Re: [2/3] gdiplus: If a 32-bit dib is selected in an hdc, use the dib directly.

[Alexandre Julliard]

Vincent Povirk  writes:
> @@ -2264,6 +2266,41 @@ GpStatus WINGDIPAPI GdipCreateFromHDC2(HDC hdc, HANDLE hDevice, GpGraphics **gra
>      if(graphics == NULL)
>          return InvalidParameter;
> - hbm = GetCurrentObject(hdc, OBJ_BITMAP);
> - if (hbm && GetObjectW(hbm, sizeof(dib), &dib) && dib.dsBm.bmBitsPixel == 32)
> - {
> -
>    /* Make a bitmap object so we can use the alpha channel */
> -
>    GpBitmap *bitmap;
> -
>    DWORD height, stride;
> -
>    BYTE *bits;
> -
> -
>    height = abs(dib.dsBmih.biHeight);
> -
>    stride = dib.dsBmih.biWidth * 4;
> -
> -
>    if(dib.dsBmih.biHeight > 0) /* bottom-up */
> -
>    {
> -
>        bits = (BYTE*)dib.dsBm.bmBits + (height - 1) * stride;
> -
>        stride = -dib.dsBmih.biWidth * 4;
> -
>    }
> -
>    else
> -
>        bits = dib.dsBm.bmBits;
> -
> -
>    retval = GdipCreateBitmapFromScan0(dib.dsBmih.biWidth, height, stride,
> -
>                                       PixelFormat32bppPARGB, bits, &bitmap);

This won't work, you won't get a negative height with GetObject, and you
won't get DIB info at all for DDBs. Also not all DIBs are in PARGB format.

[2/3] gdiplus: If a 32-bit dib is selected in an hdc, use the dib directly.

[Vincent Povirk]

> you won't get a negative height with GetObject,

Hmm, is GdipCreateBitmapFromHBITMAP doing it right, then? It assumes
all DIB objects have positive stride.
> you won't get DIB info at all for DDBs.

I don't think it makes sense to do this for DDBs, as I can't draw them
directly and don't expect them to have alpha information.
> Also not all DIBs are in PARGB format.

I'll test whether native cares.

[2/3] gdiplus: If a 32-bit dib is selected in an hdc, use the dib directly.

[Vincent Povirk]

> It assumes all DIB objects have positive stride.

Sorry, I misread, that's assuming a negative stride.

[2/3] gdiplus: If a 32-bit dib is selected in an hdc, use the dib directly.

[Alexandre Julliard]

Vincent Povirk  writes:
> > you won't get a negative height with GetObject,
>
> Hmm, is GdipCreateBitmapFromHBITMAP doing it right, then? It assumes
> all DIB objects have positive stride.

No, that's wrong. It should most likely just do a GetDIBits (in one go,
not line by line like it currently does).
> > you won't get DIB info at all for DDBs.
>
> I don't think it makes sense to do this for DDBs, as I can't draw them
> directly and don't expect them to have alpha information.

Sure, but it shouldn't crash and burn.

[2/3] gdiplus: If a 32-bit dib is selected in an hdc, use the dib directly.

[Vincent Povirk]

> > > you won't get a negative height with GetObject,
> >
> > Hmm, is GdipCreateBitmapFromHBITMAP doing it right, then? It assumes
> > all DIB objects have positive stride.
>
> No, that's wrong. It should most likely just do a GetDIBits (in one go,
> not line by line like it currently does).

Does that mean there's no way to access the bits directly given a DIB object?

I think we do it line by line so that we don't rely on
GdipCreateBitmapFromScan0 to create the bitmap with a particular
stride. I guess we could specify a stride when calling that.
> > > you won't get DIB info at all for DDBs.
> >
> > I don't think it makes sense to do this for DDBs, as I can't draw them
> > directly and don't expect them to have alpha information.
>
> Sure, but it shouldn't crash and burn.

I don't understand why it would. I'd expect the GetObject to fail
given sizeof(DIBSECTION) if the object is a DDB.

[2/3] gdiplus: If a 32-bit dib is selected in an hdc, use the dib directly.

[Alexandre Julliard]

Vincent Povirk  writes:
> Does that mean there's no way to access the bits directly given a DIB object?

If you don't know how it was created, then no.
> I think we do it line by line so that we don't rely on
> GdipCreateBitmapFromScan0 to create the bitmap with a particular
> stride. I guess we could specify a stride when calling that.

It seems to me the default is already a DIB stride.
> > Sure, but it shouldn't crash and burn.
>
> I don't understand why it would. I'd expect the GetObject to fail
> given sizeof(DIBSECTION) if the object is a DDB.

No, that's not how it works, size is an upper bound.