339 lines
13 KiB
HTML
339 lines
13 KiB
HTML
<HTML><BODY>
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<H1 ALIGN=RIGHT><A NAME=common>3 - Common Widgets and Attributes</A></H1>
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This chapter describes many of the widgets that are provided with FLTK
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and covers how to query and set the standard attributes.
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<H2>Buttons</H2>
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FLTK provides many types of buttons:
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<UL>
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<LI><TT>Fl_Button</TT> - A standard push button. </LI>
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<LI><TT>Fl_Check_Button</TT> - A button with a check box. </LI>
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<LI><TT>Fl_Light_Button</TT> - A push button with a light. </LI>
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<LI><TT>Fl_Repeat_Button</TT> - A push button that repeats when held. </LI>
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<LI><TT>Fl_Return_Button</TT> - A push button that is activated by the
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Enter key. </LI>
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<LI><TT>Fl_Round_Button</TT> - A button with a check circle. </LI>
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</UL>
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For all of these buttons you just need to include the corresponding <TT>
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<FL/Fl_xyz_Button.H></TT> header file. The constructor takes the
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bounding box of the button and optionally a label string:
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<UL>
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<PRE>
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Fl_Button *button = new Fl_Button(x, y, width, height, "label");
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Fl_Light_Button *lbutton = new Fl_Light_Button(x, y, width, height);
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Fl_Round_Button *rbutton = new Fl_Round_Button(x, y, width, height, "label");
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</PRE>
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</UL>
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Each button has an associated <A href=Fl_Button.html#Fl_Button.type><TT>
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type()</TT></A> which allows it to behave as a push button, toggle
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button, or radio button:
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<UL>
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<PRE>
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button->type(0);
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lbutton->type(FL_TOGGLE_BUTTON);
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rbutton->type(FL_RADIO_BUTTON);
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</PRE>
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</UL>
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For toggle and radio buttons, the <A href=Fl_Button.html#Fl_Button.value>
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<TT>value()</TT></A> method returns the current button state (0 = off,
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1 = on). The <A href=#Fl_Widget.set><TT>set()</TT></A> and <A href=#Fl_Widget.clear>
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<TT>clear()</TT></A> methods can be used on toggle buttons to turn a
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toggle button on or off, respectively. Radio buttons can be turned on
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with the <A href=#Fl_Widget.setonly><TT>setonly()</TT></A> method; this
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will also turn off other radio buttons in the current group.
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<H2>Text</H2>
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FLTK provides several text widgets for displaying and receiving text:
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<UL>
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<LI><TT>Fl_Input</TT> - A standard one-line text input field. </LI>
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<LI><TT>Fl_Output</TT> - A standard one-line text output field. </LI>
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<LI><TT>Fl_Multiline_Input</TT> - A standard multi-line text input
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field. </LI>
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<LI><TT>Fl_Multiline_Output</TT> - A standard multi-line text output
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field. </LI>
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</UL>
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The <TT>Fl_Output</TT> and <TT>Fl_Multiline_Output</TT> widgets allow
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the user to copy text from the output field but not change it.
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<P>The <A href=Fl_Input.html#Fl_Input.value><TT>value()</TT></A> method
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is used to get or set the string that is displayed: </P>
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<UL>
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<PRE>
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Fl_Input *input = new Fl_Input(x, y, width, height, "label");
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input->value("Now is the time for all good men...");
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</PRE>
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</UL>
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<H2>Valuators</H2>
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Unlike text widgets, valuators keep track of numbers instead of
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strings. FLTK provides the following valuators:
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<UL>
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<LI><TT>Fl_Counter</TT> - A widget with arrow buttons that shows the
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current value. </LI>
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<LI><TT>Fl_Dial</TT> - A round knob. </LI>
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<LI><TT>Fl_Roller</TT> - An SGI-like dolly widget. </LI>
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<LI><TT>Fl_Scrollbar</TT> - A standard scrollbar widget. </LI>
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<LI><TT>Fl_Slider</TT> - A scrollbar with a knob. </LI>
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<LI><TT>Fl_Value_Slider</TT> - A slider that shows the current value. </LI>
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</UL>
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The <A href=Fl_Valuator.html#Fl_Valuator.value><TT>value()</TT></A>
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method gets and sets the current value of the widget. The <A href=Fl_Valuator.html#Fl_Valuator.minimum>
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<TT>minimum()</TT></A> and <A href=Fl_Valuator.html#Fl_Valuator.maximum><TT>
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maximum</TT></A> methods set the range of values that are reported by
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the widget.
