2001-11-27 00:40:14 +03:00
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2002-02-13 06:33:53 +03:00
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<H1 ALIGN=RIGHT><A NAME="common">3 - Common Widgets and Attributes</A></H1>
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2001-11-27 00:40:14 +03:00
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<P>This chapter describes many of the widgets that are provided
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with FLTK and covers how to query and set the standard
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attributes.</P>
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1998-12-29 17:21:17 +03:00
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<H2>Buttons</H2>
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2001-11-27 00:40:14 +03:00
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<P>FLTK provides many types of buttons:</P>
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1999-01-13 22:28:54 +03:00
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<UL>
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2001-11-27 00:40:14 +03:00
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<LI><A HREF="Fl_Button.html"><TT>Fl_Button</TT></A> - A
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standard push button.</LI>
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<LI><A HREF="Fl_Check_Button.html"><TT>Fl_Check_Button</TT></A> -
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A button with a check box.</LI>
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<LI><A HREF="Fl_Light_Button.html"><TT>Fl_Light_Button</TT></A> -
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A push button with a light.</LI>
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<LI><A HREF="Fl_Repeat_Button.html"><TT>Fl_Repeat_Button</TT></A> -
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A push button that repeats when held.</LI>
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<LI><A HREF="Fl_Return_Button.html"><TT>Fl_Return_Button</TT></A> -
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A push button that is activated by the <KBD>Enter</KBD> key.</LI>
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<LI><A HREF="Fl_Round_Button.html"><TT>Fl_Round_Button</TT></A> -
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A button with a radio circle.</LI>
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1999-01-13 22:28:54 +03:00
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</UL>
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2001-11-27 00:40:14 +03:00
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<P ALIGN="CENTER"><IMG SRC="buttons.gif" ALT="FLTK Buttons"><BR>
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Figure 3-1: FLTK Button Widgets</P>
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<P>All of these buttons just need the corresponding
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<TT><FL/Fl_xyz_Button.H></TT> header file. The constructor
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takes the bounding box of the button and optionally a label
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string:</P>
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<UL><PRE>
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1999-01-13 22:28:54 +03:00
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Fl_Button *button = new Fl_Button(x, y, width, height, "label");
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1998-12-29 17:21:17 +03:00
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Fl_Light_Button *lbutton = new Fl_Light_Button(x, y, width, height);
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1999-01-13 22:28:54 +03:00
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Fl_Round_Button *rbutton = new Fl_Round_Button(x, y, width, height, "label");
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2001-11-27 00:40:14 +03:00
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</PRE></UL>
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<P>Each button has an associated
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<A href="Fl_Button.html#Fl_Button.type"><TT>type()</TT></A>
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which allows it to behave as a push button, toggle button, or
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radio button:</P>
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<UL><PRE>
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button->type(FL_NORMAL_BUTTON);
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lbutton->type(FL_TOGGLE_BUTTON);
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rbutton->type(FL_RADIO_BUTTON);
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2001-11-27 00:40:14 +03:00
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</PRE></UL>
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<P>For toggle and radio buttons, the
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<A href="Fl_Button.html#Fl_Button.value"><TT>value()</TT></A>
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method returns the current button state (0 = off, 1 = on). The
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<A href="Fl_Button.html#Fl_Button.set"><TT>set()</TT></A> and
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<A href="Fl_Button.html#Fl_Button.clear"><TT>clear()</TT></A>
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methods can be used on toggle buttons to turn a toggle button
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on or off, respectively. Radio buttons can be turned on with
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the
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<A href="Fl_Button.html#Fl_Button.setonly"><TT>setonly()</TT></A>
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method; this will also turn off other radio buttons in the same
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group.</P>
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1998-12-29 17:21:17 +03:00
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<H2>Text</H2>
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2001-11-27 00:40:14 +03:00
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<P>FLTK provides several text widgets for displaying and receiving text:</P>
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1999-01-13 22:28:54 +03:00
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<UL>
