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diff --git a/documentation/src/subclassing.dox b/documentation/src/subclassing.dox deleted file mode 100644 index a13e0a011..000000000 --- a/documentation/src/subclassing.dox +++ /dev/null @@ -1,531 +0,0 @@ -/** - - \page subclassing 7 - Adding and Extending Widgets - - -This chapter describes how to add your own widgets or extend existing -widgets in FLTK. - -\section subclassing_subclassing Subclassing - -New widgets are created by <I>subclassing</I> an existing FLTK widget, -typically <tt>Fl_Widget</tt> for controls and <tt>Fl_Group</tt> for -composite widgets. - -A control widget typically interacts with the user to receive and/or -display a value of some sort. - -A composite widget widget holds a list of child widgets and handles moving, -sizing, showing, or hiding them as needed. <tt>Fl_Group</tt> is the -main composite widget widget class in FLTK, and all of the other composite -widgets (<tt>Fl_Pack</tt>, <tt>Fl_Scroll</tt>, <tt>Fl_Tabs</tt>, -<tt>Fl_Tile</tt>, and <tt>Fl_Window</tt>) are subclasses of it. - -You can also subclass other existing widgets to provide a different -look or user-interface. For example, the button widgets are all -subclasses of <tt>Fl_Button</tt> since they all interact with the user -via a mouse button click. The only difference is the code that draws -the face of the button. - -\section subclassing_fl_widget Making a Subclass of Fl_Widget - -Your subclasses can directly descend from <tt>Fl_Widget</tt> or any -subclass of <tt>Fl_Widget</tt>. <tt>Fl_Widget</tt> has only four -virtual methods, and overriding some or all of these may be necessary. - -\section subclassing_constructor The Constructor - -The constructor should have the following arguments: - -\code -MyClass(int x, int y, int w, int h, const char *label = 0); -\endcode - -This will allow the class to be used in -<A href="fluid.html#FLUID">FLUID</A> -without problems. - -The constructor must call the constructor for the base class and -pass the same arguments: - -\code -MyClass::MyClass(int x, int y, int w, int h, const char *label) -: Fl_Widget(x, y, w, h, label) { -// do initialization stuff... -} -\endcode - -<tt>Fl_Widget</tt>'s protected constructor sets <tt>x()</tt>, <tt>y()</tt>, -<tt>w()</tt>, <tt>h()</tt>, and <tt>label()</tt> to the passed values -and initializes the other instance variables to: - -\code -type(0); -box(FL_NO_BOX); -color(FL_BACKGROUND_COLOR); -selection_color(FL_BACKGROUND_COLOR); -labeltype(FL_NORMAL_LABEL); -labelstyle(FL_NORMAL_STYLE); -labelsize(FL_NORMAL_SIZE); -labelcolor(FL_FOREGROUND_COLOR); -align(FL_ALIGN_CENTER); -callback(default_callback,0); -flags(ACTIVE|VISIBLE); -image(0); -deimage(0); -\endcode - -\section subclassing_protected Protected Methods of Fl_Widget - -The following methods are provided for subclasses to use: - -\li <A href="#clear_visible"><tt>Fl_Widget::clear_visible</tt></A> -\li <A href="#damage"><tt>Fl_Widget::damage</tt></A> -\li <A href="#draw_box"><tt>Fl_Widget::draw_box</tt></A> -\li <A href="#draw_focus"><tt>Fl_Widget::draw_focus</tt></A> -\li <A href="#draw_label"><tt>Fl_Widget::draw_label</tt></A> -\li <A href="#set_flag"><tt>Fl_Widget::set_flag</tt></A> -\li <A href="#set_visible"><tt>Fl_Widget::set_visible</tt></A> -\li <A href="#test_shortcut"><tt>Fl_Widget::test_shortcut</tt></A> -\li <A href="#type"><tt>Fl_Widget::type</tt></A> - -<A name="damage"></A> <!