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<H2>Groups</H2>
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The <TT>Fl_Group</TT> widget class is used as a general purpose
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"container" widget. Besides grouping radio buttons, the groups are
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used to encapsulate windows, tabs, and scrolled windows. The following
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group classes are available with FLTK:
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<UL>
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<LI><TT>Fl_Double_Window</TT> - A double-buffered window on the screen. </LI>
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<LI><TT>Fl_Gl_Window</TT> - An OpenGL window on the screen. </LI>
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<LI><TT>Fl_Group</TT> - The base container class; can be used to group
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any widgets together. </LI>
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<LI><TT>Fl_Scroll</TT> - A scrolled window area. </LI>
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<LI><TT>Fl_Tabs</TT> - Displays child widgets as tabs. </LI>
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<LI><TT>Fl_Window</TT> - A window on the screen. </LI>
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</UL>
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<H2>Setting the Size and Position of Widgets</H2>
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The size and position of widgets is usually set when you create them.
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You can change this at any time using the <TT>position</TT>, <TT>
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resize()</TT>, and <TT>size</TT> methods:
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<UL>
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<PRE>
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button->position(x, y);
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group->resize(x, y, width, height);
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window->size(width, height);
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</PRE>
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</UL>
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Changing the size or position of a widget will cause a redraw of that
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widget and its children.
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<H2><A NAME=colors>Colors</A></H2>
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FLTK manages a virtual color palette of "standard" colors. The
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standard colors are:
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<UL>
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<LI><TT>FL_BLACK</TT></LI>
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<LI><TT>FL_RED</TT></LI>
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<LI><TT>FL_GREEN</TT></LI>
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<LI><TT>FL_YELLOW</TT></LI>
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<LI><TT>FL_BLUE</TT></LI>
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<LI><TT>FL_MAGENTA</TT></LI>
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<LI><TT>FL_CYAN</TT></LI>
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<LI><TT>FL_WHITE</TT></LI>
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<LI><TT>FL_GRAY</TT></LI>
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</UL>
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The widget color can be set using the <TT>color()</TT> method:
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<UL>
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<PRE>
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button->color(FL_RED);
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</PRE>
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</UL>
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Similarly, the label color can be set using the <TT>labelcolor()</TT>
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method:
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<UL>
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<PRE>
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button->labelcolor(FL_WHITE);
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</PRE>
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</UL>
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<H2><A NAME=boxtypes>Box Types</A></H2>
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<P>The type <TT>Fl_Boxtype</TT> stored and returned in <A href=Fl_Widget.html#Fl_Widget.box>
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<TT>Fl_Widget::box()</TT></A> is an enumeration defined in <A href=enumerations.html#enumerations>
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<TT><Enumerations.H></TT></A>:
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<P ALIGN=CENTER><IMG src=./boxtypes.gif width=80%></P>
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<P><TT>FL_NO_BOX</TT> means nothing is drawn at all, so whatever is
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already on the screen remains. The <TT>FL_..._FRAME</TT> types only
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draw their edges, leaving the center unchanged. In the above diagram
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the blue color is the area that is not drawn by the box. </P>
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<H3>Making your own Boxtypes</H3>
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You can define your own boxtypes by making a small function that draws
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the box and adding a pointer to it to a table of boxtypes.
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<H4>The Drawing Function</H4>
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The drawing function is passed the bounding box and background color
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for the widget:
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<UL>
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<PRE>
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void xyz_draw(int x, int y, int w, int h, Fl_Color c) {
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...