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2001-11-27 00:40:14 +03:00
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<LI><A HREF="Fl_Input.html"><TT>Fl_Input</TT></A> - A
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one-line text input field.</LI>
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<LI><A HREF="Fl_Output.html"><TT>Fl_Output</TT></A> - A
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one-line text output field.</LI>
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<LI><A HREF="Fl_Multiline_Input.html"><TT>Fl_Multiline_Input</TT></A>
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- A multi-line text input field. </LI>
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<LI><A HREF="Fl_Multiline_Output.html"><TT>Fl_Multiline_Output</TT></A>
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- A multi-line text output field.</LI>
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<LI><A HREF="Fl_Text_Display.html"><TT>Fl_Text_Display</TT></A>
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- A multi-line text display widget.</LI>
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<LI><A HREF="Fl_Text_Editor.html"><TT>Fl_Text_Editor</TT></A> -
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A multi-line text editing widget. </LI>
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<LI><A HREF="Fl_Help_View.html"><TT>Fl_Help_View</TT></A> - A
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HTML text display widget.</LI>
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1999-01-13 22:28:54 +03:00
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</UL>
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2001-11-27 00:40:14 +03:00
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<P>The <TT>Fl_Output</TT> and <TT>Fl_Multiline_Output</TT>
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widgets allow the user to copy text from the output field but
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not change it.</P>
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<P>The <A href="Fl_Input.html#Fl_Input.value"><TT>value()</TT></A>
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method is used to get or set the string that is displayed:</P>
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<UL><PRE>
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1999-01-13 22:28:54 +03:00
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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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2001-11-27 00:40:14 +03:00
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</PRE></UL>
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<P>The string is copied to the widget's own storage when you set
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the <tt>value()</tt> of the widget.</P>
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<P>The <TT>Fl_Text_Display</TT> and <TT>Fl_Text_Editor</TT>
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widgets use an associated <TT>Fl_Text_Buffer</TT> class for the
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value, instead of a simple string.</P>
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1998-12-29 17:21:17 +03:00
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<H2>Valuators</H2>
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2001-11-29 22:24:00 +03:00
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<P>Unlike text widgets, valuators keep track of numbers instead of
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strings. FLTK provides the following valuators:</P>
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1999-01-13 22:28:54 +03:00
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<UL>
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2001-11-27 00:40:14 +03:00
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2001-11-29 22:24:00 +03:00
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<LI><A HREF="Fl_Counter.html"><TT>Fl_Counter</TT></A> - A widget with arrow buttons that shows the
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current value. </LI>
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<LI><A HREF="Fl_Dial.html"><TT>Fl_Dial</TT></A> - A round knob. </LI>
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<LI><A HREF="Fl_Roller.html"><TT>Fl_Roller</TT></A> - An SGI-like dolly widget. </LI>
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<LI><A HREF="Fl_Scrollbar.html"><TT>Fl_Scrollbar</TT></A> - A standard scrollbar widget. </LI>
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<LI><A HREF="Fl_Slider.html"><TT>Fl_Slider</TT></A> - A scrollbar with a knob. </LI>
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<LI><A HREF="Fl_Value_Slider.html"><TT>Fl_Value_Slider</TT></A> - A slider that shows the current value. </LI>
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1999-01-13 22:28:54 +03:00
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</UL>
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<P ALIGN="CENTER"><IMG SRC="valuators.gif" ALT="FLTK Valuators"><BR>
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<I>Figure 3-2: FLTK valuator widgets</I></P>
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<P>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
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<A href="Fl_Valuator.html#Fl_Valuator.minimum"><TT>minimum()</TT></A>
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and <A href="Fl_Valuator.html#Fl_Valuator.maximum"><TT>maximum()</TT></A>
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methods set the range of values that are reported by the
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widget.</P>
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1998-12-29 17:21:17 +03:00
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<H2>Groups</H2>
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<P>The <TT>Fl_Group</TT> widget class is used as a general
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purpose "container" widget. Besides grouping radio
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buttons, the groups are used to encapsulate windows, tabs, and
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scrolled windows. The following group classes are available
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with FLTK:</P>
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1999-01-13 22:28:54 +03:00
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<UL>
