From 09cfc1a1ea00f7edf394e647f1f32e5b0913f564 Mon Sep 17 00:00:00 2001 From: Fabien Costantini Date: Fri, 17 Oct 2008 11:22:35 +0000 Subject: Removing current broken history documentation/src dir. git-svn-id: file:///fltk/svn/fltk/branches/branch-1.3@6451 ea41ed52-d2ee-0310-a9c1-e6b18d33e121 --- documentation/src/subclassing.dox | 531 -------------------------------------- 1 file changed, 531 deletions(-) delete mode 100644 documentation/src/subclassing.dox (limited to 'documentation/src/subclassing.dox') 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 subclassing an existing FLTK widget, -typically Fl_Widget for controls and Fl_Group 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. Fl_Group is the -main composite widget widget class in FLTK, and all of the other composite -widgets (Fl_Pack, Fl_Scroll, Fl_Tabs, -Fl_Tile, and Fl_Window) 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 Fl_Button 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 Fl_Widget or any -subclass of Fl_Widget. Fl_Widget 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 -FLUID -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 - -Fl_Widget's protected constructor sets x(), y(), -w(), h(), and label() 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 Fl_Widget::clear_visible -\li Fl_Widget::damage -\li Fl_Widget::draw_box -\li Fl_Widget::draw_focus -\li Fl_Widget::draw_label -\li Fl_Widget::set_flag -\li Fl_Widget::set_visible -\li Fl_Widget::test_shortcut -\li Fl_Widget::type - - -void Fl_Widget::damage(uchar mask)
-void Fl_Widget::damage(uchar mask, int x, int y, int w, int h)
-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 damage(). Your -draw() routine can examine these bits to limit what it is -drawing. The public method Fl_Widget::redraw() simply does - Fl_Widget::damage(FL_DAMAGE_ALL), but the implementation of -your widget can call the private damage(n). - -\par -The second form indicates that a region is damaged. If only these -calls are done in a window (no calls to damage(n)) 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 damage() unless this is a Fl_Window widget. - -\par -The third form returns the bitwise-OR of all damage(n) -calls done since the last draw(). - -\par -When redrawing your widgets you should look at the damage bits to -see what parts of your widget need redrawing. The handle() -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 - - -void Fl_Widget::draw_box() const
-void Fl_Widget::draw_box(Fl_Boxtype b, ulong c) const - -\par -The first form draws this widget's box(), using the -dimensions of the widget. The second form uses b as the box -type and c as the color for the box. - - -void Fl_Widget::draw_focus() const
-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. - - -void Fl_Widget::draw_label() const
-void Fl_Widget::draw_label(int x, int y, int w, int h) const
-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 draw() 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 -FL_ALIGN_INSIDE has been forced on so the label will appear inside -the passed bounding box. This is designed for parent groups to draw -labels with. - - -void Fl_Widget::set_flag(SHORTCUT_LABEL) - -\par -Modifies draw_label() so that '&' characters cause an underscore -to be printed under the next letter. - - - -void Fl_Widget::set_visible()
-void Fl_Widget::clear_visible() - -\par -Fast inline versions of Fl_Widget::hide() and -Fl_Widget::show(). These do not send the FL_HIDE and -FL_SHOW events to the widget. - - -int Fl_Widget::test_shortcut() const
-static int Fl_Widget::test_shortcut(const char *s) - -\par -The first version tests Fl_Widget::label() against the -current event (which should be a FL_SHORTCUT event). If the -label contains a '&' character and the character after it matches the key -press, this returns true. This returns false if the SHORTCUT_LABEL -flag is off, if the label is NULL 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. - - -uchar Fl_Widget::type() const
-void Fl_Widget::type(uchar t) - -\par -The property Fl_Widget::type() can return an arbitrary 8-bit -identifier, and can be set with the protected method type(uchar t). -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 type() use a unique value. These unique values must -be greater than the symbol FL_RESERVED_TYPE (which is 100). -Look through the header files for FL_RESERVED_TYPE to find an -unused number. If you make a subclass of Fl_Window -you must use FL_WINDOW + n (n must be in the -range 1 to 7). - - -\section subclassing_events Handling Events - -The virtual method int Fl_Widget::handle(int event) is called -to handle each event passed to the widget. It can: - -\li Change the state of the widget. -\li Call - Fl_Widget::redraw() - if the widget needs to be redisplayed. -\li Call - Fl_Widget::damage(n) - if the widget needs a partial-update (assuming you provide support for - this in your - Fl_Widget::draw() - method). -\li Call - Fl_Widget::do_callback() - if