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}
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</PRE>
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</UL>
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A simple drawing function might fill a rectangle with the given color
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and then draw a black outline:
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<UL>
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<PRE>
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void xyz_draw(int x, int y, int w, int h, Fl_Color c) {
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fl_color(c);
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fl_rectf(x, y, w, h);
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fl_color(FL_BLACK);
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fl_rect(x, y, w, h);
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}
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</PRE>
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</UL>
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<H4>Adding Your Box Type</H4>
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The <TT>Fl::set_boxtype()</TT> method adds or replaces the specified
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box type:
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<UL>
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<PRE>
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#define XYZ_BOX FL_FREE_BOXTYPE
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Fl::set_boxtype(XYZ_BOX, xyz_draw, 1, 1, 2, 2);
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</PRE>
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</UL>
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The last 4 arguments to <TT>Fl::set_boxtype()</TT> are the offsets for
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the bounding box that should be subtracted when drawing the label
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inside the box.
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<H2><A NAME=labels>Labels and Label Types</A></H2>
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The <TT>label()</TT>, <TT>align</TT>, <TT>labelfont()</TT>, <TT>
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labelsize()</TT>, and <TT>labeltype()</TT> methods control the labeling
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of widgets.
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<H3>label()</H3>
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The <TT>label()</TT> method sets the string that is displayed for the
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label. For the <TT>FL_SYMBOL_LABEL</TT> and image label types the
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string contains the actual symbol or image data.
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<H3>align()</H3>
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The <TT>align()</TT> method positions the label. The following
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constants are defined:
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<UL>
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<LI><TT>FL_ALIGN_CENTER</TT> - center the label in the widget. </LI>
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<LI><TT>FL_ALIGN_TOP</TT> - align the label at the top of the widget. </LI>
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<LI><TT>FL_ALIGN_BOTTOM</TT> - align the label at the bottom of the
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widget. </LI>
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<LI><TT>FL_ALIGN_LEFT</TT> - align the label to the left of the widget. </LI>
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<LI><TT>FL_ALIGN_RIGHT</TT> - align the label to the right of the
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widget. </LI>
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<LI><TT>FL_ALIGN_INSIDE</TT> - align the label inside the widget. </LI>
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<LI><TT>FL_ALIGN_CLIP</TT> - clip the label to the widget's bounding
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box. </LI>
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<LI><TT>FL_ALIGN_WRAP</TT> - wrap the label text as needed. </LI>
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</UL>
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<H3>labeltype()</H3>
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The <TT>labeltype()</TT> method sets the type of the label. The
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following standard label types are included:
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<UL>
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<LI><TT>FL_NORMAL_LABEL</TT> - draws the text. </LI>
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<LI><TT>FL_NO_LABEL</TT> - does nothing </LI>
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<LI><TT>FL_SYMBOL_LABEL</TT> - draws "@xyz" labels, see "<A href=#symbols>
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Symbol Labels</A>" </LI>
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<LI><TT>FL_SHADOW_LABEL</TT> - draws a drop shadow under the text </LI>
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<LI><TT>FL_ENGRAVED_LABEL</TT> - draws edges as though the text is
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engraved </LI>
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<LI><TT>FL_EMBOSSED_LABEL</TT> - draws edges as thought the text is
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raised </LI>
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</UL>
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To make bitmaps or pixmaps you use a method on the <A href=drawing.html#Fl_Bitmap>
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<TT>Fl_Bitmap</TT></A> or <A href=drawing.html#Fl_Pixmap><TT>Fl_Pixmap</TT>
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</A> objects.
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<H4>Making Your Own Label Types</H4>
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Label types are actually indexes into a table of functions to draw
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them. The primary purpose of this is to let you reuse the <TT>label()</TT>
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pointer as a pointer to arbitrary data such as a bitmap or pixmap. You
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can also use this to draw the labels in ways inaccessible through the <TT>
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fl_font</TT> mechanisim (e.g. <TT>FL_ENGRAVED_LABEL</TT>) or with
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program-generated letters or symbology.
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<H5>Label Type Functions</H5>
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To setup your own label type you will need to write two functions to
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draw and measure the label. The draw function is called with a pointer
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to a <A href=#Fl_Label><TT>Fl_Label</TT></A> structure containing the
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label information, the bounding box for the label, and the label
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alignment:
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<UL>
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<PRE>
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void xyz_draw(Fl_Label *label, int x, int y, int w, int h, Fl_Align align) {
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...