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<LI><A HREF="Fl_Double_Window.html"><TT>Fl_Double_Window</TT></A> - A double-buffered window on the screen. </LI>
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<LI><A HREF="Fl_Gl_Window.html"><TT>Fl_Gl_Window</TT></A> - An OpenGL window on the screen. </LI>
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2001-11-29 22:24:00 +03:00
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<LI><A HREF="Fl_Group.html"><TT>Fl_Group</TT></A> - The base container class; can be used to group
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any widgets together. </LI>
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2002-01-15 05:17:19 +03:00
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<LI><A HREF="Fl_Pack.html"><TT>Fl_Pack</TT></A> - A collection of widgets that are packed into the group area.</LI>
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<LI><A HREF="Fl_Scroll.html"><TT>Fl_Scroll</TT></A> - A scrolled window area. </LI>
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<LI><A HREF="Fl_Tabs.html"><TT>Fl_Tabs</TT></A> - Displays child widgets as tabs. </LI>
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<LI><A HREF="Fl_Tile.html"><TT>Fl_Tile</TT></A> - A tiled window area.</LI>
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<LI><A HREF="Fl_Window.html"><TT>Fl_Window</TT></A> - A window on the screen. </LI>
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1999-01-13 22:28:54 +03:00
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</UL>
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2001-11-27 00:40:14 +03:00
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1998-12-29 17:21:17 +03:00
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<H2>Setting the Size and Position of Widgets</H2>
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2001-11-27 00:40:14 +03:00
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<P>The size and position of widgets is usually set when you
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create them. You can access them with the <tt>x()</tt>,
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<tt>y()</tt>, <tt>w()</tt>, and <tt>h()</tt> methods.</P>
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<P>You can change the size and position by using the
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<TT>position()</TT>, <TT> resize()</TT>, and <TT>size()</TT>
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methods:</P>
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<UL><PRE>
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1999-01-13 22:28:54 +03:00
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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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2001-11-27 00:40:14 +03:00
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</PRE></UL>
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<P>If you change a widget's size or position after it is
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displayed you will have to call <tt>redraw()</tt> on the
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widget's parent.</P>
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<H2><A NAME="colors">Colors</A></H2>
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<P>FLTK stores the colors of widgets as an 32-bit unsigned
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number that is either an index into a color palette of 256
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colors or a 24-bit RGB color. The color palette is <i>not</i>
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the X or WIN32 colormap, but instead is an internal table with
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fixed contents.</P>
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<P>There are symbols for naming some of the more common colors:</P>
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1999-01-13 22:28:54 +03:00
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<UL>
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<LI><TT>FL_BLACK</TT> (this is the default label color)</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> (this is the default background color of text widgets)</LI>
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<LI><TT>FL_GRAY</TT> (this is the default background color of most widgets)</LI>
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</UL>
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2001-11-27 00:40:14 +03:00
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2002-01-15 05:17:19 +03:00
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<P>RGB colors can be set using the <A HREF="enumerations.html#fl_rgb_color"><TT>fl_rgb_color()</TT></A>
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function:</P>
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<UL><PRE>
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Fl_Color c = fl_rgb_color(85, 170, 255);
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</PRE></UL>
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<P>The widget color is set using the <TT>color()</TT> method:</P>
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<UL><PRE>
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1999-01-13 22:28:54 +03:00
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button->color(FL_RED);
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2001-11-27 00:40:14 +03:00
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</PRE></UL>
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<P>Similarly, the label color is set using the <TT>labelcolor()</TT>
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method:</P>
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<UL><PRE>
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1999-01-13 22:28:54 +03:00
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button->labelcolor(FL_WHITE);
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2001-11-27 00:40:14 +03:00
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</PRE></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
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<A href="Fl_Widget.html#Fl_Widget.box"><TT>Fl_Widget::box()</TT></A>
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2002-02-13 06:33:53 +03:00
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is an enumeration defined in <A href="enumerations.html#Enumerations"><TT><Enumerations.H></TT></A>.
