## gtk_openGLWidget

gtk_openGLWidget — defines an OpenGL capable GtkWidget

## Synopsis

    void        (*RedrawMethod)                 (guint width,
                                                 guint height,
                                                 gpointer data);
    GtkWidget*  openGLWidgetNew                 (gboolean contextIsDirect);
    void        openGLWidgetSwap_buffers        (OpenGLWidget *render);
    void        openGLWidgetRedraw              (OpenGLWidget *render);
    gboolean    openGLWidgetSet_current         (OpenGLWidget *render);
    void        openGLWidgetSet_redraw          (OpenGLWidget *render,
                                                 RedrawMethod method,
                                                 gpointer data);
    guchar*     openGLWidgetGet_pixmapData      (OpenGLWidget *render,
                                                 int *width,
                                                 int *height,
                                                 gboolean offScreen);

    OpenGLWidget* openGLWidgetClassGet_currentContext
                                                ();

## Description

This is a simple implementation of GtkGlExt to create an OpenGL surface that is a full GtkWidget. When creating such a widget, one should give then a `RedrawMethod()` to tell the widget how to redraw itself when needed.

The current implementation is working on X11 and Win32.

## Details

### RedrawMethod ()

    void        (*RedrawMethod)                 (guint width,
                                                 guint height,
                                                 gpointer data);

Methods of this prototype are called when the redraw of the OpenGL zone should be done.

`width` : | the width of the drawing area ;
`height` : | the height of the drawing area ;
`data` : | some user defined informations.

### openGLWidgetNew ()

    GtkWidget*  openGLWidgetNew                 (gboolean contextIsDirect);

Create a new OpenGL area inside a GTK widget. If `contextIsDirect` then it tries to initialise the OpenGL context to a direct one.

`contextIsDirect` : | a boolean.
Returns : | a newly created widget.

### openGLWidgetSwap_buffers ()

    void        openGLWidgetSwap_buffers        (OpenGLWidget *render);

Swap the buffers of the OpenGL area.

`render` : | a OpenGLWidget object.

### openGLWidgetRedraw ()

    void        openGLWidgetRedraw              (OpenGLWidget *render);

Force redraw on the given surface, if a redraw method have been given (see `openGLWidgetSet_redraw()`).

`render` : | a OpenGLWidget object.

### openGLWidgetSet_current ()

    gboolean    openGLWidgetSet_current         (OpenGLWidget *render);

Make this object current. This means that all future OpenGL primitive will be rendered on this surface.

`render` : | a OpenGLWidget object.
Returns : | TRUE if succeed.

### openGLWidgetSet_redraw ()

    void        openGLWidgetSet_redraw          (OpenGLWidget *render,
                                                 RedrawMethod method,
                                                 gpointer data);

This method is used to defined a redraw method for the OpenGL area. By doing this the area will automatically redraw itself when necessary. Before doing it it calls `openGLWidgetSet_current()` ; and after it calls `openGLWidgetSwap_buffers()`.

`render` : | a OpenGLWidget object ;
`method` : | a redraw method ;
`data` : | a user defined pointer.

### openGLWidgetGet_pixmapData ()

    guchar*     openGLWidgetGet_pixmapData      (OpenGLWidget *render,
                                                 int *width,
                                                 int *height,
                                                 gboolean offScreen);

Create an image from the OpenGL area. The size can be changed, using `width` and `height`. If these pointers contains positive values, then they are used to set the size for the image. If not, the current size is used and stored in these pointers. The boolean offScreen is used to tell if the image is taken from current context or if an offscreen pixmap is created for the rendering.

`render` : | a OpenGLWidget object ;
`width` : | a pointer to the desired width or -1 ;
`height` : | a pointer to the desired height or -1 ;
`offScreen` : | a boolean.
Returns : | image data, row by row.

### openGLWidgetClassGet_currentContext ()

    OpenGLWidget* openGLWidgetClassGet_currentContext
                                                ();

Class routine that returns the OpenGL widget which has the current context.

Returns : | the OpenGLWidget with the current OpenGL context.