[cairo] Cairo and FLTK?

[Kai-Uwe Behrmann]

Date: Mon, 29 Oct 2007 12:00:58 +0000
From: Bill Spitzak
 
> The following code should return a cairo surfact_t that can be used to 
> draw into an fltk window. You would call this inside your 
> window/widget's draw() function:

Neighter inside or outside FLTK(1)'s draw() gives more speed in the Fl_Box 
my app uses. Drawing in a image surface is much quicker for me.

> /** Fltk cairo create surface function accepting a Window* as input */
> cairo_surface_t* fltk::cairo_create_surface(Window* wi) {
>    XWindow window = fltk::xid(wi);
>    cairo_surface_t* surface =  cairo_xlib_surface_create(xdisplay, window,
> 				   xvisual->visual, wi->w(), wi->h());
>    cairo_xlib_surface_set_size(surface, wi->w(), wi->h());
>    return surface;
> }

My test app show much flickering even though it is a Fl_Double_Window.

Alternatively using a Xrender surface brings me lots of errors for the 
first of following variants:
    Fl_Window *wi = cc->box->window();
    Window window = fl_xid(wi);
    Screen *scr = XDefaultScreenOfDisplay (fl_display);
#if defined(CAIRO_HAS_XLIB_XRENDER_SURFACE)
    XRenderPictFormat * rf = XRenderFindStandardFormat( fl_display,
                                                        PictStandardARGB32 );
    cc->surface = cairo_xlib_surface_create_with_xrender_format ( fl_display,
                                window, scr, rf,
                                w,h );
    cairo_status_t status = cairo_surface_status ( cc->surface );
#else
    cc->surface =  cairo_xlib_surface_create( fl_display, window,
                                fl_visual->visual, cc->box->w(), cc->box->h() );
    cairo_xlib_surface_set_size( cc->surface, w, h );
#endif

message:
XRequest.157: BadMatch (invalid parameter attributes) 0x0
XRequest.157: RenderBadPicture (invalid Picture parameter) 0x4c00005
XRequest.157: RenderBadPicture (invalid Picture parameter) 0x4c00005
...
XRequest.157: RenderBadPicture (invalid Picture parameter) 0x4c00956
XRequest.157: RenderBadPicture (invalid Picture parameter) 0x4c00956
XRequest.157: BadMatch (invalid parameter attributes) 0x4c00956
XRequest.157: RenderBadPicture (invalid Picture parameter) 0x4c00a0e
XRequest.157: RenderBadPicture (invalid Picture parameter) 0x4c00a0e
...


A working Cairo (X/Xrender/Quartz/...) in FLTK1 example would be a 
desired thing.



One other thing, which made me wonder, is the need for a swap of the RGB 
channels coming from a 
cairo_image_surface_create (CAIRO_FORMAT_ARGB32, w,h) created image 
surface before using fl_draw_image() in myFl_Box::draw().
Is this normal behaviour?

kind regards
Kai-Uwe Behrmann
--
developing for colour management 
www.behrmann.name + www.oyranos.org