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| author | Fabien Costantini <fabien@onepost.net> | 2008-10-14 22:12:25 +0000 |
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| committer | Fabien Costantini <fabien@onepost.net> | 2008-10-14 22:12:25 +0000 |
| commit | 497afccb07164373e0de6639e754d7d691f1926f (patch) | |
| tree | 449d0b92ceb05f39617fe8fc2876d16eecde7460 /documentation/subclassing.html | |
| parent | e08fffdfe08bbc9320e39a15d162b6501abd4925 (diff) | |
Doxygen pdf man: First version added in documentation/fltk.pdf, old doc removed, images, dox files moved to a new src directory.
git-svn-id: file:///fltk/svn/fltk/branches/branch-1.3@6431 ea41ed52-d2ee-0310-a9c1-e6b18d33e121
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diff --git a/documentation/subclassing.html b/documentation/subclassing.html deleted file mode 100644 index 873f6cd75..000000000 --- a/documentation/subclassing.html +++ /dev/null @@ -1,434 +0,0 @@ -<HTML> -<HEAD> - <TITLE>7 - Adding and Extending Widgets</TITLE> -</HEAD> -<BODY> -<H1 ALIGN=RIGHT><A NAME=subclassing>7 - Adding and Extending Widgets</A></H1> - This chapter describes how to add your own widgets or extend existing -widgets in FLTK. -<H2>Subclassing</H2> - 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. -<P>A control widget typically interacts with the user to receive and/or -display a value of some sort. </P> -<P>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. </P> -<P>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. </P> -<H2>Making a Subclass of Fl_Widget</H2> - 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. -<H2>The Constructor</H2> - The constructor should have the following arguments: -<UL><PRE> -MyClass(int x, int y, int w, int h, const char *label = 0); -</PRE></UL> - This will allow the class to be used in <A href="fluid.html#FLUID">FLUID</A> - without problems. -<P>The constructor must call the constructor for the base class and -pass the same arguments: </P> -<UL><PRE> -MyClass::MyClass(int x, int y, int w, int h, const char *label) -: Fl_Widget(x, y, w, h, label) { -// do initialization stuff... -} -</PRE></UL> -<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: -<UL><PRE> -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); -</PRE></UL> -<H2>Protected Methods of Fl_Widget</H2> - The following methods are provided for subclasses to use: -<UL> -<LI><A href=#clear_visible><TT>Fl_Widget::clear_visible</TT></A></LI> -<LI><A href=#damage><TT>Fl_Widget::damage</TT></A></LI> -<LI><A href=#draw_box><TT>Fl_Widget::draw_box</TT></A></LI> -<LI><A href=#draw_focus><TT>Fl_Widget::draw_focus</TT></A></LI> -<LI><A href=#draw_label><TT>Fl_Widget::draw_label</TT></A></LI> -<LI><A href=#set_flag><TT>Fl_Widget::set_flag</TT></A></LI> -<LI><A href=#set_visible><TT>Fl_Widget::set_visible</TT></A></LI> -<LI><A href=#test_shortcut><TT>Fl_Widget::test_shortcut</TT></A></LI> -<LI><A href=#type><TT>Fl_Widget::type</TT></A></LI> -</UL> -<H4><A name=damage>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()</A></H4> -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>. -<P>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. </P> -<P>The third form returns the bitwise-OR of all <TT>damage(n)</TT> -calls done since the last <TT>draw()</TT>.</P> -<P><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: -<UL><PRE> -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(); -} -</PRE></UL> -<H4><A name=draw_box>void Fl_Widget::draw_box() const -<BR></A>void Fl_Widget::draw_box(Fl_Boxtype b, ulong c) const</H4> - 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. - -<H4><A name="draw_focus">void Fl_Widget::draw_focus() const -<BR>void Fl_Widget::draw_focus(Fl_Boxtype b, int x, int y, int w, int h) const</A></H4> - -<P>Draws a focus box inside the widgets bounding box. The second -form allows you to specify a different bounding box. - -<H4><A name=draw_label>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</A></H4> - 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). -<P>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. </P> -<P>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. </P> -<H4><A name=set_flag>void Fl_Widget::set_flag(SHORTCUT_LABEL)</A></H4> -Modifies <TT>draw_label()</TT> so that '&' characters cause an underscore -to be printed under the next letter. -<H4><A name=set_visible>void Fl_Widget::set_visible()</A> -<BR><A name=clear_visible>void Fl_Widget::clear_visible()</A></H4> - 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. -<H4><A name=test_shortcut>int Fl_Widget::test_shortcut() const -<BR> static int Fl_Widget::test_shortcut(const char *s)</A></H4> - 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. -<P>The second