This tutorial introduces custom widgets with the "Widget" program. The program consists of a window containing a custom widget that is made up of two rectangles. It is made up of five files - the source and header for the object that contains the window, the source and header for the custom widget and the source that contains the function main.
Widget source file:
/******************************************************************************
Widget.cc
Each area inside a window
that displays a particular piece of
information is an object
derived from JXWidget. To display
something that is specialized
for your particular application,
you must create a new
class derived from JXWidget.
The minimum requirement
for classes derived from JXWidget is that
they must implement the
Draw() and DrawBorder() functions, as
shown here.
BASE CLASS = JXWindowDirector
Written by Glenn Bach - 1997.
******************************************************************************/
#include "Widget.h"
#include <JXWidget.h>
#include <JXWindowPainter.h>
#include <JXColormap.h>
#include <jXPainterUtil.h>
#include <jXConstants.h>
#include <jAssert.h>
/******************************************************************************
Constructor
******************************************************************************/
Widget::Widget
(
JXContainer* enclosure,
const HSizingOption hSizing,
const VSizingOption vSizing,
const JCoordinate x,
const JCoordinate y,
const JCoordinate w,
const JCoordinate h
)
:
JXWidget(enclosure, hSizing, vSizing, x, y,
w, h)
{
// We have to tell JXWidget
that we want a border.
// Only then will DrawBorder()
get called.
SetBorderWidth(kJXDefaultBorderWidth);
}
/******************************************************************************
Destructor
******************************************************************************/
Widget::~Widget()
{
}
/******************************************************************************
Draw
This gets called by the
event loop every time the Widget needs to
be redrawn.
p is the Painter that you
use to draw to the screen. The main reason
for Painter is to hide
the system dependent details of drawing,
and to provide a uniform
interface for drawing to the screen, to an
offscreen image, and to
a printer.
rect is the area that needs
to be redrawn. In simple cases, you
can just draw everything.
For complex widgets, you often want to
optimize and only draw
the part inside rect.
******************************************************************************/
void
Widget::Draw
(
JXWindowPainter& p,
const JRect& rect
)
{
JXColormap* cmap = GetColormap();
// This is where everything
happens
// See JPainter.h for
available functions
p.SetPenColor(cmap->GetGreenColor());
p.Rect(10, 10, 50, 50);
p.SetFilling(kTrue);
p.SetPenColor(cmap->GetBlueColor());
p.Rect(10, 70, 50, 50);
}
/******************************************************************************
DrawBorder
This gets called by the
event loop every time the Widget's border
needs to be redrawn.
******************************************************************************/
void
Widget::DrawBorder
(
JXWindowPainter& p,
const JRect& frame
)
{
JXDrawDownFrame(p, frame, kJXDefaultBorderWidth);
}
Widget header file:
/******************************************************************************
Widget.h
Interface for the Widget class
Written by Glenn Bach - 1997.
******************************************************************************/
#ifndef _H_Widget
#define _H_Widget
#include <JXWidget.h>
class Widget : public JXWidget
{
public:
Widget(JXContainer* enclosure,
const
HSizingOption hSizing, const VSizingOption vSizing,
const
JCoordinate x, const JCoordinate y,
const
JCoordinate w, const JCoordinate h);
virtual ~Widget();
protected:
virtual void Draw(JXWindowPainter&
p, const JRect& rect);
virtual void DrawBorder(JXWindowPainter&
p, const JRect& frame);
private:
// not allowed
Widget(const Widget& source);
const Widget& operator=(const Widget&
source);
};
#endif
WidgetDir source file:
/******************************************************************************
WidgetDir.cc
BASE CLASS = JXWindowDirector
Written by Glenn Bach - 1997.
******************************************************************************/
#include "WidgetDir.h"
#include "Widget.h"
#include <JXWindow.h>
#include <jAssert.h>
/******************************************************************************
Constructor
******************************************************************************/
WidgetDir::WidgetDir
(
JXDirector* supervisor
)
:
JXWindowDirector(supervisor)
{
BuildWindow();
}
/******************************************************************************
Destructor
******************************************************************************/
WidgetDir::~WidgetDir()
{
// Nothing to delete
// Window is deleted automatically
by its director
// Widget is deleted automatically
by its enclosure
}
/******************************************************************************
BuildWindow
This is a convenient
and organized way of putting all of the initial
elements into a
window. This will keep the constructor less cluttered.
******************************************************************************/
void
WidgetDir::BuildWindow()
{
// Create the window
JXWindow* window = new JXWindow(this, 300,200,
"Test Widget Program");
assert( window != NULL );
// Give the window to the
director
SetWindow(window);
// Set sizing
window->SetMinSize(300,200);
window->SetMaxSize(800,600);
// Create our custom widget
Widget* widget =
new Widget(window, JXWidget::kHElastic,
JXWidget::kVElastic,
0, 0, 300, 200);
assert( widget != NULL );
}
WidgetDir header file:
/******************************************************************************
WidgetDir.h
Interface for the WidgetDir class
Written by Glenn Bach - 1997.
******************************************************************************/
#ifndef _H_WidgetDir
#define _H_WidgetDir
#include <JXWindowDirector.h>
class WidgetDir : public JXWindowDirector
{
public:
WidgetDir(JXDirector* supervisor);
virtual ~WidgetDir();
private:
void BuildWindow();
// not allowed
WidgetDir(const WidgetDir& source);
const WidgetDir& operator=(const WidgetDir&
source);
};
#endif
Written by Glenn Bach - 1997.
******************************************************************************/
#include "WidgetDir.h"
#include <JXApplication.h>
#include <jAssert.h>
/******************************************************************************
main
******************************************************************************/
int
main
(
int argc,
char* argv[]
)
{
// Create the application
object - one per program
JXApplication* app = new JXApplication(&argc,
argv);
assert( app != NULL );
// Create our window director
WidgetDir* mainDir = new WidgetDir(app);
assert( mainDir != NULL );
// Activate the director
mainDir->Activate();
// Start the event loop
app->Run();
return 0;
}