nanogui: Thread: Transparent pixmap

Hello,

i want to copy the contents of a pixmap on to the screen. The pixmap  
contains a gif with a transparent background (=> alpha = 0). When i  
copy the pixmap to the screen the transparent background is visible. I  
run nano-x for the Linux-X86 platform using the X11 library. When  
drawing the gif directly to the screen the transparent background is,  
correctly, not visisble. I attach a simple example which demonstrates  
the problem. In the example i do not load the gif, instead i have two  
pixmaps: one painted with red color (alpha = 0) and the other with  
blue (alpha = 255). Still, the red is visible. I also tried the  
SRCTRANSCOPY mode as arhument in the GrCopyArea, but i am not sure if  
this mode of operation is actually implemented. Any help is greatly  
appreciated.

-----------------------------------------------------------------------------
#include <stdio.h>
#include <stdlib.h>
#define MWINCLUDECOLORS
#include "nano-X.h"

int main(int argc, char **argv)
{
	GR_WINDOW_ID pid1, pid2;
	GR_GC_ID gc;
	GR_EVENT event;
	int width, height;
	char c;

	if( GrOpen() < 0 )
	{
		printf("cannot open graphics\n");
		exit(1);
	}

	width = height = 100;

	GrSelectEvents(GR_ROOT_WINDOW_ID, GR_EVENT_MASK_KEY_DOWN);

	gc = GrNewGC();

	pid1 = GrNewPixmap(width, height, NULL);
	GrSetGCForeground(gc, MWARGB(0,255,0,0));
	GrFillRect(pid1, gc, 0, 0, width, height);

	pid2 = GrNewPixmap(width, height, NULL);
	GrSetGCForeground(gc, MWARGB(255,0,0,255));
	GrFillRect(pid2, gc, 0, 0, width, height);

	GrCopyArea(GR_ROOT_WINDOW_ID, gc, 100, 100, width, height, pid2, 0,  
0, MWMODE_COPY);

	GrCopyArea(GR_ROOT_WINDOW_ID, gc, 150, 150, width, height, pid1, 0,  
0, MWMODE_COPY);

	while(1)
	{
		GrGetNextEvent(&event);
		switch (event.type)
		{
			case GR_EVENT_TYPE_KEY_DOWN:
				c = event.keystroke.ch;
				if(c == 'q')
				{
					GrClose();
					exit(0);
				}
				break;
			default:
				break;
		}
	}
}
--------------------------------------------------------------------------

Thanks in advance

Hello,

i want to copy the contents of a pixmap on to the screen. The pixmap
contains a gif with a transparent background (=> alpha = 0). When i
copy the pixmap to the screen the transparent background is visible. I
run nano-x for the Linux-X86 platform using the X11 library. When
drawing the gif directly to the screen the transparent background is,
correctly, not visisble. I attach a simple example which demonstrates
the problem. In the example i do not load the gif, instead i have two
pixmaps: one painted with red color (alpha = 0) and the other with
blue (alpha = 255). Still, the red is visible. I also tried the
SRCTRANSCOPY mode as arhument in the GrCopyArea, but i am not sure if
this mode of operation is actually implemented. Any help is greatly
appreciated.

-------------------------------------------------------------------------
#include <stdio.h>
#include <stdlib.h>
#define MWINCLUDECOLORS
#include "nano-X.h"

int main(int argc, char **argv)
{
        GR_WINDOW_ID pid1, pid2;
        GR_GC_ID gc;
        GR_EVENT event;
        int width, height;
        char c;

        if( GrOpen() < 0 )
        {
                printf("cannot open graphics\n");
                exit(1);
        }

        width = height = 100;

        GrSelectEvents(GR_ROOT_WINDOW_ID, GR_EVENT_MASK_KEY_DOWN);

        gc = GrNewGC();

        pid1 = GrNewPixmap(width, height, NULL);
        GrSetGCForeground(gc, MWARGB(0,255,0,0));
        GrFillRect(pid1, gc, 0, 0, width, height);

        pid2 = GrNewPixmap(width, height, NULL);
        GrSetGCForeground(gc, MWARGB(255,0,0,255));
        GrFillRect(pid2, gc, 0, 0, width, height);

        GrCopyArea(GR_ROOT_WINDOW_ID, gc, 100, 100, width, height, pid2, 0,
0, MWMODE_COPY);