version lets you do this test against an arbitrary -string. </P> -<H4><A name=type>uchar Fl_Widget::type() const -<BR> void Fl_Widget::type(uchar t)</A></H4> - 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. -<P>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. </P> -<P>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). </P> -<H2><A NAME="handle">Handling Events</A></H2> - The virtual method <TT>int Fl_Widget::handle(int event)</TT> is called -to handle each event passed to the widget. It can: -<UL> -<LI>Change the state of the widget. </LI> -<LI>Call <A href=Fl_Widget.html#Fl_Widget.redraw><TT>Fl_Widget::redraw()</TT> -</A> if the widget needs to be redisplayed. </LI> -<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> -<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> -<LI>Call <TT>Fl_Widget::handle()</TT> on child widgets. </LI> -</UL> - 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. -<P>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: </P> -<UL><PRE> -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); - } -} -</PRE></UL> - -<P>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. - -<H2><A NAME="draw">Drawing the Widget</A></H2> - -<P>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. - -<P>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. </P> - -<P>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. </P> -<P>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>. </P> -<H2>Resizing the Widget</H2> - 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. -<P>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. </P> -<H2>Making a Composite Widget</H2> - 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. -<P>Instances of the child widgets may be included in the parent: </P> -<UL><PRE> -class MyClass : public Fl_Group { - Fl_Button the_button; - Fl_Slider the_slider; - ... -}; -</PRE></UL> - The constructor has to initialize these instances. They are -automatically <TT>add()</TT>ed to the group, since the <TT>Fl_Group</TT> - constructor does <TT>begin()</TT>. <I>Don't forget to call <TT>end()</TT> - or use the <A href=Fl_End.html#Fl_End><TT>Fl_End</TT></A> pseudo-class:</I> -<UL><PRE> -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! -} -</PRE></UL> - 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: -<UL><PRE> -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()); -} -</PRE></UL> - 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: -<UL><PRE> -int MyClass::handle(int event) { - if (Fl_Group::handle(event)) return 1; - ... handle events that children don't want ... -} -</PRE></UL> - -<P>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: - -<UL><PRE> -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 - } - } -} -</PRE></UL> -<TT>Fl_Group</TT> provides some protected methods to make drawing -easier: -<UL> -<LI><A href=#draw_child>draw_child</A></LI> -<LI><A href=#draw_outside_label>draw_outside_label</A></LI> -<LI><A href=#update_child>update_child</A></LI> -</UL> -<H4><A name=draw_child>void Fl_Group::draw_child(Fl_Widget&)</A></H4> - 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. -<H4><A name=draw_outside_label>void -Fl_Group::draw_outside_label(Fl_Widget&) const</A></H4> - 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>. -<H4><A name=update_child>void Fl_Group::update_child(Fl_Widget&)</A></H4> - 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. - -<H2>Cut and Paste Support</H2> -FLTK provides routines to cut and paste 8-bit text (in the future this -may be UTF-8) between applications: -<UL> -<LI><A href="Fl.html#Fl.paste"><TT>Fl::paste</TT></A></LI> -<LI><A href="Fl.html#Fl.selection"><TT>Fl::selection</TT></A></LI> -<LI><A href="Fl.html#Fl.selection_owner"><TT>Fl::selection_owner</TT></A></LI> -</UL> -It may be possible to cut/paste non-text data by using <A href=osissues.html#add_handler> -<TT>Fl::add_handler()</TT></A>. - -<H2>Drag And Drop Support</H2> - -FLTK provides routines to drag and drop 8-bit text between applications: - -<P>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>. - -<P>Drop attempts are handled via <A href="events.html#dnd">events</A>: -<UL> -<LI><TT>FL_DND_ENTER</TT></LI> -<LI><TT>FL_DND_DRAG</TT></LI> -<LI><TT>FL_DND_LEAVE</TT></LI> -<LI><TT>FL_DND_RELEASE</TT></LI> -<LI><TT>FL_PASTE</TT></LI> -</UL> - -<H2>Making a subclass of Fl_Window</H2> - -<P>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. - -<P>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: </P> - -<OL> - - <LI><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.</LI> - - <LI>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>.</LI> - -</OL> - -<P>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. - -</BODY> -</HTML> |