## OpenGLWidget

OpenGLWidget — defines an OpenGL capable GtkWidget.

## Synopsis

    void                (*RedrawMethod)                     (const char **lists,
                                                             VisuData *data);
                        OpenGLWidget;
    GtkWidget*          openGLWidgetNew                     (gboolean contextIsDirect);
    void                openGLWidgetSwap_buffers            (OpenGLWidget *render);
    void                openGLWidgetRedraw                  (OpenGLWidget *render);
    gboolean            openGLWidgetSet_current             (OpenGLWidget *render,
                                                             gboolean force);
    void                openGLWidgetSet_redraw              (OpenGLWidget *render,
                                                             RedrawMethod method,
                                                             VisuData *data);
    guchar*             openGLWidgetGet_pixmapData          (OpenGLWidget *render,
                                                             int *width,
                                                             int *height,
                                                             gboolean offScreen,
                                                             gboolean hasAlpha);

    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 (built-in or with GtkGlExt) and Win32.

## Details

### RedrawMethod ()

    void                (*RedrawMethod)                     (const char **lists,
                                                             VisuData *data);

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

`lists` : | a string array, NULL terminated.
`data` : | the VisuData to draw.

### OpenGLWidget

    typedef struct _OpenGLWidget OpenGLWidget;

Short name to address OpenGLWidget_struct objects.

### 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,
                                                             gboolean force);

Make this object current. This means that all future OpenGL primitive will be rendered on this surface. If `force` is TRUE, the GL routine is actually called whereas in other cases, if `render` believe being already current, nothing is done.

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

### openGLWidgetSet_redraw ()

    void                openGLWidgetSet_redraw              (OpenGLWidget *render,
                                                             RedrawMethod method,
                                                             VisuData *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` : | the VisuData to draw.

### openGLWidgetGet_pixmapData ()

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

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 ;
`hasAlpha` : | if TRUE, the returned data is RGBA, else only RGB.
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.