From 7f105bfa47e0f8a24f019f87c76bae387fbe0c1b Mon Sep 17 00:00:00 2001
From: engelsman This chapter describes many of the widgets that are provided
+This chapter describes many of the widgets that are provided
with FLTK and covers how to query and set the standard
-attributes. FLTK provides many types of buttons: All of these buttons just need the corresponding
- Each button has an associated type() which allows
-it to behave as a push button, toggle button, or radio button: For toggle and radio buttons, the value() method returns
+For toggle and radio buttons, the value() method returns
the current button state (0 = off, 1 = on). The set() and
clear() methods can be used on toggle buttons to turn a
toggle button on or off, respectively.
Radio buttons can be turned on with the setonly()
method; this will also turn off other radio buttons in the same
-group. FLTK provides several text widgets for displaying and receiving text: The Fl_Output and Fl_Multiline_Output
+The Fl_Output and Fl_Multiline_Output
widgets allow the user to copy text from the output field but
-not change it. The value() method is used to get or set the
-string that is displayed: The string is copied to the widget's own storage when you set
-the value() of the widget. The Fl_Text_Display and Fl_Text_Editor
-widgets use an associated Fl_Text_Buffer class for the
-value, instead of a simple string. Unlike text widgets, valuators keep track of numbers instead of
-strings. FLTK provides the following valuators: The value() method gets and sets the current value
-of the widget. The minimum() and maximum()
+The value() method gets and sets the current value
+of the widget. The minimum() and maximum()
methods set the range of values that are reported by the
-widget. The Fl_Group widget class is used as a general
+The Fl_Group widget class is used as a general
purpose "container" widget. Besides grouping radio
buttons, the groups are used to encapsulate windows, tabs, and
scrolled windows. The following group classes are available
-with FLTK: The size and position of widgets is usually set when you
+The size and position of widgets is usually set when you
create them. You can access them with the x(),
-y(), w(), and h() methods. You can change the size and position by using the
-position(), resize(), and size()
-methods: If you change a widget's size or position after it is
+If you change a widget's size or position after it is
displayed you will have to call redraw() on the
-widget's parent. FLTK stores the colors of widgets as an 32-bit unsigned
+FLTK stores the colors of widgets as an 32-bit unsigned
number that is either an index into a color palette of 256
colors or a 24-bit RGB color. The color palette is not
the X or WIN32 colormap, but instead is an internal table with
-fixed contents. There are symbols for naming some of the more common colors: These symbols are the default colors for all FLTK widgets. They are
+These symbols are the default colors for all FLTK widgets. They are
explained in more detail in the chapter
-Enumerations RGB colors can be set using the fl_rgb_color()
-function: The widget color is set using the color() method: Similarly, the label color is set using the labelcolor()
-method: The type Fl_Boxtype stored and returned in Fl_Widget::box()
+The type Fl_Boxtype stored and returned in Fl_Widget::box()
is an enumeration defined in Enumerations.H.
-Figure 3-3 shows the standard box types included with FLTK. FL_NO_BOX means nothing is drawn at all, so whatever is
-already on the screen remains. The FL_..._FRAME types only
+FL_NO_BOX means nothing is drawn at all, so whatever is
+already on the screen remains. The FL_..._FRAME types only
draw their edges, leaving the interior unchanged. The blue color in
-Figure 3-3 is the area that is not drawn by the frame types. You can define your own boxtypes by making a small function that draws
-the box and adding it to the table of boxtypes. This interface has changed in FLTK 2.0! This interface has changed in FLTK 2.0!
The drawing function is passed the bounding box and background color
-for the widget: A simple drawing function might fill a rectangle with the
-given color and then draw a black outline: fl_down returns the "pressed" or "down" version of a box.
+fl_down returns the "pressed" or "down" version of a box.
If no "down" version of a given box exists, the behavior of this function
is undefined and some random box or frame is returned.
See also: fl_frame drawing.
- fl_frame returns the unfilled, frame-only version of a box.
+fl_frame returns the unfilled, frame-only version of a box.
If no frame version of a given box exists, the behavior of this function
is undefined and some random box or frame is returned.
See also: fl_frame drawing.
- fl_box returns the filled version of a frame.
+fl_box returns the filled version of a frame.