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}
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</PRE>
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</UL>
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The label should be drawn <I>inside</I> this bounding box, even if <TT>
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FL_ALIGN_INSIDE</TT> is not enabled. The function is not called if the
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label value is <TT>NULL</TT>.
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<P>The measure function is called with a pointer to a <A href=#Fl_Label><TT>
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Fl_Label</TT></A> structure and references to the width and height: </P>
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<UL>
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<PRE>
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void xyz_measure(Fl_Label *label, int w int h {
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...
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}
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</PRE>
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</UL>
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It should measure the size of the label and set <TT>w</TT> and <TT>h</TT>
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to the size it will occupy.
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<H5>Adding Your Label Type</H5>
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The <TT>Fl::set_labeltype</TT> method creates a label type using your
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draw and measure functions:
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<UL>
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<PRE>
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#define XYZ_LABEL FL_FREE_LABELTYPE
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Fl::set_labeltype(XYZ_LABEL, xyz_draw, xyz_measure);
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</PRE>
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</UL>
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The label type number <TT>n</TT> can be any integer value starting at
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the constant <TT>FL_FREE_LABELTYPE</TT>. Once you have added the label
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type you can use the <TT>labeltype()</TT> method to select your label
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type.
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<P>The <TT>Fl::set_labeltype</TT> method can also be used to overload
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an existing label type such as <TT>FL_NORMAL_LABEL</TT>. </P>
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<H4><A name=symbols>Symbol Labels</A></H4>
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<P>The <TT>FL_SYMBOL_LABEL</TT> label type uses the <TT>label()</TT>
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string to look up a small drawing procedure in a hash table. For
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historical reasons the string always starts with '@', if it starts with
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something else (or the symbol is not found) the label is drawn
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normally:
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<CENTER><IMG src=./symbols.gif></CENTER>
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The @ sign may be followed by the following optional "formatting"
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characters, in this order: </P>
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<UL>
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<LI>'#' forces square scaling, rather than distortion to the widget's
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shape. </LI>
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<LI>+[1-9] or -[1-9] tweaks the scaling a little bigger or smaller. </LI>
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<LI>[1-9] - rotates by a multiple of 45 degrees. '6' does nothing,
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the others point in the direction of that key on a numeric keypad. </LI>
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</UL>
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<H2>Callbacks</H2>
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Callbacks are functions that are called when the value of a widget
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changes. A callback function is sent a <TT>Fl_Widget</TT> pointer of
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the widget that changed and optionally a pointer to data of some sort:
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<UL>
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<PRE>
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void xyz_callback(Fl_Widget *w, void *data) {
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...
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}
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</PRE>
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</UL>
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The <TT>callback()</TT> method sets the callback function for a
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widget. You can optionally pass a pointer to some data needed for the
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callback:
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<UL>
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<PRE>
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int xyz_data;
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button->callback(xyz_callback, data);
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</PRE>
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</UL>
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Normally callbacks are performed only when the value of the widget
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changes. You can change this using the <A href=Fl_Widget.html#Fl_Widget.when>
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<TT>when()</TT></A> method:
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<UL>
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<PRE>
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button->when(FL_WHEN_NEVER);
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button->when(FL_WHEN_CHANGED);
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button->when(FL_WHEN_RELEASE);
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button->when(FL_WHEN_RELEASE_ALWAYS);
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button->when(FL_WHEN_ENTER_KEY);
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button->when(FL_WHEN_ENTER_KEY_ALWAYS);
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button->when(FL_WHEN_CHANGED | FL_WHEN_NOT_CHANGED);
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</PRE>
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</UL>
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<H2>Shortcuts</H2>
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Shortcuts are key sequences that activate widgets (usually buttons or
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menu items). The <TT>shortcut()</TT> method registers a shortcut for a
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widget:
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<UL>
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<PRE>
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button->shortcut(FL_Enter);
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button->shortcut(FL_SHIFT + 'b');
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button->shortcut(FL_CTRL + 'b');
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button->shortcut(FL_ALT + 'b');
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button->shortcut(FL_CTRL + FL_ALT + 'b');
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</PRE>
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</UL>
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The shortcut value is the key event value (the ASCII value or one of
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the special keys like <TT>FL_Enter</TT>) combined with any modifiers
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(like shift, alt, and control). </BODY></HTML>
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