        GrCopyArea(GR_ROOT_WINDOW_ID, gc, 150, 150, width, height, pid1, 0,
0, MWMODE_COPY);

        while(1)
        {
                GrGetNextEvent(&event);
                switch (event.type)
                {
                        case GR_EVENT_TYPE_KEY_DOWN:
                                c = event.keystroke.ch;
                                if(c == 'q')
                                {
                                        GrClose();
                                        exit(0);
                                }
                                break;
                        default:
                                break;
                }
        }
}
--------------------------------------------------------------------------

Thanks in advance

Hi
I'm rather new to Nano-X so I do not know if this applies but you could 
try using:

GrSetGCUseBackground (gc, GR_FALSE);

Regards
Fredrik Johansson

####@####.#### skrev:
> Hello,
>
> i want to copy the contents of a pixmap on to the screen. The pixmap
> contains a gif with a transparent background (=> alpha = 0). When i
> copy the pixmap to the screen the transparent background is visible. I
> run nano-x for the Linux-X86 platform using the X11 library. When
> drawing the gif directly to the screen the transparent background is,
> correctly, not visisble. I attach a simple example which demonstrates
> the problem. In the example i do not load the gif, instead i have two
> pixmaps: one painted with red color (alpha = 0) and the other with
> blue (alpha = 255). Still, the red is visible. I also tried the
> SRCTRANSCOPY mode as arhument in the GrCopyArea, but i am not sure if
> this mode of operation is actually implemented. Any help is greatly
> appreciated.
>
> -------------------------------------------------------------------------
> #include <stdio.h>
> #include <stdlib.h>
> #define MWINCLUDECOLORS
> #include "nano-X.h"
>
> int main(int argc, char **argv)
> {
>         GR_WINDOW_ID pid1, pid2;
>         GR_GC_ID gc;
>         GR_EVENT event;
>         int width, height;
>         char c;
>
>         if( GrOpen() < 0 )
>         {
>                 printf("cannot open graphics\n");
>                 exit(1);
>         }
>
>         width = height = 100;
>
>         GrSelectEvents(GR_ROOT_WINDOW_ID, GR_EVENT_MASK_KEY_DOWN);
>
>         gc = GrNewGC();
>
>         pid1 = GrNewPixmap(width, height, NULL);
>         GrSetGCForeground(gc, MWARGB(0,255,0,0));
>         GrFillRect(pid1, gc, 0, 0, width, height);
>
>         pid2 = GrNewPixmap(width, height, NULL);
>         GrSetGCForeground(gc, MWARGB(255,0,0,255));
>         GrFillRect(pid2, gc, 0, 0, width, height);
>
>         GrCopyArea(GR_ROOT_WINDOW_ID, gc, 100, 100, width, height, pid2, 0,
> 0, MWMODE_COPY);
>
>         GrCopyArea(GR_ROOT_WINDOW_ID, gc, 150, 150, width, height, pid1, 0,
> 0, MWMODE_COPY);
>
>         while(1)
>         {
>                 GrGetNextEvent(&event);
>                 switch (event.type)
>                 {
>                         case GR_EVENT_TYPE_KEY_DOWN:
>                                 c = event.keystroke.ch;
>                                 if(c == 'q')
>                                 {
>                                         GrClose();
>                                         exit(0);
>                                 }
>                                 break;
>                         default:
>                                 break;
>                 }
>         }
> }
> --------------------------------------------------------------------------
>
> Thanks in advance
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: ####@####.####
> For additional commands, e-mail: ####@####.####
>
>   

E

Hello,

i want to copy the contents of a pixmap on to the screen. The pixmap
contains a gif with a transparent background (=> alpha = 0). When i
copy the pixmap to the screen the transparent background is visible. I
run nano-x for the Linux-X86 platform using the X11 library. When
drawing the gif directly to the screen the transparent background is,
correctly, not visisble. I attach a simple example which demonstrates
the problem. In the example i do not load the gif, instead i have two
pixmaps: one painted with red color (alpha = 0) and the other with
blue (alpha = 255). Still, the red is visible. I also tried the
SRCTRANSCOPY mode as arhument in the GrCopyArea, but i am not sure if
this mode of operation is actually implemented. Any help is greatly
appreciated.