-- For old HTML links only ! --> -void Fl_Widget::damage(uchar mask) <br> -void Fl_Widget::damage(uchar mask, int x, int y, int w, int h) <br> -uchar Fl_Widget::damage() - -\par -The first form indicates that a partial update of the object is -needed. The bits in mask are OR'd into <tt>damage()</tt>. Your <tt> -draw()</tt> routine can examine these bits to limit what it is -drawing. The public method <tt>Fl_Widget::redraw()</tt> simply does -<tt> Fl_Widget::damage(FL_DAMAGE_ALL)</tt>, but the implementation of -your widget can call the private <tt>damage(n)</tt>. - -\par -The second form indicates that a region is damaged. If only these -calls are done in a window (no calls to <tt>damage(n)</tt>) then FLTK -will clip to the union of all these calls before drawing anything. - This can greatly speed up incremental displays. The mask bits are -OR'd into <tt>damage()</tt> unless this is a <tt>Fl_Window</tt> widget. - -\par -The third form returns the bitwise-OR of all <tt>damage(n)</tt> -calls done since the last <tt>draw()</tt>. - -\par -<I>When redrawing your widgets you should look at the damage bits to -see what parts of your widget need redrawing.</I> The <tt>handle()</tt> -method can then set individual damage bits to limit the amount of drawing -that needs to be done: -\code -MyClass::handle(int event) { - ... - if (change_to_part1) damage(1); - if (change_to_part2) damage(2); - if (change_to_part3) damage(4); -} - -MyClass::draw() { - if (damage() & FL_DAMAGE_ALL) { - ... draw frame/box and other static stuff ... - } - - if (damage() & (FL_DAMAGE_ALL | 1)) draw_part1(); - if (damage() & (FL_DAMAGE_ALL | 2)) draw_part2(); - if (damage() & (FL_DAMAGE_ALL | 4)) draw_part3(); -} -\endcode - -<A name="draw_box"></A> <!-- For old HTML links only ! --> -void Fl_Widget::draw_box() const <br> -void Fl_Widget::draw_box(Fl_Boxtype b, ulong c) const - -\par -The first form draws this widget's <tt>box()</tt>, using the -dimensions of the widget. The second form uses <tt>b</tt> as the box -type and <tt>c</tt> as the color for the box. - -<A name="draw_focus"></A> <!-- For old HTML links only ! --> -void Fl_Widget::draw_focus() const <br> -void Fl_Widget::draw_focus(Fl_Boxtype b, int x, int y, int w, int h) const - -\par -Draws a focus box inside the widgets bounding box. The second -form allows you to specify a different bounding box. - -<A name="draw_label"></A> <!-- For old HTML links only ! --> -void Fl_Widget::draw_label() const <br> -void Fl_Widget::draw_label(int x, int y, int w, int h) const <br> -void Fl_Widget::draw_label(int x, int y, int w, int h, Fl_Align align) const - -\par -This is the usual function for a <tt>draw()</tt> method to call to -draw the widget's label. It does not draw the label if it is supposed -to be outside the box (on the assumption that the enclosing group will -draw those labels). - -\par -The second form uses the passed bounding box instead of the widget's -bounding box. This is useful so "centered" labels are aligned with some -feature, like a moving slider. - -\par -The third form draws the label anywhere. It acts as though <tt> -FL_ALIGN_INSIDE</tt> has been forced on so the label will appear inside -the passed bounding box. This is designed for parent groups to draw -labels with. - -<A name="set_flag"></A> <!-- For old HTML links only ! --> -void Fl_Widget::set_flag(SHORTCUT_LABEL) - -\par -Modifies <tt>draw_label()</tt> so that '&' characters cause an underscore -to be printed under the next letter. - -<A name="set_visible"></A> <!-- For old HTML links only ! --> -<A name="clear_visible"></A> <!-- For old HTML links only ! --> -void Fl_Widget::set_visible() <br> -void Fl_Widget::clear_visible() - -\par -Fast inline versions of <tt>Fl_Widget::hide()</tt> and <tt> -Fl_Widget::show()</tt>. These do not send the <tt>FL_HIDE</tt> and <tt> -FL_SHOW</tt> events to the widget. - -<A name="test_shortcut"></A> <!-- For old HTML links only ! --> -int Fl_Widget::test_shortcut() const <br> -static int Fl_Widget::test_shortcut(const char *s) - -\par -The first version tests <tt>Fl_Widget::label()</tt> against the -current event (which should be a <tt>FL_SHORTCUT</tt> event). If the -label contains a '&' character and the character after it matches the key -press, this returns true. This returns false if the <tt>SHORTCUT_LABEL</tt> -flag is off, if the label is <tt>NULL</tt> or does not have a -'&' character in it, or if the keypress does not match the character. - -\par -The second version lets you do this test against an arbitrary string. - -<A name="type"></A> <!