// newFBO will generate a new Frame Buffer Object for use with the canvas
func newFBO(texture gl.Texture) (gl.Framebuffer, uint32) {
// get currently bound fbo to reset to it later
current_fbo := gl.GetBoundFramebuffer()
framebuffer := gl.CreateFramebuffer()
gl.BindFramebuffer(gl.FRAMEBUFFER, framebuffer)
if texture.Valid() {
gl.FramebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, texture, 0)
// Initialize the texture to transparent black.
gl.ClearColor(0.0, 0.0, 0.0, 0.0)
gl.Clear(gl.COLOR_BUFFER_BIT)
}
status := gl.CheckFramebufferStatus(gl.FRAMEBUFFER)
// unbind framebuffer
gl.BindFramebuffer(gl.FRAMEBUFFER, current_fbo)
return framebuffer, uint32(status)
}
// checkCreateStencil if a stencil is set on a canvas then we need to create
// some buffers to handle this.
func (canvas *Canvas) checkCreateStencil() bool {
// Do nothing if we've already created the stencil buffer.
if canvas.depth_stencil.Valid() {
return true
}
if gl_state.currentCanvas != canvas {
gl.BindFramebuffer(gl.FRAMEBUFFER, canvas.fbo)
}
format := gl.STENCIL_INDEX8
attachment := gl.STENCIL_ATTACHMENT
canvas.depth_stencil = gl.CreateRenderbuffer()
gl.BindRenderbuffer(gl.RENDERBUFFER, canvas.depth_stencil)
gl.RenderbufferStorage(gl.RENDERBUFFER, gl.Enum(format), int(canvas.width), int(canvas.height))
// Attach the stencil buffer to the framebuffer object.
gl.FramebufferRenderbuffer(gl.FRAMEBUFFER, gl.Enum(attachment), gl.RENDERBUFFER, canvas.depth_stencil)
gl.BindRenderbuffer(gl.RENDERBUFFER, gl.Renderbuffer{})
success := (gl.CheckFramebufferStatus(gl.FRAMEBUFFER) == gl.FRAMEBUFFER_COMPLETE)
// We don't want the stencil buffer filled with garbage.
if success {
gl.Clear(gl.STENCIL_BUFFER_BIT | gl.DEPTH_BUFFER_BIT)
} else {
gl.DeleteRenderbuffer(canvas.depth_stencil)
canvas.depth_stencil = gl.Renderbuffer{}
}
if gl_state.currentCanvas != nil && gl_state.currentCanvas != canvas {
gl.BindFramebuffer(gl.FRAMEBUFFER, gl_state.currentCanvas.fbo)
} else if gl_state.currentCanvas == nil {
gl.BindFramebuffer(gl.FRAMEBUFFER, getDefaultFBO())
}
return success
}
// stopGrab will bind the context back to the default framebuffer and set back
// all the settings
func (canvas *Canvas) stopGrab(switchingToOtherCanvas bool) error {
// i am not grabbing. leave me alone
if gl_state.currentCanvas != canvas {
return nil
}
gl_state.projectionStack.Pop()
if !switchingToOtherCanvas {
// bind system framebuffer.
gl_state.currentCanvas = nil
gl.BindFramebuffer(gl.FRAMEBUFFER, getDefaultFBO())
SetViewport(canvas.systemViewport[0], canvas.systemViewport[1], canvas.systemViewport[2], canvas.systemViewport[3])
}
return nil
}
// startGrab will bind this canvas to grab all drawing operations
// multiple canvases can only be passed in on non mobile platforms
func (canvas *Canvas) startGrab(canvases ...*Canvas) error {
if gl_state.currentCanvas == canvas {
return nil // already grabbing
}
if canvases != nil && len(canvases) > 0 {
// Whether the new canvas list is different from the old one.
// A more thorough check is done below.
if maxRenderTargets < 4 {
return fmt.Errorf("Multi-canvas rendering is not supported on this system.")
}
if int32(len(canvases)+1) > maxRenderTargets {
return fmt.Errorf("This system can't simultaneously render to %v canvases.", len(canvases)+1)
}
for i := 0; i < len(canvases); i++ {
if canvases[i].width != canvas.width || canvases[i].height != canvas.height {
return fmt.Errorf("All canvases must have the same dimensions.")
}
}
}
// cleanup after previous Canvas
if gl_state.currentCanvas != nil {
canvas.systemViewport = gl_state.currentCanvas.systemViewport
gl_state.currentCanvas.stopGrab(true)
} else {
canvas.systemViewport = GetViewport()
}
// indicate we are using this Canvas.
gl_state.currentCanvas = canvas
// bind the framebuffer object.
gl.BindFramebuffer(gl.FRAMEBUFFER, canvas.fbo)
SetViewport(0, 0, canvas.width, canvas.height)
// Set up the projection matrix
gl_state.projectionStack.Push()
gl_state.projectionStack.Load(mgl32.Ortho(0.0, float32(screen_width), 0.0, float32(screen_height), -1, 1))
canvas.attacheExtra(canvases)
canvas.attachedCanvases = canvases
return nil
}