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Figure 3-3 shows the standard box types included with FLTK.</P>
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<P ALIGN="CENTER"><IMG src="boxtypes.gif" ALT="FLTK Box Types"><BR>
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<I>Figure 3-3: FLTK box types</I></P>
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2001-11-29 22:24:00 +03:00
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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 interior unchanged. The blue color in
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Figure 3-3 is the area that is not drawn by the frame types.</P>
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<H3>Making Your Own Boxtypes</H3>
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2001-11-29 22:24:00 +03:00
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<P>You can define your own boxtypes by making a small function that draws
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the box and adding it to the table of boxtypes.</P>
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|
|
<CENTER><TABLE WIDTH="80%" BORDER="1" CELLPADDING="5" CELLSPACING="0" BGCOLOR="#cccccc">
|
|
|
|
|
<TR>
|
|
|
|
|
<TD><B>Note:</B>
|
|
|
|
|
<P>This interface has changed in FLTK 2.0!</P>
|
|
|
|
|
</TD>
|
|
|
|
|
</TR>
|
|
|
|
|
</TABLE></CENTER>
|
|
|
|
|
|
1998-12-29 17:21:17 +03:00
|
|
|
<H4>The Drawing Function</H4>
|
2001-11-27 00:40:14 +03:00
|
|
|
|
2001-11-29 22:24:00 +03:00
|
|
|
<P>The drawing function is passed the bounding box and background color
|
2001-11-27 00:40:14 +03:00
|
|
|
for the widget:</P>
|
|
|
|
|
|
|
|
|
|
<UL><PRE>
|
1998-12-29 17:21:17 +03:00
|
|
|
void xyz_draw(int x, int y, int w, int h, Fl_Color c) {
|
|
|
|
|
...
|
|
|
|
|
}
|
2001-11-27 00:40:14 +03:00
|
|
|
</PRE></UL>
|
|
|
|
|
|
|
|
|
|
<P>A simple drawing function might fill a rectangle with the
|
|
|
|
|
given color and then draw a black outline:</P>
|
|
|
|
|
|
|
|
|
|
<UL><PRE>
|
1998-12-29 17:21:17 +03:00
|
|
|
void xyz_draw(int x, int y, int w, int h, Fl_Color c) {
|
|
|
|
|
fl_color(c);
|
|
|
|
|
fl_rectf(x, y, w, h);
|
|
|
|
|
fl_color(FL_BLACK);
|
|
|
|
|
fl_rect(x, y, w, h);
|
|
|
|
|
}
|
2001-11-27 00:40:14 +03:00
|
|
|
</PRE></UL>
|
|
|
|
|
|
1998-12-29 17:21:17 +03:00
|
|
|
<H4>Adding Your Box Type</H4>
|
2001-11-27 00:40:14 +03:00
|
|
|
|
|
|
|
|
<P>The <TT>Fl::set_boxtype()</TT> method adds or replaces the
|
|
|
|
|
specified box type:</P>
|
|
|
|
|
|
|
|
|
|
<UL><PRE>
|
1998-12-29 17:21:17 +03:00
|
|
|
#define XYZ_BOX FL_FREE_BOXTYPE
|
|
|
|
|
|
|
|
|
|
Fl::set_boxtype(XYZ_BOX, xyz_draw, 1, 1, 2, 2);
|
2001-11-27 00:40:14 +03:00
|
|
|
</PRE></UL>
|
|
|
|
|
|
|
|
|
|
<P>The last 4 arguments to <TT>Fl::set_boxtype()</TT> are the
|
|
|
|
|
offsets for the x, y, width, and height values that should be
|
|
|
|
|
subtracted when drawing the label inside the box.</P>
|
|
|
|
|
|
|
|
|
|