-- For old HTML links only ! --> -uchar Fl_Widget::type() const <br> -void Fl_Widget::type(uchar t) - -\par -The property <tt>Fl_Widget::type()</tt> can return an arbitrary 8-bit -identifier, and can be set with the protected method <tt>type(uchar t)</tt>. -This value had to be provided for Forms compatibility, but you can -use it for any purpose you want. Try to keep the value less than 100 -to not interfere with reserved values. - -\par -FLTK does not use RTTI (Run Time Typing Infomation), to enhance -portability. But this may change in the near future if RTTI becomes -standard everywhere. - -\par -If you don't have RTTI you can use the clumsy FLTK mechanisim, by -having <tt>type()</tt> use a unique value. These unique values must -be greater than the symbol <tt>FL_RESERVED_TYPE</tt> (which is 100). -Look through the header files for <tt>FL_RESERVED_TYPE</tt> to find an -unused number. If you make a subclass of <tt>Fl_Window</tt> -you must use <tt>FL_WINDOW + n</tt> (<tt>n</tt> must be in the -range 1 to 7). - -<A NAME="handle"></A> <!-- For old HTML links only ! --> -\section subclassing_events Handling Events - -The virtual method <tt>int Fl_Widget::handle(int event)</tt> is called -to handle each event passed to the widget. It can: - -\li Change the state of the widget. -\li Call - <A href="Fl_Widget.html#Fl_Widget.redraw"><tt>Fl_Widget::redraw()</tt></A> - if the widget needs to be redisplayed. -\li Call - <A href="Fl_Widget.html#Fl_Widget.damage"><tt>Fl_Widget::damage(n)</tt></A> - if the widget needs a partial-update (assuming you provide support for - this in your - <A href="#draw"><tt>Fl_Widget::draw()</tt></A> - method). -\li Call - <A href="Fl_Widget.html#Fl_Widget.do_callback"><tt>Fl_Widget::do_callback()</tt></A> - if a callback should be generated. -\li Call <tt>Fl_Widget::handle()</tt> on child widgets. - -Events are identified by the integer argument. Other information -about the most recent event is stored in static locations and aquired -by calling the -<A href="events.html#events"><tt>Fl::event_*()</tt></A> -functions. This information remains valid until another event is -handled. - -Here is a sample <tt>handle()</tt> method for a widget that acts as -a pushbutton and also accepts the keystroke 'x' to cause the callback: - -\code -int MyClass::handle(int event) { - switch(event) { - case FL_PUSH: - highlight = 1; - redraw(); - return 1; - case FL_DRAG: { - int t = Fl::event_inside(this); - if (t != highlight) { - highlight = t; - redraw(); - } - } - return 1; - case FL_RELEASE: - if (highlight) { - highlight = 0; - redraw(); - do_callback(); - // never do anything after a callback, as the callback - // may delete the widget! - } - return 1; - case FL_SHORTCUT: - if (Fl::event_key() == 'x') { - do_callback(); - return 1; - } - return 0; - default: - return Fl_Widget::handle(event); - } -} -\endcode - -You must return non-zero if your <tt>handle()</tt> method -uses the event. If you return zero, the parent widget will try -sending the event to another widget. - -<A NAME="draw"></A> <!-- For old HTML links only ! --> -\section subclassing_drawing Drawing the Widget - -The <tt>draw()</tt> virtual method is called when FLTK wants -you to redraw your widget. It will be called if and only if -<tt>damage()</tt> is non-zero, and <tt>damage()</tt> will be -cleared to zero after it returns. The <tt>draw()</tt> method -should be declared protected so that it can't be called from -non-drawing code. - -The <tt>damage()</tt> value contains the bitwise-OR of all -the <tt>damage(n)</tt> calls to this widget since it was last -drawn. This can be used for minimal update, by only redrawing -the parts whose bits are set. FLTK will turn on the -<tt>FL_DAMAGE_ALL</tt> bit if it thinks the entire widget must -be redrawn, e.g. for an expose event. - -Expose events (and the above <tt>damage(b,x,y,w,h)</tt>) will cause <tt> -draw()</tt> to be called with FLTK's <A href="drawing.html#clipping"> -clipping</A> turned on. You can greatly speed up redrawing in some -cases by testing <tt>fl_not_clipped(x,y,w,h)</tt> or <tt>fl_clip_box(...)