FLTK学习笔记三

Drawing Things in FLTK

There are only certain places you can execute drawing code in FLTK. Calling these functions at other places will result in undefined behavior!
• The most common place is inside the virtual Fl_Widget::draw() method. To write code here, you must subclass one of the existing Fl_Widget classes and implement your own version of draw().
• You can also create custom boxtypes and labeltypes. These involve writing small procedures that can be called by existing Fl_Widget::draw() methods. These "types" are identified by an 8-bit index that is stored in the widget’s box(), labeltype(), and possibly other properties.
• You can call Fl_Window::make_current() to do incremental update of a widget. Use Fl_Widget::window() to find the window.

Handling Events

Events are identified by the integer argument passed to a handle() method that overrides the Fl_Widget::handle() virtual method. Other information about the most recent event is stored in static locations and acquired by calling the Fl::event_*() methods.

Example:

CXX = $(shell /cygdrive/d/bin/fltk/bin/fltk-config --cxx)DEBUG = -gCXXFLAGS = $(shell /cygdrive/d/bin/fltk/bin/fltk-config --cxxflags ) -I.LDFLAGS = $(shell /cygdrive/d/bin/fltk/bin/fltk-config --ldflags )LDSTATIC = $(shell /cygdrive/d/bin/fltk/bin/fltk-config --ldstaticflags)FLTKPREFIX = $(shell /cygdrive/d/bin/fltk/bin/fltk-config --prefix)LINK = $(CXX)TARGET = helloOBJS = hello.oSRCS = hello.cxx.SUFFIXES: .o .cxx%.o: %.cxx$(CXX) $(CXXFLAGS) $(DEBUG) -c $<all: $(OBJS)$(LINK) -o $(TARGET) $(OBJS) $(LDSTATIC)$(TARGET): $(OBJS)hello.o: hello.cxxclean:rm -f hello.o 2> /dev/nullrm -f $(TARGET) 2> /dev/null

 

#include <FL/Fl.H>#include <FL/Fl_Window.H>#include <FL/Fl_Box.H>#include <FL/fl_draw.H>class MyDraw: public Fl_Widget{    void draw(){    fl_color(FL_RED);    fl_rectf(x(),y(),w(),h());    }public:    MyDraw(int X, int Y, int W, int H): Fl_Widget(X,Y,W,H){}};int main(int argc, char **argv) {    Fl_Window *window = new Fl_Window(340,180);    Fl_Box *box = new Fl_Box(20,40,300,100,"Hello, World!");    box->box(FL_UP_BOX);    box->labelfont(FL_BOLD+FL_ITALIC);    box->labelsize(36);    box->labeltype(FL_SHADOW_LABEL);    MyDraw *draw = new MyDraw(10,10,20,30);    window->end();    window->show(argc, argv);    return Fl::run();}