<H2><A NAME="labels">Labels and Label Types</A></H2>
|
|
|
|
|
|
|
|
|
|
<P>The <TT>label()</TT>, <TT>align()</TT>, <TT>labelfont()</TT>,
|
|
|
|
|
<TT>labelsize()</TT>, <TT>labeltype()</TT>, <TT>image()</TT>, and
|
|
|
|
|
<TT>deimage()</TT> methods control the labeling of widgets.</P>
|
|
|
|
|
|
1998-12-29 17:21:17 +03:00
|
|
|
<H3>label()</H3>
|
2001-11-27 00:40:14 +03:00
|
|
|
|
|
|
|
|
<P>The <TT>label()</TT> method sets the string that is displayed
|
|
|
|
|
for the label. Symbols can be included with the label string by
|
|
|
|
|
escaping them using the "@" symbol - "@@" displays a single at
|
|
|
|
|
sign. Figure 3-4 shows the available symbols.</P>
|
|
|
|
|
|
2002-01-15 05:17:19 +03:00
|
|
|
<P ALIGN="CENTER"><A name="symbols"><IMG src="symbols.gif" ALT="FLTK Symbols"><BR>
|
|
|
|
|
<I>Figure 3-4: FLTK label symbols</I></A></P>
|
2001-11-27 00:40:14 +03:00
|
|
|
|
|
|
|
|
<P>The @ sign may also be followed by the following optional
|
|
|
|
|
"formatting" characters, in this order:</P>
|
|
|
|
|
|
|
|
|
|
<UL>
|
|
|
|
|
|
|
|
|
|
<LI>'#' forces square scaling, rather than distortion to
|
|
|
|
|
the widget's shape.</LI>
|
|
|
|
|
|
|
|
|
|
<LI>+[1-9] or -[1-9] tweaks the scaling a little bigger
|
|
|
|
|
or smaller.</LI>
|
|
|
|
|
|
|
|
|
|
<LI>[1-9] - rotates by a multiple of 45 degrees. '6'
|
|
|
|
|
does nothing, the others point in the direction of
|
|
|
|
|
that key on a numeric keypad.</LI>
|
|
|
|
|
|
|
|
|
|
</UL>
|
|
|
|
|
|
1998-12-29 17:21:17 +03:00
|
|
|
<H3>align()</H3>
|
2001-11-27 00:40:14 +03:00
|
|
|
|
2001-11-29 22:24:00 +03:00
|
|
|
<P>The <TT>align()</TT> method positions the label. The following
|
2001-11-27 00:40:14 +03:00
|
|
|
constants are defined and may be OR'd together as needed:</P>
|
|
|
|
|
|
1999-01-13 22:28:54 +03:00
|
|
|
<UL>
|
2001-11-27 00:40:14 +03:00
|
|
|
|
|
|
|
|
<LI><TT>FL_ALIGN_CENTER</TT> - center the label in the widget.</LI>
|
|
|
|
|
|
|
|
|
|
<LI><TT>FL_ALIGN_TOP</TT> - align the label at the top of the widget.</LI>
|
|
|
|
|
|
2001-11-29 22:24:00 +03:00
|
|
|
<LI><TT>FL_ALIGN_BOTTOM</TT> - align the label at the bottom of the
|
2001-11-27 00:40:14 +03:00
|
|
|
widget.</LI>
|
|
|
|
|
|
|
|
|
|
<LI><TT>FL_ALIGN_LEFT</TT> - align the label to the left of the widget.</LI>
|
|
|
|
|
|
2001-11-29 22:24:00 +03:00
|
|
|
<LI><TT>FL_ALIGN_RIGHT</TT> - align the label to the right of the
|
2001-11-27 00:40:14 +03:00
|
|
|
widget.</LI>
|
|
|
|
|
|
|
|
|
|
<LI><TT>FL_ALIGN_INSIDE</TT> - align the label inside the widget.</LI>
|
|
|
|
|
|
2001-11-29 22:24:00 +03:00
|
|
|
<LI><TT>FL_ALIGN_CLIP</TT> - clip the label to the widget's bounding
|
2001-11-27 00:40:14 +03:00
|
|
|
box.</LI>
|
|
|
|
|
|
|
|
|
|
<LI><TT>FL_ALIGN_WRAP</TT> - wrap the label text as needed.</LI>
|
|
|
|
|
|
|
|
|
|
<LI><TT>FL_TEXT_OVER_IMAGE</TT> - show the label text over the image.</LI>
|
|
|
|
|
|
|
|
|
|
<LI><TT>FL_IMAGE_OVER_TEXT</TT> - show the label image over the text (default).</LI>