-------------------------------------------------------------------------
#include <stdio.h>
#include <stdlib.h>
#define MWINCLUDECOLORS
#include "nano-X.h"

int main(int argc, char **argv)
{
        GR_WINDOW_ID pid1, pid2;
        GR_GC_ID gc;
        GR_EVENT event;
        int width, height;
        char c;

        if( GrOpen() < 0 )
        {
                printf("cannot open graphics\n");
                exit(1);
        }

        width = height = 100;

        GrSelectEvents(GR_ROOT_WINDOW_ID, GR_EVENT_MASK_KEY_DOWN);

        gc = GrNewGC();

        pid1 = GrNewPixmap(width, height, NULL);
        GrSetGCForeground(gc, MWARGB(0,255,0,0));
        GrFillRect(pid1, gc, 0, 0, width, height);

        pid2 = GrNewPixmap(width, height, NULL);
        GrSetGCForeground(gc, MWARGB(255,0,0,255));
        GrFillRect(pid2, gc, 0, 0, width, height);

        GrCopyArea(GR_ROOT_WINDOW_ID, gc, 100, 100, width, height, pid2, 0,
0, MWMODE_COPY);

        GrCopyArea(GR_ROOT_WINDOW_ID, gc, 150, 150, width, height, pid1, 0,
0, MWMODE_COPY);

        while(1)
        {
                GrGetNextEvent(&event);
                switch (event.type)
                {
                        case GR_EVENT_TYPE_KEY_DOWN:
                                c = event.keystroke.ch;
                                if(c == 'q')
                                {
                                        GrClose();
                                        exit(0);
                                }
                                break;
                        default:
                                break;
                }
        }
}
--------------------------------------------------------------------------

Thanks in advance

> I
> run nano-x for the Linux-X86 platform using the X11 library.

This means the driver you will have to check for
SRCTRANSCOPY support will be drivers/scr_x11.c, see below.



> When
> drawing the gif directly to the screen the transparent background is,
> correctly, not visisble. I attach a simple example which demonstrates
> the problem. In the example i do not load the gif, instead i have two
> pixmaps: one painted with red color (alpha = 0) and the other with
> blue (alpha = 255). Still, the red is visible. I also tried the
> SRCTRANSCOPY mode as arhument in the GrCopyArea, but i am not sure if
> this mode of operation is actually implemented.

You'll want to use the SRCTRANSCOPY rather than MWMODE_COPY
to get the transparent blit.  However, not all drivers implement this.
You should look at the code in drivers/fblin16.c, as I think that
driver (RGB565) implements it (I don't have the source here, I'm
traveling).  Of course, your running on X11 which means that
scr_x11.c needs to have the support.

When I return I can look at this more deeply for you.  Also
look at the code in engine/devdraw.c::GdBlit(), as that's
what GrCopyArea calls (check in nanox/srvfunc.c)

Regards,

Greg



 Any help is greatly
> appreciated.
>
> -------------------------------------------------------------------------
> #include <stdio.h>
> #include <stdlib.h>
> #define MWINCLUDECOLORS
> #include "nano-X.h"
>
> int main(int argc, char **argv)
> {
>         GR_WINDOW_ID pid1, pid2;
>         GR_GC_ID gc;
>         GR_EVENT event;
>         int width, height;
>         char c;
>
>         if( GrOpen() < 0 )
>         {
>                 printf("cannot open graphics\n");
>                 exit(1);
>         }
>
>         width = height = 100;
>
>         GrSelectEvents(GR_ROOT_WINDOW_ID, GR_EVENT_MASK_KEY_DOWN);
>
>         gc = GrNewGC();
>
>         pid1 = GrNewPixmap(width, height, NULL);
>         GrSetGCForeground(gc, MWARGB(0,255,0,0));
>         GrFillRect(pid1, gc, 0, 0, width, height);
>
>         pid2 = GrNewPixmap(width, height, NULL);
>         GrSetGCForeground(gc, MWARGB(255,0,0,255));
>         GrFillRect(pid2, gc, 0, 0, width, height);
>
>         GrCopyArea(GR_ROOT_WINDOW_ID, gc, 100, 100, width, height, pid2,
0,
> 0, MWMODE_COPY);
>
>         GrCopyArea(GR_ROOT_WINDOW_ID, gc, 150, 150, width, height, pid1,
0,
> 0, MWMODE_COPY);
>
>         while(1)
>         {
>                 GrGetNextEvent(&event);
>                 switch (event.type)
>                 {
>                         case GR_EVENT_TYPE_KEY_DOWN:
>                                 c = event.keystroke.ch;
>                                 if(c == 'q')
>                                 {
>                                         GrClose();
>                                         exit(0);
>                                 }
>                                 break;
>                         default:
>                                 break;
>                 }
>         }
> }
> --------------------------------------------------------------------------
>
> Thanks in advance
>

> I do not know if this applies but you could 
> try using:
> 
> GrSetGCUseBackground (gc, GR_FALSE);

Depending on the driver, this may be required.  In the beginning,
it was, as we didn't support the more advanced SRCTRANSCOPY
arguments to blit, and it was faked by setting a background color
checking GrSetGCUseBackground in the driver.

Regards,

Greg