()</H3>
|
|
This callback function will call <A href=#Fl_Input.copy><TT>
|
|
input->copy()</TT></A> to copy the currently selected text to the
|
|
clipboard:
|
|
<UL>
|
|
<PRE>
|
|
void copy_cb(void) {
|
|
input->copy();
|
|
}
|
|
</PRE>
|
|
</UL>
|
|
<H3>cut_cb()</H3>
|
|
This callback function will call <A href=Fl_Input_.html#Fl_Input_.copy><TT>
|
|
input->copy()</TT></A> to copy the currently selected text to the
|
|
clipboard and then <A href=Fl_Input_.html#Fl_Input_.cut><TT>input->cut()</TT>
|
|
</A> to delete it:
|
|
<UL>
|
|
<PRE>
|
|
void cut_cb(void) {
|
|
input->copy();
|
|
input->cut();
|
|
}
|
|
</PRE>
|
|
</UL>
|
|
<H3>delete_cb()</H3>
|
|
This callback function will call <A href=Fl_Input_.html#Fl_Input_.cut><TT>
|
|
input->cut()</TT></A> to delete the selected text:
|
|
<UL>
|
|
<PRE>
|
|
void delete_cb(void) {
|
|
input->cut();
|
|
}
|
|
</PRE>
|
|
</UL>
|
|
<H3>find_cb()</H3>
|
|
This callback function asks for a search string using the <A href=functions.html#fl_input2>
|
|
<TT>fl_input()</TT></A> convenience function and then calls the <TT>
|
|
find2_cb()</TT> function to find the string:
|
|
<UL>
|
|
<PRE>
|
|
void find_cb(void) {
|
|
const char *val;
|
|
|
|
val = fl_input("Search String:", search);
|
|
if (val != NULL) {
|
|
// User entered a string - go find it!
|
|
strcpy(search, val);
|
|
find2_cb();
|
|
}
|
|
}
|
|
</PRE>
|
|
</UL>
|
|
<H3>find2_cb()</H3>
|
|
This function will find the next occurrence of the search string. If
|
|
the search string is blank then we want to pop up the search dialog:
|
|
<UL>
|
|
<PRE>
|
|
void find2_cb(void) {
|
|
const char *val, *found;
|
|
int pos;
|
|
|
|
if (search[0] == '\0') {
|
|
// Search string is blank; get a new one...
|
|
find_cb();
|
|
return;
|
|
}
|
|
|
|
val = input->value() + input->mark();
|
|
found = strstr(val, search);
|
|
|
|
if (found != NULL) {
|
|
// Found a match; update the position and mark...
|
|
pos = input->mark() + found - val;
|
|
input->position(pos, pos + strlen(search));
|
|
}
|
|
else fl_alert("No occurrences of \'%s\' found!", search);
|
|
}
|
|
</PRE>
|
|
</UL>
|
|
If the search string cannot be found we use the <A href=#fl_alert><TT>
|
|
fl_alert()</TT></A> convenience function to display a message to that
|
|
effect.
|
|
<H3>new_cb()</H3>
|
|
This callback function will clear the input widget and current
|
|
filename. It also calls the <TT>check_save()</TT> function to give the
|
|
user the opportunity to save the current file first as needed:
|
|
<UL>
|
|
<PRE>
|
|
void new_cb(void) {
|
|
if (changed)
|
|
if (!check_save()) return;
|
|
|
|
filename[0] = '\0';
|
|
input->value("");
|
|
set_changed(0);
|
|
}
|
|
</PRE>
|
|
</UL>
|
|
<H3>open_cb()</H3>
|
|
This callback function will ask the user for a filename and then load
|
|
the specified file into the input widget and current filename. It also
|
|
calls the <TT>check_save()</TT> function to give the user the
|
|
opportunity to save the current file first as needed:
|
|
<UL>
|
|
<PRE>
|
|
void open_cb(void) {
|
|
char *newfile;
|
|
|
|
if (changed)
|
|
if (!check_save()) return;
|
|
|
|
newfile = fl_file_chooser("Open File?", "*", filename);
|
|
if (newfile != NULL) load_file(newfile);
|
|
}
|
|
</PRE>
|
|
</UL>
|
|
We call the <TT>load_file()</TT> function to actually load the file.