|
|
|
|
|
|
1999-01-13 22:28:54 +03:00
|
|
|
</UL>
|
2001-11-27 00:40:14 +03:00
|
|
|
|
2001-10-01 00:25:36 +04:00
|
|
|
<H3><A NAME="labeltypes">labeltype()</A></H3>
|
2001-11-27 00:40:14 +03:00
|
|
|
|
2001-11-29 22:24:00 +03:00
|
|
|
<P>The <TT>labeltype()</TT> method sets the type of the label. The
|
2001-11-27 00:40:14 +03:00
|
|
|
following standard label types are included:</P>
|
|
|
|
|
|
1999-01-13 22:28:54 +03:00
|
|
|
<UL>
|
2001-11-27 00:40:14 +03:00
|
|
|
|
|
|
|
|
<LI><TT>FL_NORMAL_LABEL</TT> - draws the text.</LI>
|
|
|
|
|
|
|
|
|
|
<LI><TT>FL_NO_LABEL</TT> - does nothing.</LI>
|
|
|
|
|
|
|
|
|
|
<LI><TT>FL_SHADOW_LABEL</TT> - draws a drop shadow under
|
|
|
|
|
the text.</LI>
|
|
|
|
|
|
|
|
|
|
<LI><TT>FL_ENGRAVED_LABEL</TT> - draws edges as though
|
|
|
|
|
the text is engraved.</LI>
|
|
|
|
|
|
|
|
|
|
<LI><TT>FL_EMBOSSED_LABEL</TT> - draws edges as thought
|
|
|
|
|
the text is raised.</LI>
|
|
|
|
|
|
|
|
|
|
<LI><TT>FL_ICON_LABEL</TT> - draws the icon associated
|
|
|
|
|
with the text.</LI>
|
|
|
|
|
|
1999-01-13 22:28:54 +03:00
|
|
|
</UL>
|
2001-11-27 00:40:14 +03:00
|
|
|
|
|
|
|
|
<H3>image() and deimage()</H3>
|
|
|
|
|
|
|
|
|
|
<P>The <TT>image()</TT> and <TT>deimage()</TT> methods set an image that
|
|
|
|
|
will be displayed with the widget. The <TT>deimage()</TT> method sets the
|
|
|
|
|
image that is shown when the widget is inactive, while the <TT>image()</TT>
|
|
|
|
|
method sets the image that is shown when the widget is active.</P>
|
|
|
|
|
|
|
|
|
|
<P>To make an image you use a subclass of
|
|
|
|
|
<A HREF="drawing.html#Fl_Image"><TT>Fl_Image</TT></A>.</P>
|
|
|
|
|
|
1998-12-29 17:21:17 +03:00
|
|
|
<H4>Making Your Own Label Types</H4>
|
2001-11-27 00:40:14 +03:00
|
|
|
|
|
|
|
|
<P>Label types are actually indexes into a table of functions
|
|
|
|
|
that draw them. The primary purpose of this is to use this to
|
|
|
|
|
draw the labels in ways inaccessible through the
|
|
|
|
|
<TT>fl_font</TT> mechanisim (e.g. <TT>FL_ENGRAVED_LABEL</TT>) or
|
|
|
|
|
with program-generated letters or symbology.</P>
|
|
|
|
|
|
|
|
|
|
<CENTER><TABLE WIDTH="80%" BORDER="1" CELLPADDING="5" CELLSPACING="0" BGCOLOR="#cccccc">
|
|
|
|
|
<TR>
|
|
|
|
|
<TD><B>Note:</B>
|
|
|
|
|
<P>This interface has changed in FLTK 2.0!</P>
|
|
|
|
|
</TD>
|
|
|
|
|
</TR>
|
|
|
|
|
</TABLE></CENTER>
|
|
|
|
|
|
1998-12-29 17:21:17 +03:00
|
|
|
<H5>Label Type Functions</H5>
|
2001-11-27 00:40:14 +03:00
|
|
|
|
|
|
|
|
<P>To setup your own label type you will need to write two
|
|
|
|
|
functions: one to draw and one to measure the label. The draw
|
|
|
|
|
function is called with a pointer to a <TT>Fl_Label</TT>
|
|
|
|
|
structure containing the label information, the bounding box for
|
|
|
|
|
the label, and the label alignment:</P>
|
|
|
|
|
|
|
|
|
|
<UL><PRE>
|
1998-12-29 17:21:17 +03:00
|
|
|
void xyz_draw(Fl_Label *label, int x, int y, int w, int h, Fl_Align align) {
|
|
|
|
|
...