a callback should be generated. -\li Call Fl_Widget::handle() 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 -Fl::event_*() -functions. This information remains valid until another event is -handled. - -Here is a sample handle() 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 handle() method -uses the event. If you return zero, the parent widget will try -sending the event to another widget. - - -\section subclassing_drawing Drawing the Widget - -The draw() virtual method is called when FLTK wants -you to redraw your widget. It will be called if and only if -damage() is non-zero, and damage() will be -cleared to zero after it returns. The draw() method -should be declared protected so that it can't be called from -non-drawing code. - -The damage() value contains the bitwise-OR of all -the damage(n) 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 -FL_DAMAGE_ALL bit if it thinks the entire widget must -be redrawn, e.g. for an expose event. - -Expose events (and the above damage(b,x,y,w,h)) will cause -draw() to be called with FLTK's -clipping turned on. You can greatly speed up redrawing in some -cases by testing fl_not_clipped(x,y,w,h) or fl_clip_box(...) -and skipping invisible parts. - -Besides the protected methods described above, FLTK provides a large -number of basic drawing functions, which are described -below. - -\section subclassing_resizing Resizing the Widget - -The resize(int x, int y, int w, int h) method is called when -the widget is being resized or moved. The arguments are the new -position, width, and height. x(), y(), w(), -and h() still remain the old size. You must call resize() -on your base class with the same arguments to get the widget size to -actually change. - -This should not call redraw(), at least if only the -x() and y() change. This is because composite widgets like -Fl_Scroll -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 -Fl_Group. -It is possible to make a composite object that is not a subclass of -Fl_Group, but you'll have to duplicate the code in Fl_Group -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 -add()ed to the group, since the Fl_Group constructor does -Fl_Group::begin(). -Don't forget to call Fl_Group::end() or use the Fl_End pseudo-class: - -\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 parent() -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 handle() method, you can quickly pass all the -events to the children using the Fl_Group::handle() method. -You don't need to override handle() 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 draw() you need to draw all the -children. If redraw() or damage() is called -on a child, damage(FL_DAMAGE_CHILD) is done to the -group, so this bit of damage() 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 - -Fl_Group provides some protected methods to make drawing -easier: - -\li draw_child -\li draw_outside_label -\li update_child - - -void Fl_Group::draw_child(Fl_Widget&) - -\par -This will force the child's damage() bits all to one and call -draw() on it, then clear the damage(). 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 visible() or if it is -clipped. - - -void Fl_Group::draw_outside_label(Fl_Widget&) const - -\par -Draw the labels that are not drawn by -draw_label(). If you want more control over the label -positions you might want to call child->draw_label(x,y,w,h,a). - - -void Fl_Group::update_child(Fl_Widget&) - -\par -Draws the child only if its damage() 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 visible() -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 Fl::paste -\li Fl::selection -\li Fl::selection_owner - -It may be possible to cut/paste non-text data by using -Fl::add_handler(). - -\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 -Fl::dnd(). - -Drop attempts are handled via events: - -\li FL_DND_ENTER -\li FL_DND_DRAG -\li FL_DND_LEAVE -\li FL_DND_RELEASE -\li FL_PASTE - -\section subclassing_fl_window Making a subclass of Fl_Window - -You may want your widget to be a subclass of -Fl_Window, Fl_Double_Window, or -FL_Gl_Window. 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 Fl_Windowis almost exactly like -subclassing Fl_Group, and in fact you can easily -switch a subclass back and forth. Watch out for the following -differences: - --# Fl_Window is a subclass of Fl_Group so - make sure your constructor calls end() - unless you actually want children added to your window. - --# When handling events and drawing, the upper-left corner is at - 0,0, not x(),y() as in other Fl_Widget's. - For instance, to draw a box around the widget, call - draw_box(0, 0, w(), h()), rather than - draw_box(x(), y(), w(), h()). - -You may also want to subclass Fl_Window in order to -get access to different visuals or to change other attributes of -the windows. See -"Appendix F - Operating System Issues" -for more information. - -\htmlonly -
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