|
|
<H3>paste_cb()</H3>
|
|
This callback function will send a FL_PASTE message to the <TT>input</TT>
|
|
widget using the <A href=functions.html#paste><TT>Fl::paste()</TT></A>
|
|
method:
|
|
<UL>
|
|
<PRE>
|
|
void paste_cb(void) {
|
|
Fl::paste(*input);
|
|
}
|
|
</PRE>
|
|
</UL>
|
|
<H3>quit_cb()</H3>
|
|
The quit callback will first see if the current file has been
|
|
modified, and if so give the user a chance to save it. It then hides
|
|
the main window:
|
|
<UL>
|
|
<PRE>
|
|
void quit_cb(void) {
|
|
if (changed)
|
|
if (!check_save())
|
|
return;
|
|
|
|
window->hide();
|
|
}
|
|
</PRE>
|
|
</UL>
|
|
<H3>replace_cb()</H3>
|
|
The replace callback just shows the replace dialog:
|
|
<UL>
|
|
<PRE>
|
|
void replace_cb(void) {
|
|
replace_dlg->show();
|
|
}
|
|
</PRE>
|
|
</UL>
|
|
<H3>replace2_cb()</H3>
|
|
This callback will replace the next occurence of the replacement
|
|
string. If nothing has been entered for the replacement string, then
|
|
the replace dialog is displayed instead:
|
|
<UL>
|
|
<PRE>
|
|
void replace2_cb() {
|
|
const char *find, *val, *found;
|
|
int pos;
|
|
|
|
find = replace_find->value();
|
|
if (find[0] == '\0') {
|
|
// Search string is blank; get a new one...
|
|
replace_dlg->show();
|
|
return;
|
|
}
|
|
|
|
val = input->value() + input->position();
|
|
found = strstr(val, find);
|
|
|
|
if (found != NULL) {
|
|
// Found a match; update the position and replace text...
|
|
pos = input->position() + found - val;
|
|
input->replace(pos, pos + strlen(find), replace_with->value());
|
|
input->position(pos + strlen(replace_with->value()));
|
|
}
|
|
else fl_alert("No occurrences of \'%s\' found!", find);
|
|
}
|
|
</PRE>
|
|
</UL>
|
|
<H3>replall_cb()</H3>
|
|
This callback will replace all occurences of the search string in the
|
|
file:
|
|
<UL>
|
|
<PRE>
|
|
void replall_cb() {
|
|
const char *find, *val, *found;
|
|
int pos;
|
|
int times;
|
|
|
|
find = replace_find->value();
|
|
if (find[0] == '\0') {
|
|
// Search string is blank; get a new one...
|
|
replace_dlg->show();
|
|
return;
|
|
}
|
|
|
|
input->position(0);
|
|
times = 0;
|
|
|
|
// Loop through the whole string
|
|
do {
|
|
val = input->value() + input->position();
|
|
found = strstr(val, find);
|
|
|
|
if (found != NULL) {
|
|
// Found a match; update the position and replace text...
|
|
times ++;
|
|
pos = input->position() + found - val;
|
|
input->replace(pos, pos + strlen(find), replace_with->value());
|
|
input->position(pos + strlen(replace_with->value()));
|
|
}
|
|
} while (found != NULL);
|
|
|
|
if (times > 0) fl_message("Replaced %d occurrences.", times);
|
|
else fl_alert("No occurrences of \'%s\' found!", find);
|
|
}
|
|
</PRE>
|
|
</UL>
|
|
<H3>replcan_cb()</H3>
|
|
This callback just hides the replace dialog:
|
|
<UL>
|
|
<PRE>
|
|
void replcan_cb() {
|
|
replace_dlg->hide();
|
|
}
|
|
</PRE>
|
|
</UL>
|
|
<H3>save_cb()</H3>
|
|
This callback saves the current file. If the current filename is
|
|
blank it calls the "save as" callback:
|
|
<UL>
|
|
<PRE>
|
|
void save_cb(void) {
|
|
if (filename[0] == '\0') {
|
|
// No filename - get one!
|
|
saveas_cb();
|
|
return;
|
|
}
|
|
else save_file(filename);
|
|
}
|
|
</PRE>
|
|
</UL>
|
|
The <TT>save_file()</TT> function saves the current file to the
|
|
specified filename.
|
|
<H3>saveas_cb()</H3>
|
|
This callback asks the user for a filename and saves the current file:
|
|
<UL>
|
|
<PRE>
|
|
void saveas_cb(void) {
|
|
char *newfile;
|
|
|
|
newfile = fl_file_chooser("Save File As?", "*", filename);
|
|
if (newfile != NULL) save_file(newfile);
|
|
}
|
|
</PRE>
|
|
</UL>
|
|
The <TT>save_file()</TT> function saves the current file to the
|
|
specified filename.
|
|
<H3>undo_cb()</H3>
|
|
The undo callback just calls the <A href=Fl_Input_.html#Fl_Input_.undo><TT>
|
|
undo()</TT></A> method:
|
|
<UL>
|
|
<PRE>
|
|
void undo_cb(void) {
|
|
input->undo();
|
|
}
|
|
</PRE>
|
|
</UL>
|
|
<H2>Other Functions</H2>
|
|
Now that we've defined the callback functions, we need our support
|
|
functions to make it all work:
|
|
<H3>check_save()</H3>
|
|
This function checks to see if the current file needs to be saved. If
|
|
so, it asks the user if they want to save it:
|
|
<UL>
|
|
<PRE>
|
|
int check_save(void) {
|
|
if (!changed) return 1;
|
|
|
|
if (fl_ask("The current file has not been saved.\n"
|
|
"Would you like to save it now?")) {
|
|
// Save the file...