|
|
|
|
|
}
|
2001-11-27 00:40:14 +03:00
|
|
|
</PRE></UL>
|
|
|
|
|
|
|
|
|
|
<P>The label should be drawn <I>inside</I> this bounding box,
|
|
|
|
|
even if <TT>FL_ALIGN_INSIDE</TT> is not enabled. The function
|
|
|
|
|
is not called if the label value is <TT>NULL</TT>.</P>
|
|
|
|
|
|
|
|
|
|
<P>The measure function is called with a pointer to a
|
|
|
|
|
<TT>Fl_Label</TT> structure and references to the width and
|
|
|
|
|
height:</P>
|
|
|
|
|
|
|
|
|
|
<UL><PRE>
|
1999-01-27 00:36:02 +03:00
|
|
|
void xyz_measure(Fl_Label *label, int &w, int &h) {
|
1998-12-29 17:21:17 +03:00
|
|
|
...
|
|
|
|
|
}
|
2001-11-27 00:40:14 +03:00
|
|
|
</PRE></UL>
|
|
|
|
|
|
|
|
|
|
<P>The function should measure the size of the label and set
|
|
|
|
|
<TT>w</TT> and <TT>h</TT> to the size it will occupy.</P>
|
|
|
|
|
|
1998-12-29 17:21:17 +03:00
|
|
|
<H5>Adding Your Label Type</H5>
|
2001-11-27 00:40:14 +03:00
|
|
|
|
|
|
|
|
<P>The <TT>Fl::set_labeltype</TT> method creates a label type
|
|
|
|
|
using your draw and measure functions:</P>
|
|
|
|
|
|
|
|
|
|
<UL><PRE>
|
1998-12-29 17:21:17 +03:00
|
|
|
#define XYZ_LABEL FL_FREE_LABELTYPE
|
|
|
|
|
|
|
|
|
|
Fl::set_labeltype(XYZ_LABEL, xyz_draw, xyz_measure);
|
2001-11-27 00:40:14 +03:00
|
|
|
</PRE></UL>
|
|
|
|
|
|
|
|
|
|
<P>The label type number <TT>n</TT> can be any integer value
|
|
|
|
|
starting at the constant <TT>FL_FREE_LABELTYPE</TT>. Once you
|
|
|
|
|
have added the label type you can use the <TT>labeltype()</TT>
|
|
|
|
|
method to select your label type.</P>
|
|
|
|
|
|
2001-11-29 22:24:00 +03:00
|
|
|
<P>The <TT>Fl::set_labeltype</TT> method can also be used to overload
|
2001-11-27 00:40:14 +03:00
|
|
|
an existing label type such as <TT>FL_NORMAL_LABEL</TT>.</P>
|
|
|
|
|
|
1998-12-29 17:21:17 +03:00
|
|
|
<H2>Callbacks</H2>
|
2001-11-27 00:40:14 +03:00
|
|
|
|
|
|
|
|
<P>Callbacks are functions that are called when the value of a
|
|
|
|
|
widget changes. A callback function is sent a <TT>Fl_Widget</TT>
|
|
|
|
|
pointer of the widget that changed and a pointer to data that
|
|
|
|
|
you provide:</P>
|
|
|
|
|
|
|
|
|
|
<UL><PRE>
|
1998-12-29 17:21:17 +03:00
|
|
|
void xyz_callback(Fl_Widget *w, void *data) {
|
|
|
|
|
...