</tt> -and skipping invisible parts. - -Besides the protected methods described above, FLTK provides a large -number of basic drawing functions, which are described -<A href="drawing.html#drawing">below</A>. - -\section subclassing_resizing Resizing the Widget - -The <tt>resize(int x, int y, int w, int h)</tt> method is called when -the widget is being resized or moved. The arguments are the new -position, width, and height. <tt>x()</tt>, <tt>y()</tt>, <tt>w()</tt>, -and <tt>h()</tt> still remain the old size. You must call <tt>resize()</tt> -on your base class with the same arguments to get the widget size to -actually change. - -This should <I>not</I> call <tt>redraw()</tt>, at least if only the <tt> -x()</tt> and <tt>y()</tt> change. This is because composite widgets like -<A href="Fl_Scroll.html#Fl_Scroll"><tt>Fl_Scroll</tt></A> -may have a more efficient way of drawing the new position. - -\section subclassing_composite Making a Composite Widget - -A "composite" widget contains one or more "child" widgets. -To make a composite widget you should subclass -<A href="Fl_Group.html#Fl_Group"><tt>Fl_Group</tt></A>. -It is possible to make a composite object that is not a subclass of -<tt>Fl_Group</tt>, but you'll have to duplicate the code in <tt>Fl_Group</tt> -anyways. - -Instances of the child widgets may be included in the parent: - -\code -class MyClass : public Fl_Group { - Fl_Button the_button; - Fl_Slider the_slider; - ... -}; -\endcode - -The constructor has to initialize these instances. They are automatically -<tt>add()</tt>ed to the group, since the Fl_Group constructor does -Fl_Group::begin(). -<I>Don't forget to call Fl_Group::end() or use the Fl_End pseudo-class:</I> - -\code -MyClass::MyClass(int x, int y, int w, int h) : - Fl_Group(x, y, w, h), - the_button(x + 5, y + 5, 100, 20), - the_slider(x, y + 50, w, 20) -{ - ...(you could add dynamically created child widgets here)... - end(); // don't forget to do this! -} -\endcode - -The child widgets need callbacks. These will be called with a pointer -to the children, but the widget itself may be found in the <tt>parent()</tt> -pointer of the child. Usually these callbacks can be static private -methods, with a matching private method: - -\code -void MyClass::static_slider_cb(Fl_Widget* v, void *) { // static method - ((MyClass*)(v->parent())->slider_cb(); -} -void MyClass::slider_cb() { // normal method - use(the_slider->value()); -} -\endcode - -If you make the <tt>handle()</tt> method, you can quickly pass all the -events to the children using the <tt>Fl_Group::handle()</tt> method. -You don't need to override <tt>handle()</tt> if your composite widget -does nothing other than pass events to the children: - -\code -int MyClass::handle(int event) { - if (Fl_Group::handle(event)) return 1; - ... handle events that children don't want ... -} -\endcode - -If you override <tt>draw()</tt> you need to draw all the -children. If <tt>redraw()</tt> or <tt>damage()</tt> is called -on a child, <tt>damage(FL_DAMAGE_CHILD)</tt> is done to the -group, so this bit of <tt>damage()</tt> can be used to indicate -that a child needs to be drawn. It is fastest if you avoid -drawing anything else in this case: - -\code -int MyClass::draw() { - Fl_Widget *const*a = array(); - if (damage() == FL_DAMAGE_CHILD) { // only redraw some children - for (int i = children(); i --; a ++) update_child(**a); - } else { // total redraw - ... draw background graphics ... - // now draw all the children atop the background: - for (int i = children_; i --; a ++) { - draw_child(**a); - draw_outside_label(**a); // you may not need to do this - } - } -} -\endcode - -<tt>Fl_Group</tt> provides some protected methods to make drawing -easier: - -\li <A href="#draw_child">draw_child</A> -\li <A href="#draw_outside_label">draw_outside_label</A> -\li <A href="#update_child">update_child</A> - -<A name="draw_child"></A> <!