|
|
save_cb();
|
|
|
|
return !changed;
|
|
}
|
|
else return (1);
|
|
}
|
|
</PRE>
|
|
</UL>
|
|
<H3>load_file()</H3>
|
|
This function loads the specified file into the <TT>input</TT> widget:
|
|
<UL>
|
|
<PRE>
|
|
void load_file(char *newfile) {
|
|
FILE *fp;
|
|
char buffer[8192];
|
|
int nbytes;
|
|
int pos;
|
|
|
|
input->value("");
|
|
|
|
fp = fopen(newfile, "r");
|
|
if (fp != NULL) {
|
|
// Was able to open file; let's read from it...
|
|
strcpy(filename, newfile);
|
|
pos = 0;
|
|
|
|
while ((nbytes = fread(buffer, 1, sizeof(buffer), fp)) > 0) {
|
|
input->replace(pos, pos, buffer, nbytes);
|
|
pos += nbytes;
|
|
}
|
|
|
|
fclose(fp);
|
|
input->position(0);
|
|
set_changed(0);
|
|
} else {
|
|
// Couldn't open file - say so...
|
|
fl_alert("Unable to open \'%s\' for reading!");
|
|
}
|
|
}
|
|
</PRE>
|
|
</UL>
|
|
When loading the file we use the <A href=Fl_Input_.html#Fl_Input_.replace>
|
|
<TT>input->replace()</TT></A> method to "replace" the text at the end
|
|
of the buffer. The <TT>pos</TT> variable keeps track of the end of the
|
|
buffer.
|
|
<H3>save_file()</H3>
|
|
This function saves the current buffer to the specified file:
|
|
<UL>
|
|
<PRE>
|
|
void save_file(char *newfile) {
|
|
FILE *fp;
|
|
|
|
fp = fopen(newfile, "w");
|
|
if (fp != NULL) {
|
|
// Was able to create file; let's write to it...
|
|
strcpy(filename, newfile);
|
|
|
|
if (fwrite(input->value(), 1, input->size(), fp) < 1) {
|
|
fl_alert("Unable to write file!");
|
|
fclose(fp);
|
|
return;
|
|
}
|
|
|
|
fclose(fp);
|
|
set_changed(0);
|
|
} else {
|
|
// Couldn't open file - say so...
|
|
fl_alert("Unable to create \'%s\' for writing!");
|
|
}
|
|
}
|
|
</PRE>
|
|
</UL>
|
|
<H3>set_changed()</H3>
|
|
This function sets the <TT>changed</TT> variable and updates the
|
|
window label accordingly:
|
|
<UL>
|
|
<PRE>
|
|
void set_changed(int c) {
|
|
if (c != changed) {
|
|
char title[1024];
|
|
char *slash;
|
|
|
|
changed = c;
|
|
|
|
if (filename[0] == '\0') strcpy(title, "Untitled");
|
|
else {
|
|
slash = strrchr(filename, '/');
|
|
if (slash == NULL) slash = strrchr(filename, '\\');
|
|
|
|
if (slash != NULL) strcpy(title, slash + 1);
|
|
else strcpy(title, filename);
|
|
}
|
|
|
|
if (changed) strcat(title, " (modified)");
|
|
|
|
window->label(title);
|
|
}
|
|
}
|
|
</PRE>
|
|
</UL>
|
|
<H2>Compiling the Editor</H2>
|
|
The complete source for our text editor can be found in the <TT>
|
|
test/editor.cxx</TT> source file. Both the Makefile and Visual C++
|
|
workspace include the necessary rules to build the editor. You can
|
|
also compile it using a standard compiler with:
|
|
<UL>
|
|
<PRE>
|
|
CC -o editor editor.cxx -lfltk -lXext -lX11 -lm
|
|
</PRE>
|
|
</UL>
|
|
As noted in <A href=basics.html#basics>Chapter 1</A>, you may need to
|
|
include compiler and linker options to tell them where to find the FLTK
|
|
library. Also, the <TT>CC</TT> command may also be called <TT>gcc</TT>
|
|
or <TT>c++</TT> on your system.
|
|
<P>Congratulations, you've just built your own text editor! </P>
|
|
<H2>The Final Product</H2>
|
|
The final editor window should look like the image on the next page.
|
|
<P ALIGN=CENTER><IMG src="editor.gif" ALT="The completed editor window."></P>
|
|
</BODY></HTML>
|