If no filled version of a given frame exists, the behavior of this function
is undefined and some random box or frame is returned.
-See also: fl_frame.
+See also: fl_frame.
- The Fl::set_boxtype() method adds or replaces the
-specified box type: The last 4 arguments to Fl::set_boxtype() are the
+The last 4 arguments to Fl::set_boxtype() are the
offsets for the x, y, width, and height values that should be
-subtracted when drawing the label inside the box. A complete box design contains four box types in this order:
-a filled, neutral box (UP_BOX), a filled, depressed box
-(DOWN_BOX), and the same as outlines only (UP_FRAME
-and DOWN_FRAME). The function
-fl_down(Fl_Boxtype)
+A complete box design contains four box types in this order:
+a filled, neutral box (UP_BOX), a filled, depressed box
+(DOWN_BOX), and the same as outlines only (UP_FRAME
+and DOWN_FRAME). The function
+fl_down(Fl_Boxtype)
expects the neutral design on a boxtype with a numerical
value evenly divideable by two.
-fl_frame(Fl_Boxtype)
-expects the UP_BOX design at a value divideable by four. The label(), align(), labelfont(),
-labelsize(), labeltype(), image(), and
-deimage() methods control the labeling of widgets. The label() method sets the string that is displayed
+The label() 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. The @ sign may also be followed by the following optional
-"formatting" characters, in this order: Thus, to show a very large arrow pointing downward you would use the
+Thus, to show a very large arrow pointing downward you would use the
label string "@+92->".
- The align() method positions the label. The following
-constants are defined and may be OR'd together as needed: The labeltype() method sets the type of the label. The
-following standard label types are included: The image() and deimage() methods set an image that
-will be displayed with the widget. The deimage() method sets the
-image that is shown when the widget is inactive, while the image()
-method sets the image that is shown when the widget is active. To make an image you use a subclass of
-Fl_Image. Label types are actually indexes into a table of functions
+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
-fl_font mechanisim (e.g. FL_ENGRAVED_LABEL) or
-with program-generated letters or symbology. This interface has changed in FLTK 2.0! This interface has changed in FLTK 2.0!
To setup your own label type you will need to write two
+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 Fl_Label
+function is called with a pointer to a Fl_Label
structure containing the label information, the bounding box for
-the label, and the label alignment: The label should be drawn inside this bounding box,
-even if FL_ALIGN_INSIDE is not enabled. The function
-is not called if the label value is NULL. The measure function is called with a pointer to a
-Fl_Label structure and references to the width and
-height: The function should measure the size of the label and set
-w and h to the size it will occupy. The Fl::set_labeltype method creates a label type
-using your draw and measure functions:Buttons
+\section common_buttons Buttons
-
-
+\li Fl_Round_Button - A button with a radio circle.
\image html buttons.gif "Figure 3-1: FLTK Button Widgets"
-Text
+\section common_text Text
-
-
+\li Fl_Help_View - A HTML text display widget.
-Valuators
-
-
+\section common_valuators Valuators
-
+\li Fl_Value_Slider - A slider that shows the current value.
\image html valuators.gif "Figure 3-2: FLTK valuator widgets"
-Groups
+\section common_groups Groups
-
+\li Fl_Double_Window - A double-buffered window on the screen.
-
-
-Setting the Size and Position of Widgets
-
-Colors
+
+\section common_colors Colors
-
-
+\li FL_WHITE
-
-
+\li FL_SELECTION_COLOR
-Making Your Own Boxtypes
+\subsection common_boxtypes Making Your Own Boxtypes
-
Note:
-
The Drawing Function
+\par The Drawing Function
-Fl_Boxtype fl_down(Fl_Boxtype)
+
+\par Fl_Boxtype fl_down(Fl_Boxtype)
-Fl_Boxtype fl_frame(Fl_Boxtype)
+
+\par Fl_Boxtype fl_frame(Fl_Boxtype)
-Fl_Boxtype fl_box(Fl_Boxtype)
+
+\par Fl_Boxtype fl_box(Fl_Boxtype)
-Adding Your Box Type
+\par Adding Your Box Type
-label()
+\par label()
-
+\li '#' forces square scaling, rather than distortion to the widget's shape.