-- For old HTML links only ! --> -void Fl_Group::draw_child(Fl_Widget&) - -\par -This will force the child's <tt>damage()</tt> bits all to one and call <tt> -draw()</tt> on it, then clear the <tt>damage()</tt>. You should call -this on all children if a total redraw of your widget is requested, or -if you draw something (like a background box) that damages the child. -Nothing is done if the child is not <tt>visible()</tt> or if it is -clipped. - -<A name="draw_outside_label"></A> <!-- For old HTML links only ! --> -void Fl_Group::draw_outside_label(Fl_Widget&) const - -\par -Draw the labels that are <I>not</I> drawn by <A href="#draw_label"><tt> -draw_label()</tt></A>. If you want more control over the label -positions you might want to call <tt>child->draw_label(x,y,w,h,a)</tt>. - -<A name="update_child"></A> <!-- For old HTML links only ! --> -void Fl_Group::update_child(Fl_Widget&) - -\par -Draws the child only if its <tt>damage()</tt> is non-zero. You -should call this on all the children if your own damage is equal to -FL_DAMAGE_CHILD. Nothing is done if the child is not <tt>visible()</tt> -or if it is clipped. - -\section subclassing_cutnpaste Cut and Paste Support - -FLTK provides routines to cut and paste 8-bit text (in the future this -may be UTF-8) between applications: - -\li <A href="Fl.html#Fl.paste"><tt>Fl::paste</tt></A> -\li <A href="Fl.html#Fl.selection"><tt>Fl::selection</tt></A> -\li <A href="Fl.html#Fl.selection_owner"><tt>Fl::selection_owner</tt></A> - -It may be possible to cut/paste non-text data by using -<A href="osissues.html#add_handler"><tt>Fl::add_handler()</tt></A>. - -\section subclassing_dragndrop Drag And Drop Support - -FLTK provides routines to drag and drop 8-bit text between applications: - -Drag'n'drop operations are are initiated by copying data to the -clipboard and calling the function -<A href="Fl.html#Fl.dnd"><tt>Fl::dnd()</tt></A>. - -Drop attempts are handled via <A href="events.html#dnd">events</A>: - -\li <tt>FL_DND_ENTER</tt> -\li <tt>FL_DND_DRAG</tt> -\li <tt>FL_DND_LEAVE</tt> -\li <tt>FL_DND_RELEASE</tt> -\li <tt>FL_PASTE</tt> - -\section subclassing_fl_window Making a subclass of Fl_Window - -You may want your widget to be a subclass of -<tt>Fl_Window</tt>, <tt>Fl_Double_Window</tt>, or -<tt>FL_Gl_Window</tt>. This can be useful if your widget wants -to occupy an entire window, and can also be used to take -advantage of system-provided clipping, or to work with a library -that expects a system window ID to indicate where to draw. - -Subclassing <tt>Fl_Window</tt>is almost exactly like -subclassing <tt>Fl_Group</tt>, and in fact you can easily -switch a subclass back and forth. Watch out for the following -differences: - --# <tt>Fl_Window</tt> is a subclass of <tt>Fl_Group</tt> so - <I>make sure your constructor calls <tt>end()</tt></I> - unless you actually want children added to your window. - --# When handling events and drawing, the upper-left corner is at - 0,0, not <tt>x(),y()</tt> as in other <tt>Fl_Widget</tt>'s. - For instance, to draw a box around the widget, call - <tt>draw_box(0, 0, w(), h())</tt>, rather than - <tt>draw_box(x(), y(), w(), h())</tt>. - -You may also want to subclass <tt>Fl_Window</tt> in order to -get access to different visuals or to change other attributes of -the windows. See -<A href="osissues.html">"Appendix F - Operating System Issues"</A> -for more information. - -\htmlonly -<hr> -<a class="el" href="index.html">[Index]</a> -<a class="el" href="events.html">[Previous] 6 - Handling Events</a> -<a class="el" href="opengl.html">[Next] 8 - Using OpenGL</a> -\endhtmlonly -*/ |