|
|
|
|
|
}
|
2001-11-27 00:40:14 +03:00
|
|
|
</PRE></UL>
|
|
|
|
|
|
2001-11-29 22:24:00 +03:00
|
|
|
<P>The <TT>callback()</TT> method sets the callback function for a
|
|
|
|
|
widget. You can optionally pass a pointer to some data needed for the
|
2001-11-27 00:40:14 +03:00
|
|
|
callback:</P>
|
|
|
|
|
|
|
|
|
|
<UL><PRE>
|
1998-12-29 17:21:17 +03:00
|
|
|
int xyz_data;
|
|
|
|
|
|
2001-11-27 00:40:14 +03:00
|
|
|
button->callback(xyz_callback, &xyz_data);
|
|
|
|
|
</PRE></UL>
|
|
|
|
|
|
|
|
|
|
<P>Normally callbacks are performed only when the value of the
|
|
|
|
|
widget changes. You can change this using the
|
|
|
|
|
<A href="Fl_Widget.html#Fl_Widget.when"><TT>when()</TT></A>
|
|
|
|
|
method:</P>
|
|
|
|
|
|
|
|
|
|
<UL><PRE>
|
1999-01-13 22:28:54 +03:00
|
|
|
button->when(FL_WHEN_NEVER);
|
|
|
|
|
button->when(FL_WHEN_CHANGED);
|
|
|
|
|
button->when(FL_WHEN_RELEASE);
|
|
|
|
|
button->when(FL_WHEN_RELEASE_ALWAYS);
|
|
|
|
|
button->when(FL_WHEN_ENTER_KEY);
|
|
|
|
|
button->when(FL_WHEN_ENTER_KEY_ALWAYS);
|
|
|
|
|
button->when(FL_WHEN_CHANGED | FL_WHEN_NOT_CHANGED);
|
2001-11-27 00:40:14 +03:00
|
|
|
</PRE></UL>
|
|
|
|
|
|
|
|
|
|
<CENTER><TABLE WIDTH="80%" BORDER="1" CELLPADDING="5" CELLSPACING="0" BGCOLOR="#cccccc">
|
|
|
|
|
<TR>
|
|
|
|
|
<TD><B>Hint:</B>
|
|
|
|
|
|
|
|
|
|
<P>Many programmers new to FLTK or C++ try to use a
|
|
|
|
|
non-static class method instead of a static class method
|
|
|
|
|
or function for their callback. Since callbacks are done
|
|
|
|
|
outside a C++ class, the <TT>this</TT> pointer is not
|
|
|
|
|
initialized for class methods.</P>
|
|
|
|
|
|
|
|
|
|
<P>To work around this problem, define a static method
|
|
|
|
|
in your class that accepts a pointer to the class, and
|
|
|
|
|
then have the static method call the class method(s) as
|
|
|
|
|
needed. The data pointer you provide to the
|
|
|
|
|
<TT>callback()</TT> method of the widget can be a
|
|
|
|
|
pointer to the instance of your class.</P>
|
|
|
|
|
|
|
|
|
|
<UL><PRE>
|
|
|
|
|
class foo {
|
|
|
|
|
void my_callback(Widget *);
|
|
|
|
|
static void my_static_callback(Widget *w, foo *f) { f->my_callback(w); }
|
|
|
|
|
...
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
...
|
|
|
|
|
|
|
|
|
|
w->callback(my_static_callback, this);
|
|
|
|
|
</PRE></UL>
|
|
|
|
|
</TD>
|
|
|
|
|
</TR>
|
|
|
|
|
</TABLE></CENTER>
|
|
|
|
|
|
1998-12-29 17:21:17 +03:00
|
|
|
<H2>Shortcuts</H2>
|
2001-11-27 00:40:14 +03:00
|
|
|
|
|
|
|
|
<P>Shortcuts are key sequences that activate widgets such as
|
|
|
|
|
buttons or menu items. The <TT>shortcut()</TT> method sets the
|
|
|
|
|
shortcut for a widget:</P>
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<UL><PRE>
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1999-01-13 22:28:54 +03:00
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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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1999-01-19 23:53:39 +03:00
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button->shortcut(0); // no shortcut
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2001-11-27 00:40:14 +03:00
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</PRE></UL>
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<P>The shortcut value is the key event value - the ASCII value
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or one of the special keys like
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<a href="enumerations.html#key_values"><TT>FL_Enter</TT></a> -
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combined with any modifiers like <KBD>Shift</KBD>,
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<KBD>Alt</KBD>, and <KBD>Control</KBD>.</P>
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</BODY>
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</HTML>
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