-
-
-align()
-
-
-
-
+\li FL_ALIGN_WRAP - wrap the label text as needed.
-labeltype()
+\li FL_TEXT_OVER_IMAGE - show the label text over the image.
-
+
+\par labeltype()
-
+\li FL_ICON_LABEL - draws the icon associated with the text.
-image() and deimage()
+\par image() and deimage()
-Making Your Own Label Types
+\par Making Your Own Label Types
-
Note:
-
Label Type Functions
+\par Label Type Functions
-Adding Your Label Type
+\par Adding Your Label Type
-
The label type number n can be any integer value -starting at the constant FL_FREE_LABELTYPE. Once you -have added the label type you can use the labeltype() -method to select your label type.
+The label type number n can be any integer value +starting at the constant FL_FREE_LABELTYPE. Once you +have added the label type you can use the labeltype() +method to select your label type. -The Fl::set_labeltype method can also be used to overload -an existing label type such as FL_NORMAL_LABEL.
+The Fl::set_labeltype method can also be used to overload +an existing label type such as FL_NORMAL_LABEL. -It is also possible to define your own drawings and add +It is also possible to define your own drawings and add them to the symbol list, so they can be rendered as part of -any label.
+any label. -To create a new symbol, you implement a drawing function +To create a new symbol, you implement a drawing function void drawit(Fl_Color c) which typically uses the complex drawing functions to generate a vector shape inside a two-by-two units sized box around the origin. This function is then linked into the symbols -table using fl_add_symbol:
+table using fl_add_symbol: \code int fl_add_symbol(const char *name, void (*drawit)(Fl_Color), int scalable) \endcode -name is the name of the symbol without the "@"; scalable +name is the name of the symbol without the "@"; scalable must be set to 1 if the symbol is generated using scalable vector drawing -functions.
+functions. \code int fl_draw_symbol(const char *name,int x,int y,int w,int h,Fl_Color col) \endcode -This function draws a named symbol fitting the given rectangle. +This function draws a named symbol fitting the given rectangle. -
Callbacks are functions that are called when the value of a -widget changes. A callback function is sent a Fl_Widget +Callbacks are functions that are called when the value of a +widget changes. A callback function is sent a Fl_Widget pointer of the widget that changed and a pointer to data that -you provide:
+you provide: \code void xyz_callback(Fl_Widget *w, void *data) { @@ -557,9 +523,9 @@ void xyz_callback(Fl_Widget *w, void *data) { } \endcode -The callback() method sets the callback function for a +The callback() method sets the callback function for a widget. You can optionally pass a pointer to some data needed for the -callback:
+callback: \code int xyz_data; @@ -567,9 +533,9 @@ int xyz_data; button->callback(xyz_callback, &xyz_data); \endcode -Normally callbacks are performed only when the value of the +Normally callbacks are performed only when the value of the widget changes. You can change this using the Fl_Widget::when() -method:
+method: \code button->when(FL_WHEN_NEVER); @@ -589,22 +555,22 @@ button->when(FL_WHEN_CHANGED | FL_WHEN_NOT_CHANGED); widget may still be accessed by FLTK after your callback is completed. Instead, use the Fl::delete_widget() method to mark your widget for deletion when it is safe - to do so. + to do so.Hint:
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 this pointer is not - initialized for class methods.
+ outside a C++ class, the this pointer is not + initialized for class methods.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 - callback() method of the widget can be a - pointer to the instance of your class.
+ callback() method of the widget can be a + pointer to the instance of your class. \code class Foo { @@ -621,11 +587,11 @@ w->callback(my_static_callback, (void *)this); -Shortcuts are key sequences that activate widgets such as -buttons or menu items. The shortcut() method sets the -shortcut for a widget:
+Shortcuts are key sequences that activate widgets such as +buttons or menu items. The shortcut() method sets the +shortcut for a widget: \code button->shortcut(FL_Enter); @@ -636,11 +602,11 @@ button->shortcut(FL_CTRL + FL_ALT + 'b'); button->shortcut(0); // no shortcut \endcode -The shortcut value is the key event value - the ASCII value +The shortcut value is the key event value - the ASCII value or one of the special keys like -FL_Enter - +FL_Enter - combined with any modifiers like Shift, -Alt, and Control.
+Alt, and Control.