BGLView¶
Constructor and Destructor¶
BGLView()
BGLView::BGLView(BRect frame, const char *name, int32 resizingMode, int32 flags, int32 type)
Initializes the view, then creates a new OpenGL drawing context and attaches it to the view. The type argument specifies the OpenGL type specification for the view:
Constant |
Description |
|---|---|
|
Use RGB graphics instead of indexed color (8-bit). This is the default if
neither |
|
Use indexed color (8-bit graphics). Not currently supported. |
|
Use single-buffering; all rendering is done directly to the display. This
is not currently supported by the BeOS implementation of OpenGL. This is
the default if neither |
|
Use double-buffered graphics. All rendering is done to an offscreen buffer
and only becomes visible when the |
|
Requests that the view have an accumulation buffer. |
|
Requests that the view’s color buffer include an alpha component. |
|
Requests that the view have a depth buffer. |
|
Requests that the view have a stencil buffer. |
~BGLView()
virtual BGLView::~BGLView()
Disposes of the OpenGL context for the view.
Member Functions¶
~BGLView()
virtual void BGLView::~BGLView()
Calls the inherited version of AttachedToWindow() and sets the view color to
B_TRANSPARENT_32_BIT (this improves performance by
preventing the Application Server from erasing the view, since OpenGL takes
over responsibility for drawing into the view).
CopyPixelsIn(), CopyPixelsOut()
status_t BGLView::CopyPixelsIn(BBitmap *source, BPoint dest)
status_t BGLView::CopyPixelsOut(BPoint source, BBitmap *dest)
These functions copy pixel data into and out of the OpenGL draw buffer for the context.
CopyPixelsIn() copies the entire contents of the
source BBitmap into the OpenGL context, offset such
that the top-left corner of the BBitmap is drawn at the point
dest in the OpenGL buffer.
CopyPixelsOut() copies from the OpenGL draw buffer into the
specified BBitmap. The area copied is the size of the dest
bitmap and contains all data from the specified source point to
the bottom-right corner of the buffer.
Note
If the source is larger than the destination, it’s clipped at the bottom
and right edges to fit; no scaling is performed Also, the OpenGL context
and the BBitmap must be in the same color space.
Return Code |
Description |
|---|---|
|
The data was copied without error. |
|
The current draw buffer is not valid, or the destination buffer’s width or height is less than or equal to zero. |
|
The source and destination are in different color spaces. |
DirectConnected()
void BGLView::DirectConnected(direct_buffer_info *directInfo)
If the BGLView is in a BDirectWindow, you should
call this from your BDirectWindow::DirectConnected() function to
let OpenGL update the window properly.
Draw()
virtual void BGLView::Draw(BRect updateRect)
Refreshes the contents of the BGLView by copying the frontbuffer to the screen.
If the view’s color space is eight bits deep and the
GL_DITHER OpenGL option is enabled, the display is
dithered.
EmbeddedView()
BView *BGLView::EmbeddedView()
Returns a pointer to an embedded view that encompasses the current OpenGL drawing buffer, as defined by OpenGL, for the BGLView. If the view is single-buffered, this will be the frontbuffer, and if the view is double-buffered, the embedded view will encompass the backbuffer.
Note
EmbeddedView() returns NULL if, for any reason,
BView functions can’t be used in the GL buffer. Starting with
BeOS R4, this function always returns NULL, as the new,
high-performance implementation of OpenGL does not support tinkering with
the view.
EnableDirectMode()
void BGLView::EnableDirectMode(bool enabled)
Call this function to tell the BGLView whether or not it should
render in direct mode. If you’re using a BDirectWindow and
want video refreshes to be done through the direct window method, pass
true for enabled. If you don’t want to use the direct
window method, pass false.
ErrorCallback()
virtual void BGLView::ErrorCallback(GLenum errorCode)
Called when an OpenGL error occurs. By default, this function invokes the debugger with an error message reading “GL: Error code $xxxx.” You can (and probably should) reimplement this function to cope with errors more gracefully.
FrameResized()
virtual void BGLView::FrameResized(float width, float height)
Calls the inherited version of FrameResized(), releases tables that need to be recalculated, and
resizes the OpenGL buffers.
You can augment this function to perform other necessary tasks, such as adjusting your BGLView’s coordinate system.
LockGL(), UnlockGL()
void BGLView::LockGL()
void BGLView::UnlockGL()
These functions lock and unlock the OpenGL context. You must lock the context before issuing any OpenGL commands, and unlock it when you’re done—this is how OpenGL knows which context the drawing commands are intended for, since OpenGL itself isn’t encapsulated within the BGLView class. For example:
LockGL(); /* lock the OpenGL context
glEnable(GL_DITHER); /* turn on dithering support */
UnlockGL();
Failing to lock and unlock the context appropriately will result in unpredictable behavior and may cause your application to crash.
SwapBuffers()
void BGLView::SwapBuffers()
void BGLView::SwapBuffers(bool vSync)
Swaps the front buffer and back buffer, then redraws the contents of the BGLView.
This function has no effect if the view is single-buffered.
If vSync is specified and is true, the swap is synchronized with vertical blanking.